Concepts For A National 

Water-Quality Assessment Program 

By ROBERT M. HIRSCH, WILLIAM M. ALLEY, 

and WILLIAM G. WILBER 

U.S. GEOLOGICAL SURVEY CIRCULAR 1021 

1988 
U.S. DEPARTMENT OF THE INTERIOR 

MANUEL LUJAN, JR., Secretary 

U.S. GEOLOGICAL SURVEY 

Dallas l. Peck, Director 

First printing 1988 

Second printing 1990 

UNITED STATES GOVERNMENT PRINTING OFFICE 1988 

Free on application to the Books and Open-File Reports Section, 

U.S. Geological Survey, Federal Center, Box 25425, Denver, CO 80225 

Library of Congress Cataloging In Publication Data 

Hirsch, Robert M. 

Conceptual design of a national water-quality assessment 

program. 

(U.S. Geological Survey Circular ; 1021) 

Bibliography: p. 

Supt. of Docs. no.: I 19.4/2:1021 

1. Water quality-United States. 2. Water-quality-United 

States-Measurement-Case studies. I. Alley, William M. II. 

Wilber, William G. Ill. Title. IV. Series. 

TD223.H57 1989 628.1'61 88-600319 
FOREWORD 

The mission of the U.S. Geological Survey is to assess the quantity and the quality of the 

earth resources of the Nation and to provide information that will assist resource managers and policy 

makers at the Federal, the State, and the local levels in making sound decisions. Assessment of 

water-quality conditions and trends is an important part of this overall mission. 

The history of the earth sciences demonstrates that the ''scale'' at which scientists examine 

the Earth has a major effect on the kinds of insights gained from their studies. In geology, for example, roles exist for investigations at the quadrangle map scale (1 :24,000) and for continental or global 

scale studies focused on plate tectonics. Furthermore, geologic studies at one scale often enhance 

the understanding of the phenomena examined at the other scales. Similarly, in meteorology, there 

is a role for microscale climatic studies over distances of less than a mile, mesoscale studies of 

regional weather systems, and global circulation studies. Again, the overall science would be weakened 

by the lack of any one of these scales of study. 

Investigations at different temporal scales also are needed. Some studies of earthquake 

phenomena, for example, measure processes that last for seconds or even milliseconds, and others 

chart the buildup of the stresses responsible for earthquakes over periods of decades to centuries. 

This document defines an approach for examining the quality aspects of water resources at 

a unique combination of spatial and temporal scales. The spatial scale is primarily regional (several 

thousands of square miles), and the temporal scale is primarily multiyear and decadal. The study 

design stems from the view that insights about water quality, which would be of great value to resource 

managers and policy makers, can be best achieved by examining water quality at these scales and 

by aggregating the findings of the studies with time and across the Nation. These assessments would 

rely on many of the data already being collected as part of smaller scale studies focused on local 

problems, although the questions under investigation would be quite different. The primary questions 

would concern the natural and human factors that give rise to different types of widespread waterquality conditions and the long-term fate of contaminants stored in aquifers, sediments, or biota. 

Throughout its history, the Nation has made major investments in assessing natural resources, 

such as soils, minerals, and hydrocarbons, and human resources in terms of the health, the education, the employment, and the economic status of the population. The reason for these investments 

in information is that decisions our society makes about using or conserving these resources, investing in their improvement, or regulating their use will be better if they are based on sound information. The maintenance and the improvement of water quality is now one of the major areas of 

public investment and government regulation. Therefore, it is appropriate that serious attempts be 

made to document the need for, and the effects of, such governmental actions. 

The best method of conducting such an assessment is not easily determined. The difficulty 

is due to a number of considerations: the multiplicity of water-quality constituents, natural waterquality variations in time and among locations, and the high cost of collecting and analyzing samples. 

This report represents the present thoughts of the Geological Survey on a new direction for waterquality assessment in the United States. It is proposed, not as a replacement for the smaller scale 

studies presently conducted by many agencies, but as a complement, resulting in more complete 

information on the Nation's water quality that can be used for making decisions. 

The proposed National Water-Quality Assessment Program is currently in a pilot phase. As 

part of this pilot program, this report is intended as a forum for sharing and soliciting ideas on our 

concepts and approaches to water-quality assessment. 

tl4~ Philip Cohen 

Chief Hydrologist 

iii 

CONTENTS 

Page 

Foreword . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iii 

Metric conversion table. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . vii 

Executive summary. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 

Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 

Purpose and scope... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 

Acknowledgments ................... :................................................... 5 

General types of information provided by an assessment program.... . . . . . . . . . . . . . . 6 

Water-quality activities of the U.S. Geological Survey and their relation 

to water-quality assessment..... . . . . . . . . . . . .. . . .. . . . . . . . . . .. . . . . . .. . . . .. . .. . .. . .. . 7 

General concepts of the National Water-Quality Assessment Program.............. 9 

Strategic selections. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 

Selection of scales. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 

Selection of study areas. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 

Selection of chemical measurements......................................... 15 · 

Selection of biological measurements........................................ 19 

Uses of available water-quality data. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 

Development of national data bases. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 

Quality assurance....................................................................... 22 

Communication and program coordination........................................ 22 

Design of the surface-water investigations................................................ 24 

Objectives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 

Timing and duration of investigations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 

Sampling activities...................................................................... 25 

Fixed-station sampling.......................................................... 25 

Synoptic sampling............................................................... 27 

Studies of selected stream reaches........................................... 29 

Presentation of results. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 

Design of the ground-water investigations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 

Objectives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 

Timing and duration of investigations.............................................. 31 

Utility of hydrogeologic information................................................ 32 

Scope of investigations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32 

Spatial characterization......................................................... 32 

Temporal characterization...................................................... 34 

Sampling activities. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34 

Regional sampling... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34 

Targeted sampling............................................................... 35 

Long-term sampling............................................................. 36 

Presentation of results. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36 

Summary......................................................................................... 38 

References cited................................................................................ 39 

v 
FIGURES 

Page 

Figure 1. Schematic showing general types of information provided by the 

National Water-Quality Assessment Program....................... 6 

2-4. Maps showing 

2. Locations of the pilot projects of the National Water-Quality 

Assessment Program................................................. 13 

3. Locations of preliminary set of surface-water study units for 

a full-scale National Water-Quality Assessment Program.... 15 

4. Locations of preliminary set of ground-water study units for 

a full-scale National Water-Quality Assessment Program.... 16 

5-6. Schematics showing 

5. Interrelations among tasks and objectives for surface-water 

study-unit investigations for the National Water-Quality 

Assessment Program................................................. 26 

6. Interrelations among tasks and objectives for ground-water 

study-unit investigations for the National Water-Quality 

Assessment Program................................................. 33 

TABLES 

Page 

Table 1. Primary spatial and temporal scales of U.S. Geological Survey 

water-quality programs.................................................... 9 

2. Characteristics of the pilot projects of the National Water-Quality 

Assessment Program....................................................... 14 

3. Inorganic constituents and physical measurements selected as 

target variables in the pilot National Water-Quality 

Assessment Program....................................................... 18 

4. Site characteristics for sampled wells in the National Water-Quality 

Assessment Program....................................................... 22 

5. Data bases containing ancillary data to be used in the National 

Water-Quality Assessment Program.................................... 23 

6. National and candidate study-unit target variables for fixed stations 

in the surface-water part of the pilot National Water-Quality 

Assessment Program....................................................... 27 

7. Groups of target variables to be determined in samples collected 

during surface-water synoptic surveys for the National WaterQuality Assessment Program............................................ 28 

8. Anticipated products of the surface-water investigations for the 

National Water-Quality Assessment Program......................... 30 

9. Targeted sampling activities for the ground-water pilot projects of 

the National Water-Quality Assessment Program.................... 35 

10. Anticipated products of the ground-water investigations for the 

National Water-Quality Assessment Program......................... 37 

vi 
METRIC CONVERSION TABLE 

For the use of readers who prefer to use metric units (International System), conversion factors for inch-pound units used in this 

report are listed below. 

Multiply inch-pound unit By To obtain metric unit 

foot (ft) 0.3048 meter (m) 

mile (mi) 1.609 kilometer (km) 

square mile (mi2

) 2.59 square kilometer (km2

) 

vii 

Concepts For A National Water-Quality Assessment 

Program 

By Robert M. Hirsch, William M. Alley, and William G. Wilber 

EXECUTIVE SUMMARY 

Beginning in 1986, the Congress appropriated funds 

for the U.S. Geological Survey to test and refine concepts for a National Water-Quality Assessment (NA WQA) 

Program. The goals of the program would be to: 

1. Provide a nationally consistent description of current 

water-quality conditions for a large part of the Nation's 

water resources, 

2. Define long-term trends (or lack of trends) in water 

quality, and 

3. Identify, describe, and explain, as possible, the major 

factors that affect observed water-quality conditions 

and trends. 

This information, which will be obtained on a continuing 

basis, would be made available to water managers, policy 

makers, and the public to provide an improved scientific basis 

for evaluating the effectiveness of water-quality management 

programs and for predicting the likely effects of contemplated 

changes in land- and water-management practices. 

At present, the program is in a pilot phase that is to 

last about 4 years. Seven pilot projects, which represent a 

diversity of hydrologic environments and water-quality 

conditions, were selected to test and further develop the 

assessment concepts; four projects focus primarily on surface 

water, and three projects focus primarily on ground water. 

The surface-water pilot project areas are the Yakima River 

basin in Washington, the lower Kansas River basin in Kansas 

aQ.d Nebraska, the Kentucky River basin in Kentucky, and 

the Upper Illinois River basin in Illinois, Indiana, and 

Wisconsin. The ground-water pilot project areas are the 

Carson basin in Nevada and California, the Central 

Oklahoma aquifer in Oklahoma, and the Delmarva Peninsula 

in Delaware, Maryland, and Virginia. 

Each pilot project has a liaison committee, which 

consists of representatives from other Federal, State, and 

local agencies, to help ensure that the scientific information 

1 

produced by the project is relevant to local and regional 

interests. In addition, a National Coordinating Work Group, 

which consists of nine Federal members, seven non-Federal 

members, and a representative from each pilot project liaison 

committee, has been established to advise the Geological 

Survey on the pilot program. 

In 1990, a committee of the National Academy of 

Sciences will complete an evaluation of the design and potential utility of the program. A decision about proceeding to 

full-scale implementation of the program will be made upon 

completion of this evaluation. 

General Concepts 

A full-scale program would be accomplished through 

investigations of about 120 study areas that are distributed 

throughout the Nation and that incorporate about 80 percent of the Nation's water use. 

The areas studied, which are referred to as study units, 

include river basins in which the focus of attention is on 

surface-water quality and aquifer systems in which the focus 

of attention is on ground-water quality. The areas of the study 

units range from a few thousand to several tens of thousands 

of square miles. By conducting the national program as an 

aggregation of individual studies of key river basins and 

aquifer systems, the assessment will provide results that are 

useful in understanding and managing these important water 

resources, as well as in answering national questions about 

water quality. 

Each study-unit investigation will be conducted by a small 

team of individuals familiar with the river basin or aquifer 

system. 

Thus, the assessment can take full advantage of the 

region-specific knowledge of individuals in the areas under 

study. The development of interpretations and communication of findings is done largely by those who collect the data. 
The study units will be linked together to form a national 

program in several ways. 

• A prescribed set of study approaches and protocols for 

sample collection, sample handling, laboratory 

analysis, and quality assurance will be followed. 

• Data will be collected and interpreted on a nationally 

consistent set of water-quality constituents. 

• Consistent records of ancillary information will be 

recorded on streamflow and basin characteristics, 

well and aquifer characteristics, and land use and 

other measures of human activity. 

• Written reports will contain similar information for each 

study unit. 

• Data will be stored in national data files. 

The assessment program will be perennial. 

Because of the emphasis on trends in water quality, 

the program needs to be perennial. The program will evolve 

with time as a result of changes in knowledge of 

hydrogeology, improved methods of measurement, and 

changes in the types of contaminants of concern. However, 

the program will place a high emphasis on repetition of 

measurements with time and on documentation both of the 

methods of data collection and analysis and of the locations 

and the characteristics of data-collection sites. 

Assessment activities in each of the study units will be done 

on a rotational rather than continuous basis. 

Only a subset of the study units will be studied in detail 

at a given time. For each study unit, 3- to 5-year periods 

of intensive data collection and analysis will be alternated 

with loHger periods during which the assessment activities 

will be less intensive. 

The program will focus on water-quality conditions 

that are prevalent or large in scale and persistent in time. 

The program will emphasize regional water-quality 

degradation, such as occurs from nonpoint sources of pollution or from many point sources. The program will not 

diminish the need for smaller scale studies and monitoring 

presently designed and conducted by State, Federal, and local 

agencies to meet their individual needs. The program, 

however, will provide a larger scale framework for 

conducting many of these activities and a knowledge about 

regional and national water-quality conditions that cannot be 

acquired from individual, smaller scale programs and studies. 

Chemical measurements will focus on a set of target 

variables. 

A national list of target variables will consist of a 

common set of physical measurements, inorganic 

2 

constituents, and organic compounds that are included in 

sample analyses for all study units. These will enable the 

assessment to provide interpretations of water quality at the 

national scale. Additional target variables to supplement the 

national list will be selected for each study unit by the project 

team. 

Biological measurements will be used for several purposes 

in the assessment. 

Biological measurements will be used in the assessment to assist in (1) determining the occurrence and distribution of waters contaminated by fecal material, (2) determining the occurrence and distribution of potentially toxic 

substances, (3) assessing the relations between the physical 

and the chemical characteristics of streams and the functional 

or structural aspects of the biological community, and ( 4) 

defining and quantifying biological processes that affect the 

physical and the chemical aspects of water quality. 

The program will make use of available water-quality data 

to supplement the field studies. 

Considerable water-quality data have been collected 

by various agencies for various purposes. One of the first 

activities of each project will be to compile, screen, and 

interpret available data to (1) provide an initial description 

of water-quality conditions, (2) develop hypotheses about 

major factors that influence water quality, and (3) define data 

needs. 

Design of the Surface-Water Investigations 

Three major types of sampling activities will be undertaken in a surface-water study unit. 

• Fixed-station sampling, 

• Synoptic sampling, and 

• Studies of selected stream reaches. 

A network of fiXed stations will be sampled for a wide 

array of water-quality constituents each month and during high streamflows. 

The purposes of fixed-station sampling will be to (1) 

describe the temporal variation and the frequency of occurrence of selected water-quality constituents, (2) estimate loads 

past stations and attempt mass balances of selected target constituents between stations, and (3) define long-term trends 

in. water quality. Sites selected for ftxed-statio.p sampling will 

include locations (1) near the mouths of major tributaries and 

selected points on the main stem that account for a large portion of the total basin runoff, (2) upstream and downstream 

from reservoirs, urban areas, and other areas that significantly affect water quality, (3) on streams draining large areas 
that have relatively uniform land use, and (4) near major 

public water-supply intakes or other important water uses. 

Synoptic sampling will be used primarily to provide a finer 

degree of spatial resolution to the descriptions of certain 

kinds of water-quality conditions than will be attainable 

from the fiXed-station sampling network. 

Synoptic surveys are generally accomplished by making single water-quality measurements representing a specific 

hydrologic condition at many sites in a study area during a 

brief period of time. The number, the timing, and the design 

of the surveys will depend on the specific objectives of the 

survey and the factors affecting the water-quality constituents 

of interest. These surveys will typically be done in stages 

in a study unit, building on the descriptions of water-quality 

conditions in a hierarchical manner. 

Studies of selected reaches will be done to address certain 

more narrowly focused water-quality issues that are 

identified during the course of the surface-water studyunit investigations. 

The primary concern of these studies will be to provide 

an improved understanding of the sources, distribution, and 

fate of particular constituents in the selected stream reaches. 

Results from mathematical models applied during some of 

these studies will be used to test understanding of 

cause-and-effect relations and to evaluate the outcome of 

alternative management strategies. Model results could be 

tested in later study cycles to determine if conditions have 

changed and if these changes correspond to prior 

understanding. 

Design of the Ground-Water Investigations 

Three major types of sampling activities will be undertaken in a ground-water study unit. 

• Regional sampling, 

• Targeted sampling, and 

• Long-term sampling. 

Regional sampling will be conducted for a wide array of 

water-quality constituents. 

The purposes of the regional sampling will be to 

provide descriptive statistics on the occurrence and concentrations of the target variables for major hydrogeologic 

settings and to form an initial basis for describing the 

geographic distribution of water-quality conditions within the 

study unit. Sampling locations for regional sampling will be 

selected so as to be spatially distributed, areally and with 

depth, throughout each major hydrogeologic setting and 

to be unbiased with respect to known or suspected local 

problem areas. 

3 

Targeted sampling of known or suspected water-quality 

problem areas will be used to examine the spatial 

distribution of selected water-quality constituents. 

The targeted sampling designs will focus on broadly 

defined groups of water-quality constituents, such as 

agricultural chemicals, contaminants associated with urban 

and suburban areas, and naturally occurring trace elements. 

The approaches that will be used include search-oriented 

sampling within particular areas of concern, sampling to test 

particular statistical hypotheses about the regional distribution 

of contaminants, and sampling along local scale transects of 

wells. The approaches will be tailored to the major 

hydrogeologic and land-use factors that affect ground-water 

quality in different situations. Similar targeted sampling 

designs will be applied to selected study units to allow 

multistudy-unit comparisons. 

Long-term trends in ground-water quality will be 

examined by use of data from a network of wells that are 

selected in each study unit at the conclusion of the first 

high-activity period. 

Selection criteria will be established to assure a 

distribution of wells for long-term sampling that represent 

ground water of different ages and hydrogeologic settings. 

Wells screened in the upper part of water-table aquifers may 

be particularly useful for early detection of contamination 

from surface sources and for relation of observed trends to 

changes in land-use practices. 

Information Provided by the Assessment Program 

The program will provide unique regional and national 

scale information concerning the Nation's water quality. 

The intent is for the Geological Survey to provide 

information through the NA WQA Program to those who set 

policy, write regulations, establish priorities, or manage 

water resources. Information on the status, the trends, and 

the causes of water-quality conditions across the country 

should be particularly useful to other agencies who are 

involved in (1) identifying key substances for possible regulation and for which research is needed on toxicity, human 

exposure, and drinking-water treatability, (2) allocating 

budgetary resources among competing types of water-quality 

problems, (3) determining whether desired goals for waterquality improvement are being met, ( 4) designing monitoring programs in different parts of the country (in terms of 

the constituents analyzed, sampling locations, sampling 

frequency, and timing of sampling), (5) targeting regulations 

for selected water-quality constituents to particular 

geographic regions or hydrologic settings, (6) determining 

the relative effects on water quality of various types of point 

and nonpoint sources, (7) identifying aquifers requiring 
different types and degrees of water-quality protection, and 

(8) evaluating management practices in terms of their largescale effects on the water quality of river basins and aquifer 

systems. 

Statistical descriptions of water-quality conditions and 

their changes with time will be provided for many different 

types of constituents. 

These constituents include pesticides and other 

synthetic organic compounds, nutrients, certain metals and 

trace elements, and sediment. The statistical descriptions will 

consist of the following types of information: 

• Frequencies of occurrence, frequencies of exceedance of 

established water-quality standards, and concentrations of water-quality constituents at key streamflow 

stations and in the ground water of major 

hydrogeologic settings, 

• Transport of selected constituents past key streamflow 

stations, and 

• Long-term trends in water-quality constituents at key 

streamflow stations and in the ground water of major 

hydrogeologic settings. 

Information on the geographic distribution of various 

contaminants will be provided for major river basins and 

aquifer systems of the United States. 

The information will be used to identify areas that have 

water-quality problems, as well as areas that have generally 

high-quality water. This information will be useful to 

Federal, State, and local managers in the allocation of 

resources for water-quality management and protection. 

Depending on the spatial distribution of the constituents of 

4 

interest, the geographic descriptions will take the following 

forms: 

• Maps that show locations of sampling sites and results of 

water-quality analyses, 

• Descriptions and maps that distinguish reaches or zones 

that differ in their average values or in their frequencies of exceedance of given concentrations of waterquality constituents, 

• Descriptions and maps of the locations of water-quality 

anomalies that cover large areas (tens of river-miles 

or tens of square miles in an aquifer system), and 

• Descriptions of ground-water-quality changes that occur 

with depth in different hydrogeologic settings. 

Information on key factors that affect water quality will be 

provided to relate the occurrence and the concentrations 

of the target constituents to different hydrologic 

environments, land uses, and human activities. 

An understanding of these relations will provide a basis 

for predicting where and when certain types of contamination problems are likely to occur and for determining the 

large-scale effects of alternative water-quality management 

strategies. This information will include the following: 

• Statistical models of expected levels of contamination or 

probabilities of exceeding certain levels that are based 

on readily measured variables related to soils, 

hydrogeology, land use, population, streamflow, and 

climate, 

• Explanations of the causes of observed geographic and 

temporal variations in water quality, 

• Information on the portions of surface-water constituent 

loads that are derived from various point and nonpoint sources, and 

• Descriptions of factors that affect the vulnerability of 

aquifer systems to contamination. 
INTRODUCTION 

Background 

The protection and the enhancement of the quality of 

the Nation's ground- and surface-water resources are 

high-priority concerns of the public and of government at 

its various levels. Over the past two decades, several large 

water-quality spending and regulatory programs have been 

enacted into law. In addition, many major decisions that will 

determine the directions of water-quality management for 

future decades have yet to be made. Many of these decisions 

will be made in areas of great scientific uncertainty; for 

example, many will relate to controlling nonpoint sources 

of contamination, which commonly are much more complex 

to control than the point sources of contamination addressed 

by past regulations. 

