A Framework for

ANALYZING the

HYDROLOGIC

CONDITION of

WATERSHEDS

U.S. Department of Agriculture

Forest Service

—June 1998—

U.S. Department of the Interior

Bureau of Land Management
Though this document was produced through an interagency effort, the following BLM numbers

have been assigned for tracking and administrative purposes:

BLM Technical Note 405

BLM/RS/ST-98/004+7210
A Framework for

ANALYZING the

HYDROLOGIC

CONDITION of

WATERSHEDS

—June 1998—

U.S. Department of Agriculture

Forest Service

by

Bruce McCammon

John Rector

Karl Gebhardt

U.S. Department of the Interior

Bureau of Land Management
A Framework for Analyzing the Hydrologic Condition of Watersheds i

Interagency coordination among the Forest

Service (FS), Bureau of Land Management (BLM),

and other agencies was essential to successful

completion of this guidance. The following

individuals participated on teams that developed

various portions of the information contained in

this document.

The core team was responsible for steering the

developmental phases of this guidance and for

overall coordination. The team consisted of:

Warren Harper . . . .FS

Ron Huntsinger . . . .BLM

Nancy Lopez . . . . . .U.S. Geological Survey

Larry Schmidt . . . . . .FS

Dan Muller . . . . . . . .BLM

Bruce McCammon . .FS

Karl Gebhardt . . . . .BLM

John Rector . . . . . . .FS

Keith McLaughlin . . .FS

Ervin Cowley . . . . . .BLM

Doug Ryan . . . . . . . .FS

Don Brady . . . . . . . .Environmental Protection

Agency

Jack Frost . . . . . . . . .Natural Resources

Conservation Service

The hydrometeorological protocols team was

responsible for developing national-scale basic

data presentation requirements. The team was

led by Keith McLaughlin and consisted of:

Dennis Murphy . . . .BLM

Dennis Kelly . . . . . .FS

Joe Frazier . . . . . . . .BLM

Mike Solomon . . . . .FS

Lee Chavez . . . . . . . .FS

Chester Novak . . . . .BLM

Mike Kuehn . . . . . . .FS

Jim Harte . . . . . . . . .BLM

Acknowledgments

The hydrologic condition protocols team was

responsible for developing the overall analytic

process. Initial team members faced an extremely

difficult task of developing an analytic approach

to be applied extensively throughout the

United States. The following individuals initially

consulted on this effort and were members of a

team led by John Rector:

Richard Burns . . . . .FS

Jim Fogg . . . . . . . . . .BLM

Leslie Reid . . . . . . . .FS

Chris Knopp . . . . . . .FS

Bruce Zander . . . . . .Environmental Protection

Agency

The hydrologic unit protocol team, consisting of

Bruce McCammon and Ervin Cowley, worked to

adopt current national standards for delineating

watersheds. Bob Pierce of USGS also provided

significant contributions.

The core team extends its appreciation to

individuals who assisted with documenting and

preparing this guidance. These individuals

include:

Penny Williams . . . . .FS

Margaret Trujillo . . . .BLM

Linda Hill . . . . . . . . .BLM

Janine Koselak . . . . . .BLM

Further acknowledgement is extended to Jim

Greenfield (EPA) for his support and willingness

to test and apply this guidance on the Chattooga

River in Georgia.
A Framework for Analyzing the Hydrologic Condition of Watersheds iii

Table of Contents

Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .i

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1

Purpose . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1

Overview of the Analysis Process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1

Analysis Preparation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3

Delineating Watersheds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3

Developing Case Files for Core Hydrometeorological Data . . . . . . . . . . . . . . . . . . . . . . . . . . .3

The Hydrologic Condition Analysis Process . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5

Step 1: Characterize the Watershed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5

Step 2: Rate Factors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7

Step 3: Identify Important Factors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12

Step 4: Establish Current Levels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16

Step 5: Establish Reference Levels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .17

Step 6: Identify Changes and Interpret Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .18

Appendix A: Core Hydrometeorological Data and Information Protocols . . . . . . . . . . . . . . . . . .25

Appendix B: Watershed Case File . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .29

Appendix C: Interdisciplinary Team Planning—Using the Results . . . . . . . . . . . . . . . . . . . . . . .33

Appendix D: Glossary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .35

Literature Cited . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .37
A Framework for Analyzing the Hydrologic Condition of Watersheds 1

Introduction

Purpose

The Bureau of Land Management (BLM) and

the Forest Service (FS) are responsible for managing natural resources on public lands. While

the numerous resources on the public lands are

diverse, they are also interrelated, which means

that management actions pertaining to one

resource will also impact others.

