Water Quality in the

Central Nebraska Basins

Nebraska, 1992–95

U.S. Department of the Interior

U.S. Geological Survey Circular 1163

science for a changing world
A COORDINATED EFFORT

Chief, NAWQA Program

U.S. Geological Survey

Water Resources Division

12201 Sunrise Valley Drive, M.S. 413

Reston, VA 20192

FOR ADDITIONAL INFORMATION ON THE

NATIONAL WATER-QUALITY ASSESSMENT (NAWQA) PROGRAM:

Coordination among agencies and organizations is an integral part of the NAWQA Program. W

the following agencies and organizations that contributed data used in this report, participated 

study liaison committee, or assisted in field work.

Federal Organizations

U.S. Army Corps of Engineers

U.S. Bureau of Reclamation

U.S. Department of Agriculture, Natural Resources Conservation

Service

U.S. Environmental Protection Agency, Region VII

U.S. Fish and Wildlife Service

Universities and State Agencies

Nebraska Department of Agriculture

Nebraska Department of Environmental Quality

Nebraska Department of Water Resources

Nebraska Game & Parks Commission

Nebraska Natural Resources Commission

University of Nebraska at Lincoln, Conservation and Survey Division

University of Nebraska at Lincoln, Department of Agricultural

Economics

University of Nebraska at Lincoln, Water Center

Local Agencies

Central Nebraska Public Power and Irrigation District

Central Platte Natural Resources District

City of Grand Island, Nebraska

City of Lincoln, Nebraska

Lower Elkhorn Natural Resources District

Lower Loup Natural Resources District

Lower Platte North Natural Resources District

Lower Platte South Natural Resources District

Nebraska Public Power District

Papio-Missouri River Natural Resources District

Tri-Basin Natural Resources District

Twin Platte Natural Resources District

Upper Loup Natural Resources District

Private Organizations

Platte River Whooping Crane Maintenance Trust, Inc.

Much appreciation is extended to the following U.S. Geological Survey employees for their contrib

Illustrations by Jennifer B. Sharpe, Geographer, and Christopher P. Stanton, GIS Specialist

Edited by: Katherine E. Wilson, Technical Editor

Reviews by: Lan H. Tornes, Supervisory Hydrologist, and Jill D. Frankforter, Hydrologist

Central Nebraska Basins Study Unit, contact:

District Chief

U.S. Geological Survey

406 Federal Building

100 Centennial Mall North

Lincoln, NE 68508

402-437-5082

Information on the NAWQA Program is also available on the Internet via the World Wide Web. You may

connect to the NAWQA Home Page using the Universal Resources Locator (URL):

http://wwwrvares.er.usgs.gov/nawqa/nawqa_home.html

The Central Nebraska Basins Study Unit’s Home Page is at URL:

http://www-ne.cr.usgs.gov/Nawqa/Welcome.html

Front cover photograph and back cover photograph of cranes are by Jon Farrar, Nebraskaland Magazine, Nebraska Game and Parks

Commission
WATER QUALITY IN THE CENTRAL

NEBRASKA BASINS, NEBRASKA, 1992–95

By S.A. Frenzel, R.B. Swanson, T.L. Huntzinger, J.K. Sta

P.J. Emmons, and R.B. Zelt

U.S. GEOLOGICAL SURVEY CIRCULAR 1163

CONTENTS

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

Summary of major issues and findings........................................................................................................................

Environmental setting and hydrologic

conditions.................................................................................................................................................................

Major issues and findings............................................................................................................................................

Nitrate content in water is related to agricultural land management.......................................................................

Agricultural activities potentially affect the management of public water supplies ...............................................

Water quality in the Platte River alluvial aquifer may be affected by surface-water quality

in areas of ground-water withdrawals .......................................................................................................

Aquatic environments potentially are altered by human activities..........................................................................

Aquatic and migratory species are affected directly by changes in the physical characteristics

of the Platte River......................................................................................................................................

Water-quality conditions in anational context .............................................................................................................

Study design and data collection.................................................................................................................................

Summary of compound detections and concentrations ..............................................................................................

References ...................................................................................................................................................................

Glossary.......................................................................................................................................................................

Throughout this report, numbers in brackets [1] refer to References.
Library of Congress Cataloging-in-Publication Data

The use of firm, trade, and brand names in this report is for identification purposes only and

does not constitute endorsement by the U.S. Government

Free on application to the:

U.S. Geological Survey

Branch of Information Services

Box 25286 Federal Center

Denver, CO 80225

U.S. DEPARTMENT OF THE INTERIOR

BRUCE BABBITT, Secretary

U.S. GEOLOGICAL SURVEY

Thomas J. Casadevall, Acting Director

Water quality in the central Nebraska basins, Nebraska, 1992-95/ by S.A. Frenzel, R.B. Swanson,

T.L. Huntzinger, J.K. Stamer, P.J. Emmons, and R.B. Zelt

 p. c.m.—(U.S. Geological Survey Circular ; 1163)

Includes bibliographical references

ISBN 0-607-89115-7

1. Water quality--Nebraska--Platte River Watershed. I. Frenzel, S. A. II. Series.

TD224.N18W37 1998

363.739’42’09782--dc21

98-14501

CIP

1998
U.S. Geological Survey Circular 1163 

NATIONAL WATER-QUALITY ASSESSMENT PROGRAM

“In Nebraska, the issue

water quantity and qual

paramount policy conc

The NAWQA process

provides the scientific

foundation on which so

public policy can be

developed and pursued

E. Benjamin Nelson,

Governor, State of Neb

“The Central Nebraska

NAWQA Study is an

invaluable benchmark o

water quality data. The

facilitative approach be

federal, state and local 

of government in data

development lends unde

credibility to the proces

data, and to programma

applications.”

Dayle E. Williamson

Director, Nebraska Nat

Resources Commission

“The basic research app

used in the NAWQA st

greatly expands our sci

knowledge of aquatic sy

in Central Nebraska an

provides a comprehens

view of their water qua

This study should serve 

invaluable reference fo

to come.”

Paul J. Currier, Execut

Director, Platte River

Whooping Crane

Maintenance Trust, Inc

Began in 1991

Began in 1994

Began in 1997

Not scheduled yet

EXPLANATION

Knowledge of the quality of the Nation's streams and aquifers is important because

of the implications to human and aquatic health and because of the significant costs

associated with decisions involving land and water management, conservation, and

regulation. In 1991, the U.S. Congress appropriated funds for the U.S. Geological

Survey (USGS) to begin the National Water-Quality Assessment (NAWQA) Program

to help meet the continuing need for sound, scientific information on the areal extent

of the water-quality problems, how these problems are changing with time, and an

understanding of the effects of human actions and natural factors on water-quality

conditions.

The NAWQA Program is assessing the water-quality conditions of more than 50 of

the Nation's largest river basins and aquifers, known as Study Units. Collectively,

these Study Units cover about one-half of the United States and include sources of

drinking water used by about 70 percent of the U.S. population. Comprehensive

assessments of about one-third of the Study Units are ongoing at a given time. Each

Study Unit is scheduled to be revisited every decade to evaluate changes in waterquality conditions. NAWQA assessments rely heavily on existing information collected by the USGS and many other agencies as well as the use of nationally consistent study designs and methods of sampling and analysis. Such consistency simultaneously provides information about the status and trends in water-quality conditions

in a particular stream or aquifer and, more importantly, provides the basis to make

comparisons among watersheds and improve our understanding of the factors that

affect water-quality conditions regionally and nationally.

This report is intended to summarize major findings that emerged between 1992

and 1995 from the water-quality assessment of the Central Nebraska Basins Study

Unit and to relate these findings to water-quality issues of regional and national concern. The information is primarily intended for those who are involved in waterresource management. Indeed, this report addresses many of the concerns raised by

regulators, water-utility managers, industry representatives, and other scientists, engineers, public officials, and members of stakeholder groups who provided advice and

input to the USGS during this NAWQA Study-Unit investigation. Yet, the information

contained here may also interest those who simply wish to know more about the quality of water in the rivers and aquifers in the area where they live.

Robert M. Hirsch, Chief Hydrologist
2 Water Quality in the Central Nebraska Basins, Nebraska, 1992–95

SUMMARY OF MAJOR ISSUES AND FINDINGS

IN THE CENTRAL NEBRASKA BASINS STUDY UNIT

 WHAT FACTORS ARE IMPORTANT IN DETERMINING WATER–QU

CONDITIONS IN THE CENTRAL NEBRASKA BASINS?

Land use in central Nebraska appears to affect water quality significantly; streams in 

lands generally had fewer occurrences and smaller concentrations of pesticides than d

streams in croplands where corn and soybeans were planted extensively. Subbasins w

greater proportions of rangeland, such as the Dismal River, had negligible herbicide concentrations. The largest pestic

centrations were in storm runoff following pesticide applications. Because some pesticide concentrations may exceed 

U.S. Environmental Protection Agency’s (USEPA) drinking-water Maximum Contaminant Levels (MCLs) in storm ru

timing and intensity of rainfall has implications for drinking-water supplies. Pesticides in streams from storm runoff m

alluvial aquifers as a consequence of ground-water withdrawals. Sites with degraded water chemistry commonly had d

physical habitats as well. Streamflow regulation of the Platte River has affected water quality through habitat alteratio

are deleterious to native species. The combination of degraded physical and chemical environments commonly resulte

structurally simple fish communities.

Nitrate content in water is related to agricultural land management (p. 6–7)

• Nitrate1 concentrations in ground water were greatest where more than 60 percent of the area was in corn produ

water tables were within 50 feet of the land surface, and soils were most permeable. Nitrate concentrations in gr

water often exceeded the MCLs in the Platte Valley, where fertilizer is applied to large areas that produce corn ev

• Nitrate concentrations varied substantially and tended to be smaller in surface water than in ground water for sim

environmental settings. The smallest concentrations were measured in streams during the summer when nitrate u

aquatic plants was greatest.

• Land-management practices in the central part of the Platte Valley include constraints on the application of ferti

areas where these constraints are most restrictive, median nitrate concentrations in domestic wells have decrease

edly.

Agricultural activities potentially affect the management of public-water supplies withdrawn from the Platte Ri

the alluvial aquifer (p. 8–9)

• Alachlor, atrazine, cyanazine, and metolachlor, all organonitrogen herbicides, were the four most commonly app

detected pesticides for corn, sorghum, and soybean production in the Study Unit.

• Concentrations of these herbicides in surface water varied seasonally and were generally larger in the spring and 

following application than in the fall and winter.

• The Elkhorn River drainage basin contributed the majority of the herbicides flushed from the Study Unit.

1Nitrate, as used in this report, was analyzed as nitrite plus nitrate and concentrations were reported as total nitrogen.

Agricultural chemicals are applied to enhance crop

production.
U.S. Geological Survey Circular 1

SUMMARY OF MAJOR ISSUES AND FIN

IN THE CENTRAL NEBRASKA BASINS STUDY 

• Of 46 pesticides analyzed in water samples from the Platte River at Louisville, it appears that alachlor, atrazine, 

cyanazine are the most likely to influence the quality of public-water supplies withdrawn from the Platte River a

aquifer downstream from the confluence of the Platte and Elkhorn Rivers. Atrazine is most likely to exceed the M

public-water supplies withdrawn from the alluvial aquifer downstream from this part of the aquifer.

• Nutrient concentrations in the Platte River increase downstream as it flows through the Study Unit; however, all 

sured concentrations were well below the MCLs.

Water quality in the Platte River alluvial aquifer may be affected by surface-water quality in areas of ground-w

withdrawals (p. 10–11)

• Ground water is the principal source of drinking water for public- and self-supplied domestic uses in Nebraska.

• The Platte River alluvial aquifer that underlies the Platte Valley subunit is the single most important source of w

public supply and is connected hydraulically to the Platte River.

• The increase in ground-water withdrawals in the Platte Valley has induced additional recharge from the river, and 

potential to change ground-water quality near the river where many of the public supply wells are located.

Aquatic environments potentially are altered by human activities (p. 12–13)

• Streams where row crops dominate the drainage basin had large concentrations of nutrients and pesticides in the 

the largest residues of pesticides in fish tissues, and degraded fish communities. Conversely, streams draining ran

had small concentrations of pesticides in water and fish tissues and supported diverse fish communities. Chemic

mally associated with urban and industrial sources were detected at small concentrations in water, streambed sed

and fish tissues throughout the Study Unit.

• Organochlorine concentrations in fish tissues generally were near minimum reporting limits; however, more freq

detection and somewhat larger concentrations of p,p'-DDE, polychlorinated biphenyls (PCBs), trans-nonachlor, 

dieldrin were detected from areas dominated by row-crop agriculture. One of three fish-tissue samples from the 

River at Louisville exceeded a water-quality criterion for protection of fish-eating wildlife because of large conc

tions of p,p'-DDE.

• Streams that drain basins with large percentages of cropland had fish communities tolerant of physical or chemic

quality degradation. Fish communities from the Dismal River, which drains primarily rangelands, contained a m

erant species, species with intermediate tolerance, and intolerant species. In contrast, the fish communities at Pra

Shell Creeks, where nearly all the land is used for corn production, were characterized by a few tolerant species 

green sunfish, common carp, and fathead minnow; no pollution-intolerant species were present. Habitat quality a

degraded at sites draining areas where cropland was the predominant land use.

• Wetlands in drainage basins dominated by row crops had herbicide (atrazine and total organonitrogen herbicides

centrations that were significantly greater than those from wetlands in either rangelands or mixed land uses. The

ings imply that a mixture of land use may reduce the potential for water-quality degradation from agricultural so

Aquatic and migratory species are affected directly by changes in the physical characteristics of the Platte Rive

(p. 14-15)

• Channel width has been reduced by as much as 90 percent near North Platte. The narrowing process is continuing 

downstream. Near Grand Island, the channel has narrowed from 40 to 60 percent of its historical width, and tree

become established on sandbars, which develop into permanent islands. Flow regulation upstream from the Stud

water withdrawals, and possibly climate changes have been the primary causes of channel-width reductions.