Nationally consistent information on the status and the 

trends of the Nation's water quality is needed to help 

determine the degree to which past investments in 

water-quality management are working and to provide 

a base of knowledge for evaluating future decisions. To 

meet this need, the Congress appropriated funds in 1986 

for the U.S. Geological Survey to test and refine concepts 

for a National Water-Quality Assessment (NAWQA) 

Program. The long-term goals of the program would be 

to: 

1. Provide a nationally consistent description of current 

water-quality conditions for a large part of the Nation's 

water resources, 

2. Define long-term trends (or lack of trends) in water 

quality, and 

3. Identify, describe, and explain, as possible, the major 

factors that affect observed water-quality conditions 

and trends. 

This information, which will be obtained on a continuing basis, would be made available to water managers, 

policy makers, and the public to provide an improved scientific basis for evaluating the effectiveness of water-quality 

management programs and for predicting the likely effects 

of contemplated changes in land- and water-management 

practices. 

At present, the program is in a pilot phase that is to 

last about 4 years. In 1990, a committee of the National 

Academy of Sciences is scheduled to complete an evaluation of the design and potential utility of the program. A 

decision about proceeding to full-scale implementation will 

be made upon completion of this evaluation. 

5 

Purpose and Scope 

The purpose of this report is to describe the conceptual 

design of the NA WQA Program. The design concepts 

represent a set of views which were originally developed by 

a committee of Geological Survey scientists (Rubin, 1987) 

that subsequently were refined and revised in response to 

comments by other Geological Survey scientists, officials of 

a large number of Federal and State water agencies, the 

Department of the Interior Water Policy Working Group, 

and the Water Science and Technology Board of the National 

Research Council (National Research Council, 1985, 1987). 

The emphasis in this report is on the principles that 

should govern the long-term national acquisition and analysis 

of water-quality data for assessment purposes. Some current 

activities of the pilot NA WQA Program are described to 

illustrate these concepts. 

The approaches of the program will continue to evolve 

as experience is gained, measurement and analysis techniques 

advance, and water-quality issues change. In this regard, 

although considerable use of the word ''will'' is used in this 

report, it should be interpreted within the context of the pilot 

nature of the present effort and the requirement for an 

independent evaluation before proceeding to a full-scale 

program. 

Acknowledgments 

The authors of this report have drawn heavily on the 

assistance, suggestions, and contributions of a large group 

of people within and outside of the U.S. Geological Survey. 

Members of the National Research Council, Water 

Science and Technology Board, provided valuable insight 

and perspectives, particularly on the design of the groundwater component and the role of biology. Contributors from 

the Water Science and Technology Board include Stephen 

D. Parker, Director; Edward J. Bouwer, Johns Hopkins 

University; Thomas Dunne, University of Washington; Allen 

Kneese, Resources for the Future; Orie Loucks, Butler 

University; Dean Mann, University of California, Santa 

Barbara; Donald R. Nielsen, University of California, Davis; 

Daniel A. Okun, University of North Carolina, Chapel Hill; 

Betty H. Olson, University of California, Irvine; Wayne A. 

Pettyjohn, Oklahoma State University; George F. Pinder, 

Princeton University; Kenneth W. Potter, University of 

Wisconsin; and Philip Singer, University of North Carolina. 

Members of other Federal, State, and local agencies 

participating on the National Coordinating Work Group for 

the pilot NAWQA Program have provided numerous 

suggestions to help ensure that the information produced by 
the program will have maximum utility to the public and 

water-management agencies. Current (1988) members of 

the National Coordinating Work Group are Lee Barclay, 

U.S. Fish and Wildlife Service; Carroll Curtis, Council on 

Environmental Quality; Norbert Dee, U.S. Environmental 

Protection Agency; Lewis Dodgion, Nevada Department of 

Conservation and Natural Resources; Judith A. Duncan, 

Oklahoma State Department of Health; Earl E. Eiker, 

U.S. Army Corps of Engineers; Ivai V. Goslin, engineering consultant; Donald C. Haney, Kentucky Geological 

Survey; Dirk C. Hofman, Interstate Conference on Water 

Policy; U. Gale Hutton, Association of State and Interstate 

Water Pollution Control Administrators; Leon Hyatt, 

U.S. Bureau of Reclamation; Carol Jolly, Washington 

Department of Ecology; Gyula Kovach, Kansas Department 

of Health and Environment; James N. Krider, Soil Conservation Service; Richard Lanyon, Metropolitan Sanitary 

District of Greater Chicago; Frederick D. Leutner, 

U.S. Environmental Protection Agency; Robert E. Raschke, 

National Association of Conservation Districts; Gray F. 

Reynolds, U.S. Forest Service; Andrew Robertson, National 

Oceanic and Atmospheric Administration; Kenneth D. 

Schmidt, American Water Resources Association; Russell 

H. Susag, Chemical Manufacturers Association; Peter S. 

Tinsley, Maryland Office of Environmental Programs; and 

Hugo F. Thomas, Association of American State Geologists. 

Although individual credit is not feasible for all 

U.S. Geological Survey reviewers and contributors who 

made the report possible, their helpful cooperation is 

greatfully acknowledged. John D. Bredehoeft, John N. 

Fischer, Irwin H. Kantrowitz, P. Patrick Leahy, Samuel N. 

Luoma, Gail Mallard, David A. Rickert, Jacob Rubin, and 

VerneR. Schneider are specifically acknowledged for their 

critical review of the concepts as they have evolved. Timothy 

A. Cohn, Kenneth J. Lanfear, Eugene P. Patten, 

and Kenneth L. Wahl assisted in the development and 

implementation of a process to select a preliminary set of 

study units for a possible full-scale program. Alene McCuen, 

Iris M. Oos, and Joan Patton contributed greatly to the layout 

of the report. 

Finally, the seven project teams and regional 

coordinators for the pilot NA WQA Program have contributed 

immeasurably to the concepts in this report through exchange 

of ideas on the feasibility of various aspects of the design 

and through their implementation of concepts in the pilot 

projects. These contributors include Stephen F. Blanchard, 

Robert C. Bubeck, Scott C. Christenson, Donald A. 

Goolsby, JohnS. McLean, Stuart W. McKenzie, W. David 

Nichols, Gary L. Pederson, Robert J. Shedlock, James L. 

Smoot, John K. Stamer, Lindsay A. Swain, Wayne E. Webb, 

and Alan H. Welch. 

GENERAL TYPES OF INFORMATION PROVIDED 

BY AN ASSESSMENT PROGRAM 

The NA WQA Program is designed to provide 

statistical descriptions of water-quality conditions and their 

6 

changes with time, descriptions of the geographic distribution of water quality across the Nation and within particular 

regions, and explanations of the observed water-quality 

conditions and trends (see fig. 1). 

Provides a · 

.----~ statistical 

deserlptl()~ 

Program 

Explains 

observed 

conditions 

p:iOVi&i ·::::, $tati$t~ Q·* 

me•sures of current water 

Describes time trendS in 

wt.ter . quality 

Helps !P locate and describe 

areas of Jmpsired 

water quality 

Defines the oausn of observed 

geog~hic and temporal 

va.rlat.lons 

Provides ,,a basis for predlc1iog." the ett$!;1$ of contempla~ : 

water-quality management actions 

Figure 1. General types of information provided by the National 

Water-Quality Assessment Program. 

Statistical descriptions will be provided on a continuing 

basis for many different types of contaminants, including 

pesticides and other synthetic organic compounds, nutrients, 

certain metals and trace elements, and sediment. The 

statistical descriptions are needed to obtain a perspective on 

the frequency of occurrence and concentrations of these 

water-quality constituents in the Nation's surface and ground 

water. Statistical data to describe current conditions are 

particularly sparse for many synthetic organic compounds 

of concern, while consistent long-term water-quality data are 

lacking both for inorganic and organic constituents. 

Information on the geographic distribution of various 

contaminants will be used to help identify locations of 

impaired water quality and the nature and the severity of the 

problems, as well as to help identify and describe those parts 

of the water resource that are generally problem free. For 

ground water, the results will include descriptions of areal 

variations in water quality and of water-quality changes that 

occur with depth in different hydrogeologic environments. 

The consistently derived information on the geographic 

distribution of water quality across the Nation and within 
particular regions will be helpful to various agencies in 

allocating resources for water-quality management and 

protection; for example, knowledge about regional 

differences in the occurrence of particular chemicals could 

lead to reductions in the list of substances that require 

monitoring in specific regions or in the frequency of their 

analysis at monitoring sites. 

Finally, statistical relations and knowledge of waterquality processes will be used to relate the occurrence and 

the concentrations of various chemicals to different 

hydrologic environments, land uses, and human activities. 

An understanding of these relations is important for several 

reasons. First, they provide a basis for predicting where and 

when certain types of contamination problems are likely to 

occur; for example, statistical models would be used to 

calculate expected levels of contamination or the 

probabilities of exceeding certain concentrations, based on 

readily measured variables related to soils, hydrogeology, 

land use, population, streamflow, and climate. Second, 

understanding of causal relations will help Federal, State, 

and local water-management officials predict the 

consequences of various policy and regulatory options; for 

example, an understanding of major factors affecting water 

quality would provide a basis for estimating the different 

effects of an activity in different geographic settings and, 

therefore, a starting point for targeted regulation. 

WATER-QUALITY ACTIVITIES OF THE U.S. 

GEOLOGICAL SURVEY AND THEIR RELATION 

TO WATER-QUALITY ASSESSMENT 

The U.S. Geological Survey has collected and interpreted data on water quality for more than 100 years. A brief 

review of some of these activities is useful as background 

for discussion of the plans for the NA WQA Program. Two 

points should be considered in this review. First, virtually 

every aspect of the NA WQA Program plan has some 

precedent in other Geological Survey programs. The 

NA WQA Program is an evolutionary step in organizational 

concepts, goals, and level of effort rather than the start of 

a totally new set of activities. Second, the NA WQA Program 

is not intended to be the total water-quality program of the 

agency. Many existing Geological Survey water-quality 

projects serve other purposes and provide information at 

different levels of detail than would the NA WQA Program; 

moreover, many of these activities provide a base on which 

the NA WQA Program would build. 

Geological Survey involvement in water-quality 

investigations dates back to the latter part of the 19th century. 

Initial water-quality investigations were directed toward the 

suitability of water for domestic consumption, irrigation, and 

industrial use (Durum, 1978). The first major Geological 

Survey report addressing water quality was on the use of 

7 

sewage for irrigation of crops (Rafter, 1897). Results of the 

first regional assessment of water-quality conditions were 

published in 1909 for the Eastern United States (Dole, 1909). 

Since these early investigations, the Geological Survey 

has conducted studies directed at a wide array of waterquality issues. Detailed process-oriented and larger scale 

studies of prominant water-quality issues have been 

conducted. These studies cover a range of disciplines from 

hydrology to interdisciplinary biogeochemical studies. 

Examples of issues addressed include nutrient enrichment 

(Mattraw and Elder, 1984), dissolved oxygen depletion in 

rivers (Rickert and Hines, 1978), contamination of streambed sediments by trace elements (Rickert and others, 1977), 

acid rain ( Turk, 1983; Smith and Alexander, 1983), the 

transport of radionuclides in rivers (Hubbell and Glenn, 

1973; Pickering, 1969), and the contamination of aquifers 

and rivers by potentially toxic, anthropogenic organic compounds (Schroeder and Barnes, 1983a, b; LeBlanc, 1984; 

Mattraw and Franks, 1986). 

Presently, the Geological Survey's water-quality 

programs are supported by three sources of funds-the 

Federal-State Cooperative Program, other Federal agencies, 

and the Geological Survey Federal programs. These 

programs are described below. 

The Federal-State Cooperative Program has existed 

since 1895 and involves agreements wherein State and local 

agencies provide at least one-half of the funding for investigations by the Geological Survey on regional and local waterresources issues. The Geological Survey presently has such 

agreements with about 950 agencies (Gilbert and Mann, 

1988). Many of the resulting investigations involve assessing 

water-quality conditions in a particular river reach or part 

of an aquifer. These studies include extensive data acquisition 

(forming the core of some State's ambient monitoring programs), analysis and interpretation of existing data, and 

modeling of hydrologic systems to understand the probable 

consequences of various management actions. In a number of 

States, the Cooperative Program has provided extensive longterm data bases that are extremely valuable to regional and 

national assessment efforts, such as the NA WQA Program. 

The Cooperative Program has been instrumental in keeping 

the Geological Survey abreast of the emerging water problems and the needs and interests of water-management 

officials. Close involvement with State and local governments 

has helped identify needs that have guided many of the 

research efforts in the Geological Survey water programs. 

The Geological Survey does a significant amount of 

water-quality data acquisition, interpretation, and research 

at the request of other Federal agencies; for example, the 

Geological Survey is assessing the long-term changes in the 

salinity of the Colorado River and its tributaries as part of 

the U.S. Bureau of Reclamation's salinity-control program 

(Liebermann and others, in press). Additional activities on 

behalf of other Federal agencies include assessing the effects 
of irrigation drainage on selected National Wildlife Refuges 

in cooperation with the U.S. Bureau of Reclamation and the 

U.S. Fish and Wildlife Service, evaluation of ground-water 

quality near toxic waste-disposal sites for the Department 

of Defense and the U.S. Environmental Protection Agency 

(EPA); and studies of the local and regional water resources 

in conjunction with present or planned nuclear waste 

repositories for the Department of Energy. 

As part of its Federal program (activities funded 

entirely by direct appropriations from the Congress), the 

Geological Survey operates two national networks to measure 

surface-water quality. The first of these is the Hydrologic 

Benchmark Network, which consists of 53 stations in 

relatively small, pristine watersheds. The Hydrologic 

Benchmark Network provides a baseline of ''near natural'' 

water quality and an understanding of the inherent variability 

of water quality where humans have little influence on the 

water resources. This network proved useful, for example, 

in detecting the effects of atmospheric deposition on water 

quality, including long-term trends in sulfate concentrations 

in streams in relation to regional changes in sulfur dioxide 

emissions (Smith and Alexander, 1983). 

The second network is the National Stream Quality 

Accounting Network (NASQAN), which presently consists 

of 423 stations that collectively measure outflows from most 

of the surface-water hydrologic accounting units (Seaber and 

others, 1986) in the country. NASQAN data have been used 

to detect trends and to estimate transport rates of more than 

30 different constituents and have been compared to data 

on climate, geology, population, agriculture, industrial 

activities, and point-source effluents. These comparisons 

(Peters, 1984; Smith and others, 1987) have shown a number 

of significant relations between water quality and human 

activities. Examples include relations between lead in streams 

and the use of leaded gasoline, nitrate in streams and 

atmospheric emissions of nitrous and nitric oxides, and 

dissolved solids in streams and climate, geology, and human 

population. NASQAN data also provide extensive information on the fluxes of nutrients and metals into the Nation's 

estuaries and reservoirs. 

In addition to the two national networks, the Federal 

Program of the Geological Survey supports studies of acid 

rain and toxic substances hydrology. The acid rain work 

includes deposition monitoring that enables the detection of 

long-term trends in acid rain (Peters and others, 1982; 

Schertz and Hirsch, 1986) and evaluation of the effects of 

acid deposition on aquatic systems (Kramer and others, 1986, 

p. 231-299). The Geological Survey coordinates and operates 

part of the Federal National Trends Network, which collects 

and analyzes samples of wet deposition on a weekly basis 

nationwide (Robertson and Wilson, 1985). 

The Toxic Substances Hydrology Program (Franks, 

1987; Ragone, 1987; Mallard, 1988), which was started in 

8 

1982, provides increased understanding of the occurrence, 

movement, and fate of hazardous substances in.the Nation's 

ground and surface waters and sediments. The program focus 

is on the development of new methods for sampling and 

analysis oftrace elements and organic compounds; research 

on the chemical, physical, and biological processes that 

govern the behavior of these substances in surface and ground 

water; and development of methods to define the relation 

of water quality to land use and hydrogeology. Much of the 

work occurs through interdisciplinary field investigations of 

highly contaminated aquifers or streams; thus, the results are 

directly useful for developing restoration plans for existing 

contaminated sites and for designing improved waste-disposal 

practices. 

The Regional Aquifer-Systems Analysis (RASA) 

Program (Sun, 1986) provides an understanding of regional 

aquifer and flow characteristics of fundamental importance 

to large-scale water-quality studies, such as the NAWQA 

Program. Many of the studies also provide regional descriptions of the distribution of major ionic species. 

The National Research Program of the Water 

Resources Division is engaged in studies of fundamental 

hydrogeologic processes and has developed many of the 

methodologies that the NA WQA Program will use. Some 

of the various water-quality-related research activities for 

which the National Research Program are recognized internationally include those related to the chemistry and 

geochemistry of natural waters (Hem, 1985; Thurman, 1985; 

Back and Hanshaw, 1970), the development of widely used 

geochemical computer models (Truesdall and Jones, 1974; 

Plummer and others, 1983), the development of simulation 

models for solute transport in ground water (Konikow and 

Bredehoeft, 1978; Voss, 1984) and in surface water (Jobson, 

1985), hydrology and chemistry of the unsaturated zone 

(Weeks and others, 1982; Winograd, 1981), the study of 

metal bioavailability and partitioning in sediments (Luoma, 

1983), the hydrogeochemistry at ground-water contamination 

sites (Baedecker and Apgar, 1984), and the transport and 

role of sediment (Meade, 1982). 

Finally, in addition to the water-quality programs 

described above, the Geologic and the National Mapping 

Divisions of the Geological Survey will contribute geologic, 

geochemical, and mapping expertise. These Divisions are 

involved in the pilot program in studies of the distribution 

of naturally occurring trace elements and in helping to meet 

the mapping needs. 

The NA WQA Program will differ from past and 

present programs in the emphasis placed on various 

approaches and in its overall structure. When fully 

implemented, it will not replace existing programs because 

there will continue to be significant need for programs 

focused on different temporal and spatial scales. However, 

the NA WQA Program will lead to modifications of 
Geological Survey water-quality programs; for example, data 

collected at NASQAN sites in NA WQA study units will be 

coordinated with other data collected as part of the NA WQA 

projects. In addition, the NA WQA Program will identify 

local problem areas that would be candidates for investigation under other programs of the Geological Survey, such 

as the Federal-State Cooperative Program and the National 

Research Program. 

GENERAL CONCEPTS OF THE NATIONAL 

WATER-QUALITY ASSESSMENT PROGRAM 

Strategic Selections 

The challenge of organizing an effort to acquire and 

interpret data, and to assess the Nation's water quality is 

formidable. Difficulties result from the large area involved, 

the high degree of spatial and temporal variability of water 

quality, the large number of water-quality constituents of 

interest, and the high cost of field work and laboratory 

analyses (especially for trace organic chemicals). 

Several strategic selections have been made in designing the proposed program to make the assessment tractable. 

The first is the spatial and temporal scales at which the 

program will focus. The second is the selection of that part 

of the total national resource to be examined and the manner 

in which this examination will be organized, geographically 

and with time. The third choice is selection of the chemical 

measurements, and the fourth is selection of biological 

measurements. 

Selection of Scales 

Water-quality data are collected to address problems 

at a wide range of scales. It is useful to consider three spatial 

scales and three temporal scales and then to identify which 

of them are the focus of the assessment program. 

Spatial Scales 

Water-quality programs provide information at 

different spatial scales. For Geological Survey water-quality 

programs, three of these scales are shown in table 1. 

A local scale program attempts to describe the pattern 

of water-quality characteristics within small areas. Often, 

these areas are associated with known point sources of 

contamination. In surface water, an example is the study of a 

Table 1. Primary spatial and temporal scales of U.S. Geological Survey water-quality programs 

Temporal 

scale 

Local 

Short term Federal-State Cooperative Program. 

Multiyear 

Decade(s) 

Urban hydrology. 

Some research on rivers. 

Federal-State Cooperative Program. 

Toxic Substances Hydrology 

Program. 

Acid-rain studies. 

Acid-rain studies. 

Nuclear hydrology. 

Spatial scale 

Regional 

Federal-State Cooperative Program. 

Toxic Substances Hydrology 

Program (regional studies). 

Acid-rain studies. 

Regional Aquifer-Systems Analysis 

(geochemical studies). 

Federal-State Cooperative Program 

(water-quality networks). 

9 

National 

National Stream Quality Accounting Network (NASQAN). 

Hydrologic Benchmark Network. 

National Trends Network 

(acid rain). 
dissolved oxygen sag (occurring over a stream reach of 

perhaps several miles). In ground water, an example is the 

study of a contaminant plume from a hazardous-wastedisposal site (perhaps several acres in area). Some local scale 

studies also may be conducted in conjunction with a regional 

scale study to examine representative river reaches or parts 

of aquifers in more detail. 

A regional scale program attempts to characterize 

water-quality conditions within areas of hundreds to tens of 

thousands of square miles. Depending on the spatial distribution of the variable of interest, the descriptions resulting from 

a regional scale study might take several forms-areawide 

average levels of water-quality constituents, maps of the locations of water-quality anomalies that cover large areas (tens 

of river miles, or tens of square miles in an aquifer system), 

maps that distinguish reaches or zones that differ in their 

average values (or frequencies of exceedance of given levels) 

of one or more water-quality constituents, or statements that 

relate geologic, soils, land-use, and other information to 

water-quality characteristics. A regional scale program will 

identify local scale anomalies that are prevalent or that occur 

with high frequency; however, it should not be expected to 

find or characterize all or even many of these local scale 

features. 