• Migratory birds, including sandhill cranes and the endangered whooping cranes, rely on critical habitats in the Pl

ley. Habitat loss has created overcrowded conditions, which may lead to outbreaks of diseases such as avian cho

• Native fish species also have been adversely affected by habitat loss. Some fish species may be absent or in decl

result of reductions in habitat. The current fish community contains non-native species that are tolerant of degra

itats. Some sensitive native species are no longer found or are rarely collected.
4 Water Quality in the Central Nebraska Basins, Nebraska, 1992–95

ENVIRONMENTAL SETTING AND HYDROLOGIC CONDITIONS

IN THE CENTRAL NEBRASKA BASINS STUDY UNIT

Vast grasslands and fertile soils drew Native Americans to

hunt and farm in the area that became the State of Nebraska.

These same qualities appealed to settlers moving west during

the 19th century in search of affordable land. Cattle ranchers

found room to sustain their herds in the Sandhills, where

grass roots have all but stopped the progression of sand

dunes. The development of surface- and ground-water irrigation led to dependable harvests of corn, alfalfa, soybeans,

and sorghum. Today the region is still an important agricultural production center for the Nation.

The Central Nebraska Basins Study Unit includes about

30,000 mi2 (square miles) of the Platte River Basin from the

confluence of the North and South Platte Rivers near North

Platte, Nebraska, to its mouth near Omaha, Nebraska [1].

The environmental settings of the Central Nebraska Basins

are characterized by differences in soils, precipitation, and

land use and are divided into the Sandhills, Loess Hills, Glaciated Area, and Platte Valley subunits.

The Platte River is regulated by a series of up

dams producing similar patterns of streamflow 

year.

Greater rainfall and relief, less permeable soils, a

regulation result in highly variable streamflow.

Along the southern part of the Study Unit is the Platte 

subunit, where sandy soils and a shallow water table p

favorable conditions for crop production.

Hydrologic conditions affect water quality because 

cesses by which many chemicals enter water bodies ar

Permeable soils of the Sandhills result in stable streamflow

sustained by ground-water discharge.

In the northwest part of the Study Unit, the Sandhills subunit

has sandy soils, is semiarid, and is used as rangeland. Nearly all

the precipitation in the Sandhills subunit infiltrates directly to

ground water with very little runoff. Progressing eastward, precipitation increases, soil textures are finer, and runoff increases. The

Loess Hills subunit, in central Nebraska, is characterized by a mixture of rangeland and cropland, whereas the Glaciated Area subunit, in the eastern part of the Study Unit, is nearly all cropland.
U.S. Geological Survey Circular 11

ENVIRONMENTAL SETTING AND HYDROLOGIC COND

IN THE CENTRAL NEBRASKA BASINS STUD

of precipitation running off the land surface and entering

streams or aquifers. For example, herbicides commonly are

applied to row-cropped areas in the spring. If this application is

followed by intense rainfall, herbicides can be transported

overland to streams [2] or downward to ground water. Therefore, any description of current water-quality conditions should

consider present and typical hydrologic conditions. In the

accompanying figures, the blue-shaded area represents the

range of streamflows that occurred 25 to 75 percent of the time

Streamflow in the eastern part of the Study Unit was much

greater than normal during this study.

from 1954 to 1991 (a period of data available for a

shown).

Generally, streamflows throughout the Study U

greater than normal during 1992 to 1995. This was 

noticeable in the eastern part of Nebraska where s

has a strong seasonal pattern. In contrast, the Dism

the Nebraska Sandhills, had a fairly uniform stream

was slightly above the normal range from 1992 to 

Streamflow in the Platte River is regulated by rele

dams outside of the Study Unit and by diversions f

The sharp declines each year are the result of irrigation

withdrawals. Wet conditions have recently increased water levels.

Comparisons of streamflow between the 

Brady and the Platte River near Louisville s

of precipitation and streamflow regulation i

Nebraska Basins. Because flow and runoff w

than normal for streams sampled during the 

study, constituent loads associated with non

such as nutrients and pesticides, might be e

larger than would be found at normal flows

Ground-water withdrawals for irrigation 

stantial declines in ground-water levels duri

Ground water may be susceptible to contam

nonpoint sources where unconfined aquifer

and overlying soil texture is coarse, such as 

Valley. Generally, ground-water levels in th

declined from the 1950s to the early 1980s. 

normal precipitation during 1992 to 1995 in

levels, and increased nutrient and pesticide 

could be expected.

Runoff from the Central Nebraska Basins gen

unregulated by dams and thus shows substa
6 Water Quality in the Central Nebraska Basins, Nebraska, 1992–95

MAJOR ISSUES AND FINDINGS

IN THE CENTRAL NEBRASKA BASINS STUDY UNIT

.Nitrate Content in Water is

Related to Agricultural Land

Management

Land use in the Central Nebraska

Basins Study Unit is primarily

agricultural—typically, large areas are

rangeland, mixed rangeland and

cropland, or cropland. Rangeland

characterizes most of the western part

of the basin whereas cropland is more

typical in the eastern part [1]. Irrigated

corn dominates the land use in the

central Platte Valley subunit, where

extensive applications of nitrate

fertilizers and irrigation water are

made each year to sustain crop yields.

Nitrate concentrations in water at

different locations reflect the

differences in agricultural land

management within the Study Unit.

Percentage of major land use in

drainage basins for selected streams

Stream

sampling

site

Crops,

pasture

(percent)

Rangeland

(percent)

1 6.3 92.9

2 26.5 72.6

3 98.4 1.1

4 99.5 No data

5 84.1 14.1

The Platte Valley subunit includes

extensive areas of irrigated corn,

permeable soils, and shallow ground

water—all characteristics that increase

the vulnerability of ground water to

agricultural contaminants. The

Glaciated Area subunit also has

extensive areas of corn and other row

crops. Consequently, concentrations of

nitrate in shallow ground water are

substantially larger in the Platte Valley

and the Glaciated Area than in the

Sandhills subunit, which is mostly

rangeland, and the Loess Hills area,

which is predominantly rangeland

mixed with cropland. As the graph

indicates, 45 percent of the shallow

wells sampled in the Platte Valley and

more than 25 percent of the shallow

wells in the Glaciated Area exceeded

the USEPA’s MCL [3] of 10 milligrams

per liter (mg/L) for nitrate in drinking

water. In contrast, 75 percent of the

shallow wells sampled in the Sandhills

contained less than 2 mg/L of nitrate,

and 75 percent of the shallow wells in

the Loess Hills contained less than

5 mg/L. Nitrate concentrations in the

deeper wells in the Platte Valley and

the Glaciated Area were significantly

smaller than in the shallow wells.

Median nitrate concentrations in

samples from the deep wells were

similar (2 to 4 mg/L) among subunits.

Nitrate concentrations in streams

generally were substantially smaller

than those from shallow groun

of the same subunits [4].

Annual applications of up to 

200 pounds of nitrogen per acr

made to achieve large corn yie

Streams draining areas where 

production is extensive and fer

applied every year at rates that 

high-yielding corn (sampling s

and 5) tended to have larger ni

concentrations than areas like 

and 2. Nitrate concentrations i

streams vary seasonally; larger

concentrations of nitrate were 

during winter when aquatic pl

growth was minimal, whereas 

Corn production dominates the land use in the Platte Valley and Glacia

Area subunits.

Nitrate concentrations were largest in the shallow

ground water in areas of intense corn production.

Nitrate concen

larger in stream

intense crop p
U.S. Geological Survey Circular 1

MAJOR ISSUES AND FIN

IN THE CENTRAL NEBRASKA BASINS STUDY 

concentrations of nitrate were detected

during summer when aquatic plant

growth was greatest [5].

Irrigated cropland can affect nitrate

concentrations in ground water. The

Central Nebraska Basins Study Unit

team examined data from Druliner and

others [6] for selected wells in three

areas (G1, G2, and G3, which extend

beyond the Study Unit) that represent

contrasting amounts of irrigated

cropland ranging from 13 percent to

about 50 percent. Median nitrate

concentrations in areas with shallow

depths to ground water and underlying

intensely irrigated cropland that is

dominated by corn production, like

area G1 in the table, were more than

twice the MCL of 10 mg/L for

drinking water. The area G2 is similar

to area G1 in the total percentage of

land irrigated, but with generally larger

depths to ground-water level and a

median nitrate concentration that is

one-fourth that of area G1. In both the

G1 and G2 areas, more than 60 percent

of the cropland is planted in corn. In

these areas, median nitrate

concentrations approached or

exceeded the MCL. In comparison,

area G3 had 35 percent of the cropland

planted to corn, only 13 percent of the

total land area irrigated, and relatively

shallow depth to ground water, yet had

a median nitrate concentration of

6.4 mg/L.

The Central Platte Natural

Resources District (CPNRD) has

established fertilizer-management

areas in part of the central Platte Valley

based on corn acreages and nitrate

concentrations in ground water, similar

to area G1. This area has concentrations of nitrate in ground water up to

40 mg/L. The CPNRD has imposed

stringent guidelines on the timing and

application rate of fertilizer in this

area. In addition, the amount of fertilizer applied must be decreased by the

amount of nitrate contained in the irrigation water that is applied. Moderate

guidelines on fertilizer application are

enforced in areas that are less vulnerable to contamination. A third area with

the smallest percentage of cropland

has minimal guidelines. This management strategy began during 1986–88.

The Study Unit team analyzed

CPNRD data collected from 1974

through 1994 from selected irrigation

and domestic wells [7]. Median nitrate

concentrations, in areas that were

assigned the most stringent guidelines,

increased from about 8 mg/L in 1974

to about 18 mg/L in 1986. After

implementation of the fertilizermanagement strategy, the median

nitrate concentrations in domestic

wells decreased from 18 mg/L in 1986

to less than 2 mg/L in 1994.

However, despite the most stringent

guidelines, nitrate concentrations in

nearly 25 percent of the wells in the

area continued to exceed 20 mg/L in

1994. Therefore, it is possible that

some areas where the most stringent

guidelines apply have not been as

responsive to the management strategy

as others. Nitrate concentrations for

different years, under moderate

guidelines, did not differ signific

Median nitrate concentrations in 

samples from the domestic well

minimal management areas show

change.

—Thomas L. Hu

Nitrate concentrations in selected ground-water areas in central Nebraska reflect the agricultural land use

[%, percent; acre-ft/acre, acre-foot per acre; mg/L, milligrams per liter; <, less than; Source: modified from Druliner and others [6]]

Sampling

area

(see map)

Cropland

(%)

Total land

area

irrigated

(%)

Estimated

irrigation

water used

(acre-ft/acre)

Major crops

(% cropland,

as of 1989)

Nitrate, 25th

percentile

(mg/L)

Median

nitrate

(mg/L)

Nitrate, 75th

percentile

(mg/L)

G1 59 50 0.82 Corn (64), hay (12),

soybeans (10)

9.8 25.0 32.0

G2 67 48 1.0 Corn (68), wheat (9)

soybeans (8)

3.8 7.6 10.0

G3 30 13 0.99 Hay (58), corn (35),

soybeans (4)

1.6 6.4 18.0

Since 1986, median nitrate co

trations from domestic wells 

decreased where the most str

fertilizer-management guideli

have been followed.
8 Water Quality in the Central Nebraska Basins, Nebraska, 1992–95

MAJOR ISSUES AND FINDINGS

IN THE CENTRAL NEBRASKA BASINS STUDY UNIT

(μg/L), and mean daily stream

ranged from 3,750 to 18,100 cu

per second (ft3/s). In contrast, 

concentrations in February ran

from 0.08 to 0.10 μg/L, and m

daily streamflows ranged from 

to 8,150 ft3/s. The decrease in 

of atrazine available for entrain

Agricultural Activities Potentially

Affect the Management of Public

Water Supplies

Contamination of surface and ground

water from nonpoint sources is a national

issue. Examples of nonpoint-source contaminants from agricultural activities are

pesticides (fungicides, herbicides, and

insecticides), sediment, nutrients (nitrogen

and phosphorus), and fecal bacteria [8]. Of

the many possible contaminants, pesticides

receive the most attention because of the

potential toxicity to aquatic life and

humans. Pesticides often are used to

increase crop yields and values. Herbicides

prevent or inhibit the growth of weeds that

compete for nutrients and moisture needed

by the crops. Herbicides are applied before,

during, or following planting. Herbicides

also are used for weed control in urban

areas, often with large rates of application.

 Alachlor, atrazine, cyanazine, and

metolachlor, which are referred to as organonitrogen herbicides, were the four most

commonly applied herbicides for corn, sorghum, and soybean production in the Central Nebraska Basins Study Unit. Of all

pesticides used in the Study Unit, atrazine

was the most extensively applied.

Insecticides are used to protect the crop

seeds in storage prior to planting and also to

protect the plants once the seeds germinate.

Like herbicides, insecticides are used in

urban areas to protect property, including

buildings, lawns, trees, and ornamental

shrubs.

Row-crop agriculture dominates much

of the Central Nebraska Basins Study

Unit.

The temporal distributions of

alachlor, atrazine, cyanazine, and

metolachlor and the concentrations of

each were defined on the basis of

analyses of water samples collected

from the Platte River at Louisville

from September 1, 1991, through

August 31, 1992 [9, 10]. These data

were collected more often when the

temporal variability of concentrations was expected to be large and

less often when variability was

expected to be small. The graph

shows the temporal distribution of the

concentrations of atrazine in relation

to streamflow. Although the graph

shows only how atrazine concentrations vary with time, concentrations

of alachlor, cyanazine, and metolachlor varied in a similar manner.

Concentrations of atrazine were

larger in the spring and summer,

when nearly all atrazine is applied,

and smaller in the fall and winter.

During this period of data collection,

the largest herbicide concentrations

were measured during the growing

season following intense rainfall

shortly after the herbicide had been

applied [11]. Herbicide concentrations peaked in May and then generally declined in the months that

followed [9]. For example, atrazine

concentrations in May ranged from

0.17 to 30 micrograms per liter

Alachlor Malathio

Atrazine Methyla

Benfluralin Methylp

Butylate Metolac

Carbaryl Metribuz

Carbofuran Molinate

Chlorpyrifos Napropa

cis-Permethrin p,p'-DDE

Cyanazine Pebulate

DCPA Pendime

Diazinon Phorate

Dieldrin Prometo

Diethylanaline Pronam

Dimethoate Propach

Disulfoton Propani

EPTC Proparg

Ethalfluralin Simazin

Ethoprop Tebuthiu

Ethylparathion Terbacil

Fonofos Terbufos

HCH, alpha- Thioben

HCH, gamma- Triallate

Linuron Triflurali

Atrazine concentrations in the Platte River are a function of the timing and

intensity of rainfall with respect to the application of the herbicide.

Water samples from the Platte R

Louisville site were analyzed fo

pesticides.
U.S. Geological Survey Circular 11

MAJOR ISSUES AND FIN

IN THE CENTRAL NEBRASKA BASINS STUDY 

surface runoff is a result of factors

such as volatilization into the atmosphere as a result of high land-surface

temperatures, photo decomposition

and bacterial degradation, adsorption

onto soil particles, and uptake by

plants.

Of the 46 pesticides, it appears that

only atrazine, cyanazine, and alachlor

may at times pose potential concern

for public water supplies withdrawn

downstream from the confluence of the

Elkhorn River with the Platte River

[12]. Presently, the USEPA has established only a Health Advisory Level

(HAL) for cyanazine and not an MCL;

a HAL is a guideline whereas an MCL

is enforceable. Thus, based on current

MCLs, atrazine is the herbicide most

likely to exceed the MCL at the Platte

River at Louisville. However, the compliance of a public water-supply system relative to an MCL or a HAL for a

pesticide is based on an average annual

concentration. Therefore, one or more

exceedances of the specified value

does not necessarily indicate noncompliance. Also the MCL or HAL for a

pesticide applies only to the pesticide

and not to any of its degradation products.

An analysis of these four herbicides

at the Platte River at Louisville site

indicated that the source of the herbicides was almost entirely in the Study

Unit and most was contributed 

Elkhorn River [12]. Most herb

movement in streams occurred 

the growing season (May throu

August).

Lincoln, Omaha (outside th

Unit), and smaller cities along 

Platte River withdraw water fr

adjacent alluvial aquifer for pu

supplies. The aquifer adjacent 

direct hydraulic connection to 

and thus is affected appreciabl

quantity and quality of water i

river [13, 8].

 Studies have shown that c

tional water treatment is ineffe

removing organonitrogen herb

such as alachlor, atrazine, cyan

and metolachlor from finished 

ing water. These herbicides rem

solution, in contrast to many o

taminants that are more easily r

by conventional treatment proc

such as coagulation and sand fi

—John K

Atrazine movement from the Platte River through alluvial aquifers can be induced by

ground-water withdrawals for drinking water.

Alachlor, atrazine, and cyanazine pose potential concerns for drinking-water s
10 Water Quality in the Central Nebraska Basins, Nebraska, 1992–95

MAJOR ISSUES AND FINDINGS

IN THE CENTRAL NEBRASKA BASINS STUDY UNIT

Water Quality in the Platte

River Alluvial Aquifer may be

Affected by Surface-Water

Quality in Areas of GroundWater Withdrawals

Ground water is the principal source

of water for public- and self-supplied

domestic uses in Nebraska. Ground

water supplied about 235 million gallons per day (Mgal/d) or about 78 percent of the estimated public-supplied

water in Nebraska in 1990. The Platte

River alluvial aquifer that underlies the

Platte Valley is connected hydraulically to the Platte River. The aquifer is

the single most important source of

water for public supply. It provides

about 117 Mgal/d, or about half of the

total daily ground-water public-supply

production for Nebraska. This aquifer

supplies water to Nebraska’s largest

cities, including Omaha, Lincoln,

Grand Island, and Kearney. In addition, ground water supplies about 83

percent, or about 1,017 Mgal/d, of the

irrigation water in the valley [14].

Increased ground-water withdrawals from the alluvial aquifer may

increase infiltration from the Platte

River [15]. This increase in infiltration

has the potential to change the groundwater quality near the river where

many of the public-supply wells are

located. The quality of the Platte River

water can differ significantly with

respect to location in the valley.

Median concentrations of dissolved

solids tend to decrease with distance

downstream, whereas nitrate and pesticide concentrations increase with distance downstream. Median dissolvedsolids concentrations for samples collected between 1992 and 1995 were

663 mg/L from the Tri-County Canal

near North Platte, which represents

stream water quality entering the

Study Unit from the west, 578 mg/L

from the Platte River near Grand

Island near the middle of the Study

Unit, and 380 mg/L from the Platte

with 0.14 μg/L from Tri-County 

near North Platte, 0.62 μg/L from 

Platte River near Grand Island, a

0.91 μg/L from the Platte River a

ville.

Dissolved solids and pesticide 

trations in ground water are not g

different than those in surface wa

nitrate concentrations in intensiv

cultural areas are usually much g

ground water than in surface wat

1978–90 median dissolved-solids 

centration was 533 mg/L and me

nitrate was 12 mg/L for the shall

than 82 ft) Platte River alluvial a

[16]. Of the 12 pesticides listed i

table with median concentrations 

than the method detection limit, a

was less than 0.2 μg/L, atrazine w

0.3 μg/L, cyanazine was less than

0.1 μg/L, and metolachlor was le

0.1 μg/L. These pesticide concen

are generally greater than the me

these compounds in surface wate

most upstream surface-water site 

County Canal and less than the m

concentrations at the most downs

surface-water site at Louisville.

Three locations in the Platte V

were studied to assess the effects 

withdrawals on ground-water qua

Median herbicide concentrations 

stream sites in the Platte River, 1

[μg/L, micrograms per liter; <, less than]

Herbicide

Concentration (μ

TriCounty

(upstream)

Grand

Island

(middle)

Acetochlor <0.05 <0.05 

Alachlor <0.05 <0.05 

Ametryn <0.05 <0.05 

Atrazine 0.14 0.62 

Cyanazine <0.05 <0.05 

Metolachlor <0.05 0.07 

Metribuzin <0.05 <0.05 

Prometon <0.05 <0.05 

Prometryn <0.05 <0.05 

Propazine <0.05 <0.05 

Simazine <0.05 <0.05 

Terbutryn <0.05 <0.05 

Stream-water quality in the Platte River with

distance downstream.

River at Louisville at the

most downstream point

where streamflow leaves

the Study Unit. Median

nitrate concentrations

were 0.68 mg/L in samples from the Tri-County

Canal, 1.4 mg/L from the

Platte River near Grand

Island, and 1.2 mg/L

from the Platte River at

Louisville. The median

concentrations of

12 herbicides in surface

water at these locations

are listed in the table.

Five of the twelve—acetochlor, alachlor, atrazine, cyanazine, and

metolachlor— indicate

that herbicide loads

increase with distance

downstream in the Study

Unit. Atrazine displayed

the highest increase in

median concentrations
U.S. Geological Survey Circular 11

MAJOR ISSUES AND FIN

IN THE CENTRAL NEBRASKA BASINS STUDY 

the river [17]. The areas studied were a

wet meadow area located about

15 miles east of Kearney, the city of

Grand Island’s Indian Island wellfield,

and the city of Lincoln’s Ashland wellfield.

The wet meadow is an area that has

had very little ground-water development and represents essentially

unstressed ground-water conditions. A

number of observation wells were

installed in the wet meadow at selected

depths and distances downgradient

from a corn field to study the areal and

vertical differences in concentrations

of selected water-quality constituents.

The median dissolved-solids concentration of samples collected in February and June 1994 was 822 mg/L,

somewhat above the medians for dissolved solids in surface water at sites

upstream and downstream from the

wet meadow site. The most pronounced changes in dissolved-solids

concentrations occurred with depth.

For example, the dissolved-solids concentration for December 1994 was 956

mg/L in the shallowest well in a cluster

of wells completed closest to the corn

field; the concentrations decreased to

575 mg/L in the deepest well of the

cluster, completed at the bottom of the

alluvial aquifer. The latter is nearly the

same as the median dissolved-solids

concentration in the streamflow just

downstream at Grand Island. Nitrate

concentrations in water samples from

the shallow wells in the wet meadow in

1994 ranged from 5.0 to 15 mg/L.

These concentrations were generally

much larger than those detected in the

associated deeper (30 and 45 ft) wells

where nitrate concentrations ranged

from 1.3 to 6.8 mg/L. Atrazine was

detected in small concentrations of 0.1

to 0.6 μg/L in water from all of the

wells sampled in February and June

1994, similar to the range of median

atrazine concentrations detected in surface water at the upstream and middle

sites. Concentrations of the other 11

herbicides were at or below the detection limit of 0.05 μg/L.

Grand Island is typical of cities in

the Platte Valley. Concerns about adequate future supplies and the potential

for ground-water contamination led to

the development of the Indian Island

wellfield site in the Platte River. It was

anticipated that, with an island location, recharge from the river would act

as a barrier to potential ground-water

contamination of the wellfield and provide an additional source of good quality water to the aquifer. Control of land

use within the wellfield also has the

potential to minimize ground-water

contamination from land-surface activities in the valley (Gary Mader, Utilities Director, City of Grand Island,

written commun., 1994).

Observation wells were installed in

four clusters of five wells each in the

wellfield. An additional cluster of four

observation wells was installed immediately north of the river. The wells in

the wellfield clusters were completed

at depths ranging from 20 to 123 ft,

and wells in the cluster located north

of the river were completed at depths

of about 13 to 114 ft. Dissolved-solids

concentrations varied with location

and depth of the observation well. The

concentrations ranged from 443 to

746 mg/L in the wellfield, with a

median concentration of 578 mg/L.

Because of controlled land use and the

river barrier, the nitrate concentrations

were very low. The median concentration of nitrate for samples collected

during late 1994 and early 1995 was

1.37 mg/L. In late August to early September 1995, nitrate concentrations

ranged from less than the detection

limit of 0.05 mg/L to a maximum of

0.59 mg/L.

Water collected between December

1994 and September 1995 from the

observation wells in the Grand Island

wellfield also was analyzed for the

same 12 pesticides shown in the table.

Of the 12, only atrazine, prometon, and

propazine were detected at concentrations of 0.05 μg/L or greater. Atrazine

was detected at all five observationwell clusters but only in small concentrations. Atrazine was not dete

samples from any of the 123-f

wells. At the cluster most affec

pumping, atrazine was detected 

the shallowest well. The maxim

concentration of atrazine from 

47 samples collected at the fiv

sites was 0.38 μg/L. Prometon 

detected in three and propazin

detected in two of 47 samples 

five well clusters. Maximum c

trations of prometon and propa

were 0.06 and 0.41 μg/L.

The Ashland wellfield prov

almost all of the public supply 

for the city of Lincoln, which 

population of about 200,000. B

ground-water withdrawals are 

and the supply wells are near t

major ion and nutrient concen

in ground water are comparab

Platte River water at the Louis

site. In studies conducted by o

[18, 19], atrazine detected in s

from the observation and supp

were traced to the river. Atrazi

centrations in water sampled f

observation wells in the wellfie

reported as high as 20 μg/L.

Inducing infiltration from th

River may have the effect of re

nitrates to below that of the ne

ground water but also may hav

effect of increasing pesticide c

trations. This is particularly tru

lower basin where the surface 

may carry higher levels of pes

and especially during the late 

and early summer when pestic

centrations in the streams are a

highest. Generally, the closer a 

to a stream and the higher the p

rate, the more the quality of th

water will be influenced by the 

of the stream.

 —Patrick J. 
12 Water Quality in the Central Nebraska Basins, Nebraska, 1992–95

MAJOR ISSUES AND FINDINGS

IN THE CENTRAL NEBRASKA BASINS STUDY UNIT

only 1 of 28 samples had detectable

levels of organochlorine pesticides.

There were no detections of these

compounds from 8 ground-water samples or 159 stream-water samples.

Volatile organic compounds

(VOCs) generally are associated with

industrial activities, although some

also are used as inert ingredie

pesticide formulations. Becau

VOCs are carcinogenic, their p

in water supplies would be of c

In the Platte Valley, environm

conditions are more likely to a

contamination than in other su

of the Study Unit, yet no VOC

detected in any of the 4 surfac

and 11 ground-water samples 

streams or the alluvial aquifer

The same samples were an

for alpha and beta radioactivit

radioactivity has an MCL of 1

picocuries per liter (pCi/L) in 

water and generally indicates 

presence of naturally occurrin

radium or radon. Alpha radioa

ranged from 9.9 to 18 pCi/L in

streams and from 1.5 to 79 pC

ground water. Beta radioactivi

concentrations greater than 50 

may indicate the presence of fi

products such as potassium-40 

strontium-90. Beta radioactivi

ranged from 11 to 35 pCi/L in 

and from 5.2 to 55 pCi/L in gr

water. Areas upstream from th

Central Nebraska Basins Stud

contain uranium-rich rock tha

likely source of alpha and beta

radioactivity in the Platte Vall

Generally, trace elements in 

tissue, and streambed sedimen

Central Nebraska Basins Stud

were not an issue. Water samp

streams and aquifers with trac

ment concentrations greater th

detection limit of 1 mg/L were 

mon. No samples exceeded dr

water MCLs for any trace elem

However, streambed-sedimen

ples from the Platte River betw

North Platte and Grand Island 

had notable selenium concent

The North Channel of the Plat

at Brady, with 1.2 micrograms 

gram (μg/g), the Platte River a

Overton (2.6 μg/g), and the Pl

River near Grand Island (2.1 μ

exceeded the median value of 

from the 20 NAWQA Study U

submitting samples from 1992 

1995. Samples collected durin

at Brady and near Grand Islan

following high flows, had sele

Although some organochlorine compounds have not

been used for decades, they remain persistent in the

environment.

the Midwest during 1993, may

resuspend compounds long buried in

streambed and flood-plain sediments.

The largest concentration of

organochlorine residues was detected

in common carp sampled near the

mouth of the Platte River following

the flooding in 1993. The p,p'-DDE

concentration of 1,600 micrograms

per kilogram (μg/kg) was large

enough to exceed the National

Academy of Sciences and National

Academy of Engineering guideline for

the protection of fish-eating wildlife

[21].

Organochlorine pesticides may also

be found associated with organic carbon in streambed sediments. However,

the less than 2-mm (millimeter) size

fraction analyzed from streams in central Nebraska is mostly sand and has

little organic carbon. Consequently

Aquatic Environments

Potentially are Altered by

Human Activities

Basins in which row crops dominate tended to have larger concentrations of agricultural chemicals in the

water, residues of pesticides in fish tissues, and degraded fish communities

[20]. Conversely, streams draining

rangelands had smaller concentrations of agricultural chemicals in

water or fish tissue and supported

diverse fish communities. Urban and

industrial chemicals generally were

detected at small concentrations in

water, streambed sediments, and fishtissue samples throughout the Central

Nebraska Basins Study Unit.