A national scale study is concerned with characterizing water-quality conditions over much of the Nation; for 

example, the fluxes in nutrients, metals, and other inorganic 

and organic constituents transported to estuaries, oceans, and 

large lakes or from one region to another and the trends in 

the fluxes are of great concern. There are also national scale 

concerns that involve developing clearer inferences about the 

primary effects of human activities, climate, geology, and 

soils on the status and the trends of water quality by analyzing 

consistent data from a wide variety of locations. 

Many agencies at various levels of government collect 

water-quality data to address questions relevant to the local 

scale. The data are collected for a host of purposes that 

include research on specific water-quality issues and many 

regulatory, monitoring, and remediation purposes. Less 

attention is given to collection of data at the regional scale, 

and many of these efforts tend to focus at the level of counties 

or small drainage basins. At the national scale, water-quality 

data generally have been collected through national networks 

of fixed-location monitoring stations for surface water and 

through selected one-time sampling surveys for ground 

water. At present in the United States, no program exists 

to integrate information from the regional scale to the national 

scale to provide a consistent description of water quality 

across the Nation and insight on the major factors that control 

water quality in different regions. This integrated information is the focus of the NA WQA Program. 

Temporal Scales 

Water-quality programs also provide information at 

different temporal scales. Three scales are included in 

10 

table 1; the shortest of these, referred to as the short-term 

scale, relates to phenomena that occur at time scales of 

minutes to a few days, primarily in surface water. The purposes of short -term scale data collection include the prediction or documentation of naturally influenced events, such 

as a fish kill caused by natural low-flow conditions in a river 

with a high oxygen demand, and of human-caused events 

resulting from toxic-waste spills, sudden industrial accidents, 

and treatment plant upsets or shutdowns. 

The second temporal scale is the multiyear scale. It 

involves collecting sufficient data to make inferences about 

probability distributions of concentrations and surface-water 

transport rates and probabilities of exceedance of given levels 

of water-quality constituents. Multiyear scale assessments 

require enough consistent data so that one can separate out 

seasonal variation, annual climatic variation, and human 

influences. If the repeated occurrence of transient phenomena 

is significant to the usefulness of the resource, then a description of the magnitude and frequency of these conditions is 

an important part of these multiyear descriptions. 

The third temporal scale for water-quality studies is 

the decadal scale. Such studies focus on long-term trends in 

water quality that arise due to changes in population, land 

use, technology, waste-disposal practices, water-resource 

development, or climate. These longer term studies also focus 

on the fate of hazardous materials that are intentionally or 

inadvertently stored in bed sediments, flood plains, and 

aquifers. Such studies may be required to ascertain the rates 

at which substances migrate and transform in these types of 

systems. 

As with spatial scales, the lower end of the range of 

temporal scales-the short-term scale-is addressed by a 

large number of water-quality programs, many of them at 

the State and the local government level. Fewer programs 

focus at the longer time scales, particularly at the scale of 

a decade or longer. 

Scales of Focus for Water-Quality Assessment 

The scales of focus for the NA WQA Program are the 

regional and national spatial scales and the multiyear and 

decadal temporal scales. Although the local and the shortterm scales are not the focus of the assessment, the program 

will alert others of the discovery of previously unknown local 

scale problems or identification of short -term threats to 

human health or ecosystems. 

The multidecade or perennial nature of the NA WQA 

Program is required to discover unexpected changes in water 

quality and to reveal the presence of important, slowly evolving trends. A perennial study also will allow a progressive 

understanding of water quality in specific study areas. 

The goal of documenting long-term trends in water 

quality creates some fairly stringent demands on the way that 
data are collected; the NA WQA design is influenced heavily 

by these demands. First, field-sampling techniques and 

laboratory procedures and their associated analytical 

precision and bias will be documented throughout the 

program. Thus, knowledge about changes in procedures can 

be incorporated into the analysis of water-quality changes. 

Second, the criteria for selection of sampling sites will be 

documented and consistent among locations. Third, longterm sampling networks will be designed so that each 

sampling location can be placed in its hydrologic and landuse context to achieve an appropriate mixture of sampling 

locations. 

The scales of focus in the assessment program affect 

the issues that will be addressed and vice versa. Examples 

of issues addressed by the surface-water part of the program 

include effects of large urban, agricultural, or mining areas 

on surface-water quality. The program will allow these areal 

sources to be contrasted in magnitude with the estimated point 

sources of contamination. The surface-water program also 

will provide information about the long-term delivery of 

contaminants from geologic sources or from past discharges 

of pollutants. 

Examples of issues addressed by the ground-water 

part of the program include those due to widespread 

application of materials at the surface (for example, 

pesticides and fertilizers) and from aggregations of a 

large number of small sources at or near the land surface 

(for example, household chemicals and wastes resulting 

from a large number of septic tanks or leaky sewers). 

Additional issues include the regional effects of irrigation 

on the movement of naturally occurring trace elements, 

problems related to surface- and ground-water interaction, 

prevalent problems resulting from cross contamination 

(movement of water between aquifers), and natural 

geologically related water-quality problems. 

Selection of Study Areas 

The program is not intended to consider all parts of 

the Nation's water resources. The target will be freshwater 

rivers and aquifers; waters so saline as to have little potential 

for consumptive use will not be examined. To achieve a 

manageable size, the program will not assess saline estuaries 

or the Great Lakes, although it will measure the quantity and 

the quality of the water flowing into many of these water 

bodies. 

Study-Unit Design 

One design considered to accomplish the assessment 

goals was a national statistical design. This approach would 

lead to random sampling, stratified random sampling, or 

clustered stratified random sampling. The selection of 

sampling sites would be directed from a central office. The 

11 

role of local personnel would be to establish the sampling 

sites and to collect the samples. The data analysis would 

occur at the national level. This design has not been selected 

for reasons that will be discussed. 

An alternative design, and the one selected, will be to 

investigate a large set of hydrologic systems by using 

nationally consistent methods; the results will be aggregated 

to provide large regional and national overviews. These study 

units will include river basins where the focus is on surfacewater quality and aquifer systems where the focus is on 

ground-water quality. The relative emphasis on surface- and 

ground-water quality in each study unit will depend on the 

degree of interconnection between the two resources. The 

areas of the study units will range from a few thousand to 

several tens of thousands of square miles. 

The results will be linked together to form a national 

assessment in the following ways: 

1. A prescribed set of study approaches and protocols 

for sample collection, sample handling, laboratory 

analysis, and quality assurance will be followed, 

2. The data will be collected and interpreted on a nationally 

consistent set of water -quality constituents, 

3 . Consistent records of ancillary information will be 

recorded on streamflow and basin characteristics, well 

and aquifer characteristics, and land use and other 

measures of human activity, 

4. Written reports will contain similar information for each 

study unit, and 

5. The data will be stored in national data files. 

Because the program is an assessment program (as 

opposed to a monitoring program) and because a feasible 

design needed to be achieved, the major activities in these 

study units will be periodic rather than continuous. For 

surface water, the data-collection activities will occur in 

3-year segments, followed by 1 year for completing data 

interpretation and report preparation. Between the 3-year 

high-activity periods, there will be a 6-year period during 

which only a relatively small amount of data collection and 

analysis will occur. The 9-year cycle will be repeated, and 

a new 3-year data set will become available to compare with 

past 3-year data sets. Under this scheme, one-third of the 

surface-water study units will be in an active data-collection 

mode at any one time. 

Because ground-water quality changes more slowly, 

the program cycle will be longer than the 9 years used in 

surface water and will be of different lengths in different 

study units. The high-activity periods will consist of 3 to 

5 years of data collection and interpretation followed by a 

year for final interpretation and report writing. Between these 

active phases, there will be an ongoing lower level datacollection and analysis effort. 
The study-unit design has several key advantages over 

a national statistical design. These include the following: 

1. Major river basins and aquifer systems have unique 

characteristics and are a natural focus for individual 

regional scale investigations that are the building 

blocks for a national assessment. Important regional 

differences in climate, geology, land use, and other 

major factors can lead to large regional differences in 

water quality among the major river basins and aquifer 

systems of the country. Information on the Nation's 

water quality will be more meaningful if interpreted 

and presented in the context of these regional 

variations. In addition, comprehensive studies of the 

water quality of individual river basins and aquifer 

systems can contribute valuable information that assists 

in understanding and managing these water resources. 

A key feature is the ability to conduct studies across 

State boundaries. Much of the water, sediment, and 

chemicals in a river basin, for example, can originate 

in adjacent States; thus, it can be very difficult for an 

individual State to develop a comprehensive understanding of water-quality problems in the basin and 

their solutions. Likewise, it is often more efficient to 

conduct large regional ground-water investigations 

based on natural hydrogeologic boundaries rather than 

State boundaries. 

2. The benefits to having persons familiar with individual 

study areas do most of the data interpretation are 

considerable. The objectives for the NA WQA Program 

include providing general statistical measures of water 

quality and information on the location, nature, and 

causes of principal water-quality problem areas. The 

second type of information is most effectively 

developed from region-specific knowledge of 

hydrologists familiar with a particular river basin or 

aquifer system. The overall area to be described is too 

large and diverse, and the problems are too complex 

to be adequately addressed from a central office. A 

major advantage of the structure of the Geological 

Survey is that the bulk of the work in water resources 

is conducted by hydrologists in offices located in the 

50 States. Most of the work within the NA WQA 

Program will be done by these personnel who are 

assigned the task of describing water quality in the 

selected study unit. 

3. The study-unit design facilitates an approach that can 

adapt to, and build effectively on, increasing 

knowledge. A characteristic of virtually all sampling 

programs is that considerable knowledge is attained 

about a more efficient design after the sampling is 

completed and the results are analyzed. In recognition 

of this characteristic, the study-unit design relies 

12 

heavily on the need for an iterative approach that adapts 

to improved knowledge over time. Effective feedback 

between sampling design and data interpretation is 

made possible by having close interactions among those 

who select sampling sites, those who collect the data, 

and those who interpret the data. 

4. Conducting the investigations at the regional scale 

provides an opportunity for more effective use of 

existing data as pan ·of the assessment. It is very 

difficult to effectively use existing water-quality data 

within the framework of a national statistical design. 

There are two reasons for this. First, a national 

statistical design would place rigid requirements on the 

selection of sampling sites. Second, before any use, 

existing data should be screened for their suitability 

to address the issues under study. It is difficult to perform this function at a national scale. The problem is 

much more tractable at the scale of river basins and 

aquifer systems, through direct communication with 

the State and local agencies and the local offices of the 

Federal agencies that collected many of the data. At 

this scale, there is also the opportunity to coordinate 

activities to mutual benefit between a national assessment program and ongoing State and local monitoring. 

The Geological Survey streamflow-gaging program is 

an example. The Geological Survey mission requires 

long-term collection and analysis of these data, whereas 

other agencies have short-term uses related to flood 

warning and real-time management. The Geological 

Survey and other agencies cooperate on the streamgaging program to achieve both purposes. 

Study Units Selected for the Pilot Program 

Seven project areas, which represent a diversity of 

hydrologic environments and water-quality conditions, were 

selected for the pilot program to test and refine the assessment concepts. The seven pilot project areas, shown in 

figure 2, include four that focus primarily on surface water 

and three that focus primarily on ground water. The surfacewater pilot project areas are the Yakima River basin in 

Washington (McKenzie and Rinella, 1987), the lower Kansas 

River basin in Kansas and Nebraska (Stamer and others, 

1987), the Upper Illinois River basin in lllinois, Indiana, and 

Wisconsin (Mades, 1987), and the Kentucky River basin in 

Kentucky (White and others, 1987). The ground-water pilot 

project areas are the Carson basin in Nevada and California 

(Welch and Plume, 1987), the Central Oklahoma aquifer in 

Oklahoma (Christenson and Parkhurst, 1987), and the 

Delmarva Peninsula in Delaware, Maryland, and Virginia 

(Bachman and others, 1987). Table 2 describes the important water-quality issues, the major categories of climate and 

land use, and other characteristics for each project area. 
;... ... ____ - .. -~···---· ... ~ 

': ____ _,.;--··-·--·--~-- - ---~ 

i 

i -~---- --1 :··- ~- . ~- -- ~,. .. -. -- ~·---2 

it!Jc;;:i~n / ~ -r · ----- i 

,o 

<Q.-'I)!P 

~0 MILES-{) 

0 100 KILOMETERS 

\ I 

\, 1--------

'-! 

/ 

0 500 MILES I I I I I I 

0

1 1 1 1

500 KILOMETERS 

·--·---f-. 

0 500MILES 

I r'r ,r r 'r 

0 500 KILOMETERS 

EXPLANATION 

1· . · .. 1 ~[~tiio%1:~ER 

•

. GROUND-WATER 

PILOT PROJECT 

Figure 2. locations of the pilot projects of the National Water-Quality Assessment Program. 

Preliminary Selection of Study Units for a Full-Scale Program 

A set of 123 study units have been selected as a 

preliminary set that could constitute a full-scale NA WQA 

Program. These study units were selected so that they would 

be well dispersed around the Nation and would represent a 

large percentage of the Nation's freshwater use. The surfacewater study units account, in aggregate, for about 80 percent 

of the fresh surface-water withdrawals (excluding thermal 

and hydropower uses) in the Nation and about 80 percent 

of the population served by public surface-water supplies. 

The ground-water study units account, in aggregate, for about 

80 percent of the fresh ground-water withdrawals in the 

Nation and about 80 percent of the population served by 

public ground-water supplies. 

The first step in the selection process was to select 

candidate study units (CSU's). A set of 200 surface-water 

CSU's was selected primarily on the basis of hydrologic 

subregions (Seaber and others, 1986). In some cases; where 

a given subregion is too large, individual accounting units 

or groups of accounting units were aggregated to form a set 

of smaller CSU's. In other cases, subregions were joined 

together or an accounting unit from one subregion was added 

to an adjoining subregion. Several factors were considered 

in selecting the surface-water CSU's. An attempt was made 

13 

to select CSU's that had similar area (although study units 

in arid regions typically are larger than those in humid 

regions). In some cases, modifications were made so that 

all sources of water to a major lake or estuary were included 

in the same study unit. Finally, where possible, an attempt 

was made to select CSU' s that had environmental and landuse characteristics that are relatively homogeneous 

throughout the study unit. , 

A set of 116 ground-water CSU' s also were identified. 

The boundaries of these units are hydrogeologic boundaries, 

some of which coincide with 'those of a surface-water CSU. 

In many cases, the boundaries of the ground-water study units 

are less obvious than those for surface water, particularly 

where several overlying aquifers are involved. Thus, many 

of these boundaries will be further defined as part of the planning for a full-scale program. 

A modified linear programming model (Fox and 

Scudder, 1986), which is a mathematical optimization 

technique, was used as a screening tool in the selection process (T. A. Cohn and K. J. Lanfear, U.S. Geological Survey, 

written commun., 1988). The objective function of the linear 

program was to minimize the number of study units that were 

selected subject to a set of constraints. The constraints 

included the above-mentioned SO-percent requirements on 
Table 2. Characteristics of the pilot projects of the National Water-Quality Assessment Program 

Study unit name, 

location, and size 

Upper Illinois River 

basin of Illinois, 

Indiana, and Wisconsin (10,950 mi2). 

Kentucky River basin 

of Kentucky 

(6,970 mi2). 

Lower Kansas River 

basin of Kansas 

and Nebraska 

(15,000 mi2). 

Yakima River basin 

of Washington 

(6,200 mi2). 

Delmarva Peninsula 

of Delaware, 

Maryland, and 

Virginia 

(6,050 mi2). 

Central Oklahoma 

aquifer 

(3,000 mil). 

Carson basin of 

Nevada 

(3, 980 mi2

). 

Climate and land use 

Humid climate; very large city 

(Chicago), suburbs, heavy 

industry and intensive 

agriculture. 

Humid climate; coal mining, 

timber harvesting, grazing, 

some urban and industrial 

areas (Lexington). 

Subhumid climate; intensive 

irrigated and nonirrigated 

agriculture, urban area 

(Topeka). 

Arid to semiarid climate; 

forest, irrigated agriculture, 

grazing, and food processing 

industry, Indian fishing 

grounds. 

Humid climate; irrigated and nonirrigated agriculture; chemical 

industry in north near Wilmington, Del.; many small urban 

areas that have food processing 

and light industry; poultry farming common; forested lands 

interspersed among agricultural 

lands. 

Subhumid climate; large urban 

area (Oklahoma City) surrounded by farmland and rangeland; oil and gas industry very 

intensive. 

Semiarid climate; irrigated agriculture and growing urban 

areas; significant wildlife. 

14 

Water-quality concerns and 

other characteristics 

The project area has a broad array of water-quality issues 

including sedimentation, nutrient enrichment, and toxic 

contamination and potential sources of contamination, 

including agricultural and urban runoff and municipal 

and industrial effluent. 

The project area has a broad array of water-quality concerns associated with varied land uses, including coal 

mining, oil and gas production, and timber harvesting in 

the upper basin and row crops, grazing, urban land, and 

industry in the lower basin. 

The project area is typical of the midwestern agricultural 

region. There are concerns about sediment, pesticides, 

other nonpoint-source contaminants, and reservoir 

eutrophication. 

The project area is typical of many agricultural areas in 

the western part of the Nation. Water quality is affected 

by forestry, grazing, and large reservoirs in the mountainous upper basin, and by about 420,000 acres of 

irrigated agriculture and small urban areas in the lower 

basin. Fish habitat is a key concern. 

The project area is part of the Atlantic Coastal Plain that 

extends from Long Island to Florida. Ground water is 

the source of supply for about 90 percent of water use 

and occurs in a surficial aquifer of large areal extent 

and in deeper aquifers. The high recharge rates to the 

surficial aquifer make it vulnerable to contamination. 

Nitrate contamination is known to occur in the shallow 

aquifer system. 

The Central Oklahoma aquifer supplies the greatest 

volume of water for public supplies of any aquifer in 

Oklahoma. The aquifer supplies water for all the 

municipalities in the Oklahoma City area, except for 

Oklahoma City, which is supplied by surface water. 

Water-quality concerns include high levels of naturally 

occurring trace elements and radionuclides and the 

effects of urban and suburban development on groundwater quality. 

The project area includes several basin-fill ground-water 

reservoirs that are traversed by, and interact with, the 

Carson River. Concerns include naturally occurring 

trace elements, such as arsenic, as well as the effects of 

irrigation practices and increased urban development. 

There is considerable competition for limited water 

resources that are affected by and affect water quality. 
water withdrawals and population served and a requirement 

that all States be represented by at least one study unit having 

at least 30 percent of its area within the State. The results 

were found to be relatively insensitive to the 30-percent State 

requirement-only two additional study units were needed 

to meet this constraint. Overall, the linear program process 

led to the selection of a total of 119 study units in the conterminous United States-67 surface-water and 52 groundwater study units. 

Once available, the results of the linear program were 

reviewed by Geological Survey District and Regional Offices 

to assure good coverage of key areas, and a few modifications were made to the screening model selections. In 

addition, ground-water study units were selected for Alaska 

and Hawaii. To date, the results of this selection process are 

the 69 surface-water and 54 ground-water study units shown 

in figures 3 and 4, respectively. 

Additional planning for the full-scale program will be 

undertaken during the pilot program to further evaluate the 

preliminary set of study units, to inventory their properties, 

and to refine the boundaries of the ground-water study units. 

The surface- and ground-water study units will be grouped 

into major categories based on climate, hydrogeology, and 

land-use characteristics. Investigations of the study units will 

be staged so that, at any given time, the units are spatially 

,o 

~-•s::> 

~0 MILES v 0 I 00 KILOMETERS 

distributed throughout the country and represent a mix 

of the major factors that influence water-quality conditions. 

For those areas having surface- and ground-water study 

units, the surface- and ground-water quality generally will 

be studied simultaneously or during closely spaced time 

periods. 

As the NA WQA Program evolves, a greater understanding of the association of water-quality problems with 

climate, geography, land use, geology, and other factors will 

develop. This information will provide insight on the need 

for alternate or additional study units to incorporate conditions not sufficiently covered or to account for major shifts 

in environmental concerns, in water use, or in land-use 

practices. 

Selection of Chemical Measurements 

Surface- and ground-water quality may be characterized by literally thousands of properties, elements, and 

compounds. One of the key elements of the NA WQA design 

is the selection of a set of chemical constituents to comprise 

the suite of target variables on which the program will focus. 

Selection of these target variables will be based on their 

relevance to important water-quality issues and on the 

existence of appropriate analytical methodologies. 

500 MILES 

I I I 

0 500 KILOMETERS 

EXPLANATION 

D SURFACE-WATER 

STUDY UNIT 

Figure 3. Locations of the preliminary set of surface-water study units for a full-scale National Water-Quality Assessment 

Program. 

15 
, o 

"" ~;\:::> 

~0 MILES{) 

0 I 00 KILOMETERS 

0 

I ~~~ 

0 

I I 

500 MILES I 

500 KILOMETERS 

EXPLANATION 

D GROUND-WATER STUDY UNIT 

Figure 4. Locations of the preliminary set of ground-water study units for a full-scale National Water-Quality Assessment 

Program. 

For some water-quality issues, the choice of target 

variables is a relatively simple task; for example, the 

substances relevant to the issues of nutrient enrichment, 

acidification, salinity, and sedimentation are of limited 

number, and their chemical analysis is relatively inexpensive. 

In contrast, for the issue of chemical contamination, the 

selection of target variables is much more difficult because 

of the large number of substances to consider and their 

relatively high cost of measurement. 