In general, chemicals discussed

here enter the aquatic environment

through nonpoint-source runoff from

agricultural lands that dominate the

Nebraska landscape.

Because some chemicals

may be hundreds or thousands of times more concentrated in the tissues of

aquatic organisms or in fine

sediments these media are

well suited for the detection

of certain classes of chemicals. Other chemicals are

highly soluble and therefore

most likely detected in water.

Residues of

organochlorine compounds

were present in bottomfeeding fish. Generally,

concentrations were near

method detection limits;

however, p,p'-DDE (a

degradation product of

DDT), PCBs, transnonachlor, and dieldrin were

detected more frequently and

in somewhat larger concentrations in

areas dominated by row-crop

agriculture. Although some of these

compounds, or their parent

compounds, have not been used in the

United States for a quarter of a

century, they persist in the

environment. Large-magnitude

flooding, such as was experienced in
U.S. Geological Survey Circular 11

MAJOR ISSUES AND FIN

IN THE CENTRAL NEBRASKA BASINS STUDY 

sediment and nutrient retention, groundwater recharge, and wildlife habitat.

Decades of agricultural activities in

Nebraska have resulted in substantial

decreases in wetland acreage. Remaining

wetlands in the predominantly agricultural landscape are subjected to a variety

of effects from surrounding land use.

Some of the herbicides used in Nebraska

are among those reported to have reproductive and endocrine disruptive effects

on wildlife. With fewer acres of wetland

habitat available to wildlife, the quality

of remaining habitat becomes increasingly important.

Thirty-one wetlands representing

dominant local land uses were sampled

for organonitrogen herbicides in May and

August 1994. Analysis of land use within

0.6 mile of each wetland revealed three

groups of sites. One group of sites had an

average of 74 percent rangeland, a second group of sites averaged no more than

30 percent in a single land-use category,

and the third group had an average of

78 percent cropland surrounding the

sites. The median concentrations of atrazine and the total of all herbicides analyzed in water samples were significantly

smaller in rangeland-dominated sites

than in cropland-dominated sites in both

sampling periods. Sites without a 

dominant land use had significan

smaller atrazine and total herbici

centrations than sites in cropland

nated landscapes, but were not

significantly different than those 

lands [23]. These results suggest 

bicide concentrations are elevated 

water bodies where most of the s

ing land is used for row-crop pro

 —Steven A

Fish communities were degraded at streams draining mostly

cropland.

Measures of fish communities’ tolerance to pollution

suggest that degraded water quality is associated wi

percentage of cropland in a basin.

Wetlands surrounded mostly by 

significantly greater herbicide co

than wetlands in other land-use a

concentrations of 2.6 μg/g and

1.8 μg/g.

Because many specific factors

should be considered when evaluating

water quality, it is often difficult to provide a single result that represents the

integration of these factors. However,

aquatic biota that are continually subjected to all aspects of physical and

chemical factors of their environment

provide a means for making an integrated assessment. Species composition reveals information about local

environmental conditions. If tolerant

species, such as common carp, dominate the community to the exclusion of

less-tolerant species, such as smallmouth bass, the implication is that

water quality is degraded.

Fish communities were sampled at

nine sites in the Central Nebraska

Basins and evaluated using an index of

biotic integrity (IBI). In this study, the

lowest IBI scores (indicating degraded

water quality) resulted from the identification of only a few individual fish,

all of highly tolerant species. Shell and

Prairie Creeks had the lowest IBI

scores. Higher scores are associated

with samples collected at the Dismal

River and Platte River sites. These sites

had fish communities represented by

species of all tolerance classes. Sites

with larger percentages of cropland in

a drainage basin had fish communities

indicative of degraded water quality

[22]. Although cropland does not

directly affect a fish community, factors related to the presence of cropland, as well as the effects of cropland

on water chemistry

and the physical habitat, likely are responsible for this relation.

Wetlands provide a

variety of functions

including flood and

erosion moderation,
14 Water Quality in the Central Nebraska Basins, Nebraska, 1992–95

MAJOR ISSUES AND FINDINGS

IN THE CENTRAL NEBRASKA BASINS STUDY UNIT

The Platte River Valley has been

called “the foremost physical geographic feature of South Central

Nebraska” [24]. The river bears little

resemblance to the one that led tens of

thousands of Native Americans, trappers, and settlers westward.

Though the Platte Valley still serves

as a major overland interstate and rail

artery, the river and its tributaries also

are situated along another “highway.”

This corridor runs north-south, but

instead of settlers, it is one of the major

transcontinental routes for migratory

birds and waterfowl. The Central Flyway serves as a conduit to bring half a

million sandhill cranes, endangered

whooping cranes, and vast numbers of

other migratory species through the

Platte Valley each year. These birds use

the Platte Valley for nesting and to

replenish their strength for their semiannual journey. The channels of the

Platte also provide habitat for more

than 50 species of fish [25].

Physical characteristics of a river

can be used to assess habitat for biota.

These characteristics at a basin scale

include basin shape, area, percentage

of the basin contributing to runoff, the

frequency and timing of floods, and

land-use features [26]. Stream segment

characteristics include streamflow, the

shape of the channel, the stream stage

at overflow into the flood plains, and

sinuosity (or how curved the river is).

Stream reach characteristics include

the depth, width, and velocity of the

stream, composition of the riverbed,

and the available habitat. Different

species of plants and animals prefer

and are limited to living in the rivers

and streams where these physical characteristics are compatible with their

preferences and tolerances.

Streamflow regulation on the North

Platte River has reduced the magnitude

of spring floods in the main stem of the

Platte River and, along with possible

long-term climate change, has resulted

in substantial channel-width reductions [25]. Since the completion of the

last major dam on the North Platte

River more than 50 years ago, channel

width has been reduced by 90 percent

immediately downstream from the

confluence of the North and South

Platte Rivers and from 40 to 60 percent

in the middle reaches of the river [27].

Abandoned channels of the stream are

now colonized by woodlands [28].

Nearly all researchers agree that birds

that use the wide, active channels of

the Platte River will lose valuable habitat with further channel narrowing.

The Central Nebraska Basins Study

Unit team determined that, though the

channel width appears to be stabilized

at about 10 percent of its former width

near Brady, the nature of its shape has

changed markedly. Where the river

was once a fairly straight and highly

braided stream, it is now in the process

of becoming a meandering river.

Although the channel near Grand

Island has retained some braided charreleased by vegetation clearing 

the reach. Regardless of the rela

effects of water development an

etation clearing on channel narr

ing, it is apparent that the river i

reach below Grand Island is stil

engaged in the reshaping proces

further changes can be expected

Traditionally, the Platte Valle

served the sandhill cranes and th

endangered whooping cranes as 

secure place to rest while they f

[30]. Crane populations are rela

stable, but the habitat that crane

fer for roosting has been substan

reduced. These habitat areas stil

near Grand Island and are know

the Critical Habitat Reach of the

Platte River. The cranes prefer t

roost in unobstructed channel ar

that are greater than 450 feet (ft) 

 1962 1993

Channel narro

the Platte Rive

Grand Island. Islands and bars of the Platte River

east of Grand Island have become

densely wooded.

Endangered whooping cranes in the

Platte River.

Species must adap

in habitat. Native spec

cranes, use open wate

sandbars for roosting 

Other smaller migrato

such as the piping plo

rior least tern, use barr

as nesting areas. The w

Platte River near Gran

decreased. Many sand

become permanently v

the past 30 years, chan

habitat in this reach o

River.

Aquatic and Migratory Species

are Affected Directly by

Changes in the Physical

Characteristics of the Platte

River

acteristics, it continues to narrow

Since 1962, approximately one-

of the channel width has been lo

[25]. Evidence suggests that the

forces reshaping the Platte Rive

progressing at differing rates alo

the river. W.C. Johnson [29] fou

that since the 1960s, open chann

and woodland areas in most rea

of the Platte River have remaine

atively stable. Johnson suggests 

channel narrowing downstream 

Grand Island has continued bec

of the accumulation of sedimen

Sandbars and

shoreline

Platte River
U.S. Geological Survey Circular 11

MAJOR ISSUES AND FIN

IN THE CENTRAL NEBRASKA BASINS STUDY 

and they are rarely seen where the channel

is less than 150 ft wide [31]. The same

number of cranes in a smaller area results

in crowding. High population densities

brings the threat of cholera and other diseases to the bird populations [32]. Tens of

thousands of cranes have been killed by

tornadoes and storms passing over areas

with high crane populations. Other birds,

such as the endangered piping plover and

threatened least tern, build their nests on

the barren sandbars of the river. Channel

narrowing also has reduced habitat for

these species.

R.E. Johnson [33] described Nebraska

fish distribution from 1939 to 1940. Goldowitz [34] demonstrated that the number

of fish species had declined through 1995

in the reaches of the Platte River with the

greatest channel-width reductions. R.E.

Johnson collected fish using seines and

2-person crews, whereas Goldowitz collected fish with a combination of seining

and electrofishing with a similar crew size.

The Study Unit team used electrofishing

with 4–5 personnel, resulting in 200 to

300 percent higher species catches at

Brady and up to 40 percent higher species

catches at Grand Island than either the

R.E. Johnson or the Goldowitz surveys.

Even though these sites had highly diverse

fish communities, the Central Nebraska

Basins Study Unit team, like Goldowitz,

noted an absence of some native minnows.

The brassy minnow, plains minnow, western silvery minnow, speckled chub, and

flathead chub were not found during the

Central Nebraska Basins study [22] in

1993 or 1994 at Grand Island, but were

recorded by R.E. Johnson in the 1939

or 1940 collections. In addition, the

number of moderately tolerant species,

such as catfish, bullheads, mosquitofish, and the brook silverside,

increased in both the Central Nebraska

Basins study and the Goldowitz survey. All species found by the Study

Unit team that were exclusive of the

Goldowitz and R.E. Johnson surveys

were classified as either tolerant species or moderately tolerant species,

with the exception of the intolerant

longnose dace.

Researchers of similar streams in

Kansas had similar results [35]. Where

dewatering and habitat destruction

have occurred along streams, fis

nities have changed in favor of m

ant native and introduced fish. T

plains minnow, cited as the most 

and widespread minnow in the c

plains region [36], was absent in 

tions of the Central Nebraska Ba

study in 1993 and 1994.

One reason that some fish spe

absent or in decline may be a sc

critical habitats. Critical habitats 

that are essential for certain spec

ing breeding and early stages of 

Flood plains may be a critical ha

many aquatic species. The flood 

the area adjacent to streams that 

dated on a recurrence interval of 

every 2 years. The Platte River h

torical flood plain extending up 

dreds of feet from the bank; how

current regulated flows infreque

flow the bank onto the flood plai

study by Williams [27] of the Pl

has shown that the streambed ha

lowered by 1.6 ft near Brady as a 

flow regulation. The Study Unit 

firmed this finding by repeated s

the Brady site that showed bank

and the top of a large sandbar th

1.6 ft below the former flood pla

figure). A new flood plain has be

established in the incised channe

only a few feet wide, leaving on

fraction of the flood plain availa

habitat on a frequent basis [25].

—Robert B. Swanson and Rona

Sandhill cranes prefer unobstructed river channels as a roosting site.

Bankfull-flow elevation at the North Channel of the Platte River a

Brady is lower today than in 1940.
16 Water Quality in the Central Nebraska Basins, Nebraska, 1992–95

WATER-QUALITY CONDITIONS IN A NATIONAL CONTEXT

Greater than the 75th percentile

(Among the highest 25 percent nationally

Between the median and the 75th percentile

Between the 25th percentile and the median

Less than the 25th percentile

(Among the lowest 25 percent nationally)

Insufficient data for analysis

Five of seven sites in the

Central Nebraska Basin

Study Unit scored higher

than the 75th percentile for

nutrients, when compared to

the other NAWQA sites.

Three of the seven—Prairie

Creek near Ovina, Shell

Creek near Columbus, and Maple Creek near Nickerson—ranked above 

percentile when compared nationally. Water samples collected from drai

basins dominated by the production of corn, soybeans, and sorghum had 

concentrations among the largest in the Nation. At Prairie Creek, monthl

ammonia concentrations exceeded the USEPA’s criterion for protection o

life more than 30 percent of the time. Prairie Creek’s basin, like other tri

basins in the Platte Valley, is largely dedicated to the production of corn, 

stock and dairy production near the streams may contribute to elevated n

concentrations. Drainage basins with a large percentage of rangeland, su

Dismal and Loup Rivers drainage basins, had nutrient concentrations in 

more typical of sites in other NAWQA Study Units.

Pesticide concentrations in the Central Nebraska Basins Study Unit were among the highest in the Nation. At all of the 

sites—Prairie Creek near Ovina, Shell Creek near Columbus, Maple Creek near Nickerson, and the Platte River at Loui

ville—included in the national comparison, pesticide scores exceeded the median scores for sites in the 20 NAWQA Stu

and also exceeded the aquatic-life criteria for atrazine. At both Prairie Creek and Shell Creek, monthly median pesticid

tions exceeded the aquatic-life criteria 25 percent of the time and median pesticide concentrations were about 10 times 

the median for other NAWQA Study Unit sites. Prairie Creek had the second highest monthly median atrazine concentra

nationally. Sites in the eastern part of the Study Unit—Shell Creek, Maple Creek, and the Platte River at Louisville—w

likely to exceed the aquatic-life criteria for cyanazine. Maple Creek had the highest monthly median cyanazine concent

(24.1 μg/L in June 1993) of any site in the NAWQA Program.

EXPLANATION

Ranking relative to national conditions—

Darker colored circles generally indicate

poorer quality. Bold outline indicates one or

more aquatic-life criteria were exceeded.

Seven major water-quality characteristics were evaluated for stream sites in each

NAWQA Study Unit. Summary scores for each characteristic were computed for 

with adequate data. Scores for each site in the Central Nebraska Basins were com

to scores for all sites sampled in the 20 NAWQA Study Units during 1992–95. T

parison provides a ranking of each site relative to national conditions for each ch

istic. Results are summarized by national percentiles; higher percentile values ge

indicate poorer quality compared with other NAWQA sites. Water-quality condit

each site also are compared to established criteria for protection of aquatic life. A

ble criteria are limited to nutrients and pesticides in water, and to organochlorine 

cides, PCBs, and semivolatile organic compounds in sediment. Methods used to c

rankings and evaluate aquatic-life criteria are described by Gilliom and others [3

PESTICIDES in surface water

NUTRIENTS in surface water

Comparison of Central Nebraska Basins Study Unit Surface-Water Results with Nationwid

NAWQA Findings

Semivolatile organic

compounds were

present at concentrations comparable to

national medians. The

most commonly

detected compound

was p-cresol.