Several levels of target variables will be selected. A set 

of national target variables will be established to enable the 

assessment to provide interpretations of water quality at the 

national scale. The national target variables will consist of 

a common set of physical measurements, inorganic constituents, and organic compounds that are included in sample 

analyses for all study units. Specified laboratory analytical 

methods will be used for each constituent. 

Study-unit target variables will be selected for each 

study unit by the project team to supplement the national list. 

Under a full-scale NA WQA Program, the selection of studyunit target variables will be coordinated within a geographical 

region of the country; as a result, regional target variables 

will be established. 

16 

All sets of target variables--the national, regional, and 

study unit-will evolve with time. Changes are expected as 

analytical capabilities improve and become less costly and 

as knowledge increases about production of chemicals, 

geographical usage patterns, and other factors affecting the 

likelihood of water-quality problems associated with particular constituents. As used in this report, the term "target 

variable,'' unless specified otherwise, refers to the combined 

set of national, study unit, and regional target variables. 

All samples collected within a study unit will not be 

automatically analyzed for the complete set of target 

variables. Many samples will be analyzed for a subset of the 

complete list. Often, a hierarchical approach will be used 

in which initial samples are analyzed for all or many target 

variables and, based on periodic reviews of the data, some 

target variables are excluded from further measurement or 

analyzed less frequently . Some of the strategies that will be 

used in determining the target variables for individual 

samples are described in the sections "Design of the SurfaceWater Investigations" and "Design of the Ground-Water 

Investigations." 

In some cases, the analytical methods chosen for the 

target variables will provide information on other constituents 
of less concern; for example, the emission spectrophotometric method used for simultaneous analysis of 

many of the target trace elements in the pilot program also 

will provide results on other trace elements. These additional 

constituents will be included in the NA WQA data base as 

a contribution to the description of water quality, but less 

emphasis will be placed on their interpretation. When these 

nontarget constituents are detected more frequently or at 

higher levels than expected, they may be designated as target 

variables. 

Inorganic Constituents and Physical Measurements 

Table 3 provides information on the inorganic constituents and physical measurements that were selected as 

national target variables for the pilot program. These were 

selected primarily on the basis of their effects on human 

health, ecosystems, and agriculture and on their relevance 

to the listed water-quality issues. Guidance in selecting these 

constituents was provided by a group of scientists from the 

Geological Survey and other agencies. Many of the constituents listed in table 3 are presently targeted on lists for 

regulatory purposes, such as those lists developed under the 

1986 Amendments to the Safe Drinking Water Act. Some 

constituents, such as many of the major ions in ground water, 

were selected to provide information on the geochemical 

environment associated with each sample. 

Organic Compounds 

The selection of organic target compounds is more 

difficult. It has been estimated that more than 60,000 synthetic organic compounds are used in manufacturing 

processes today (Shackelford and Cline, 1986); moreover, 

the number of byproducts and degradation products from 

these compounds is unknown. Only a small fraction of the 

total number can be measured by using existing analytical 

techniques, particularly on a routine basis. Because health 

concerns are primarily associated with synthetic rather than 

naturally occurring organic compounds, analyses for the 

former will be emphasized. In some situations, naturally 

occurring organic compounds may be measured to improve 

understanding of the transport and the fate of other constituents of concern. 

It is difficult to select a few, or even a few dozen, 

organic compounds as the set of national target variables. 

Thus, an exploratory component to the selection of organic 

target compounds will be needed. Otherwise, much effort 

might be expended looking for substances of infrequent 

occurrence, while others, possibly more important, go 

unnoticed. As an example, industrial wastewaters have been 

under continuous scrutiny for a set of specific priority 

pollutants since 1977. Yet, examination of some broadspectrum analytical results (Shackelford and Cline, 1986) 

17 

shows that many other potentially toxic organic compounds 

may be occurring more frequently than many of the organic 

priority pollutants. This also may be true of ambient waters. 

Part of the problem is that, based purely on their 

physical and chemical properties, misleading predictions of 

the potential for compounds to move into surface and ground 

waters may be made. In addition, some chemicals may 

undergo transformations to other potentially toxic compounds 

that are not detected by standard analytical procedures; for 

example, premarket evidence concerning the pesticide 

aldicarb led to the conclusion that it would not move through 

soils into ground water. Yet, data collected on Long Island 

(Soren and Stelz, 1985; Suffolk County Department of Health 

Services, 1984; Zaki and others, 1982), in Wisconsin (Harkin 

and others, 1986), and in other States (Cohen and others, 

1986) have demonstrated that this pesticide (primarily as 

metabolites) has reached ground water. Unexpected frequencies of detection of other pesticides have been found in water 

from a number of wells-notably dibromochloropropane in 

California and Hawaii and ethylene dibromide in Florida. 

Almost all samples for organic analyses will be 

routinely analyzed by several broad-spectrum methods, each 

capable of detecting a number of target compounds. In 

addition, certain selected samples will be analyzed for a wider 

array of additional, less expected, compounds by using such 

techniques as high-resolution mass spectrometry combined 

with computerized searches of comprehensive ''libraries'' 

of mass spectra. These exploratory analyses will yield tentative identifications of additional compounds for which 

internal records will be kept. For those compounds that are 

repeatedly noted as tentative identifications, efforts will be 

made to obtain standards and to include the compounds within 

the laboratory's analytical capabilities, possibly as national 

or regional target variables. Selection of the samples for 

exploratory analyses will be based on various indicators of 

possible organic contamination. These will include the 

hydrologic and the land-use setting associated with the 

sampling location, the presence of indicator constituents, and 

the number and the nature of peaks associated with either 

the broad-spectrum analyses for target variables or screening techniques. Undoubtedly, knowledge and technology in 

trace organic analysis will improve rapidly with time; as it 

does, the list of organic target variables will be modified. 

In general, the suites of synthetic organic compounds 

analyzed for surface water will be different than those for 

ground water. In surface water, organochlorine compounds 

[for example, polychlorinated biphenyls (PCB's) and 

chlorinated insecticides], and selected herbicides, phenols, 

and polycyclic aromatic hydrocarbons will be emphasized 

in the pilot projects. Organic compounds of primary concern in ground water include volatile organic compounds 

(Westrick and others, 1984; Barbash and Roberts, 1986) and 

various pesticides (Cohen and others, 1986; Holden, 1986). 
Table 3. Inorganic constituents and physical measurements selected as target variables in the pilot National Water-Quality 

Assessment Program 

Principal effects Water-quality issues Target variables 

Constituent Human Eco- Agri- Toxic Nutrient Acidi- General Surface Ground 

health systems culture contami- enrich- fica- Salinity suit- water• water nation ment tion ability 

Major metals and trace elements 

Aluminum ................... + + + + + 

Antimony .................... + + + + + 

Arsenic ....................... + + + + + + + 

Barium ....................... + + + + 

Beryllium .................... + + .,,_ + 

Boron ......................... + + + + 

Cadmium .................... + + + + + + 

Chromium ................... + + + + + + 

Copper ....................... + + + + + + 

Fluoride ...................... + + + + 

Iron ........................... + + + 

Lead .......................... + + + + + + 

Manganese ................... + + + 

Mercury ...................... + + + + + + + 

Molybdenum ................ + + + + + + 

Nickel ........................ + + + + + 

Selenium ..................... + + + + + + + 

Silver ......................... + + + 

Vanadium .................... + + + + 

Zinc ........................... + + + + 

Nutrients 

Ammonium .................. + + + + + 

Nitrate ........................ + + + + + + + + 

Nitrite ........................ + + + + + + + 

Total nitrogen ............... + + + + 

Orthophosphate ............. + + + 

Total phosphorus ........... + + + 

Major constituents and dissolved solids 

Calcium ...................... + + + + + + + 

Magnesium .................. + + + + + + + 

Potassium .................... + + 

Sodium ....................... + + + + + + + + 

Chloride ...................... + + + + + + + 

Sulfate ........................ + + + + + + + 

Total dissolved solids ..... + + + + + + 

Field measurements 

Acidity ....................... + + + 

Alkalinity .................... + + + + + + 

Dissolved oxygen .......... + + + + 

pH ............................. + + + + 

Specific conductance ...... + + + 

Temperature ................. + + + + 

Radionuclides 

Gross alpha .................. + + + + 

Gross beta ................... + + + + 

Radon-222 ................... + + + 

•Includes national target variables and candidate study-unit target variables measured initially in all surface-water study units. 

18 
Accordingly, these groups will be emphasized in the groundwater pilot projects. 

In addition to providing information on specific contaminants, the NAWQA study-unit results will be used to 

evaluate the utility of various screening techniques and certain 

constituents that have the potential to be inexpensive 

indicators of contamination; for example, screening techniques that scan a sample for the presence or absence of 

selected groups of organic compounds will be tested on 

samples for which detailed analyses are being made. If the 

screening techniques prove successful, then considerable 

efficiencies in sampling for organic compounds could be 

obtained. Likewise, potential indicator constituents will be 

evaluated in various study units. These will include nitrate 

as an indicator of the occurrence of selected pesticides in 

ground water or a particular organic compound (or a suite 

of organic compounds) as an indicator of the presence of 

other synthetic organic compounds. 

Selection of Biological Measurements 

Another challenging aspect of designing an assessment 

program is deciding upon the role(s) of and the emphasis 

to place on biological measurements. Much of the concern 

about water quality is biologically motivated, particularly the 

protection of public health and fish and wildlife resources. 

In addition, the fate and the transport of many inorganic and 

organic contaminants in water are affected by biological 

processes. 

As presently envisioned, biological measurements will 

be used in the assessment to assist in ( 1) determining the 

occurrence and distribution of waters contaminated by fecal 

material, (2) determining the occurrence of potentially toxic 

substances, including trace elements and organic compounds, 

through the use of tissue analyses and ambient toxicity tests, 

(3) assessing the relations between the physical and the 

chemical characteristics of streams and the functional or 

structural aspects of the biological community through 

ecological surveys, and (4) defining and quantifying 

biological processes that affect the physical and the chemical 

aspects of water quality. Development and testing of specific 

approaches is being undertaken in the pilot program. Progress 

in each is summarized below. 

Fecal Contamination 

Water contaminated by fecal matter has served as a 

medium for the spread of a large number of diseases, 

including cholera, typhoid fever, and bacillary and amoebic 

dysentery. Thus, knowledge of the sanitary quality of water 

can be very important in assessing its suitability for public 

supply and recreational uses. Relatively elaborate procedures 

are required for the detection of most pathogens in natural 

waters. The most widely accepted procedures to indicate the 

19 

presence of fecal matter in water rely on the detection of nonpathogenic bacteria, which are native to the intestines of 

humans and other warm-blooded animals. 

In the scientific community, a lack of consensus exists 

as to what bacterium or group of bacteria should be used 

to indicate the presence of fecal contamination. In some European countries, Escherichia coli (E. coli) is preferred as an 

indicator because of its specific association with the source 

of pathogens-fecal waste from humans and other warmblooded animals. Until recently, professionals from other 

countries, including the United States and Canada, preferred 

to use fecal coliform bacteria (Dufour, 1977, p. 57). 

Based on the results of studies by Cabelli ( 1977, 

p. 222-238), the EPA has revised the bacteriological, 

ambient water-quality criteria for marine and freshwaters 

(U.S. Environmental Protection Agency, 1986) and recommended that criteria for E. coli and the enterococci organisms 

replace criteria for fecal coliform and total coliform bacteria 

in State water-quality standards for the protection of primary 

contact recreation. 

The approach for assessing the occurrence and the 

distribution of fecal indicator bacteria in a surface-water study 

unit generally will consist of a review and an analysis of 

available information and several synoptic surveys during 

which concentrations of E. coli will be determined at many 

sites within a basin. 

Untreated ground water is a major source of waterborne disease in the United States. Contamination generally 

occurs in local areas by seepage of sewage into aquifers and 

improperly developed wells or the entry of sewagecontaminated surface water into poorly protected wells 

(Craun, 1984). Unlike surface water, however, it is not clear 

which organisms are appropriate indicators of fecal contamination in ground water. Discussions are being held with 

scientists outside the Geological Survey to consider 

appropriate measures of fecal contamination that could be 

tested for ground water before implementation in a full-scale 

program. 

Occurrence of Potentially Toxic Substances 

In combination with physical and chemical 

measurements, analyses of plant and animal tissues and 

ambient toxicity tests (using local waters and sediments) are 

being evaluated to determine their utility for providing 

information about the occurrence of potentially toxic contaminants in surface waters. 

Plant and animal tissues will be analyzed in the surfacewater study-unit investigations to help determine the occurrence of certain trace elements and organic compounds, to 

provide a measure of the availability of these contaminants 

in water and sediment to biota, and to help understand their 

fate. The utility of tissues as indicators of the distribution 
and bioavailability of trace elements is widely recognized 

(Huggett and others, 1973; Phillips, 1980). However, their 

use in determining the distribution and availability of 

synthetic organic compounds is less well established. One 

reason is that current analytical procedures for organic compounds in tissues are not as well suited to the task of scanning for a broad list of compounds as are the procedures for 

water. Considerably more effort is required to prepare tissue 

samples than water samples for organic analysis. Moreover, 

specific ' 'cleanup'' procedures are needed to distinguish the 

compounds of interest, which are often present in small concentrations, from the background organic matrix. These 

procedures become more important and more difficult as 

attempts are made to lower the detection levels for specific 

compounds of interest. 

As part of the pilot program, a study is underway (in 

consultation with scientists from other agencies and universities) to develop, test, and evaluate a protocol for the 

collection of organisms, analysis of tissues, and interpretation of data to assess trace contaminants in rivers. Questions 

that are being addressed include (1) which organisms or suites 

of organisms are best suited for use in different types of 

rivers, (2) what are the appropriate procedures for collection 

of organisms, preparation and analysis of tissues, and interpretation of data, and (3) who should do the field sampling 

and laboratory analyses? 

Toxicity tests involve measuring a physiological or 

behavioral response of organisms to certain environmental 

conditions. One of the potential benefits of using toxicity tests 

is that they may provide an indication of the occurrence of 

contaminants that would not be detected by current laboratory 

analytical methods. In samples for which other analyses did 

not indicate the occurrence of potentially toxic substances, 

positive results of toxicity tests would result in more detailed 

chemical analyses of waters and sediments at the locations 

in question. 

Toxicity tests also have been used in water-quality 

assessments to assess or predict the environmental effects 

of contaminants, but it is unlikely that they would be used 

routinely for this purpose in the NA WQA Program. It is 

extremely difficult, if not impossible, for toxicity tests to truly 

mimic natural systems. Responses of selected test organisms 

to contaminants in a controlled environment are unlikely to 

be representative of the responses of a complex natural community to the same contaminants. Further, even though a 

test may indicate a biological response, other studies are 

needed to identify the substance(s) or the concentration(s) 

causing the response. 

Several questions will be considered in the evaluation 

of toxicity tests as part of the pilot program. What are the 

characteristics of different toxicity tests and their 

applications? How well can the results be related to physical 

and chemical measurements and (or) the "health" of an 

20 

ecosystem? Will different toxicity tests result in different conclusions about the ''health'' of an ecosystem? How 

reproducible are the results? and When should toxicity tests 

be conducted on water and when should they be conducted 

on sediment? 

Ecological Surveys 

Developing an improved understanding of how the 

aquatic biological community is a~ected b~ (and, in ~urn, 

affects) the physical and the cheiiDcal environment IS an 

important component of an integrated assessment of surfacewater resources. During the pilot program, methods and 

approaches for conducting an ecological surve~ will be 

reviewed and tested. Goals of the survey will be to 

( 1) document the current status of the biological community, 

(2) describe and explain, as possible, the relations of the 

biological communities to the physical and the che~­

ical characteristics of the environment, and (3) provide 

background information that would serve as a framework 

for the design and the interpretation of other assessment 

activities. 

Aquatic ecosystems are influenced by many 

environmental factors, including (1) the amount, character, 

and temporal distribution of energy entering the syste.m, 

(2) the physical and chemical quality of the stream, (3) habitat 

quality, (4) the flow regime, and (5) biotic interac:ti~~s. Thus, 

distinguishing changes induced by human activities from 

natural variation is a very difficult task. An ecological survey 

must assess the structure (number of species and individuals 

within a community) and the function (means by which 

organisms interact to utilize food and other resources) of 

biological communities, as well as the factors (for example, 

habitat, riparian vegetation, and hydrologic regime) .th~t .are 

expected to influence their spatial and temporal vanabihty. 

During early phases of the NA WQA Program, comprehensive characterizations of communities will . not ~e 

possible. Thus, an important aspect of the survey design will 

be the development of manageable components that will 

contribute to a knowledge base and from which more comprehensive assessments can be developed (either in later 

phases of the NAWQA Program or sup~ort~d by o~er 

agencies). Ecological surveys in all study uruts will be gmded 

by a similar set of focused objectives relating different aspects 

of community ecology to physical and chemical characteristics of the watershed. 

Biogeochemical Processes 

Explanations of water-quality observations often rely 

on understanding biogeochemical processes. Where deemed 

important in the early phases of study, rel~tively simp~e 

biological measures may be used to help descnbe and explam 

certain observations; for example, measurements of plant 
biomass or productivity could be used with other physical 

and chemical data to assess the characteristics and the causes 

of dissolved-oxygen depletion in a designated stream reach. 

As knowledge of water-quality conditions in a study unit 

grows, more complex biogeochemical investigations may be 

conducted. Examples include determining the role of 

biological processes affecting the sources, transport, and fate 

of nutrients in a stream reach; the fate of nitrogen compounds 

in soil and the unsaturated zone; and the fate of pesticides 

applied in a study area. Definition of relevant biogeochemical 

processes may not occur until the later stages or after the 

initial round of investigation in a study unit. Past and ongoing 

activities in universities and in the National Research and 

the Federal-State Cooperative Programs of the Geological 

Survey will provide a base of experience for development 

of studies and protocols. 

Uses of Available Water-Quality Data 

Over the years, a large amount of water-quality data 

has been collected by many organizations for a wide range 

of purposes. Many of these data are useful for water-quality 

assessment provided that care is taken to ascertain the manner 

in which they were collected and analyzed and the individual 

settings they represent. Because of the varied methods and 

sampling approaches, existing data cannot be aggregated in 

an automatic fashion to form a meaningful national 

assessment. The limitations of some of these data sets are 

discussed in a variety of reports, including those by Blodgett 

(1983), van Belle and Hughes (1983), U.S. Congress (1983, 

1984), Judy and others (1984), U.S. Environmental Protection Agency ( 1985), Association of State and Interstate Water 

Pollution Control Administrators (1985), U.S. General 

Accounting Office (1986), Hren and others (1987), 

Resources for the Future (1987), and Smith and others 

( 1987). Some of the constraints on the direct use of existing 

data for water-quality assessment are (1) the data often 

represent treated wastewater or water supplies rather than 

ambient water in a stream or an aquifer, (2) the data often 

are not publicly available or else not adequately indexed and, 

thus, cannot be readily located or accessed for use in 

assessments, (3) analytical procedures vary among 

laboratories and with time, (4) sampling locations may be 

difficult or impossible to determine, (5) historically, few 

samples have been analyzed for trace elements and organic 

compounds, (6) water-quality sampling sites are often 

clustered around known or suspected areas of contamination; 

thus, assessments based only on these data have a potential 

for substantial bias, (7) few sites have been sampled sufficiently to assess changes in water-quality conditions, and 

(8) few stream sites have been sampled frequently enough 

to estimate the transport of constituents. 

Within these limitations, considerable amounts of 

existing water-quality data will be utilized in the assessment 

21 

program. One of the first activities in each project is to 

compile, screen, and interpret available water-quality data 

to provide an initial description of water-quality conditions 

and to assist in formulating plans for project field activities. 

These data will be used to help identify areas and reaches 

that have significant water-quality problems, to select 

appropriate sampling locations, to establish the list of studyunit target variables, and to develop hypotheses about the 

causative factors that influence water-quality conditions. 

Many of the water-quality data will be obtained from 

Geological Survey and EPA computerized data bases. 

Additional water-quality data (some of which may not be in 

computer files) will be obtained through literature reviews 

and contacts with other organizations. Information about field 

and laboratory procedures will be obtained to ensure that the 

data are compatible with their use in the assessment. 

Development of National Data Bases 

The NA WQA study teams will need to store, retrieve, 

and manipulate large amounts of water-quality data, site 

characteristics, and geographic information. To avoid 

duplicating existing data bases, the pertinent files of the 

National Water Information System will be used as the 

primary repository of the water-quality data, streamflow data, 

and site information (Edwards and others, 1986). Other 

systems such as the EPA BIOS system (U.S. Environmental Protection Agency, 1987) for biological data will be used when needed. 

A computerized geographic information system (GIS) 

will be used to analyze and display spatially referenced 

information (Rennick, 1986). Once data are associated with 

a geographic location, digitized, and stored within a GIS, 

they can be combined with other natural and human factors 

and the results readily displayed; for example, water-quality 

data originally referenced to hydrologic units can be cross 

referenced and linked with socioeconomic data on population and economic activity. 

The assessment will use various types of ancillary data 

to examine relations between water-quality conditions and 

natural and human factors. Consistent ancillary data on site 

characteristics, such as streamflow rates, ground-water 

levels, and well screen intervals, will be collected for all 

sampled sites and will be included in the national data bases. 