SEMIVOLATILE ORGANIC COMPOUNDS in streambed se

Central Nebraska Basins Study Unit

White areas indicate other NAWQA

Study Units sampled during 1992–95.
U.S. Geological Survey Circular 1

WATER-QUALITY CONDITIONS IN A NATIONAL CON

Eroding banks with little vegetative cover c

not only to degraded quality habitats for fish 

yield sediments and associated contaminant

stream. When evaluated using these criteria

condition was best in rangelands and along 

stem of the Platte River. Both the Dismal R

Thedford and the Platte River near Grand Is

among the 25 percent of the NAWQA sites 

best habitat scores. Prairie, Shell, and Mapl

which drain croplands, had stream-habitat q

among the lowest 25 percent of the NAWQA 

nationally.

Fish community

degradation in

central Nebraska

as indicated by

large percentages

of pollutiontolerant species

was correlated

with the amount of cropland in a basin. Prairie and Shell Creeks, both

basins dominated by corn production, had fish communities that were

among the top 25 percent of the most degraded of the 20 NAWQA

Study Unit stream sites across the nation. In contrast, the Platte River

at Brady drainage basin has little cropland and supports a relatively

diverse fish community. However, even the Platte River at Brady displayed signs of historical trends towards a degraded fish community.

The large-river sites at the Loup River at Palmer, the Elkhorn River at

Waterloo, and the Platte River at Grand Island all ranked in the lower

half of the NAWQA sites in the nation.

CONCLUSIONS

In the Central Nebraska Basins Study 

compared to other NAWQA Study Un

Physical, chemical, and biological me

indicate that streams and rivers in the 

crop-dominated areas of central Nebr

are generally of degraded water quali

the other 19 NAWQA Study Units of t

Nation assessed during 1992–95 for t

NAWQA Program. Elevated herbicide 

nutrient concentrations contribute to t

degraded water-quality conditions. Th

elevated contaminant concentrations 

be of concern to communities that wit

drinking water from shallow wells adja

the Platte River.

Streams in basins with greater propor

rangeland, such as the Dismal River, 

negligible herbicide concentrations. S

with degraded water chemistry comm

have degraded physical habitats as w

combination of degraded physical and

chemical environments often results i

communities with fewer total species 

higher percentage of tolerant species

Concentrations of PCBs

and organochlorine

insecticides such as DDT

and chlordane in the

Central Nebraska Basins

Study Unit were comparable to median concentrations nationally. Because PCBs and organochlorine insecticides have an affinity for fatty tissue, they tend to concentrate

in fish rather than in water or sediments. Sampling efforts at Prairie and

Shell Creeks did not yield sufficient tissue for analysis; therefore, results

from those two sites include only sediment data and may not be comparable to other NAWQA Study Unit sites. One fish sample from the Platte

River at Louisville that was collected following widespread flooding in

the Midwest had DDT concentrations that exceeded the criterion for the

protection of fish-eating wildlife.

TRACE ELEMENTS in streambed sediment

PCBs and ORGANOCHLORINES in streambed sediment and

fish tissue

FISH COMMUNITY DEGRADATION

STREAM HABITAT DEGRADATION

Trace elements in

streambed sediments

ranked similarly to

those from other

NAWQA Study

Units, although

upstream sites on the

Platte River had

larger-than-average

concentrations of

selenium. Platte River sediments at Grand Island contained selenium

concentrations three times greater than the median for the 20 NAWQA

Study Units.
18 Water Quality in the Central Nebraska Basins, Nebraska, 1992–95

WATER-QUALITY CONDITIONS IN A NATIONAL CONTEXT

Five major water-quality characteristics were evaluated for ground water in e

NAWQA Study Unit. Ground-water resources were divided into two categor

(1) drinking-water aquifers, and (2) shallow ground water underlying agricul

urban areas. The Central Nebraska Basins Study Unit team conducted one li

survey of 11 wells completed in the Platte River alluvial aquifer, a shallow a

underlying an agricultural area. Summary scores were computed for each

characteristic for the Platte River alluvial aquifer and compared with scores 

aquifers and shallow ground-water areas sampled in the 20 NAWQA Study U

during 1992–95. This comparison provides a ranking of aquifers and shallow

ground-water areas relative to national water-quality conditions. Results are

summarized by national percentiles; higher percentile values generally indic

poorer quality compared with other NAWQA ground-water studies. Water-q

conditions in the alluvial aquifer also are compared to established standards 

criteria for protection of drinking water. Methods used to compute rankings 

evaluate standards and criteria are described by Gilliom and others [37].

Comparison of Central Nebraska Basins Study Unit Ground-Water Results with Nationwid

NAWQA Findings

NUTRIENTS in ground water

The median nitrate concentration in the Platte

River alluvial aquifer was among the highest

when compared with the other NAWQA Study

Units. Fertilizer is the principal source of the

nutrients. Nitrate in ground water is a concern in

some parts of the Study Unit, especially in areas

having a shallow water table, sandy soils, and

intense row-crop production. Nitrate concentrations commonly exceed USEPA’s MCL of

10 mg/L for drinking water in these areas.

EXPLANATION

Ranking relative to national

conditions—Darker colored circles generally

indicate poorer quality. Bold outline indicates

one or more drinking-water standards or

criteria were exceeded.

Greater than the 75th percentile

(Among the highest 25 percent nationally)

Between the median and the 75th percentile

Between the 25th percentile and the median

Less than the 25th percentile

(Among the lowest 25 percent nationally)

Insufficient data for analysis

Platte River alluvial aquifer

DISSOLVED SOLIDS in ground water

The median dissolve- solids concentration in the

Platte River alluvial aquifer was in the highest

25 percent of all sites when compared to the other

Study Units.

Central Nebraska Basins Study Unit

White areas indicate other NAWQA

Study Units sampled during 1992–95.
U.S. Geological Survey Circular 116

WATER-QUALITY CONDITIONS IN A NATIONAL CON

The Platte River alluvial aquifer scored among

the highest 25 percent nationally for percent

detections of pesticides. Pesticides were detected

in 100 percent of the ground-water samples;

however, no concentrations exceeded the

USEPA’s MCLs or HALs for drinking water.

Pesticides are used extensively for weed control

in row-crop production, and some of the

compounds percolate to the ground water. This

occurs primarily in areas with permeable sandy

soils and shallow ground water.

The median volatile organic compound (VOC) concentration 

the ground water of the Platte River alluvial aquifer was amo

the lowest when compared with the other Study Units; howe

the findings are represented by a limited number of samples. 

VOC concentrations in water in the alluvial aquifer were all

below the detection limit. Urban and industrial land use is m

compared to agricultural land use, limiting both the sources 

quantities of potential VOCs that could enter the ground wat

CONCLUSIONS

In the Platte River alluvial aquifer, compared to other NAWQA Study Units:

Nitrate concentrations in ground water

exceeded the USEPA’s MCL in areas with

shallow water tables, sandy soils, and

extensive row-crop production. Although

pesticides were detected frequently in

ground water, the concentrations

measured were well below the USEPA’s

MCLs or HALs.

RADON in ground water

Not enough samples for analysis.

PESTICIDES in ground water

VOLATILE ORGANIC COMPOUNDS in ground wate
20 Water Quality in the Central Nebraska Basins, Nebraska, 1992–95

STUDY DESIGN AND DATA COLLECTION

List of Basic Fixed and ecological sites

Site

number Site name Sitenumber Site name

1 Tri-County Canal 1.25 mi below diversion 5 Prairie Creek near Ovina

1A North Channel of Platte River at Brady 6 Shell Creek near Columbus

2 Dismal River near Thedford 7 Elkhorn River at Waterloo

3 Loup River at Palmer 8 Maple Creek near Nickerson

4 Platte River near Grand Island 9 Platte River at Louisville

Ground-Water Chemistry

The ground-water quality 

Platte River alluvial aquifer was 

on the basis of a small survey of 

supply and monitoring wells. Ele

wells provided water-chemistry 

describe the occurrence and distr

of chemical constituents in the P

River alluvial aquifer. Samples a

collected along ground-water flo

at a site near Gibbon, Nebraska, 

site near Grand Island, Nebraska

Wetland Chemistry and Ecology

The wetland water quality of the Central

Nebraska Study Unit was assessed using chemical,

physical, and biological evidence. A network of 31

permanent wetland sites provided water chemistry,

bedsediment chemistry, and ecological data for

determining the relation between land use and wetland water quality.

Stream Chemistry and Ecology

The stream-water quality of the

Central Nebraska Basins Study Unit was

assessed using chemical, physical, and

biological evidence. The network of nine

basic, intensive, and intensive prototype

fixed sites provided water-chemistry data

over a wide range of hydrologic conditions

and ecological data for assessing streamwater quality. Synoptic sampling provided

additional water chemistry, bed-sediment

chemistry, tissue chemistry, and ecological

data for increased spatial resolution of

specific constituents and ecological

investigations
U.S. Geological Survey Circular 116

STUDY DESIGN AND DATA COLL

Summary of data collection in the Central Nebraska River Basins Study Unit, 1992–95

Study

component What data were collected and why Types of sites sampled Numberof sites

Sampling freque

period

Stream Chemistry

Basic Fixed

Sites—

general water

quality

Major ions, organic carbon, suspended sediment,

organonitrogen herbicides, nutrients, and physical

parameters to describe spatial and temporal

variability.

Stream sites representing

cropland, rangeland, and a

mixture of land uses from

across the area.

9 Monthly plus flow-ba

(1993–94)

Intensive Fixed

Sites—

pesticides

Same as Basic Fixed Sites plus a suite of 82 pesticides to

characterize their seasonal distribution.

Subset of Basic Fixed Sites had

intensive agriculture and a

site at the basin outflow.

4 Monthly plus flow-ba

(1993–94)

Intensive

Prototype

Fixed Sites

Major ions, suspended sediment, nutrients, 46

pesticides, and physical parameters to determine

adequate sampling frequency of agriculture-related

compounds that enter streams in runoff.

A subset of the Intensive Fixed

Sites.

2 Six weeks of alternate

sampling plus one 

spring; four weekly 

early summer; and 

alternate-day samp

storm in summer (M

August 1992).

High flow

synoptic

studies

Organonitrogen herbicides, nutrients, suspended

sediment, and streamflow to describe the transport of

agriculture-related compounds during runoff.

Streams were sampled to

include most Basic Sites

from a variety of land uses.

10 Sampled up to seven t

the rise and fall of 

(1992–93)

Base flow

synoptic

studies

Organonitrogen herbicides, nutrients, and streamflow to

determine their concentrations at base-flow

conditions.

Streams sites were selected to

provide wide spatial

distribution.

28 Two times during the 

season (1994)

Stream Ecology

Contaminants in

bed sediments

and fish tissues

Streambed sediments for trace elements, polycyclic

aromatic hydrocarbons, and organic compounds; and

whole-fish composites for organic compounds and

fish liver composites for trace elements to determine

the presence and distribution of contaminants.

Basic Fixed Sites were

supplemented by stream sites

in spatially underrepresented areas.

16 (1992)

 8 (1993)

 5 (1994)

Once per year during 

Intensive

ecological

assessments

Fish, macroinvertebrates, and algae were sampled to

assess biological communities and to relate

community attributes to water quality. Stream habitat

also was described.

Basic Fixed Sites described in

the stream chemistry section

were sampled.

9 All sites once per yea

three sites again in 

Ground-Water Chemistry

Aquifer survey Major ions, nutrients, pesticides, trace elements, volatile

organic compounds, organic carbon, and

radionuclides to describe water quality of a heavily

used alluvial aquifer.

Shallow wells in the Platte

River alluvial aquifer were

sampled.

11 Once in 1995

Variation along

flow paths

Major ions, nutrients, pesticides, and age-dating

constituents in water samples to describe land-use

effects on surficial aquifers along ground-water flow

paths from areas of recharge beneath the land use to

discharge to a stream.

Wells were sampled at two flow

paths in the Platte Valley: one

in a wet meadow, near corn

production, and the other in a

public-supply wellfield in an

agricultural area.

61 wells

installed in

clusters at

two sites

Wet meadow flow pat

quarterly in 1994 a

1995; public-suppl

sampled three time

Special Studies

Ecological

synoptic study

Stream macroinvertebrate and algal samples were

collected and stream habitat features were measured

in conjunction with similar activities in the South

Platte River NAWQA Study Unit to describe

variability of streams in the plains environment.

Stream sites representing a

range of conditions in the

Great Plains were sampled.

12

(Central

Nebraska

Basins)

Once (August 1993)

Wetlands

synoptic—

water and bedsediment

chemistry

Water-column samples were collected and analyzed for

major ions, nutrients, organonitrogen herbicides, and

chlorophyll-a. Sediment samples were collected and

analyzed for nutrients and herbicides to provide

baseline information on wetland sediment chemistry.

At selected sites, water, sediment, and invertebrate

tissues were analyzed for trace elements.

Wetlands characteristic of

agricultural landscapes were

sampled in late spring

following herbicide

application and in late

summer.

31 May and August 1994

Wetlands

synoptic—

aquatic

communities

Sample and identify macroinvertebrates, aquatic plants,

and algae to provide baseline information on aquatic

communities in wetlands.

The same wetlands sampled for

chemical analysis were

sampled for biological

attributes.

31 May and August 1994
22 Water-Quality Assessment of the Central Nebraska Basins, Nebraska, 1992–95

SUMMARY OF COMPOUND DETECTIONS AND CONCENTRATIONS

Herbicide

(Trade or common

name)

Rate

of

detection b

Concentration, in μg/L

0.001 0.01 0.1 1 10 100 1,000

The following tables summarize data collected for NAWQA studies from 1992–95 by showing results for the Central Nebraska

Basins Study Unit compared to the NAWQA national range for each compound detected. The data were collected at a wide variety of

places and times. In order to represent the wide concentration ranges observed among Study Units, logarithmic scales are used to

emphasize the general magnitude of concentrations (such as 10, 100, or 1,000), rather than the precise number. The complete dataset

used to construct these tables is available upon request.