Records of site characteristics are particularly important for 

ground water because local scale factors are likely to be very 

important determinants of ground-water quality. Table 4 lists 

site characteristics that will be recorded to the extent possible 

at all wells. In addition, available spatial data bases on various 

aspects of soils, geology, population, land and resource uses, 

and waste discharges will be obtained. Several of these data 

bases are described in table 5. Smith and others (1987) used 

many of these data to develop hypotheses about possible 

causes of trends detected in water-quality variables. 
Table 4. Site characteristics for sampled wells in the National 

Water-Quality Assessment Program 

Unique site identification number 

Type of site (well, drain, and others) 

Data reliability 

Project identification number 

District, State, and county codes 

Latitude and longitude of site 

Altitude of land surface 

Topographic setting 

Use of site (observation well, withdrawal well, and so forth) 

Primary use of water 

Aquifer name code 

Aquifer type code (unconfined, confined, mixed) 

Depth of well 

Water level 

Depth to top and bottom of each open interval 

Depth to top and bottom of each geohydrologic unit 

Rated pump capacity 

Type of lift 

Date of well construction 

Method of construction 

Type of finish 

Type of surface seal 

Casing material 

Sampling method 

Primary reason for well selection (with or without regard to 

known or suspected local problem areas) 

Occurrence of various land uses and local features such as gas 

stations and septic tanks within a 100-ft and lA-mi radius of 

the sampling well 

Predominant land use within 100-ft radius of the sampling well 

Predominant land use within lA -mi radius of the sampling well 

Percent of total area within a lA -mi radius of the well that consists of predominant land use 

Known occurrences of major changes in land use near the well 

within the last decade 

Local agricultural practices 

Quality Assurance 

As part of the pilot NA WQA Program, a quality 

assurance (QA) program has been established to assure that 

technically sound procedures are used to test the assessment 

concepts and that data collection, analysis, and interpretation procedures are documented and capable of being 

verified. The QA program includes a plan that sets forth 

programwide requirements and defines program managers' 

responsibilities for the pilot project studies. The QA program 

also includes protocols for surface- and ground-water field 

procedures. 

Communication and Program Coordination 

Communication and coordination are critical components of the NA WQA Program. The results from the 

22 

program will be communicated through publications and 

meetings. Interpretive reports, which will be published as 

part of each study-unit investigation and as national and 

multistudy-unit summaries, will be the principal method of 

disseminating results from the program. Initial reports that 

summarize the analysis of available information for a study 

unit and final reports that summarize the results from each 

high-activity period will have a high degree of consistency 

among study units. Press notices announcing release of 

reports will contain summaries of significant findings for the 

general public. 

Each pilot project has a liaison committee to help 

ensure that the scientific information produced by the 

program is relevant to local and regional interests. The 

committees are comprised of non-Geological Survey 

members who represent a balance of technical and management interests. Represented organizations include Federal, 

State, interstate, and local agencies, Indian Nations, and 

universities. Specific activities of each liaison committee 

include (1) exchanging information about water-quality issues 

of local and regional interest, (2) helping to identify sources 

of relevant data and information, (3) discussing potential 

adjustments in the project design, (4) assisting in the design 

of information products from the projects, and (5) reviewing 

and commenting on planning documents and project reports. 

In addition to the liaison committees, a National 

Coordinating Work Group has been established to advise the 

Geological Survey on national aspects of the NA WQA 

Program. The work group functions under the general 

auspices of the Interagency Advisory Committee on Water 

Data and the Advisory Committee on Water Data for Public 

Use. The work group advises the Geological Survey on 

water-quality information needs of non-Federal and Federal 

communities of water information users and on procedures 

for making the data and the information from the assessment 

appropriate to planning needs and available in a timely 

manner. 

The work group is chaired by the Chief Hydrologist 

of the Geological Survey and currently consists of nine 

Federal members, seven non-Federal members, and 

representatives from each of the pilot-project liaison 

committees. Organizations represented include the American 

Water Resources Association, the Association of American 

State Geologists, the Association of State and Interstate Water 

Pollution Control Administrators, the Chemical Manufacturers Association, the Interstate Conference on Water 

Policy, the National Association of Conservation Districts, 

the U.S. Army Corps of Engineers, the U.S. Bureau of 

Reclamation, the U.S. Environmental Protection Agency, 

the U.S. Fish and Wildlife Service, the U.S. Forest Service, 

the National Oceanic and Atmospheric Administration, the 

U.S. Soil Conservation Service, and the Council on 

Environmental Quality. 
Table 5. Data bases containing ancillary data to be used in the National Water-Quality Assessment Program 

Data base 

Acid Deposition System 

National Uranium 

Resource Evaluation. 

Natural Resources Inventory 

Resources for the Future, 

Environmental Data 

Inventory. 

Resources for the Future, 

Pesticide Usage Inventory. 

U.S. Census of Agriculture 

U.S. Census of Population 

U.S. Coal Production 

U.S. Environmental 

Protection Agency 

Industrial Facility 

Discharge File. 

U.S. Environmental 

Protection Agency 

Needs Survey. 

U.S. Environmental 

Protection Agency 

River-Reach File. 

U.S. Environmental 

Protection Agency 

STOrage and 

RETrieval System 

(STORET). 

U.S. Fish and Wildlife 

Service National 

Contaminant Riomonitoring Program. 

Description 

Information on the chemistry of wet atmospheric deposition 

collected at about 400 sites in North America. 

Information on the concentrations of a broad array of trace 

elements for nearly one million samples in water and sediments from the 48 conterminous States and Alaska, identified 

by 1° x 2° quadrangle. 

Estimates of sheet and rill erosion for about 800,000 sample 

plots, aggregated by county and identified according to land 

use, including cropland, pasture land, rangeland, and forest 

land. 

Estimates of biochemical-oxygen demand, nutrient, and metal 

loads discharged to U.S. streams and lakes from about 

32,000 industrial and municipal waste treatment facilities 

and from runoff from major land types, including urban, 

cropland, pastureland, rangeland, and forest land. 

Inventory of 184 pesticides used in the United States, identified 

by crop type and by county. 

Census of farm operators, including county-based estimates of 

crop, forest, pasture, and range acreage, agricultural 

chemical and fertilizer use, and inventories and sales of 

livestock and poultry. 

Population in the United States summarized for about 400,000 

block groups and enumeration districts; identified by latitude 

and longitude. 

Surface and underground coal production by county. 

Estimated discharge from about 54,000 industrial and municipal facilities having U.S. Environmental Protection 

Agency permits; identified by permit number in the National 

Pollution Discharge Elimination System (NPDES) and by 

river-reach number. 

Estimates of flow and concentrations of biochemical-oxygen 

demand in the effluent discharged from about 30,000 publicly 

owned sewage treatment plants identified by NPDES permit 

number and river-reach number. 

Numeric listing of about 67,000 stream reaches arranged 

systematically to provide hydrologic linkages among major 

U.S. rivers. 

A computerized data base containing geographic and other 

descriptive data for water-quality data-collection sites; data 

related to the physical characteristics and chemical constituents of water, fish tissue, and sediment; information on 

municipal waste sources and disposal systems; data on 

pollution-caused fish kills; and daily streamflow data. 

Formerly referred to as the National Pesticide Monitoring 

Program, the program was established to monitor temporal 

and geographic trends in organochlorine chemical and 

elemental contaminants in the Nation's freshwater fish. 

23 

Reference 

Olsen and Slavich, 1986. 

Averett, 1984. 

U.S. Department of 

Commerce, 1984a. 

Gianessi and Peskin, 1984. 

Gianessi and others, 1986. 

Gianessi and Puffer, 1986. 

U.S. Department of 

Commerce, 1984b. 

U.S. Census Bureau, 1983. 

Mining Informational 

Services, 1983. 

Philip Taylor, U.S. Environmental Protection 

Agency, verbal 

commun., 1988. 

U.S. Environmental Protection Agency, 1982b. 

Dewald and others, 1987. 

U.S. Environmental Protection Agency, 1982a. 

May and McKinney, 1981, 

and Lowe and others, 

1985. 
Table 5. Data bases containing ancillary data to be used in the National Water-Quality Assessment 

Program-Continued 

Data base Description Reference 

U.S. Geological Survey 

National Digital 

Cartographic Data 

Base. 

Base categories of cartographic data at standard scales, 

accuracies, and formats suitable for computer-based analysis. 

The categories include the Public Land Survey System, 

boundary, hydrography, transportation, and altitude data at 

1:24,000 scale; hydrography and transportation data at 

McEwen and others, 1983. 

1: 100,000 scale; boundary, Census tract, hydrologic unit, 

Federal land ownership, land use and land cover, and altitude 

data at 1:250,000 scale; and boundary, transportation, and 

hydrography data at 1:300,000 scale. 

U.S. Geological Survey 

Rock Analysis Storage 

System. 

Chemical analyses for more than 500,000 samples of sediments, 

surficial materials, plants, and rocks from the United States; 

identified by State, county, and latitude and longitude. 

U.S. Geological Survey, 

1983. 

U.S. Geological Survey 

National Water Information System. 

A computerized system to provide for the processing, storage, 

and retrieval of water data pertaining to surface water, 

ground water, and water quality. 

Edwards and others, 1986. 

U.S. Geological Survey 

National Water-Use 

Information Program. 

Information compiled for 12 categories of water use for Mann and others, 1982. 

47 States. Each State has an automated data system that 

contains site-specific information about the water use in each 

category. The National Water-Use Data System contains 

information for the 12 categories summarized by counties and 

river basins within each State. 

DESIGN OF THE SURFACE-WATER 

INVESTIGATIONS 

Earlier sections of this report have focused on general 

design concepts and on the goals and the scope of the assessment. This section describes the specific objectives, sampling 

activities, and anticipated products of the surface-water part 

of the assessment program. 

Objectiv~s 

The surface-water investigations have the following 

major objectives, which are to: 

1. Describe the occurrence and the spatial distribution of a 

broad array of water-quality constituents, 

2. Estimate loads of selected water-quality constituents at key 

locations, 

3. Provide information on the seasonal variation and the frequency of occurrence of selected water-quality constituents at key locations, 

4. Define long-term trends in the concentrations and (or) 

loads of selected constituents, and 

5. Identify, describe, and explain, as possible, the major 

factors that affect observed conditions and trends in 

surface-water quality. 

In addition to an analysis of available data, described 

earlier, three major types of sampling activities will be 

24 

undertaken in a study unit to achieve these objectives. These 

activities, described in the section "Sampling Activities," 

are fixed-station sampling, synoptic sampling, and studies 

of selected reaches. 

Timing and Duration of Investigations 

The surface-water part of the assessment will be done 

on a rotational basis in a 9-year cycle; about one-third of 

the designated study units will undergo intensive study at any 

one time. For any given study unit, a 3-year period of concentrated data acquisition, interpretation, and publication of 

results will be followed by publication of a final summary 

report. Following the 3-year period, data acquisition in the 

study unit will be reduced for 6 years to a level sufficient 

only to document major changes in water quality. In any 

given year, if the total number of study units in the program 

is 69, then most of the effort will be focused on 23 study 

units that are widely dispersed about the Nation, while the 

activities in the remaining 46 study units will be conducted 

at a low level of intensity. In this manner, the national level 

of effort will remain constant and reasonably uniform. 

The choice of a 3-year period is a compromise between 

achieving a quick "snapshot" of conditions and observing 

a wide range of flow conditions over each of the seasons 

within each cycle. Sufficient time is also needed to carry out 

exploratory sampling, to develop and test hypotheses, and 
to document and begin to publish findings. Conceptually, 

the approach is similar to the U.S. Census of Population and 

Housing, wherein a set of variables is measured over a period 

of a few weeks every 10 years. In this case, the period of 

measurement must be longer, but the interval between 

measurements is approximately decadal (9 years), and the 

data collection is rotational rather than simultaneous. 

Figure 5 shows the major interrelations among 

activities and objectives and the general timing of activities. 

The first high-activity period is preceded by 1 to 2 years for 

project planning, preliminary analysis of available information, and, as appropriate, reconnaissance-level sampling. 

Sampling Activities 

Fixed-Station Sampling 

The network of fixed-location river-sampling stations, 

which will be operated in each study unit, will have the 

following objectives: 

1. Describe the seasonal variations and the frequency of 

occurrence of selected water-quality constituents, 

2. Estimate loads past stations and attempt mass balances of 

selected target constituents between stations, and 

3. Define long-term trends in water quality. 

The locations of sampling stations will be determined by the 

objectives of the assessment, knowledge of the factors that 

affect water-quality conditions in each basin, and the suitability and the accessibility of sites for sampling. Although several 

techniques have been proposed for locating sampling sites 

for assessment purposes (Sharp, 1970, 1971; Lettenmaier, 

1978), the task does not lend itself easily to the formulation 

of a mathematical objective function. At present, a less formal approach for locating sites is appropriate. Sites that are 

suitable for addressing the objectives of fixed-station sampling in the NA WQA Program include locations (1) at the 

mouths of major tributaries and at selected points on the main 

stem that account for a large portion of the total basin runoff, 

(2) upstream and downstream from reservoirs, urban areas, 

agricultural drains, and other areas that significantly affect 

water quality, (3) on streams draining large areas that have 

relatively homogenous land use, and (4) near major public 

water-supply intakes or other important water uses. Where 

appropriate, existing stations operated as part of State 

monitoring efforts and other Federal programs, such as 

NASQAN, the Hydrologic Benchmark Network, and the 

Federal-State Cooperative Program will be used to take 

advantage of available data and minimize duplication of 

effort. 

Operation of the fixed stations in the pilot projects 

began in April 1987. Initially, 7 fixed stations were selected 

for the Kentucky River and Yakima River basins, 8 for the 

Upper illinois River basin, and 13 for the lower Kansas River 

25 

basin. The selection of fixed stations in each project area 

represents initial efforts to balance the fixed-station sampling 

activities against other planned project activities, given 

available resources. As data become available, the fixedstation networks will be evaluated as to the benefits and the 

costs of adding, moving, and deleting stations. 

Fixed stations will be sampled for selected target 

variables at least once a month during the 3-year, highactivity period. In addition to regularly scheduled sampling, 

three to six additional high-flow samples will be collected 

annually at each station. The need for repetitive sampling 

arises from the considerable temporal variability of surfacewater quality that can result from variations in river 

discharge, temperature, municipal and industrial discharges, 

and seasonal variations in agricultural practices. In each 

3-year, high-activity period, the newly collected data will 

be compared with data collected before the program began 

and with data collected from earlier cycles to detect and 

describe water-quality trends. The approaches that will be 

used to detect and describe these water-quality trends are 

designed to remove variation in water quality associated with 

variation in discharge and season (Hirsch and others, 1982). 

Table 6 shows the lists of national and candidate studyunit target variables to be determined at fixed stations. During the first year, the candidate study-unit target variables 

will be measured seasonally at all fixed stations-four to five 

times-over a range of hydrologic conditions to determine 

their occurrence and relative importance in the basin. After 

the first year of sampling, data collected seasonally for the 

candidate study-unit target variables will be reviewed and 

decisions made about which of these constituents to continue 

measuring at fixed stations in the study units. These decisions 

will be made by the study-unit teams in consultation with 

the liaison committees and regional and national coordinators. 

They will be based largely on the occurrence of the 

constituents relative to appropriate analytical detection limits, 

regional and national norms, and existing water-quality 

criteria and standards. 

Initial division of target variables between the two 

groups assumes no prior knowledge of the occurrence and 

of the relative magnitude of concentrations of certain waterquality constituents in a study unit. Where knowledge exists 

that one or more of the candidate study-unit target variables 

occur at significant concentrations or are highly relevant to 

important water-quality issues, the specific constituents will 

be determined at the same frequency as the national target 

variables. 

Gross-alpha and gross-beta radioactivity will be determined seasonally during the first year of sampling at fixed 

stations to screen for the occurrence of radiochemicals. 

Should either of these measures indicate significant levels 

in all or parts of a basin, more specific radiochemical analyses 

will be made during subsequent years. 
GENERAL TIMEFRAME 

I 

-Tto 2 years 

l 

1 

\. ·• .· .. u .. • • ·• ·• ·• •· •• •• •• ·• .• •• ~u~~i~~~~ • ,., • ~ ·• .• · •· •• •• ·• •• · • ·• .• ·. ......... ·.·.-: :-::::. ··: :-: 

. v·. . .. : .:.:::: ..... :::: ...... :, :• .. · 

1: . . • :. ···•·;;:·:• ( :::,:. 

3 years 

~ Vo:jective 1: '\ f Objective 2: \ 

1 Spatial t= 1 Estimates 11 distributions /:!'\ of loads i 

I > ., -, ..~4 I •.-._.:.· .- ..._ ~ :• < ""'-

7 1 ubjective 4,) r Objective 3: t Estimates of \. 

Seasonal long-term trends, .J 

\. variations \ 'f ff' · t L \~ ,('I ... ,,,>I~ SU ICien ('\ 

~ A ::~data '-

:: ) :: -:·:: } > ·-··- ::: 

1><•<:•::.:::·.·.······ ····-··· 1•·•: <<>·)_ _ -·•· ~ •:h'\ ... :ective 5: I>:' .•••• _.:::·:-::< .. - ,./ VUJ 

1 •< > < ••-•·=< :<•-·· :.- Explanations of ::::::: 

=·····i>··········· :.=· ::, I' 

.-...... water-qua 1ty ~· 

•. :.::.=.=:} }::············•···•••::. _._-<.- ···· -.<• •\. observations / 

_.:.< <::::.·:: :< ... :·-: <C:.•:: :·: .• ·:•: ··········~ L < ·······.<: •••••• 

- - - -

t 

1 year 

w -

t- UL .· 5 years 

J, : . : . -:e.$; / ............... - '::_: -:: ·: ">'<.· :f :-

- - - -

-

"0 

0 

·;:: 

(1) 

Q. 

-

"0 

0 

.... 

(1) 

Q. 

~ 

·:; 

:;:::; 

0 

cu 

~ 0 

...J 

Figure 5. Interrelations among tasks and objectives for surface-water study-unit investigations for the National Water-Quality 

Assessment Program. 

26 
Table 6. National and candidate study-unit target variables 

for fixed stations in the surface-water part of the pilot 

National Water-Quality Assessment Program 

National target variables1 Candidate 

study-unit target variables 2 

Field measurements 

Alkalinity 

pH 

Specific conductance 

Temperature 

Acidity 

Major constituents (dissolved) 

Chloride 

. Dissolved solids 

Sulfate 

Calcium 

Magnesium 

Sodium 

Potassium 

Fluoride 

Nutrients 

Nitrogen: 

Ammonia plus organic (total) 

Ammonia (dissolved) 

Nitrite (dissolved) 

Nitrite plus nitrate (dissolved) 

Phosphorus: 

Ortho (dissolved) 

Total 

Major metals and trace elements (dissolved and suspended) 

Arsenic Aluminum Molybdenum 

Cadmium Antimony Nickel 

Chromium Barium Selenium 

Copper Beryllium Silver 

Lead Boron Vanadium 

Mercury Iron Zinc 

Manganese 

Suspended sediment 

Organic carbon (dissolved 

and suspended) 

Other 

Cyanide (dissolved) 

Gross-alpha radioactivity (dissolved and suspended) 

Gross-beta radioactivity (dissolved and suspended) 

1 Field measurements and constituents to be determined in all water samples 

collected from fixed stations. 2

Field measurements and constituents to be determined in water samples 

collected seasonally (four to five times) from fixed stations during at least 

the first 12 months of operation. 

Because of resource constraints, initial analyses for 

organic substances in samples from fixed stations will be 

restricted to gross measures-dissolved and suspended 

organic carbon. In most cases, these measures will be used 

to help interpret other water-quality constituents. Analyses 

for specific organic compounds at fixed stations will be considered for those study units where a widely used pesticide 

or particular industrial compound is of such concern that 

information is warranted about its frequency of occurrence 

and transport. Likewise, no biological measurements are 

27 

listed in table 6. Trace organic substances and biological 

measurements will be emphasized in synoptic surveys and, 

possibly, in some studies of selected stream reaches. 

Synoptic Sampling 

Synoptic sampling surveys are generally accomplished 

by taking single or multiple water-quality measurements at 

many sites in a study area during a brief period of time, 

usually 1-2 weeks, representing a specific hydrologic 

condition. 

The synoptic surveys in the assessment will have the 

following primary uses, which are to: 

1. Provide a finer degree of spatial resolution to the descriptions of certain kinds of water-quality conditions than 

will be attainable from the fixed-station sampling network, and 

2. Document the spatial distribution of concentrations and 

loads of selected target variables in relation to land and 

water uses and to land- and waste-management 

practices. 

In addition to their primary uses, synoptic surveys will 

serve several other purposes. Early in each project, results 

from reconnaissance-level synoptic surveys of streambed 

materials and water will be used to help decide which trace 

elements and synthetic organic compounds should be 

included as study-unit target variables. Results from synoptic 

surveys also will be used in the initial selection of locations 

for the fixed-station network and in future modifications to 

the network. These modifications will occur where the results 

from synoptic surveys indicate major changes in water quality 

that are not apparent from the results of fixed-station 

sampling. 

Synoptic surveys will generally be done in stages in 

a study unit and will build on the descriptions of water-quality 

conditions in a hierarchical manner. By conducting the 

surveys in stages, project teams will be able to use the 

knowledge gained from early reconnaissance-level efforts to 

make appropriate modifications to the design of larger 

surveys. A phased approach also will allow project teams 

to balance the need for nationally consistent approaches 

against the need for flexibility so that the assessments can 

appropriately address local and regional issues. 

The number, the timing, and the design of the synoptic 

surveys will depend on the specific objectives of the surveys 

and the factors affecting the water-quality constituents of 

interest. Groups of target variables to be determined in water 

and bed-material samples collected during synoptic surveys 

are presented in table 7. Surveys used to describe the 

geographic distribution of concentrations of major dissolved 

constituents, nutrients, and suspended sediment in water 

usually will be repeated several times during a 3-year intensive phase of investigation. The timing of these surveys will 
Table 7. Groups of target variables to be determined in 

samples collected during surface-water synoptic surveys 

for the National Water-Quality Assessment Program 

[Groups of target variables to be included in each synoptic survey will 

depend upon the specific objectives of the survey and the factors affecting 

the water-quality constituents of interest] 

Target variables 

Field measurements ... 

Major dissolved 

constituents ........... 

Nutrients ................ 

Suspended sediment ... 

Dissolved oxygen ...... 

Escherichia coli ........ 

Major metals and 

trace elements ....... 

Hydrophilic 

trace organic 

compounds ........... 

Hydrophobic 

trace organic 

compounds ........... 

Other biological 

measurements (for 

example, ecosystem 

surveys) ............... 

Stable flows Unstable 

flows 

Bottom . Other 

Water materials T1ssue biota Water 

+ 

+ 

+ 

+ 

+ 

+ 

+ 

+ 

+ 

+ 

+ 

+ 

+ 

+ 

+ 

+ 

+ 

+ 

generally represent different seasons or hydrologic conditions within a study unit. 

The design of the surveys will depend on whether the 

streamflow conditions of interest will be relatively stable or 

unstable. For stable conditions where streamflows are not 

expected to change significantly over the duration of the 

survey, sites to be sampled will include all fixed stations, 

other sites on the main stem and major tributaries to ensure 

a resolution of at least 50 river miles, and a group of 

randomly selected sites on small-order streams stratified by 

land use. The group of randomly selected sites will represent 

a balance between the goal of providing information that is 

reasonably uniform in geographic coverage and the goal of 

relating the information to causative factors. In the absence 

of any knowledge about the statistical variances in concentrations for the target variables of interest, uniform geographic coverage could be accomplished by making the 

allocation of sites for each land-use strata proportional to the 

area it represents within the study unit; however, if information is available for the target variables, such that estimates 

of the variances for individual strata can be made and compared, then this information will be incorporated into the 

sampling design. Use of existing information may result in 

a less uniform density of sampling sites for small-order 

streams across a study unit but will result in more information 

28 

in areas where the concentrations are expected to be the most 

variable. 

The design of synoptic surveys for unstable flows 

(runoff events) is much more difficult because the timing, 

the duration, and the areal extent of runoff events is difficult 

to predict. Further, the effect of changing streamflow on concentrations of target variables must be determined to make 

interstation comparisons or to discern differences caused by 

other factors, such as land use. Sampling strategies to address 

these considerations at the study-unit scale are infeasible. 

Thus, the scope of synoptic surveys for runoff events will 

be focused on parts of a study unit (major tributaries or parts 

of the main stem) that can be sampled at enough sites and 

at a high enough frequency to allow comparisons among sites 

and identification of reaches that have major point- and 

nonpoint-source loadings of selected target variables. Over 

time (severa13-year active periods of investigation), project 

teams will attempt to sample runoff events of different 

magnitudes for different seasons for different parts of a study 

unit. 

It is envisioned that about 5 to 10 sites will be sampled 

during a single storm event. The objectives of sampling at 

a site will be to estimate the flow-weighted average concentrations, peak concentrations, and storm loads of selected 

target variables. Sampling sites will include sites at the 

upstream and downstream ends of the reach, at major 

tributaries, and downstream from areas of fairly 

homogeneous land use. Preference will be given to any fixedstation sampling sites and sites where streamflow is 

monitored within the area. 

Planning for runoff-event sampling will include a 

review of existing discharge records for sites to be sampled 

or other sites that have similar drainage area, physiography, 

climate, and land use to determine the range of conditions 

(duration, magnitude, and rate of change in discharge) for 

storms that might be expected to be sampled during the 

season. Knowledge of the range of conditions will be useful 

for scheduling of field crews and for estimating the frequency 

of sampling that will be needed at the different sites. 

In addition to streamflow, other environmental factors 

need to be considered in the timing and the design of the 

synoptic surveys for certain target variables; for example, 

concentrations of dissolved oxygen in streams can vary 

widely in space and time in response to physical, chemical, 

and biological processes interacting in the water column, bed 

materials, and biota. These processes need to be considered 

in determining the appropriate season(s) for conducting a 

survey and times of day for sample collection. In much of 

the continental United States, the lowest concentrations of 

dissolved oxygen generally occur in late summer or early 

fall. This seasonal pattern is due to low streamflows that 

provide less dilution of oxygen-demanding wastes and high 

water temperatures that reduce the solubility of oxygen in 
water and result in higher rates of microbial oxidation of 

oxygen-demanding material. Consequently, the timing of 

synoptic surveys to describe dissolved-oxygen conditions in 

a study unit will be restricted to these conditions, which will 

increase the probability of detecting stream reaches that have 

significant dissolved-oxygen deficits. Another characteristic 

of dissolved-oxygen concentrations in streams that must be 

considered is the significant diurnal variations that can occur 

due to plant photosynthesis and respiration. To make intersite 

comparisons and to detect stream reaches that have significant 

dissolved-oxygen deficits, measurements will be made during a specified time window (2-3 hours) during the day when 

concentrations are lowest. Typically, these conditions occur 

in early morning before net photosynthesis begins. In some 

cases, the restricted time period for which a large number 

of sites must be sampled may preclude the possibility of 

sampling for other target variables at the same time. 

The timing and the design of synoptic surveys for determining the occurrence and the distribution of trace elements 

and organic compounds also will be influenced by certain 

environmental factors; for example, surveys to determine the 

occurrence of water-soluble pesticides will be done during 

those seasons when the compounds are applied and are most 

likely to be detected. Bed-material synoptic surveys to determine the occurrence of trace elements and hydrophobic 

organic compounds will be done during periods of sustained 

low flow to increase the chances of sampling recently 

deposited material. Sampling locations will be carefully 

chosen to maximize the probability of detecting the target 

variables of interest; for example, sampling sites for watersoluble pesticides will include locations on small-order 

streams and irrigation drains near where the compounds are 

applied. Sampling sites for trace elements and hydrophobic 

organic contaminants will include depositional areas rich in 

organic matter, because these constituents and compounds 

are frequently found in association with fine-grained sediment 

that has a high organic carbon content. Water samples will 

be analyzed during the reconnaissance phase for the more 

persistent hydrophilic organic compounds including the 

chlorophenoxy-acid and triazine herbicides and acidextractable compounds. Bed-material samples will be 

analyzed for the same lists of trace elements determined in 

water samples from fixed stations as well as organochlorine 

insecticides, gross PCB's1 and other selected hydrophobic 

organic compounds. 

Products from synoptic surveys will include information about the occurrence of potentially toxic trace elements 

and synthetic organic compounds in a study unit, maps showing sampling locations and concentrations of these and other 

target variables, and summary statistics for the study unit 

and for areas within the study unit that represent different 

land uses and geochemical terranes. 

Studies of Selected Stream Reaches 

During the course of the study-unit investigations, 

certain water-quality topics and questions will be identified 

29 

from the analysis of available information and from the fixedstation and synoptic-sampling data that warrant more detailed 

study. Thus, some studies will be conducted to better understand the sources, the distribution, and the fate of particular 

constituents in selected stream reaches. Mathematical models 

may be useful in these types of studies to test understanding 

of cause-and-effect relations and to evaluate the outcome of 

alternative management strategies. Model results could be 

tested in later study cycles to determine if conditions have 

changed and if these changes correspond to prior understanding of the relevant biogeochemical processes at work. Some 

of these studies will be likely candidates for other programs 

of the Geological Survey, such as the Federal-State 

Cooperative Program and the National Research Program. 

Examples of studies that have been proposed as part of the 

pilot projects include the following: 

• A detailed assessment of the lower reaches of the Des 

Plaines River in the Upper illinois River Basin before 

and after implementation of the Tunnel and Reservoir 

Plan. The purpose would be to measure the changes 

in water quality caused by the temporary storage and 

the subsequent treatment of combined sewer 

overflows. 

• An evaluation of the effects of changes in agricultural 

practices and management alternatives on the distribution, the transport, the fate, and the effects of triazine 

herbicides in selected reaches of the lower Kansas 

River basin. 

• An investigation of the factors affecting the formation of 

trihalomethane compounds during chlorination of 

Kentucky River water. These compounds are 

carcinogenic and difficult to remove by using conventional water-treatment practices. Of particular 

interest is the effect of bromine and other constituents 

and compounds in brines produced during oil and gas 

production on the type and the rate of trihalomethane 

compounds produced. 

• An assessment of the occurrence and the distribution of 

pesticides and selected inorganic constituents in 

shallow ground water in an agricultural subbasin of 

the Yakima watershed and their relation to concentrations in surface water. 

Presentation of Results 

Anticipated products of the surface-water investigations 

are listed by objective in table 8 along with an indication of 

the principal sampling activity that will be used to prepare 

each product and the relative degree of difficulty of 

preparation. Products will include (1) tables listing summary 

statistics of concentrations and estimates of loads and trends 

for target variables at individual sites and groups of sites 

that represent a particular area, land use, or other factor, 
Table 8. Anticipated products of the surface-water investigations for the National Water-Quality Assessment Program 

Objective 

1. Describe the occurrence 

and spatial distribution of 

a broad array of waterquality constituents. 

2. Estimate loads of selected 

water-quality constituents 

at key locations. 

3. Provide information on 

the seasonal variation 

and the frequency of 

occurrence of selected 

water-quality constituents 

at key locations. 

4. Define long-term trends 

in the concentrations 

and (or) loads of 

selected constituents. 

5. Identify, describe, and 

explain, as possible, 

the major factors that 

affect observed conditions and trends in 

surface-water quality. 

Principal 

design 

component 

Synoptic surveys 

Fixed-station 

sampling. 

Fixed-station 

sampling. 

Fixed-station 

sampling. 

All sampling 

activities. 

Examples of products 

1. Maps showing locations of sampling sites and 

concentrations of water-quality constituents. 

2. Descriptive statistics of constituent concentrations within a drainage basin. 

3. Maps showing stream reaches that have persistent water-quality problems and reaches 

that have generally high-quality water. 

1. Estimates of loads for selected constituents 

delivered from parts of the watershed. 

2. Information on the portions of constituent loads 

derived from point, as compared to nonpoint, 

sources. 

1. Descriptive statistics of constituent concentrations at sampling sites within a drainage 

basin. 

2. Frequencies of detection or exceedance of 

water-quality standards by site. 

3. Tests for significant differences in constituent 

concentrations among sampling sites or for 

different seasons. 

1. Comparisons of descriptive statistics for a 

drainage basin with historic data and among 

high-activity periods. 

2. Maps showing general direction of trends 

(increasing, decreasing, no trend) and rate 

of change for sampling sites within a drainage basin. 

1. Descriptive statistics of constituent concentrations, frequencies of occurrence, and loads 

grouped by various factors and tests for 

significant differences among groups. 

2. Regression relations between water-quality 

characteristics and natural and human factors. 

3. Explanations of observed conditions within a 

basin, such as the sources of constituents, 

factors influencing the losses of constituents, 

and the characteristics and factors influencing 

the stream ecosystem. 

4. Explanations of similarities and differences in 

surface-water quality among drainage basins. 

5. Explanations of water-quality trends and their 

relation to causal factors, such as changes in 

land-management practices. 

30 

Relative 

degree of 

difficulty 

Low. 

Do. 

Medium-high. 

Medium-high. 

High. 

Low. 

Do. 

Low-medium 

Low. 

Medium. 

Low-medium. 

Medium. 

Medium-high. 

Do. 

Do. 
(2) graphs depicting relations of different factors to concentrations, loads, and trends for selected target variables, 

(3) maps showing the geographic distribution of median concentrations, frequencies of exceedance of criteria or 

standards, loads, and trends of selected target variables, and 

( 4) explanations describing observed conditions and trends 

within a study unit and their relation to causal factors. 

Similar products will be prepared for regional and 

national assessments. Multistudy-unit descriptions of current 

conditions and trends in surface-water quality will be 

prepared by aggregating comparable summary statistics and 

estimates for individual study units or for subbasins within 

study units. Insights into the major factors affecting surfacewater quality will be gained by developing statistical relations 

that use comparable summary statistics and ancillary data 

from the study units. 

DESIGN OF THE GROUND-WATER 

INVESTIGATIONS 

Ground water flows in a heterogeneous, threedimensional framework of geologic materials, and the 

patterns of flow can be complex. Whereas surface water 

generally is confined to a small percentage of an area, ground 

water can be found almost anywhere if drilling is done to 

sufficient depth. The resource can be sampled, however, only 

where a well is present, a test hole is drilled, or a spring 

or seep occurs. Moreover, only wells that meet certain 

criteria should be sampled (Barcelona and others, 1985; 

Gillham and others, 1983). Information on well construction and the local hydrogeology is needed for each well to 

properly interpret the sampling results and to assure that the 

well is suitable for sampling the constituents of concern. 

Logistical complications can occur-wells need to be 

inventoried over large areas and permission obtained for 

sampling from a large number of owners. 

The chemical quality of ground water is a function of 

the quality of recharge water and the reactions that occur 

along the flow path, particularly between the moving fluids 

and the geologic materials. The spatial variability of groundwater quality tends to be very large, areally and with depth. 

Relative to surface water, however, two simplifying 

characteristics exist for ground water. First, ground-water 

velocities are generally low; thus, contaminants move slowly, 

and the quality of ground water tends to change slowly with 

time. Second, in the absence of movement of near-surface 

water down wells or their annuli and outside of karst or 

fractured-rock terraines, contamination from surface sources 

tends to diminish with depth. Most manmade contaminating 

substances have been heavily used only in the past half 

century. In many cases, these contaminants have not reached 

great depths because of the slow rate of ground-water flow; 

moreover, sorptive processes and the chemical and the 

31 

biological transformations that occur in the subsurface retard 

the movement of many contaminants and attenuate their 

concentrations. 

Objectives 

Ground-water investigations conducted as part of the 

assessment program have the following major objectives, 

which are to: 

1. Describe general ground-water quality conditions for 

major hydrogeologic settings, 

2. Describe the geographic distribution within the study units 

of selected water-quality constituents and problem 

areas; 

3. Define long-term trends in ground-water quality; and 

4. Identify, describe, and explain, as possible, the major 

factors that affect observed current conditions and 

trends in ground-water quality. 

Several major types of sampling activities will be 

undertaken in a study unit to achieve these objectives. These 

activities are (1) regional sampling for a wide array of waterquality constituents, (2) targeted sampling in selected 

locations of the study unit for specific groups of water-quality 

constituents, and (3) long-term sampling of selected wells. 

Before describing these sampling activities, three key 

aspects of the ground-water investigations are discussed. 

These are the approach to rotating periods of intensive sampling with periods of low-intensity sampling, the importance 

of conducting the investigations within a hydrogeologic 

context, and the scope of the investigations, particularly in 

light of the large spatial variability of ground-water quality. 

Timing and Duration of Investigations 

Each high-activity period within a study unit will 

consist of 3 to 5 years of intensive sampling and data interpretation, followed by a year to complete reports. Because 

ground-water quality tends to change more slowly than 

surface-water quality, the duration of low-activity periods 

will likely exceed the 6 years planned for the surface-water 

activities and will vary among study units, depending upon 

the expected rates of change in ground-water quality and the 

nature of the water-quality problems. The purposes of the 

returns to the high-activity periods will be to improve the 

resolution of the spatial descriptions of ground-water quality, 

to apply techniques that have been developed since the last 

high-activity period, to adapt to changing water-quality 

concerns, and to document changes in water quality that have 

occurred since the previous intensive sampling period. 

The low-activity periods will include lower intensity 

sampling and recordkeeping for important ancillary information, such as on pesticide and fertilizer usages and landuse changes. Long-term trends will be examined through 
continued sampling at a subset of those wells sampled during 

the high-activity periods. In addition, some investigative 

studies may be conducted to enhance the comparability of 

results among study units. Specific studies may be designed 

to verify findings of recent investigations in other similar 

study units or to explain significant similarities or differences 

discovered between study units. 

A general flowchart of the study-unit investigations 

(fig. 6) illustrates the major interrelations among activities 

and objectives. The arrows indicate the general sequence of 

events. The first high-activity period is preceded by 1 to 2 

years for project planning and for preliminary analysis of 

available data. Some initial reconnaissance sampling, such 

as a geochemical study to further define the movement of 

ground water in parts of the study unit, also might be done 

during this period. 

Utility of Hydrogeologic Information 

A conceptual hydrogeologic framework for each study 

unit is important to lay the foundation for judicious selection 

of sampling sites and proper interpretation of the waterquality measurements at each site; for example, 

hydrogeologic and geochemical data will be used to provide 

estimates of the age of ground water (time since recharge) 

and knowledge about the locations of recharge and (or) 

discharge areas, flow paths, hydraulic connections between 

aquifers, and how the flow paths are affected by pumping. 

This information is important to help identify those parts of 

the ground-water system that are most likely to be affected 

by human activities. In addition, a major unifying concept 

in providing national overviews of ground-water quality will 

be to place the observed water-quality results in the context 

of major hydrogeologic settings across the country. 

Each project team will rely heavily on existing regional 

knowledge of hydrogeology and geochemistry. For most, 

if not all, projects, the hydrogeologic framework will have 

been described for the study unit through the RASA Program 

(Sun, 1986) or through other regional hydrogeologic 

investigations. However, additional hydrogeologic investigations will be necessary in some cases; for example, in some 

study units, further definition of shallow-flow systems may 

be necessary to understand the sources and the movement 

of contaminants to deeper aquifers. 

Various types of data on the geochemical environment 

of the aquifer system will be valuable to the assessments. 

Often, geochemical data can be used to corroborate 

hydrogeologic results and vice versa. Knowledge of the 

geochemistry of major elements can help to explain the 

chemical reactions that affect the distribution of naturally 

occurring contaminants and, in general, how substances will 

react. In addition, sampling activities will sometimes include 

geochemical surveys of solid-phase materials, such as soils, 

32 

cores, and drill cuttings. Attempts will be made to determine 

relations between the occurrence and concentrations of the 

constituents in ground water and both the distribution of 

constituents among the solid-phase materials and known 

geologic features. 

Some samples will be analyzed for selected isotopic 

measurements (including hydrogen and oxygen isotopes) to 

provide information on flow paths and ages of water (International Atomic Energy Agency, 1983); for example, 

measurements of tritium (a hydrogen isotope associated with 

atmospheric testing of nuclear weapons) often can be used 

to estimate whether ground water withdrawn from a well is 

older or younger than about 1952. Many synthetic organic 

compounds were not manufactured before that time. Hence, 

ground waters that are estimated to be younger than 1952 

may be more likely to contain synthetic organic chemicals 

than older water. 

Scope of Investigations 

Spatial Characterization 

Ideally, the assessment program would provide a 

detailed three-dimensional characterization of water quality 

throughout all the aquifers of a study unit. Because this is 

infeasible, tradeoffs must be made in the proportion of sampling effort allocated to different parts of the ground-water 

system. 

In general, each of the major aquifers of a study unit 

will be sampled to provide a statistical description of the 

water-quality conditions. More detailed sampling to further 

characterize the geographic distribution of water quality will 

be directed only toward selected parts of each ground-water 

system. Often, the initial sampling for this purpose will be 

focused on water-quality problems that occur either in the 

shallow parts of the more intensively used aquifers or in 

aquifers that are important sources of recharge to the 

principal water-use aquifers. Information on the distribution 

of water-quality problems at shallow depths will be combined 

with information on ground-water flow paths to provide 

guidance for sampling deeper ground water. 

The quality of shallow ground water should be more 

likely than that of deeper ground water to exhibit correlations with the overlying land use and other measures of 

human activities. Thus, sampling of shallow ground water 

may be critical to the development of explanations of 

observed water-quality conditions. 

Typically, for a given study unit, a few major 

hydrogeologic settings naturally arise from an analysis of 

general hydrogeologic information. Water-quality conditions 

often will be referenced to these settings. Some will correspond to aquifers, and others may be combinations of 

aquifers. Some thick aquifers may be subdivided into two 

or more hydrogeologic settings based on depth. To illustrate 
.-.·· 

' , . . . . .. . . . .. 

. .·. ,':':'f~·~: ·: .1:.: 

.·.·. ;Ji.JJIIIY • 

:.o. 

. ::::::.:.::.:.::::: .. :::.:. :- . . . . . . . . . . . . . 

:: :. ·_ ::::::::.:::;;:. ... :: ... illill.· .. 

1:•: • .!"1. : . · .. : .· .· :. : .. : .: :: \:•.,. ·. 

'\ , 

······:· ....• . . :: -:: :::::.::- .... · .. ·. ::.:::.:: . . . . . . . . . . . . . . ... 

· · ·• , · · : • .• , ·• ~~~~~ I ~· ,m~~• .~~;~ · __ . A·~·· !. 

' 

: .. I .. 

1 ' 1 Objective 1 : '\ ..... 1 

I::_J Statistical [{ 

Objective. 2: ~\.i )~ ~~~~~:~: ~0 i 

Geog_ra~hic I long-term trends, r 

descnpttons ' 1 if sufficient 

1 ,., .... \ data ,l ..•....... :.•:t- _J /)" :•:-: 

\\ descriptions ':\ I: ·' /I .... , 1<'-::••:.:.:<·····.:·~ .... ••·•. 

·.:: 

····· ,- -···1~?'::::;::::.: 

Objective 4: "~ ··· 

Explanations of 

> > \ water-quality 

> :< :\..observations A ......... ::::, / ······ ···:::::.• ...... ~ _,. .. , ..... . ....... 