Concentrations of herbicides, insecticides, volatile organic compounds, and nutrients detected in ground and surface waters of the

Central Nebraska Basins Study Unit

[mg/L, milligrams per liter; μg/L, micrograms per liter; pCi/L, picocuries per liter; %, percent; <, less than; - -, not measured; trade names may vary]

EXPLANATION

Range of surface-water detections in all 20 Study Units

Detection in the Central Nebraska Basins Study Unit

Range of ground-water detections in all 20 Study Units

Drinking water standard or guideline a

Freshwater-chronic criterion for the protection of aquatic life a

Herbicide

(Trade or common

name)

Rate

of

detection b

Concentration, in μg/L

0.001 0.01 0.1 1 10 100 1,000

Napropamide

(Devrinol)

1%

0%

Pebulate (Tillam) <1%

0%

Pendimethalin

(Prowl, Stomp)

37%

0%

Prometon (Gesagram, Pramitol)

69%

29%

Propachlor (Ramrod,

propachlore)

32%

0%

Propanil (Stampede,

Surcopur)

<1%

0%

Simazine (Aquazine,

Princep, Weedex)

64%

14%

Tebuthiuron (Spike,

Perflan)

12%

14%

Terbacilc (Sinbar) 3%

0%

Trifluralin (Treflan,

Trinin, Elancolan)

20%

0%

Insecticide

(Trade or common

name)

Rate

of

detection b

Concentration, in μg/L

Azinphos-methylc

(Guthion, Gusathion)

<1%

0%

Carbarylc (Sevin,

Savit)

7%

0%

Carbofuranc

(Furadan)

22%

0%

Chlorpyrifos (Dursban, Lorsban)

24%

0%

0.001 0.01 0.1 1 10 100 1,000

Acetochlor --

5%

Alachlor (Lasso) 78%

5%

2,6-Diethylaniline

(Alachlor metabolite)

3%

0%

Atrazine (AAtrex,

Gesaprim)

100%

81%

Deethylatrazinec

(Atrazine metabolite)

78%

76%

Bentazon (Basagran,

bentazone)

2%

--

Bromoxynil (Buctril,

Brominal, Torch)

4%

--

Butylate (Sutan,

Genate Plus, butilate)

1%

0%

Cyanazine (Bladex,

Fortrol)

91%

5%

2,4-D (2,4-PA) 8%

--

DCPA (Dacthal, chlorthal-dimethyl)

<1%

0%

Dinoseb (DNBP,

Dinitro, dinosebe)

2%

--

EPTC (Eptam) 6%

0%

Ethalfluralin (Sonalan,Sonalen)

<1%

0%

Metolachlor (Dual,

Pennant)

93%

5%

Metribuzin (Lexone,

Sencor)

25%

0%
U.S. Geological Survey Circular 1163 23

SUMMARY OF COMPOUND DETECTIONS AND CONCENTRATIONS

p,p’-DDE (p,p’-DDT

metabolite)

<1%

<1%

Diazinon 7%

0%

Dieldrin (Panoram D31, Octalox)

<1%

0%

Fonofos (Dyfonate) 22%

10%

alpha-HCH (alphaBHC, alpha-lindane)

<1%

0%

gamma-HCH <1%

0%

Malathion (maldison,

malathon, Cythion)

4%

0%

Methyl parathion 1%

0%

Parathion (Thiophos,

Bladan, Folidol)

1%

0%

cis-Permethrinc

(Ambush, Pounce)

<1%

0%

Propargite (Comite,

Omite, BPPS)

<1%

0%

Terbufos (Counter) 2%

0%

Nutrient Rate

of

detection b

Concentration, in mg/L

Dissolved ammonia 96%

49%

Dissolved ammonia

plus organic nitrogen

as nitrogen

95%

43%

Dissolved phosphorus as phosphorus

98%

95%

Dissolved nitrite plus

nitrate

86%

93%

0.01 0.1 1 10 100 1,000 10,000 100,000

Insecticide

(Trade or common

name)

Rate

of

detection b

Concentration, in μg/L

0.001 0.01 0.1 1 10 100 1,000

Insecticide

(Trade or common

name)

Rate

of

detection b

Concentration, in μg/L

0.001 0.01 0.1 1 10 100 1,000

Concentrations of herbicides, insecticides, volatile organic compounds, and nutrients detected in ground and surface waters of the Central

Nebraska Basins Study Unit—Continued
24 Water-Quality Assessment of the Central Nebraska Basins, Nebraska, 1992–95

SUMMARY OF COMPOUND DETECTIONS AND CONCENTRATIONS

Herbicides, insecticides, volatile organic compounds, and nutrients not detected in ground and surface waters of the Central Nebraska

Basins Study Unit

Herbicides

2,4,5-T

2,4,5-TP (Silvex, Fenoprop)

2,4-DB (Butyrac, Butoxone, Embutox Plus, Embutone)

Acifluorfen (Blazer, Tackle

2S)

Benfluralin (Balan, Benefin,

Bonalan, Benefex)

Bromacil (Hyvar X, Urox

B, Bromax)

Chloramben (Amiben,

Amilon-WP, Vegiben)

Clopyralid (Stinger, Lontrel, Reclaim, Transline)

Dacthal mono-acid (Dacthal

metabolite)

Dicamba (Banvel, Dianat,

Scotts Proturf)

Dichlorprop (2,4-DP, Seritox 50, Kildip, Lentemul)

Diuron (Crisuron, Karmex,

Direx, Diurex)

Fenuron (Fenulon, Fenidim)

Fluometuron (Flo-Met,

Cotoran, Meturon)

Linuron (Lorox, Linex, Sarclex, Linurex, Afalon)

MCPA (Rhomene, Rhonox,

Chiptox)

MCPB (Thistrol)

Molinate (Ordram)

Neburon (Neburea, Neburyl, Noruben)

Norflurazon (Evital, Predict, Solicam, Zorial)

Oryzalin (Surflan, Dirimal)

Picloram (Grazon, Tordon)

Pronamide (Kerb, Propyzamid)

Propham (Tuberite)

Thiobencarb (Bolero, Saturn, Benthiocarb, Abolish)

Triallate (Far-Go, Avadex

BW, Tri-allate)

Triclopyr (Garlon, Grandstand, Redeem, Remedy)

Insecticides

3-Hydroxycarbofuran (Carbofuran metabolite)

Aldicarb sulfone (Standak,

aldoxycarb, aldicarb metabolite)

Aldicarb sulfoxide (Aldicarb metabolite)

Aldicarb (Temik, Ambush,

Pounce)

Disulfoton (Disyston, DiSyston, Frumin AL,

Solvirex, Ethylthiodemeton)

Ethoprop (Mocap, Ethoprophos)

Methiocarb (Slug-Geta,

Grandslam, Mesurol)

Methomyl (Lanox, Lannate, Acinate)

Oxamyl (Vydate L, Pratt)

Phorate (Thimet, Granutox,

Geomet, Rampart)

Propoxur (Baygon, Blattanex, Unden, Proprotox)

2,2-Dichloropropane

Benzene

Bromobenzene (Phenyl

bromide)

Bromochloromethane

(Methylene chlorobromide)

Bromomethane (Methyl

bromide)

Chlorobenzene

(Monochlorobenzene)

Chloroethane (Ethyl chloride)

Chloroethene (Vinyl chloride)

Chloromethane (Methyl

chloride)

Dibromomethane (Methylene dibromide)

Dichlorodifluoromethane

(CFC 12, Freon 12)

Dichloromethane (Methylene chloride)

Dimethylbenzenes

(Xylenes (total))

Ethenylbenzene (Styrene)

Ethylbenzene (Phenylethane)

Isopropylbenzene

(Cumene)

Methyl tert-butyl etherd

(MTBE)

Methylbenzene (Toluene)

Tetrachloroethene (Perchloroethene)

Tetrachloromethane (Carbon tetrachloride)

Volatile organic

compounds

1,1,1,2-Tetrachloroethane

(1,1,1,2-TeCA)

1,1,1-Trichloroethane

(Methylchloroform)

1,1,2,2-Tetrachloroethane

1,1,2-Trichloro-1,2,2-trifluoroethane (Freon 113,

CFC 113)

1,1,2-Trichloroethane

(Vinyl trichloride)

1,1-Dichloroethane (Ethylidene dichloride)

1,1-Dichloroethene

(Vinylidene chloride)

1,1-Dichloropropene

1,2,3-Trichlorobenzene

(1,2,3-TCB)

1,2,3-Trichloropropane

(Allyl trichloride)

1,2,4-Trimethylbenzene

(Pseudocumene)

1,2-Dibromo-3-chloropropane (DBCP, Nemagon)

1,2-Dibromoethane (EDB,

Ethylene dibromide)

1,2-Dichloroethane (Ethylene dichloride)

1,2-Dichloropropane (Propylene dichloride)

1,3,5-Trimethylbenzene

(Mesitylene)

1,3-Dichloropropane (Trimethylene dichloride)

1-Chloro-2-methylbenzene (o-Chlorotoluene)

1-Chloro-4-methylbenzene (p-Chlorotoluene)

Total Trihalomethanes

(Trichloromethane (Chloroform), Dibromochloromethane,

Bromodichloromethane,

Tribromomethane (Bromoform))

Trichloroethene (TCE)

Trichlorofluoromethane

(CFC 11, Freon 11)

cis-1,2-Dichloroethene

((Z)-1,2-Dichloroethene)

cis-1,3-Dichloropropene

((Z)-1,3-Dichloropropene)

n-Butylbenzene (1-Phenylbutane)

n-Propylbenzene (Isocumene)

p-Isopropyltoluene (pCymene)

sec-Butylbenzene

tert-Butylbenzene

trans-1,2-Dichloroethene

((E)-1,2-Dichlorothene)

trans-1,3-Dichloropropene

((E)-1,3-Dichloropropene)

Nutrients

No non-detects
U.S. Geological Survey Circular 1163 25

SUMMARY OF COMPOUND DETECTIONS AND CONCENTRATIONS

1-Methylphenanthrene

--

7%

1-Methylpyrene --

7%

2,6-Dimethylnaphthalene

--

93%

2-Methylanthracene --

10%

3,5-Dimethylphenol --

7%

4,5-Methylenephenanthrene

--

10%

9H-Carbazole --

3%

9H-Fluorene --

7%

Acenaphthene --

3%

Acenaphthylene --

13%

Anthracene --

17%

Anthraquinone --

14%

Benz[ a ]anthracene --

27%

Benzo[ a ]pyrene --

20%

Benzo[ b ]fluoranthene

--

37%

Benzo[ ghi ]perylene --

7%

Benzo[ k ]fluoranthene

--

37%

Concentrations of semivolatile organic compounds, organochlorine compounds, and trace elements detected in fish tissue and bed

sediment of the Central Nebraska Basins Study Unit

[μg/g, micrograms per gram; μg/kg, micrograms per kilogram; %, percent; <, less than; - -, not measured; trade names may vary]

EXPLANATION

Range of detections in fish and clam tissue in all 20 Study Units

Detection in bed sediment or fish tissue in the Central Nebraska Basins Study Unit

Range of detections in bed sediment in all 20 Study Units

Guideline for the protection of aquatic life e

Semivolatile

organic compound

Rate of

detection b

Concentration, in μg/kg

0.1 10 100 1,000 10,000 100,000 1

Semivolatile

organic compound

Rate of

detection b

Concentration, in μg/kg

0.1 10 100 1,000 10,000 100,000 1

Butylbenzylphthalate --

40%

Chrysene --

33%

Di- n -butylphthalate --

93%

Di- n -octylphthalate --

13%

Dibenzothiophene --

3%

Diethylphthalate --

30%

Dimethylphthalate --

7%

Fluoranthene --

69%

Indeno[1,2,3- cd ]

pyrene

--

10%

Isoquinoline --

13%

Naphthalene --

3%

Phenanthrene --

27%

Phenol --

87%

Pyrene --

55%

Quinoline --

7%

bis(2-Ethylhexyl)phthalate

--

93%

p-Cresol --

67%
26 Water-Quality Assessment of the Central Nebraska Basins, Nebraska, 1992–95

SUMMARY OF COMPOUND DETECTIONS AND CONCENTRATIONS

total-Chlordane 34%

7%

p,p’-DDE 89%

3%

total-DDT 89%

3%

Dieldrin 54%

7%

Heptachlor epoxide 20%

0%

PCB, total 29%

0%

Arsenic 90%

100%

Cadmium 100%

100%

Chromium 57%

100%

Copper 100%

100%

Lead 55%

100%

Mercury 71%

34%

Nickel 48%

100%

Selenium 100%

100%

Zinc 100%

100%

Organochlorine

compound

(Trade name)

Rate

of

detection b

Concentration, in μg/kg

0.01 0.1 1 10 100 1,000 10,000 100,000

Trace element Rate

of

detection b

Concentration, in μg/g

0.01 0.1 1 10 100 1,000 10,000

Concentrations of semivolatile organic compounds, organochlorine compounds, and trace elements detected in fish tissue and bed

sediment of the Central Nebraska Basins Study Unit—Continued
U.S. Geological Survey Circular 1163 27

SUMMARY OF COMPOUND DETECTIONS AND CONCENTRATIONS

Semivolatile organic compounds, organochlorine compounds, and trace elements not detected in fish tissue and bed sediment of the

Central Nebraska Basins Study Unit

Semivolatile

organic

compounds

1,2,4-Trichlorobenzene

1,2-Dichlorobenzene (oDichlorobenzene, 1,2-

DCB)

1,2-Dimethylnaphthalene

1,3-Dichlorobenzene (mDichlorobenzene)

1,4-Dichlorobenzene (pDichlorobenzene, 1,4-

DCB)

1,6-Dimethylnaphthalene

1-Methyl-9H-fluorene

2,2-Biquinoline

2,3,6-Trimethylnaphthalene

2,4-Dinitrotoluene

2,6-Dinitrotoluene

2-Chloronaphthalene

2-Chlorophenol

2-Ethylnaphthalene

4-Bromophenylphenylether

4-Chloro-3-methylphenol

4-Chlorophenyl-phenylether

Acridine

Azobenzene

Benzo [c] cinnoline

C8-Alkylphenol

Dibenz [a,h] anthracene

Isophorone

N-Nitrosodi-n-propylamine

N-Nitrosodiphenylamine

Nitrobenzene

Pentachloronitrobenzene

Phenanthridine

bis (2-Chloroethoxy)methane

Organochlorine

compounds

Aldrin (HHDN, Octalene)

Chloroneb (chloronebe,

Demosan, Soil Fungicide

1823)

DCPA (Dacthal, chlorthaldimethyl)

Endosulfan I (alphaEndosulfan, Thiodan,

Cyclodan, Beosit, Malix,

Thimul, Thifor)

Endrin (Endrine)

Heptachlor (Heptachlore,

Velsicol 104)

Hexachlorobenzene (HCB)

Isodrin (Isodrine, Compound 711)

Mirex (Dechlorane)

Pentachloroanisole (PCA,

pentachlorophenol metabolite)

Total Trihalomethanes

(Trichloromethane (Chloroform), Dibromochloromethane,

Bromodichloromethane,

Tribromomethane (Bromoform))

Toxaphene (Camphechlor,

Hercules 3956)

alpha-HCH (alpha-BHC,

alpha-lindane, alphahexachlorocyclohexane,

alpha-benzene hexachloride)

beta-HCH (beta-BHC,

beta-hexachlorocyclohexane, alpha-benzene

hexachloride)

cis-Permethrin (Ambush,

Astro, Pounce, Pramex,

Pertox, Ambushfog, Kafil,

Perthrine, Picket, Picket

G, Dragnet, Talcord, Outflank, Stockade, Eksmin,

Coopex, Peregin, Stomoxin, Stomoxin P, Qamlin, Corsair, Tornade)

delta-HCH (delta-BHC,

delta-hexachlorocyclohexane, delta-benzene

hexachloride)

gamma-HCH (Lindane,

gamma-BHC, Gammexane, Gexane, Soprocide,

gamma-hexachlorocyclohexane, gamma-benzene

hexachloride, gammabenzene)

o,p’-Methoxychlor

p,p’-Methoxychlor

(Marlate, methoxychlore)

trans-Permethrin

(Ambush, Astro, Pounce,

Pramex, Pertox, Ambushfog, Kafil, Perthrine,

Picket, Picket G, Dragnet,

Talcord, Outflank, Stockade, Eksmin, Coopex, Peregin, Stomoxin, Stomoxin

P, Qamlin, Corsair, Tornade)

Trace elements

No non-detects

a

 Selected water-quality standards and guidelines [37].

b Rates of detection are based on the number of analyses and detections in the Study Unit, not on national data. Rates of detection for herbicides and insecticides were computed by only counting detections equal to or greater than 0.01 μg/L in order to facilitate equal comparisons among compounds, which had widely varying detection limits. For herbicides and insecticides, a detection rate of “<1%” means that

all detections are less than 0.01 μg/L, or the detection rate rounds to less than one percent. For other compound groups, all detections were

counted and minimum detection limits for most compounds were similar to the lower end of the national ranges shown. Method detection

limits for all compounds in these tables are summarized in [37]. c

 Detections of these compounds are reliable, but concentrations are determined with greater uncertainty than for the other compounds and are

reported as estimated values [38].

d The guideline for methyl tert-butyl ether is between 20 and 40 μg/L; if the tentative cancer classification C is accepted, the lifetime health

advisory will be 20 μg/L [37]. e

 Selected sediment-quality guidelines [37].

Summary of Compound Detections and Concentrations tables were designed and built by Sarah Ryker, Jonathon Scott, and Alan Haggland,

U.S. Geological Survey.
28 Water-Quality Assessment of the Central Nebraska Basins, Nebraska, 1992–95

REFERENCES

* Central Nebraska Basins NAWQA

products

1. *Huntzinger, T.L., and Ellis, M.J.,

1993, Central Nebraska river

basins, Nebraska: Water

Resources Bulletin, v. 29, no. 4,

p. 533–574.

2. *Stamer, J.K., Swanson, R.B., and

Jordan, P.R., 1994, Atrazine in

spring runoff as related to environmental setting in Nebraska, 1992:

Water Resources Bulletin, v. 30,

no. 5, p. 823–831.

3. U.S. Environmental Protection

Agency, 1996, Drinking water

regulations and health advisories:

Washington, D.C., U.S. Environmental Protection Agency, EPA

822–B–96–002, 11 p.

4. *Helgesen, J.O., Zelt, R.B., and

Stamer, J.K., 1994, Nitrogen and

phosphorus in water as related to

environmental setting in

Nebraska: Water Resources Bulletin, v. 30, no. 5, p. 809–822.

5. *Boyd, R.A., 1996, Distribution of

nitrate and orthophosphate in

selected streams in central

Nebraska: Water Resources

Bulletin, v. 32, no. 6, p. 1247–

1257.

6. Druliner, A.D., Chen, H.H., and

McGrath, T.S., 1995, Relations of

nonpoint-source nitrate and

atrazine concentrations in the

High Plains aquifer to selected

explanatory variables in six

Nebraska study areas: U.S.

Geological Survey WaterResources Investigations

Report 95–4202, 51 p.

7. Central Nebraska Natural Resources

District, 1993, Groundwater quality management program—Groundwater quality

improvement for the Central

Platte Valley: Central Platte Natural Resources District Report,

16 p.

8. *Stamer, J.K., and Wieczorek, M.E.,

1995, Pesticides in streams in central Nebraska: U.S. Geological

Survey Fact Sheet FS–232–95,

4 p.

9. *Stamer, J.K., 1996, Water-supply

implications of herbicide sampling: Journal of the American

Water Works Association, v. 88,

no. 2, p. 76–85.

10. *Stamer, J.K., and Huntzinger,

T.L., 1994, Spring herbicide

“flush” may deal cities a problem:

Nebraska Farmer, v. 136, no. 8,

p. 10–11, 13.

11. Stamer, J.K., and Wieczorek, M.E.,

1996, Pesticide distributions in

surface water: Journal of American Water Works Association,

v. 88, no. 11, p. 79-87.

12. *Stamer, J.K., and Zelt, R.B., in

press, Estimating herbicide flux in

streams using a nonparametric

approach: Journal of Environmental Quality.

13. *Huntzinger, T.L., and Stamer,

J.K., 1995, Herbicides and nitrates

in water supply sources in central

Nebraska, in Clean Water—Clean

Environment—21st Century, Kansas City, Mo., 1995, Proceedings,

v. 3: St. Joseph, Mich., American

Society of Agricultural Engineers, p. 149–152.

14. Nebraska Natural Resources Commission, 1994, Estimated water

use in Nebraska, 1990: Lincoln,

Nebr., Natural Resources Commission, 58 p.

15. McGuire, V.L., and Kilpatrick,

J.M., 1998, Hydrogeology in the

vicinity of the Nebraska Management Systems Information Area

site, central Nebraska: U.S. Geological Survey Water-Resources

Investigations Report 97–4266,

26 p.

16. *Zelt, R.B., and Jordan, P.R

Water-quality assessment 

Central Nebraska Basins—

mary of data for recent co

through 1990: U.S. Geolo

Survey Open-File Report 

179 p.

17. *Emmons, P.J., 1996, Wat

quality in a wet meadow, 

River Valley, central Nebr

U.S. Geological Survey Fa

FS–097–96, 4 p.

18. Blum, D.A., Carr, J.D., Da

R.K., and Pederson, D.T., 

Atrazine in a stream-aquif

system—Transport of atra

its environmental impact n

Ashland, Nebraska: Groun

Monitoring and Remediat

v. 13, no. 2, p. 125–133.

19. Davis, R.K., Pederson, D.T

D.A., and Carr, J.D., 1993

Atrazine in a stream-aquif

system—Estimation of aq

properties from atrazine

concentration profiles: Gr

Water Monitoring and

Remediation, v. 13, no. 2, 

141.

20. *Frenzel, S.A., 1996, Occu

of selected contaminants i

fish tissue, and streambed 

ments in central Nebraska

95: U.S. Geological Surve

Open-File Report 96–223

21. Nowell, L.H., and Resek, E

1994, National standards 

guidelines for pesticides i

sediment, and aquatic org

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ity assessments, in Nation

Academy of Sciences and

National Academy of Eng

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U.S. Environmental Prote

Agency, U.S. Environmen

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R3-73-033.
U.S. Geological Survey Circular 1

REFER

22. *Frenzel, S.A., and Swanson, R.B.,

1996, Relations of fish community

composition to environmental

variables in central Nebraska

streams: Environmental Management, v. 20, no. 5, p. 689–705.

23. *Frankforter, J.D., 1995, Association between local land use and

herbicide concentrations in wetlands of the Platte River Basin,

Nebraska, in Campbell, K.L., ed.,

Versatility of wetlands in the agricultural landscape: American

Water Resources Association and

American Society of Agricultural

Engineers Joint Conference,

Tampa, Fla., 1995 [Proceedings],

p. 539–547.

24. Jenkins, Allan, 1993, Introduction,

in Jenkins, Allan, George, S.K.,

and Barrett, Elizabeth, eds., The

Platte River—An atlas of the Big

Bend region: Kearney, Nebr., University of Nebraska-Kearney,

p. 1–7.

25. *Zelt, R.B., and Frenzel, S.A.,

1996, Physical-habitat characteristics of the Platte River,

Nebraska—Assessment using surveys and spatial analyses: ESRI

User Conference, 16th, Palm

Springs, Calif., 1996 [Proceedings], compact disc.

26. *Zelt, R.B., 1996, Basin-level habitat characteristics of selected

streams in central Nebraska: U.S.

Geological Survey Open-File

Report 96–361, 25 p.

27. Williams, G.P., 1978, The case of

the shrinking channels—The

North Platte and Platte Rivers in

Nebraska: U.S. Geological Survey

Circular 781, 48 p.

28. Johnson, W.C., 1994, Woodland

expansion in the Platte River,

Nebraska—Patterns and causes:

Ecological Monographs, v. 64,

no. 1, February 1994, p. 45–84.

 29. _____1997, Equilibrium response

of riparian vegetation to flow regulation in the Platte River, in Proceedings of the 1997 Platte River

Basin Ecosystem Symposium,

Feb. 18 and 19, 1997, Kearney,

Nebraska: Lincoln, Nebr., 1997,

University of Nebraska Cooperative Extension-Platte Watershed

Program, p. 1997, Kearney,

Nebraska: Lincoln, Nebr., 1997,

University of Nebraska Cooperative Extension-Platte Watershed

Program.

30. Springer, Joseph, 1993, Tradition

of the sandhill cranes, in Jenkins,

Allan, George, S.K., and Barrett,

Elizabeth, eds., The Platte

River—An atlas of the Big Bend

region: Kearney, Nebr., University

of Nebraska-Kearney, p. 44–51.

31. Krapu, G.L., Facey, D.E., Fritzell,

E.K., and Johnson, D.H., 1984,

Habitat use by migrant sandhill

cranes in Nebraska: Journal of

Wildlife Management, v. 48,

no. 2, p. 407–417.

32. Stutheit, 1988, Work plan S–97—

mortality and disease investigations: Nebraska Game and Parks

Commission, W–15–R–44, 23 p.

33. Johnson, R.E., 1942, The distribution of Nebraska fishes: Ann

Arbor, Mich., Ph.D. dissertation,

University of Michigan, 152 p.

34. Goldowitz, E.S., 1997, Long term

changes in the fish fauna of the

Platte River—A comparative

study, in Proceedings of the 1997

Platte River Basin Ecosystem

Symposium, February 18 and 19,

1997, Kearney, Nebraska: Lincoln, Nebr., 1997, University of

Nebraska Cooperative ExtensionPlatte Watershed Program, p. 97.

35. Tabor, V.M., 1993, Declining fishes

characteristics of the central Great

Plains: Manhattan, Kans., U.S.

Fish and Wildlife Service, 11 p.

36. Lee, D.S., Gilbert, C.R., H

C.H., Jenkins, R.E., McA

D.E., and Stauffer, J.R., 1

Atlas of North American 

ter fishes: Raleigh, N.C., N

Carolina State Museum of 

History, 854 p.

37. Gilliom, R.J., Mueller, D.K

Nowell, L.H., in press, M

for comparing water-qual

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Quality Assessment Study 

1992–95: U.S. Geological 

Open-File Report 97–589

38. Zaugg, S.D., Sandstrom, M

Smith, S.G., and Fehlberg

1995, Methods of analysi

U.S. Geological Survey N

Water Quality Laboratory—Determination of p

cides in water by C-18 sol

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gas chromatography/mass 

trometry with selected-ion 

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Open-File Report 95–181
30 Water-Quality Assessment of the Central Nebraska Basins, Nebraska, 1992–95

GLOSSARY

The terms in this glossary were compiled from numerous sources. Some

definitions have been modified and

may not be the only valid ones for

these terms.

Acre-foot - A volume of water equal to 1

foot in depth and covering 1 acre;

equivalent to 43,560 cubic feet or

325,851 gallons.

Algae - Chlorophyll-bearing nonvascular,

primarily aquatic species that have no

true roots, stems, or leaves; most

algae are microscopic, but some

species can be as large as vascular

plants.

Alluvial aquifer - A water-bearing deposit

of unconsolidated material (sand and

gravel) left behind by a river or other

flowing water.

Ammonia - A compound of nitrogen and

hydrogen (NH3) that is a common byproduct of animal waste. Ammonia

readily converts to nitrate in soils and

streams.

Aquifer - A water-bearing layer of soil,

sand, gravel, or rock that will yield

usable quantities of water to a well.

Background concentration - A

concentration of a substance in a

particular environment that is

indicative of minimal influence by

human (anthropogenic) sources.

Bank - The sloping ground that borders a

stream and confines the water in the

natural channel when the water level,

or flow is normal.

Basic Fixed Sites - Sites on streams at

which streamflow is measured and

samples are collected for

temperature, salinity, suspended

sediment, major ions and metals,

nutrients, and organic carbon to

assess the broad-scale spatial and

temporal character and transport of

inorganic constituents of streamwater

in relation to hydrologic conditions

and environmental settings.

Basin -See Drainage basin.

Bed sediment - The material that

temporarily is stationary in the

bottom of a stream or other

watercourse.

Bed sediment and tissue studies -

Assessment of concentrations and

distributions of trace elements and

hydrophobic organic contaminants in

streambed sediment and tissues of

aquatic organisms to identify

potential sources and to assess spatial

distribution.

Benthic - Refers to plants or animals that

live on the bottom of lakes, streams,

or oceans.

Benthic invertebrates - Insects, mollusks,

crustaceans, worms, and other

organisms without a backbone that

live in, on, or near the bottom of

lakes, streams, or oceans.