'V .. _.;: .. ·;:···::·, :· . . . 

:: ....... _,.· . 

. :·: ·····:::: ·;,-::: 

.. "<.: .: ::< . '! . 

', . .-. · .... "<<_:;..... ······:·<. :'_:'.".·-::: ....... ,:•:.: :::::-·.·. ·•·=-•• :;::.·:·< .. 

. . :·-:·:. . :::=·: .• 1"::·· . . . ·n. . . . . . . . . . . . . . . . ... 

···d. :tr· · ., ...... ,,, .•.• ··::.::.: .. : . 

I::=. •.• nt :v 

... :: 

.:::.: 

::•: 

:\.:: ::·: 

.· 

::". 

•.. :::=:: 

: ( < • •••..••.••• :.<::::·· 

::. ? 

,,. ~~~·~:· 

iiJ 

GENERAL TIMEFRAME 

to 2· years 

l 

3 to 5 years 

:0 

.g 

Q) 

a. 

-

"0 

0 

·.::: 

Q) 

a. 

Figure 6. Interrelations among tasks and objectives for ground-water study-unit investigations for the National Water-Quality 

Assessment Program. 

33 
some of the concepts, the major hydrogeologic settings 

defined for the three ground-water pilot areas and an indication of the general allocation of sampling effort among these 

settings are discussed below. 

The aquifer system of the Delmarva Peninsula consists 

of a relatively horizontal surficial aquifer and a sequence of 

nine underlying confined aquifers that dip generally eastward. 

The surficial aquifer is the main source of recharge to the 

underlying confined aquifers, supplies about one-half of 

the current ground-water use, and is more susceptible to 

contamination than the underlying aquifers. Furthermore, the 

majority of future development likely will come from the 

surficial aquifer because of limitations on well construction 

and water-level drawdowns in the confined aquifers (Cushing 

and others, 1973). For these reasons, sampling in the pilot 

program will focus on the surficial aquifer. Information 

obtained on the underlying aquifers will consist primarily 

of a statistical description of general water-quality conditions, 

as well as information on the potential for contaminants to 

move into the different deeper aquifers. 

There are two major hydrogeologic settings for the 

Central Oklahoma pilot study area-alluvial and terrace 

deposits along major streams and a dipping bedrock aquifer. 

More detailed sampling in the Oklahoma City metropolitan 

area will focus on both the alluvial and terrace deposits and 

the shallow unconfined part of the bedrock aquifer. There 

are also concerns about elevated levels of naturally occurring 

trace elements and radionuclides. The distribution and 

principal causes of these high levels will be investigated in 

the bedrock aquifer in selected areas. 

The third ground-water study unit, the Carson basin, 

is underlain by a variety of rocks that can be grouped broadly 

into (1) a series of interconnected basin-fill deposits in 

different alluvial valleys and (2) consolidated rocks that form 

both the mountainous uplands of the project area and the 

bedrock that underlies each alluvial valley. Virtually all the 

ground-water use is derived from the basin-fill aquifers; 

hence, the sampling will focus on this setting. Many of the 

ground-water quality concerns in the Carson basin are 

associated with naturally occurring trace elements, such as 

arsenic. The concentrations of these trace elements, as well 

as the extent of ground-water development, differ markedly 

among the different alluvial basins; thus, the sampling effort 

will be allocated differently among these basins. The effects 

of increased urban development on ground-water quality are 

of concern; therefore, as a case study, more detailed sampling will be done from shallow ground water in the vicinity 

of Carson City. 

Temporal Characterization 

Seasonal and other short -term variations in water 

quality generally are less important to the assessment of 

ground water than of surface water. Nevertheless, in some 

34 

circumstances short-term variations in ground-water quality 

may be important (Pettyjohn, 1976; Schmidt, 1977); for 

example, pesticides are applied seasonally and may degrade 

considerably within weeks or months. In general, shallow 

ground water should exhibit the most pronounced short -term 

variability in water quality. 

Initial sampling during a study-unit investigation will 

consist primarily of a single sample from each sampling well. 

As the investigations of each study unit evolve, specific 

hypotheses regarding monthly and seasonal variations in 

ground-water quality will be tested, as needed, through 

multiple sampling of selected wells, particularly those 

screened in shallow ground water. Seasonal sampling also 

will be conducted on wells that are being considered for 

inclusion in the long-term sampling network. 

Sampling Activities 

Regional Sampling 

Regional sampling for a wide array of water-quality 

constituents will be conducted throughout each major 

hydrogeologic setting. These constituents will include most 

of, if not all, the target variables. The purposes of the regional 

sampling will be to provide descriptive statistics on the 

occurrence and the concentrations of the target variables for 

each major hydrogeologic setting and to form an initial basis 

for describing the geographic distribution of water-quality 

conditions within the study unit. 

Regional sampling locations will be selected so as to 

be spatially distributed, areally and with depth, throughout 

each major hydrogeologic setting and to be unbiased with 

respect to known or suspected local problem areas. For the 

pilot program, 150 to 200 samples will be collected for each 

study unit as part of the first 2 years of regional sampling. 

These data will be used to provide the initial statistical 

summary information. The needs for subsequent regional 

sampling will be determined based on the results from this 

initial sampling. 

Results from the regional sampling will be useful to 

provide a perspective on the extent of ground-water contamination in each hydrogeologic setting. Cartwright and 

Shafer (1987) noted ''the majority of ground-water monitoring in the United States seems to be special purpose and 

provides a very biased sample of national ground-water 

quality and trends.'' At the national scale, the regional sampling results will be used to compare general water-quality 

conditions in various hydrogeologic settings across the 

Nation. Within study units, broad spatial relations determined 

from the regional sampling and from existing data will be 

used as a frame of reference to interpret results from targeted 

samplings of particular areas. The regional sampling results 

also could be used to supplement background information 

for site-specific studies conducted by others; for example, 
some constituents of interest are ubiquitous in certain areas. 

Without knowing these "background" levels, it is sometimes 

difficult to delineate contaminated areas. 

Targeted Sampling 

The problem of characterizing the geographic distribution of water-quality problem areas is one of the most 

challenging objectives of the assessment program. The 

problem is complicated by the high spatial variability of 

ground-water quality in general and of contaminated groundwater quality in particular. Simple use of very intensive areal 

sampling will not produce meaningful results within the funding and the personnel constraints of the assessment. Instead, 

it is important to have a major aspect of the investigations 

in which wells are selected for sampling based on knowledge 

of factors likely to control the distribution of particular types 

of contaminants in ground water. 

Thus, targeted sampling of known or suspected waterquality problem areas will be used to examine the spatial 

distribution of selected, broadly defined groups of waterquality constituents (selected target variables), such as 

agricultural chemicals, contaminants associated with urban 

and suburban areas, or naturally occurring trace elements. 

The targeted sampling approaches will be tailored to the 

major hydrogeologic and land-use factors that affect groundwater quality in different situations. Similar designs for 

targeted sampling will be applied, however, to selected study 

units to permit multistudy-unit comparisons within and across 

particular regions of the country. As successful techniques 

are developed in one study unit, they will be applied to similar 

situations in other study units. 

Three general approaches will be used, either 

individually or in combination. These are search-oriented 

sampling within particular areas of concern, sampling to test 

particular statistical hypotheses about the regional distribution 

of contaminants, and sampling along local scale transects 

of wells. The targeted sampling activities for the three pilot 

projects are listed in table 9. 

Search-oriented sampling will involve sampling for 

selected constituents within the particular settings in which 

they are most expected; these efforts usually will be iterative, 

and will involve multiple-sampling sequences. In some cases, 

indicator variables that are relatively inexpensive to measure 

will be used at the outset to help identify potential problem 

areas. Initially, the searches will be based on general 

knowledge about sources of the constituents and the 

controlling hydrogeologic and soil characteristics. As 

knowledge increases, it may be possible to design statistical 

search procedures. 

The second targeted sampling approach will involve 

testing particular hypotheses about the regional distribution 

of contaminants in a statistical hypothesis-testing framework. 

Examples of these types of studies are reported by Cain and 

others (in press); for example, a sampling program could 

be designed to examine ground-water quality underlying 

areas that have different land-use practices or within different 

depth zones. Sometimes this approach to sampling will be 

used to test hypotheses based on statistical relations found 

in the initial phases of sampling. 

The above two approaches will be conducted at scales 

that vary widely in size, from several hundred square miles 

to areas that approach the size of the study unit. The third 

approach, which will often supplement such regional scale 

investigations, is to sample a higher density of wells 

(generally, one or more wells per square mile) along local 

scale transects. The purpose of these studies will be to 

characterize representative settings that are commonly 

occurring throughout a large part of the study unit. These 

studies often will involve locating wells along shallow 

ground-water flow paths (hundreds of feet to several miles 

Table 9. Targeted sampling activities for the ground-water pilot projects of the National Water-Quality Assessment Program 

Pilot project Sampling activity Principal approach 

Carson basin 

Central Oklahoma aquifer 

Delmarva Peninsula 

More detailed sampling of shallow ground water 

underlying the Carson City area. 

Higher density sampling along shallow groundwater transects in major alluvial valleys. 

More detailed sampling to define the distribution 

and the causes of elevated levels of naturally 

occurring trace elements and radio nuclides. 

More detailed sampling in shallow ground water 

underlying the Oklahoma City area. 

Higher density sampling along shallow groundwater transects in six distinct regions of the 

surficial aquifer. 

1

Design currently under development (1988). 

35 

Statistical hypothesis testing and 

(or) search-oriented sampling. 1 

Local scale transects. 

Search-oriented sampling. 

Statistical hypothesis testing and 

(or) search-oriented sampling. 1 

Local scale transects. 
in length). Results from the local scale studies will help to 

place observed regional water-quality variations in the context 

of smaller scale variability and to identify local scale features 

that may have a major effect on regional water quality. It 

will be possible, for example, to develop more detailed 

ancillary data bases for the local scale study areas than is 

feasible for the entire study unit. This information can lead 

to identification of key factors that were not originally considered in the regional scale interpretations. Factors identified 

in these local scale studies then will be tested for correlations 

with water quality at the regional scale. Local scale studies 

also may be very useful for examining the effects of surfacewater quality on ground-water quality and vice versa. 

As an example of the use of local scale studies, the 

surficial aquifer of the Delmarva Peninsula has been subdivided by the project team into six regions that are based 

on a combination of factors that include geologic and geomorphic characteristics, soils, degree of drainage, and land 

use. These regions will be tested for differences in water 

quality by using regional scale data. In addition, local scale 

networks are being installed in selected areas within each 

of these regions to examine differences in local scale groundwater-quality patterns. Hydrogeologic and geochemical data 

also will be collected from these local scale networks to 

examine differences among the regions in recharge patterns 

and in the size and the vertical penetration of shallow groundwater flow systems. This information will be useful to 

evaluate the potential for shallow contamination to move into 

the underlying aquifers. Dependent on the outcome of these 

studies, additional focus may be placed on individual confined 

aquifers during future high-activity periods. 

long-Term Sampling 

Temporal; trends in ground-water quality will be 

examined by using data from a long-term sampling network 

that is established in each study unit at the conclusion of the 

first high-activjty period. In addition, some sampling activities within selected study units will be repeated over several 

high-activity periods to supplement the long-term network. 

Selection criteria for the long-term sampling wells will 

be established to assure a distribution of wells that represent 

ground water of different ages and hydrogeologic settings. 

As a basis for selection, candidate wells will be assigned to 

different age groups based on the estimated age of the ground 

water; for example, less than 1 year, 1 to 30 years, 30 to 

100 years, and greater than 100 years. A set of wells then 

will be selected from each age group; a greater percentage 

of the wells will be from the younger groups. Wells screened 

in the upper part of water-table aquifers may be particularly 

useful for early detection of contamination from surface 

sources and for relating observed trends to changes in landuse practices. In addition to long-term sampling from a 

regionally distributed set of wells, sampling also will continue 

from wells in some of the local scale networks. 

36 

The frequency of long-term sampling will vary among 

wells. Initially, wells under consideration will be sampled 

seasonally or monthly for selected constituents to examine 

seasonal and other short -term variations in water quality that 

might confound identification of long-term trends. Some 

wells that are initially selected to sample very young water 

and that have considerable short-term variability in water 

quality might be dropped from the long-term network. For 

wells in the eventual network, those that contain younger 

water will be sampled more frequently than wells that contain 

older water, because conditions in the former are likely to 

change more rapidly. After the initial sampling periods, the 

interval between sampling may be extended to as long as 

several years for many wells. 

Analyses of samples to determine long-term trends will 

emphasize the current set of target variables. At individual 

wells, target variables that occur below environmentally 

significant concentrations or that are not detected will be 

analyzed much less frequently than those occurring at greater 

concentrations. 

Finally, because long-term sampling will continue during the low-activity periods, the approach will continually 

provide data that are useful for making concurrent statistical 

comparisons of water quality among study units. 

Presentation of Results 

Interpretive reports will be published as part of each 

study-unit investigation, and periodic reports will be 

published that present interpretations at multistudy-unit and 

national scales. As appropriate, these reports will integrate 

information from surface- and ground-water studies. 

Examples of products associated with each of the 

objectives of the ground-water-quality investigations are 

listed in table 10. The relative degree of difficulty in developing each of these products is also indicated in this table. 

For each objective, different approaches will be used 

to aggregate the results to the multistudy-unit and the national 

scales. Information about general conditions and trends in 

ground-water quality (objectives 1 and 3, table 1 0) will be 

aggregated by providing comparable statistical descriptions 

for each major hydrogeologic setting. Information used to 

describe the geographic distribution of water quality within 

study units (objective 2, table 10) will be aggregated 

primarily by comparing results from targeted sampling 

designs that have been applied to selected study units. Finally, 

information on major factors that affect ground-water quality 

(objective 4, table 10) will be aggregated through development of statistical relations that use consistent ancillary data. 

In addition, key explanatory results that may have significant 

implications at broader scales will be summarized for each 

study unit. 

National reports will include, for each key waterquality constituent, a U.S. map that shows the major 
Table 10. Anticipated products of the ground-water investigations for the National Water-Quality Assessment Program 

Objective 

1. Describe general groundwater quality conditions 

for major hydrogeologic 

settings. 

2. Describe the geographic 

distribution within the 

study units of selected 

water-quality constituents and problem areas. 

3. Define long-term trends 

in ground-water quality. 

4. Identify, describe, and 

explain, as possible, 

the major factors that 

affect observed current conditions and 

trends in groundwater quality. 

Principal 

sampling 

activity 

Regional sampling 

Targeted sampling 

that builds on 

regional sampling. 

Long-term sampling 

All sampling 

activities. 

Examples of products 

1. Descriptive statistics of constituent concentrations 

by hydrogeologic setting. 

2. Frequencies of detection or exceedance of waterquality standards by major hydrogeologic setting. 

3. Tests for significant differences in constituent concentrations among major hydrogeologic settings. 

1. Maps showing locations of sampling wells and 

results of water-quality analyses. 

2. Descriptive statistics for different areal and depth 

zones and tests for significant differences. 

3. Illustrations showing water-quality variations with 

depth. 

4. Cross sections showing variations in water quality 

along transects. 

5. Maps showing general delineation of areas with a 

particular type of water-quality problem. 

6. Maps showing areal and depth zones of different 

water quality. 

1. Comparisons of descriptive statistics among highactivity periods. 

2. Figures showing changes over time in the relation 

between water quality and depth. 

3. Maps showing general direction of trends (increasing, decreasing, no trend) and rate of change by 

major hydrogeologic setting. 

1. Descriptive statistics of constituent concentrations 

and frequencies of occurrence grouped by various factors and tests for significant differences 

among groups. 

2. Regression relations between water-quality characteristics and natural and human factors. 

3. Maps, cross sections, or both showing hydrogeologic factors that can affect the vulnerability 

of ground water to contamination. 

4. Maps, cross sections, or both showing different age 

zones of ground water. 

5. Explanations of observed conditions within major 

hydrogeologic settings. 

6. Explanations of similarities and differences in 

ground-water quality among major hydrogeologic settings. 

7. Explanations of water-quality trends and their 

relation to causal factors, such as changes in 

land-management practices. 

37 

Relative 

degree of 

difficulty 

Low. 

Do. 

Do. 

Low. 

Medium. 

Do. 

Do. 

Medium-high. 

High. 

Low. 

Medium. 

Do. 

Low-medium. 

Medium. 

Do. 

Do. 

Medium-high. 

Do. 

High. 
hydrogeologic settings sampled by the program and indicates 

the relative concentrations of the constituent in each of the 

hydrogeologic settings. As the program evolves, similar maps 

will be included to summarize and display the results of trend 

analyses for particular constituents within each hydrogeologic 

setting. Certain hydrogeologic settings will be identified by 

these national scale maps as having relatively high concentrations or trends in particular constituent(s). These identified 

settings often will be the focus of more detailed descriptions 

and presentations of explanatory results in the national 

reports. For some other hydrogeologic settings, however, 

the maps of descriptive statistics may indicate relatively low 

constituent concentrations in general, but there are particular 

areas of high concentrations. Key results from these areas 

also will be presented in the national summaries. The end 

result will be a broad overview of general conditions and 

trends in the constituent concentrations across the Nation and 

more detail provided for particular areas of concern. 

SUMMARY 

During recent decades, the Nation has made major 

investments in water-quality management and protection, and 

the potential is there for much larger investments in the 

future. During the same period, considerable sums of money 

also have been spent on water-quality data acquisition for 

various purposes. However, to date, no cohesive program 

exists that can provide consistent information on the status, 

the trends, and the causes of surface- and ground-waterquality conditions across the country. This information is 

needed to determine the effects of past investments in waterquality improvement and to provide a sound basis for future 

decisions. The NAWQA Program described in this report 

is designed to provide the needed information. 

The NA WQA Program will be conducted at a combination of spatial and temporal scales that are unique for waterquality assessment. The large spatial scales (river basins and 

aquifer systems) and long temporal scales (multiyear and 

decadal) are critical to allow the program to address the 

factors that give rise to different types of widespread waterquality problems and to address long-term trends in water 

quality. The program will not diminish the need for smaller 

scale studies and monitoring presently designed and 

conducted by State, Federal, and local agencies to meet their 

individual needs. The program, however, will provide a 

larger scale framework for conducting many of these activities and a knowledge about regional and national waterquality conditions that cannot be acquired from individual 

smaller scale programs and studies. 

The design of the NA WQA Program differs significantly from any other assessment activities. By conducting 

the national program as an aggregation of individual studies 

38 

of key river basins and aquifer systems, the assessment will 

provide results that are useful in understanding and managing these important water resources, as well as in answering 

national questions about water quality. The program will 

build on knowledge gained from an analysis of existing data 

but will also collect new data, as necessary, to achieve the 

program's goals. The results of the NAWQA Program will 

be based primarily on physical, chemical, and biological 

measurements of waters in streams and aquifers. Professional 

judgements, mathematical model output, and effluent data 

will be used, but will not be the sole basis for conclusions. 

Perhaps most importantly, many assessments have involved 

interpretation and reporting of results by persons other than 

those who collect the data. In this assessment, the development of interpretations and the communication of findings 

is done largely by those who collect the data. The design 

is based on the philosophy that integration of data collection 

and data interpretation is the key to assuring that the data 

are of high quality and that they are continually evaluated, 

thus leading to relevant and meaningful interpretations. 

Information to be provided by the NAWQA Program 

will help to answer some of the major questions concerning 

the Nation's water quality. The intent is for the Geological 

Survey to provide information through the NA WQA 

Program that those who set policy, write regulations, 

establish priorities, or manage water resources can use. 

Information on the status, the trends, and the causes of waterquality conditions across the country should be particularly 

useful to other agencies who are involved in (1) identifying 

key substances for possible regulation and for which research 

is needed on toxicity, human exposure, and drinking-water 

treatability, (2) allocating budgetary resources among 

competing types of water-quality problems, (3) determining 

whether the desired goals for water-quality improvement are 

being met, (4) designing monitoring programs in different 

parts of the country (in terms of the constituents analyzed, 

sampling locations, sampling frequency, and timing of sampling), (5) targeting regulations for selected water-quality 

constituents to particular geographic regions or hydrologic 

settings, (6) determining the relative effects on water quality 

of various types of point and nonpoint sources, (7) identifying aquifers requiring different types and degrees of waterquality protection, and (8) evaluating management practices 

in terms of their large-scale effects on the water quality of 

river basins and aquifer systems. 

At present (1988), the assessment program, which is 

in a pilot phase, has investigations under way in seven project 

areas. In 1990, a committee of the National Academy of 

Sciences will complete an evaluation of the design and the 

potential utility of the program. A decision about proceeding 

to full-scale implementation will be made upon completion 

of this evaluation. 
REFERENCES CITED 

Association of State and Interstate Water Pollution Control 

Administrators, 1985, America's clean water-The State's 

nonpoint source assessment 1985: Washington, D.C. , 24 p. 

Averett, W. R., 1984, National uranium resources evaluationGuide to data reports of the hydrogeochemical and streamsediment reconnaissance: Grand Junction, Colo., Bendix 

Field Engineering Corporation, GJBX-5(84), Variable 

pagination. 

Bachman, L. J., Shedlock, R. J., and Phillips, P. J., 1987, Groundwater quality assessment of the Delmarva Peninsula, 

Delaware, Maryland, and Virginia-Project description: U.S. 

Geological Survey Open-File Report 87-112, 18 p. 

Back, William, and Hanshaw, B. B., 1970, Comparison of chemical 

hydrogeology of the carbonate peninsulas of Florida and 

Yucatan: Journal of Hydrology, v. 10, no. 4, p. 330-368. 