Best Management Practice (BMP) - An

agricultural practice that has been

determined to be an effective,

practical means of preventing or

reducing nonpoint-source pollution.

Biota - Living organisms.

Community - In ecology, the species that

interact in a common area.

Concentration - The amount or mass of a

substance present in a given volume

or mass of sample. Usually expressed

as microgram per liter (water sample)

or micrograms per kilogram

(sediment or tissue sample).

Confined aquifer (artesian aquifer) - An

aquifer that is completely filled with

water under pressure and that is

overlain by material that restricts the

movement of water.

Confluence - The flowing together of two

or more streams; the place where a

tributary joins the main stream.

Constituent - A chemical or biological

substance in water, sediment, or biota

that can be measured by an analytical

method.

Cubic foot per second (ft3

/s, or cfs) - Rate

of water discharge representing a

volume of 1 cubic foot passing a

given point during 1 second,

equivalent to approximately 7.48

gallons per second or 448.8 gallons

per minute or 0.02832 cubic meter

per second.

Degradation products - Compou

resulting from transformatio

organic substance through c

photochemical, and/or bioch

reactions.

Detection limit - The concentrati

which a particular analytical 

cannot determine, with a hig

of certainty, a concentration

DDT - Dichloro-diphenyl-trichlor

An organochlorine insectici

longer registered for use in th

States.

Dieldrin - An organochlorine ins

no longer registered for use 

United States. Also a degrad

product of the insecticide al

Discharge - Rate of fluid flow pa

given point at a given mome

time, expressed as volume p

time.

Dissolved constituent - Operatio

defined as a constituent that 

through a 0.45-micrometer fi

Dissolved solids - Amount of min

such as salt, that are dissolv

water; amount of dissolved 

an indicator of salinity or ha

Diversion - A turning aside or alte

the natural course of a flow 

normally considered physica

leave the natural channel. In 

States, this can be a consum

direct from another stream, 

by livestock watering. In oth

a diversion must consist of s

actions as taking water throu

canal, pipe, or conduit.

Drainage basin - The portion of 

surface of the Earth that con

water to a stream through ov

runoff, including tributaries 

impoundments.

Drinking-water standard or gui

A threshold concentration in 

drinking-water supply, desig

protect human health. As de

here, standards are U.S. Env

mental Protection Agency re

that specify the maximum co

tion levels for public water s

required to protect the public 

guidelines have no regulator

and are issued in an advisory

capacity.
U.S. Geological Survey Circular 1

GLO

Environmental setting - Land area

characterized by a unique

combination of natural and humanrelated factors, such as row-crop

cultivation or glacial-till soils.

Fecal bacteria - Microscopic single-celled

organisms (primarily fecal coliforms

and fecal streptococci) found in the

wastes of warm-blooded animals.

Their presence in water is used to

assess the sanitary quality of water

for body-contact recreation or for

consumption. Their presence

indicates contamination by the wastes

of warm-blooded animals and the

possible presence of pathogenic

(disease-producing) organisms.

Fertilizer - Any of a large number of

natural or synthetic materials,

including manure and nitrogen,

phosphorus, and potassium

compounds, spread on or worked into

soil to increase its fertility.

Fish community - See Community.

Fixed Sites - NAWQA's most

comprehensive monitoring sites. See

also Basic Fixed Sites and Intensive

Fixed Sites.

Flood - Any relatively high streamflow that

overtops the natural or artificial banks

of a stream.

Flood plain - The relatively level area of

land bordering a stream channel and

inundated during moderate to severe

floods.

Flow path - An underground route for

ground-water movement, extending

from a recharge (intake) zone to a

discharge (output) zone such as a

shallow stream.

Fungicide - A substance or mixture of

substances intended for the purpose

of killing undesirable fungi.

Ground water - In general, any water that

exists beneath the land surface, but

more commonly applied to water in

fully saturated soils and geologic

formations.

Habitat - The part of the physical

environment where plants and

animals live.

Health advisory levels (HALs) -

Nonregulatory levels of contaminants

in drinking water that may be used as

guidance in the absence of regulatory

limits. Advisories consist of estimates

of concentrations that would result in

no known or anticipated health

effects (for carcinogens, a specified

cancer risk) determined for a child or

for an adult for various exposure

periods.

Herbicide - A chemical or other agent

applied for the purpose of killing

undesirable plants. See also Pesticide.

Index of Biotic Integrity (IBI) - An

aggregated number, or index, based

on several attributes or metrics of a

fish community that provides an

assessment of biological conditions.

Infiltration - Movement of water, typically

downward, into soil or porous rock.

Insecticide - A substance or mixture of

substances intended to destroy or

repel insects.

Intensive Fixed Sites - Basic Fixed Sites

with increased sampling frequency

during selected seasonal periods and

analysis of dissolved pesticides for 1

year. Most NAWQA Study Units

have one to two integrator Intensive

Fixed Sites and one to four indicator

Intensive Fixed Sites.

Intolerant organisms - Organisms that are

not adaptable to human alterations to

the environment and thus decline in

numbers where human alterations

occur. See also Tolerant species.

Invertebrate - An animal having no

backbone or spinal column. See also

Benthic invertebrate.

Land-use study - A network of existing

shallow wells in an area having a

relatively uniform land use. These

studies are a subset of the Study-Unit

Survey and have the goal of relating

the quality of shallow ground water to

land use. See also Study-Unit Survey.

Loess - Homogeneous, fine-grained

sediment made up primarily of silt

and clay, and deposited over a wide

area (probably by wind).

Macroinvertebrate - An animal t

large enough to be seen with

magnification and has no bac

spinal column. See Inverteb

Main stem - The principal course 

or a stream.

Major ions - Constituents commo

present in concentrations ex

1.0 milligram per liter. Disso

cations generally are calcium

magnesium, sodium, and po

the major anions are sulfate, 

fluoride, nitrate, and those

contributing to alkalinity, m

generally assumed to be bic

and carbonate.

Maximum contaminant level (M

Maximum permissible level 

contaminant in water that is 

to any user of a public water 

MCLs are enforceable stand

established by the U.S. Envi

mental Protection Agency.

Mean - The average of a set of

observations, unless otherwi

specified.

Median - The middle or central v

distribution of data ranked in 

magnitude. The median is al

as the 50th percentile.

Method detection limit - The mi

concentration of a substance 

be accurately identified and m

with present laboratory tech

Micrograms per liter (μg/L) - A 

expressing the concentration 

constituents in solution as w

(micrograms) of solute per u

volume (liter) of water; equi

one part per billion in most

streamwater and ground wat

thousand micrograms per lit

1 mg/L.

Milligrams per liter (mg/L) - A 

expressing the concentration 

chemical constituents in solu

weight (milligrams) of solut

volume (liter) of water; equi

one part per million in most 

water and ground water. On

thousand micrograms per lit

1 mg/L.
32 Water-Quality Assessment of the Central Nebraska Basins, Nebraska, 1992–95

GLOSSARY

Minimum reporting level (MRL) - The

smallest measured concentration of a

constituent that may be reliably

reported using a given analytical

method. In many cases, the MRL is

used when documentation for the

method detection limit is not

available.

National Academy of Sciences/National

Academy of Engineering

(NAS/NAE) recommended

maximum concentration in water -

Numerical guidelines recommended

by two joint NAS/NAE committees

for the protection of freshwater and

marine aquatic life, respectively.

These guidelines were based on

available aquatic toxicity studies, and

were considered preliminary even at

the time (1972). The guidelines used

in the summary reports are for

freshwater.

Natural Resources Districts (NRDs) -

Local districts created in 1969 by the

Nebraska legislature and charged

with properly conserving and

developing the State of Nebraska’s

natural resources. The NRDs’

boundaries were established

primarily in accordance with

Nebraska’s natural river basin

boundaries. The activities of the 23

NRDs include the management of

surface-water and ground-water

resources, the construction and

operation of flood-control structures,

and the administration of landmanagement plans to prevent soil

erosion and sediment problems. The

NRDs also have some responsibility

for drainage and stream-channel

improvement, forestry and range

management, management of fish and

wildlife habitat, recreational and park

facility management, and solid waste

disposal and sanitary drainage.

Nitrate - An ion consisting of nitrogen and

oxygen (NO3

-

). Nitrate is a plant

nutrient and is very mobile in soils.

Nonpoint source - A pollution source that

cannot be defined as originating from

discrete points such as pipe

discharge. Areas of fertilizer and

pesticide applications, atmospheric

deposition, manure, and natural

inputs from plants and trees are types

of nonpoint-source pollution.

Nutrient - Element or compound essential

for animal and plant growth.

Common nutrients in fertilizer

include nitrogen, phosphorus, and

potassium.

Organonitrogen herbicides - A group of

herbicides consisting of a nitrogen

ring with associated functional

groups and including such classes as

triazines and acetanilides. Examples

include atrazine, cyanazine, alachlor,

and metolachlor.

Organochlorine compound - Synthetic

organic compounds containing

chlorine. As generally used, term

refers to compounds containing

mostly or exclusively carbon,

hydrogen, and chlorine. Examples

include organochlorine insecticides,

polychlorinated biphenyls, and some

solvents containing chlorine.

Organochlorine insecticide - A class of

organic insecticides containing a high

percentage of chlorine. Includes

dichlorodiphenylethanes (such as

DDT), chlorinated cyclodienes (such

as chlordane), and chlorinated

benzenes (such as lindane). Most

organochlorine insecticides were

banned because of their

carcinogenicity, tendency to

bioaccumulate, and toxicity to

wildlife.

Organochlorine pesticide - See

Organochlorine insecticide.

Pesticide - A chemical applied to crops,

rights-of-way, lawns, or residences to

control weeds, insects, fungi,

nematodes, rodents or other "pests."

Picocurie (pCi) - One trillionth (10-12) of

the amount of radioactivity

represented by a curie (Ci). A curie is

the amount of radioactivity that yields

3.7 x 1010 radioactive disintegrations

per second (dps). A picocurie yields

2.22 disintegrations per minute (dpm)

or 0.037 dps.

Point source - A source at a discrete

location such as a discharge pipe,

drainage ditch, tunnel, well,

concentrated livestock operation, or

floating craft.

Point-source contaminant - Any

substance that degrades wate

and originates from discrete 

such as discharge pipes, dra

ditches, wells, concentrated 

operations, or floating craft.

Polychlorinated biphenyls (PCB

mixture of chlorinated deriv

biphenyl, marketed under th

name Aroclor with a numbe

designating the chlorine con

(such as Aroclor 1260). PCB

used in transformers and cap

for insulating purposes and 

pipeline systems as a lubrica

Further sale for new use was 

by law in 1979.

Polycyclic aromatic hydrocarbo

- A class of organic compou

a fused-ring aromatic structu

result from incomplete comb

organic carbon (including w

municipal solid waste, and f

fuels, as well as from natura

anthropogenic introduction 

uncombusted coal and oil. P

include benzo(a)pyrene, fluo

and pyrene.

Precipitation - Any or all forms o

particles that fall from the

atmosphere, such as rain, sn

and sleet.

Public-supply withdrawals - Wa

withdrawn by public and pri

water suppliers for use with

general community. Water is 

a variety of purposes such a

domestic, commercial, indus

public water use.

Recharge - Water that infiltrates t

ground and reaches the satu

zone.

Runoff - Excess rainwater or sno

that is transported to stream

overland flow, tile drains, or 

water.

Sediment - Particles, derived from 

biological materials, that hav

transported by a fluid or othe

process and are suspended o

in water.
U.S. Geological Survey Circular 1

GLO

Semivolatile organic compound (SVOC)

- Operationally defined as a group of

synthetic organic compounds that are

solvent-extractable and can be

determined by gas

chromatography/mass spectrometry.

SVOCs include phenols, phthalates,

and polycyclic aromatic

hydrocarbons (PAHs).

Species - Populations of organisms that

may interbreed and produce fertile

offspring having similar structure,

habits, and functions.

Stage - The height of the water surface

above an established datum plane,

such as in a river above a

predetermined point that may (or may

not) be near the channel floor.

Streamflow - A type of channel flow,

applied to that part of surface runoff

in a stream whether or not it is

affected by diversion or regulation.

Stream reach - A continuous part of a

stream between two specified points.

Study Unit - A major hydrologic system of

the United States in which NAWQA

studies are focused. Study Units are

geographically defined by a

combination of ground- and surfacewater features and generally

encompass more than 4,000 square

miles of land area.

Surface water - An open body of water,

such as a lake, river, or stream.

Suspended (as used in tables of chemical

analyses) - The amount

(concentration) of undissolved

material in a water-sediment mixture.

It is associated with the material

retained on a 0.45-micrometer filter.

Synoptic sites - Sites sampled during a

short-term investigation of specific

water-quality conditions during

selected seasonal or hydrologic

conditions to provide improved

spatial resolution for critical waterquality conditions.

Tolerant species - Those species that are

adaptable to (tolerant of) human

alterations to the environment.

Total concentration - Refers to the

concentration of a constituent

regardless of its form (dissolved or

bound) in a sample.

Trace element - An element found in only

minor amounts (concentrations less

than 1.0 milligram per liter) in water

or sediment; includes arsenic,

cadmium, chromium, copper, lead,

mercury, nickel, and zinc.

Tracer - A stable, easily detected

substance or a radioisotope added to a

material to follow the location of the

substance in the environment or to

detect any physical or chemical

changes it undergoes.

Unconfined aquifer - An aquifer whose

upper surface is a water table; an

aquifer containing unconfined ground

water.

Volatile organic compounds (VOCs) -

Organic chemicals that have a high

vapor pressure relative to their water

solubility. VOCs include components

of gasoline, fuel oils, and lubricants,

as well as organic solvents,

fumigants, some inert ingredients in

pesticides, and some by-products of

chlorine disinfection.

Watershed - See Drainage basin.

Wetlands - Ecosystems whose soil is

saturated for long periods seasonally

or continuously, including marshes,

swamps, and ephemeral ponds.
Frenzel and others • Water Quality in the Central Nebraska Basins

USGS Circular 1163 • 1998

IOWA

North Platte

Grand

Island Lincoln

Omaha North Platte R.

South Platte R.

Platte River

Platte River

Missouri River

North Loup River Middle Loup River

South Loup River

Dismal River

NEBRASKA

Elkhorn

C

River

ed ar River

National Water-Quality Assessment (NAWQA) Program

Central Nebraska Basins

NAWQA