Baedecker, M. J., and Apgar, M. A., 1984, Hydrogeochemical 

studies at a landfill in Delaware, in Groundwater contamination studies in geophysics: Washington, D.C., National 

Academy Press, p. 127-138. 

Barbash, Jack, and Roberts, P. V., 1986, Volatile organic chemical contamination of groundwater resources in the U.S.: 

Journal of the Water Pollution Control Federation, v. 58, 

no. 5, p. 343-348. 

Barcelona, M. J., Gibb, F. P., Helfrich, J. A., and Garske, E. E., 

1985, Practical guide for ground-water sampling: lllinois 

State Water Survey Contract Report 374, 94 p. 

Blodgett, J. E., 1983, Summary of hearings on "National Environmental Monitoring'': Washington, D.C. , Congressional 

Research Service, 20 p. 

Cabelli, V. J., 1977, Indicators of recreational water quality, 

in Hoadley, A. W., and Dutka B. J., eds., Bacterial indicators/health hazards associated with water: American Society for Testing and Materials, ASTM STP 635, 

p. 222-238. 

Cain, Doug, Helsel, D. R., and Ragone, S. E., in press, Preliminary evaluations of regional ground-water quality in relation 

to land use: Ground Water, v. 27, no. 2. 

Cartwright, K., and Shafer, J. M., 1987, Selected technical considerations for data collection and interpretation-Ground 

water, in National water quality monitoring and assessment: 

Report on a colloquium sponsored by the Water Science and 

Technology Board, May 21-22, 1986: Washington, D.C., 

National Academy Press, p. 33-56. 

Christenson, S.C., and Parkhurst, D. L., 1987, Ground-water 

quality assessment of the Central Oklahoma aquifer, 

Oklahoma-Project description: U.S. Geological Survey 

Open-File Report 87-235, 30 p. 

Cohen, S. Z., Eiden, C., and Lorber, M. N., 1986, Monitoring 

ground water for pesticides, in Evaluation of pesticides in 

ground water: American Chemical Society, ACS Symposium 

Series 315, p. 170-196. 

Craun, G. F., 1984, Health aspects of groundwater pollution, 

in Britton, Gabriel, and Gerba, C. P., eds., Groundwater 

pollution microbiology: New York, John Wiley and Sons, 

p. 135-179. 

39 

Cushing, E. M., Kantrowitz, I. H., and Taylor, K. R., 1973, Water 

resources of the Delmarva Peninsula: U.S. Geological Survey 

Professional Paper 822, 58 p. 

Dewald, T. G., and others, 1987, STORET reach retrieval: 

Washington, D.C., U.S. Environmental Protection Agency, 

56 p. 

Dole, R. B., 1909, The quality of surface waters in the United 

States, Part 1, Analysis of waters east of the one-hundredth 

meridian: U.S. Geological Survey Water-Supply Paper 236, 

123 p. 

Dufour, A. P., 1977, Escherichia Coli-The fecal coliform, in 

Hoadley, A. W., and Dutka, B. J., eds., Bacteria 

indicators/health hazards associated with water: American Society for Testing and Materials, ASTM STP635, 

p. 48-58. 

Durum, W. H., 1978, Historical profile of quality of water 

laboratories and activities, 1879-1973, Part 2, History of 

water-quality activities: U.S. Geological Survey Open-File 

Report 78-432, p. 81-235. 

Edwards, M. D., Putnam, A. L., and Hutchinson, N. E., 1986, 

Conceptual design for the National Water Information 

System: U.S. Geological Survey Open-File Report 86-604, 

37 p. 

Fox, G. E., and Scudder, G. D., 1986, A simple strategy for solving a class of 0-1 integer programming models: Computers 

and operations research, v. 13, no. 6, p. 707-712. 

Franks, B. J., ed., 1987, U.S. Geological Survey program on toxic 

waste-ground-water contamination, Technical Meeting, 3rd, 

Pensacola, Fla., 1987, Proceedings: U.S. Geological Survey 

Open-File Report 87-109, variable pagination. 

Gianessi, L. P., and Peskin, H. M., 1984, An overview of the 

Resources for the Future environmental data inventoryMethods, sources and preliminary results: Washington, D.C., 

Resources for the Future, NTIS PB 134-988, 122 p. 

Gianessi, L. P., Peskin, H. M., and Puffer, C. A., 1986, A national 

data base of nonurban nonpoint source discharges and their 

effect on the Nation's water quality: Washington, D.C., 

Resources for the Future, 297 p. 

Gianessi, L. P., and Puffer, C. A., 1986, Identification of counties 

ranking highest in the use of selected pesticides: Washington, 

D.C., Resources for the Future, 99 p. 

Gilbert, B. K., and Mann, W. B., IV, 1988, The U.S. Geological 

Survey Federal-State Cooperative Water-Resources Program, 

fiscal year 1987: U.S. Geological Survey Open-File Report 

88-174, 36 p. 

Gillham, R. W., Robin, M. J. L., Barker, J. F., and Cherry, J. A., 

1983, Groundwater monitoring and sample bias: American 

Petroleum Institute, Publication 4367, 206 p. 

Harkin, J. M., Jones, F. A., Fathulla, R.N., Dzantor, E. K., and 

Kroll, D. G., 1986, Fate of aldicarb in Wisconsin ground 

water, in Evaluation of pesticides in ground water: American 

Chemical Society, ACS Symposium Series 315, p. 219-255. 

Hem, J. D. , 1985, Study and interpretation of the che~cal 

characteristics of natural water (3d ed.): U.S. Geologtcal 

Survey Water-Supply Paper 2254, 263 p. 

Hirsch, R. M., Slack, J. R., and Smith, R. A., 1982, Techniques 

of trend analysis for monthly water-quality data: Water 

Resources Research, v. 18, p. 107-121. 
Holden, P. W. , 1986, Pesticides and groundwater quality-Issues 

and problems in four states: Washington, D.C., National 

Academy Press, 124 p. 

Hren, Janet, Chaney, T. H., Norris, J. M., and Oblinger-Childress, 

C. J., 1987, Water-quality data-collection activities in 

Colorado and Ohio: Phase !-Inventory and evaluation of 

1984 programs and costs: U.S. Geological Survey WaterSupply Paper 2295-A, 89 p. 

Hubbell, D. W., and Glenn, J. L., 1973, Distribution of 

radionuclides in bottom sediments of the Columbia River 

estuary: U.S. Geological Survey Professional Paper 433-L, 

63 p. 

Huggett, R. J., Bender, M. E., and Stone, H. D., 1973, Utilizing 

metal concentration relationships in the Eastern oysters 

(Crassostrea virginica) to detect heavy metal pollution: Water 

Research, v. 7, p. 451-460. 

International Atomic Energy Agency, 1983, Guidebook on nuclear 

techniques in hydrology: Vienna, Austria, International 

Atomic Energy Agency, Technical Report Series no. 91, 

439 p. 

Jobson, H. E., 1985, Simulating unsteady transport of nitrogen, 

biochemical oxygen demand, and dissolved oxygen in the 

Chattahoochee River downstream from Atlanta, Georgia: 

U.S. Geological Survey Water-Supply Paper 2264, 36 p. 

Judy, R. D., Jr., Seeley, P. N., Murray, T. M., Svirsky, S.C., 

Whitworth, M. R., and Ischinger, L. S., 1984, 1982 

National Fisheries Survey, v. 1, Technical report, Initial 

findings: U.S. Fish and Wildlife Service, Report no. 

FWS/OBS-84/06, 140 p. 

Konikow, L. F., and Bredehoeft, J.D., 1978, Computer model 

of two-dimensional solute transport and dispersion in ground 

water: U.S. Geological Survey Techniques of WaterResources Investigations, book 7, chapt. C2, 90 p. 

Kramer, J. R., Andren, A. W., Smith, R. A., Johnson, A. H., 

Alexander, R. B., and Oehlert, Gary, 1986, Streams and 

lakes, in Acid deposition, long-term trends: Washington, 

D.C., National Academy Press, p. 231-299. 

LeBlanc, D. R., 1984, Sewage plume in a sand and gravel aquifer, 

Cape Cod, Massachusetts: U.S. Geological Survey WaterSupply Paper 2218, 28 p. 

Liebermann, T. D., Mueller, D. K., Kircher, J. E., and Choquette, 

A. F., in press, Characteristics and trends of streamflow and 

dissolved solids in the Upper Colorado River basin, Arizona, 

Colorado, New Mexico, Utah, and Wyoming: U.S. 

Geological Survey Water-Supply Paper 2358. 

Lettenmaier, D. P., 1978, Design considerations for ambient 

stream-quality monitoring: Water Resources Bulletin, v. 14, 

no. 4, p. 884-902. 

Lowe, T. P., May, T. W., Brumbaugh, W. G., and Kane, D. A., 

1985, National Contaminant Biomonitoring ProgramConcentrations of seven elements in freshwater fish, 

1978-1981: Archives of Environmental Contamination and 

Toxicology, v. 14, p. 363-388. 

Luoma, S. N., 1983, Bioavailability of trace metals to aquatic 

organisms: Science of the Total Environment, v. 28, p. 1-22. 

40 

Mades, D. M., 1987, Surface-water-quality assessment of the Upper 

Illinois River Basin in Illinois, Indiana, and WisconsinProject description: U.S. Geological Survey Open-File 

Report 87-473, 35 p. 

Mallard, G. E., ed., 1988, U.S. Geological Survey Toxic 

Substances Hydrology Program-Surface-water contamination: Proceedings of technical meeting, Denver, Colo., 

February 2-4, 1987: U.S. Geological Survey Open-File 

Report 87-764, 160 p. 

Mann, W. B., IV, Moore, J. E., and Chase, E. B., 1982, A 

National Water-Use Information Program: U.S. Geological 

Survey Open-File Report 82-862, 13 p. 

Mattraw, H. C., Jr., and Elder, J. F., 1984, Nutrient m;td detritus 

transport in the Appalachicola River, Florida: U.S. 

Geological Survey Water-Supply Paper 2196-C, 62 p. 

Mattraw, H. C., Jr., and Franks, B. J., 1986, Movement and fate 

of creosote waste in ground water, Pensacola, Florida-U.S. 

Geological Survey Toxic Waste-Ground Water Contamination Program: U.S. Geological Survey Water-Supply 

Paper 2285, 63 p. 

May, T. W., and McKinney, G. L., 1981, Cadmium, lead, mercury, arsenic, and selenium concentrations of freshwater fish, 

1976-1977, National Pesticide Monitoring Program: 

Pesticide Monitoring Journal, v. 15, p. 14-38. 

McEwen, R. B., Witmer, R. E.,.and Ramey, B. S., 1983, U.S. 

Geological Survey digital cartographic data standardsOverview and USGS activities: U.S. Geological Survey 

Circular 895-A, 20 p. 

McKenzie, S. W., and Rinella, J. F., 1987, Surface-water-quality 

assessment of the Yakima River basin, WashingtonProject description: U.S. Geological Survey Open-File 

Report 87-238, 35 p. 

Meade, R. H., 1982, Sources, sinks, and storage of river sediment 

in the Atlantic drainage of the United States: Journal of 

Geology, v. 90, no. 3, p. 235-252. 

Mining Informational Services, 1983, Keystone coal industry 

manual: New York, McGraw-Hill, 574 p. 

National Research Council, 1985, Letter report of the Water Science 

and Technology Board to Dallas Peck, October 7, 1985: National Research Council, 3 p. 

___ 1987, National water quality monitoring and assessmentReport on a colloquium sponsored by the Water Science and 

Technology Board, 1986: Washington, D.C., National 

Academy Press, 110 p. 

Olsen, A. R., and Slavich, A. L., 1986, Acid precipitation in North 

America: 1984 annual data summary from acid deposition 

system data base: U.S. Environmental Protection Agency, 

EPA/600/4-86/033, variable pagination. 

Peters, N. E. , 1984, Evaluation of environmental factors affecting 

yields of major dissolved ions of streams in the United States: 

U.S. Geological Survey Water-Supply Paper 2228, 39 p. 

Peters, N. E., Schroeder, R. A., and Troutman, D. E., 1982, 

Temporal trends in the acidity of precipitation and surface 

waters of New York: U.S. Geological Survey Water-Supply 

Paper 2188, 35 p. 

Pettyjohn, W. A., 1976, Monitoring cyclic fluctuations in groundwater quality: Ground Water, v. 14, no. 6, p. 472-480. 
Philips, D. J. H., 1980, Quantitative aquatic biological indicators: 

Barking, Essex, United Kingdom, Applied Science Publication, 487 p. 

Pickering, R. J., 1969, Distribution of radionuclides in bottom 

sedimen of the Clinch River, eastern Tennessee: U.S. 

Geological Survey Professional Paper 433-H, 25 p. 

Plummer, L. N., Parkhurst, D. L., and Thorstenson, D.C., 1983, 

Development of reaction models for ground-water systems: 

Geochemica et Cosmochimica Acta, v. 47, p. 665-686. 

Rafter, G. W., 1897, Sewage irrigation: U.S. Geological Survey 

Water-Supply Paper 3, 100 p. 

Ragone, S. E., 1987, Program overview and selected papers from 

the Toxic Waste Program technical meeting, Tucson, Ariz., 

1984: U.S. Geological Survey Open-File Report 86-324, 

116 p. 

Rennick, W. L. , 1986, Implementation of geographic information 

systems in the Water Resources Division of the United States 

Geological Survey, in Hydrologic applications of space 

technology: International Association of Hydrological 

Sciences Publication no. 160, p. 469-473. 

Resources for the Future, 1987, Water quality information for policy 

purposes-Evaluating NA WQA as a tool for policy design 

and assessment: Report to U.S. Department of the Interior 

under Cooperative Agreement 14-08-0001-A0464, 92 p. 

Rickert, D. A., and Hines, W. G., 1978, River quality 

assessment-Implications of a prototype project: Science, 

v. 200, no. 4346, p. 1113-1118. 

Robertson, J. K., and Wilson, J. W., 1985, Design ofthe National 

Trends Network for monitoring the chemistry of atmospheric 

precipitation: U.S. Geological Survey Circular 964, 46 p. 

Rubin, Jacob, 1987, Development of national water quality assessment program: A perspective of the U.S. Geological Survey, 

in National water quality monitoring and assessment-Report 

on a colloquium sponsored by the Water Science and 

Technology Board, 1986: Washington, D.C., National 

Academy Press, p. 57-70. 

Schertz, T. L., and Hirsch, R. M., 1986, Trend analysis of weekly 

acid rain data-1978-83: U.S. Geological Survey Water 

Resources Investigations Report 85-4211, 64 p. 

Schmidt, K. D. , 1977, Water quality variations for pumping wells: 

Ground Water, v. 15. no. 2, p. 130-137. 

Schroeder, R. A., and Barnes, C. R., 1983a, Polychlorinated 

biphenyl concentrations in Hudson River water and treated 

drinking water at Waterford, New York: U.S. Geological 

Survey Water-Resources Investigations Report 83-4188, 

13 p. 

___ 1983b, Trends in polychlorinated biphenyl concentrations 

in Hudson River water five years after elimination of point 

sources: U.S. Geological Survey Water-Resources Investigations Report 83-4206, 28 p. 

Seaber, P. R., Kapinos, F. P., Knapp, G. L., 1986, Hydrologic unit maps: U.S. Geological Survey Water-Supply 

Paper 2294, 63 p. 

Shackelford, W. M., and Cline, D. M., 1986, Organic compounds 

in water: Environmental Science and Technology, v. 20, 

no. 7, p. 652-657. 

41 

Sharp, W. E., 1970, Stream order as a measure of sample 

source uncertainty: Water Resources Research, v. 6, no. 3, 

p. 919-926. 

___ 1971, A topologically optimum water sampling plan for 

rivers and streams: Water Resources Research, v. 7, no. 6, 

p. 1641-1646. 

Smith, R. A., and Alexander, R. B., 1983, Evidence for 

acid-precipitation-Reduced trends in stream chemistry 

at hydrologic bench-mark stations: U.S. Geological Survey 

Circular 910, 12 p. 

Smith, R. A., Alexander, R. B., and Wolman, M. G., 1987, 

Water-quality trends in the Nation's rivers: Science, v. 235, 

p. 1607-1615. 

Soren, Julian, and Stelz, W. G., 1985, Aldicarb-pesticide contamination of ground water in eastern Suffolk County, Long 

Island, New York: U.S. Geological Survey Water Resources 

Investigations 84-4251, 34 p. 

Stamer, J. K., Jordan, P. R., Engberg, R. A., and Dugan, J. T., 

1987, Surface-water quality assessment of the lower Kansas 

River basin, Kansas and Nebraska-Project description: U.S. 

Geological Survey Open-File Report 87-105, 36 p. 

Suffolk County Department of Health Services, 1984, Report on 

water supply priorities: Suffolk County Department of Health 

Services, 26 p. 

Sun, R. J., ed., 1986, Regional aquifer-system analysis program 

of the U.S. Geological Survey-Summary of projects 

1978-84: U.S. Geological Survey Circular 1002, 264 p. 

Thurman, E. M., 1985, Organic geochemistry of natural waters: 

Boston, Martinus Nijhoff/Dr. W. Junk, 497 p. 

Truesdall, A. H., and Jones, B. F., 1974, WATEQ-A computer 

program for calculating chemical equilibria in natural 

waters: U.S. Geological Survey Journal of Research, v. 2, 

p. 233-248. 

Turk, J. T., 1983, An evaluation of trends in the acidity of precipitation and the related acidification of surface water in North 

America: U.S. Geological Survey Water-Supply Paper 2249, 

18 p. 

U.S. Census Bureau, 1983, Census of population and housing, 

1980-Master area reference file: Washington, D.C., U.S 

Census Bureau, p. 97-104. 

U.S. Congress, House Subcommittee on Natural Resources, 

Agriculture and Environment of the Committee on Science 

and Technology, 1983, National Environmental Monitoring, 

Hearings: U.S. Ninety-eighth Congress, first session, 406 p. 

___ 1984, Environmental Monitoring Improvement Act, Hearing: U.S. Ninety-eighth Congress, second session, 189 p. 

U.S. Department of Commerce, 1984a, Census of agriculture, 1982, 

Final county file: Technical documentation, Washington, 

D.C., 62 p. 

___ 1984b, National resources inventory-A guide for users of 

the 1982 NRI data files: Washington, D.C., 32 p. 

U.S. Environmental Protection Agency, 1982a, Manager's guide 

to STORET: Washington, D.C., Government Printing Office 

publication 1982-373-096, 131 p. 

___ 1982b, 1982 Needs survey: Cost estimates for construction of publicly-owned wastewater treatment facilities: 

U.S. Environmental Protection Agency, Washington, D.C., 

EPA 430/9-82-009, 85 p. 
U.S. Environmental Protection Agency, 1985, A ground-water 

monitoring strategy for the U.S Environmental Protection 

Agency: Washington, D.C., Office of Ground-Water 

Protection, 42 p. 

___ 1986, Bacteriological ambient water quality criteriaAvailability: Federal Register, v. 51, no. 45, p. 8012-8016. 

___ 1987, BIOS-EPA's National Biological Data Management 

System: Washington, D.C., Office of Information Resource 

Management, U.S. Environmental Protection Agency, 4 p. 

U.S. General Accounting Office, 1986, The Nation's water: Key 

unanswered questions about the quality of rivers and streams: 

Report to the Chairman, Subcommittee on Investigations and 

Oversight, Committee on Public Works and Transportation, 

House of Representatives, GAO/PEMD-86-6, 163 p. 

U.S. Geological Survey, 1983, Scientific, technical, spatial, and 

bibliographic data bases and systems of the U.S. Geological 

Survey: U.S. Geological Survey Circular 817, variable 

pagination. 

van Belle, Gerald, and Hughes, J. P., 1983, Monitoring for water 

quality: Fixed stations versus intensive surveys: Journal 

Water Pollution Control Federation, v. 55, p. 400-404. 

Voss, C. 1., 1984, SUTRA-A finite-element simulation model 

for saturated-unsaturated fluid-density-dependent groundwater flow with energy transport or chemically-reactive 

42 

single-species solute transport: U.S. Geological Survey 

Water-Resources Investigations Report 84-4263, 409 p. 

Weeks, E. P., Earp, D. E., and Thompson, G. M., 1982, Use of 

atmospheric fluorocarbons F-11 and F-12 to determine the 

diffusion parameters of the unsaturated zone in the Southern 

High Plains of Texas: Water Resources Research, v. 18, 

no. 5, p. 1365-1378. 

Welch, A. H., and Plume, R. W., 1987, Water-quality assessment 

of the Carson River ground-water basin, Nevada and 

California-Project description: U.S. Geological Survey 

Open-File Report 87-104, 27 p. 

Westrick, J. J., Mello, J. W., and Thomas R. F., 1984, The 

groundwater supply survey: Journal American Water Works 

Association, v. 76, p. 52-59. 

White, K. D., Smoot, J. L., Jackson, J. K., and Choquette, A. F., 

1987, Surface water-quality assessment of the Kentucky River 

basin, Kentucky-Project description: U.S. Geological 

Survey Open-File Report 87-234, 39 p. 

Winograd, I. J., 1981, Radioactive waste disposal in thick unsaturated zones: Science, v. 212, no. 4502, p. 1457-1464. 

Zaki, M. H., Moran, Dennis, and Harris, David, 1982, Pesticides 

in ground water-The aldicarb story in Suffolk County, New 

York: American Journal of Public Health, v. 72, no. 12, 

p. 1391-1395.