Water is one resource that has the potential to

impact numerous other resources. For the BLM

and FS, an important part of fulfilling their

resource management responsibilities involves

gaining an understanding of the physical

processes that govern the flow (F), quality (Q),

and/or timing (T) of water. Understanding these

processes requires, among other things, information about precipitation, ground cover, vegetation, soils, geology, runoff, channels, floodplains,

and riparian areas for each watershed.

Watersheds are characterized by meteorological,

surface- and ground-water, and physical and biological factors functioning within the context of

natural and human disturbance regimes. The

flow, quality, or timing of water within a watershed is regulated by these factors. Watershed

characteristics must be analyzed and interpreted

using known scientific principles about hydrologic and hydrometeorological processes to

describe hydrologic condition. The analysis and

interpretation require basic hydrologic knowledge, knowledge of the area, and competency in

using hydrologic tools and making judgments

regarding hydrologic processes.

Hydrologic interpretations provide fundamental

information about the linkages between terrestrial features or processes and associated aquatic

or biological resources. They are intended to be

combined with information developed by other

disciplines to achieve an integrated and

comprehensive analysis of the watershed. When

merged and integrated with other resource

information, hydrologic condition becomes

part of the basis for identifying management

opportunities and priorities, and for developing

alternatives to maintain, enhance, or restore

watershed function.

The purpose of this guidance is to provide a

national framework for hydrologic analysis and

related protocols as components of more comprehensive interdisciplinary watershed analysis.

This guidance outlines a process for identifying

the essential factors needed to describe hydrologic condition from a vast array of possible

factors. The information assembled during the

process enables those who conduct hydrologic

analyses to participate effectively with other

interdisciplinary team members in addressing

ecosystem and resource management planning

issues. The process helps to organize existing

information about a watershed in the form of a

watershed case file, which displays and interprets

critical hydrologic information and supplements

other resource information during decisionmaking

processes.

Overview of the

Analysis Process

Hydrologic condition analysis results in an

understanding of the interrelationships among

meteorological, surface- and ground-water, and

physical and biological factors that influence the

flow, quality, and/or timing of water. The

magnitude, direction, and rate of change are the

expression of hydrologic condition. The determination of hydrologic condition should, therefore, focus on the analysis of the factors that

most directly influence changes in the specific

watershed of interest. Watershed characteristics
2 A Framework for Analyzing the Hydrologic Condition of Watersheds

that are not subject to change by management

activities (e.g., geology, landform, precipitation)

are fundamental in defining physical limits within

which management actions can be expected to

influence water flow, quality, or timing. Analysis

and documentation of these characteristics are

needed to support interpretations of hydrologic

condition and to defining the limits of

management influence over the physical system.

Because watersheds vary tremendously across

the country, analysts need the flexibility to

select the watershed characteristics that are

most relevant for the watershed they are considering. The analysis procedure outlined in this

document is intended to provide the needed

flexibility. The focus is on a process of analysis

rather than on a prescribed or fixed set of factors that drive the analysis. This approach

allows analysts to use existing tools (e.g., regional curves, nomographs) and to adapt the process

based on available information (local watershed

case files) and local or regional conditions and

needs. It is expected that standard procedures

will be used to analyze factors indicative of

hydrologic condition [e.g., Techniques of Water

Resources Investigations of the United States

Geological Survey and An Approach to Water

Resources Evaluation of Non-Point Silvicultural

Sources (A Procedural Handbook - USDA)].

Use of existing information brings with it a wide

range of reliability and confidence in the values.

It is very important for analysts to document the

level of confidence and the reliability of their

estimates and conclusions. It is important to

document data voids that have decreased the

reliability of conclusions.

The analysis steps follow a logical sequence that

will provide the basis for supporting professional

estimates and judgements resulting in credible

conclusions. The products of one step provide

information for subsequent steps. The following

steps presume that some prework has been

accomplished, including delineating the

watershed and assembling pertinent data:

Step 1. Characterize the watershed

Step 2. Rate factors

Step 3. Identify important factors

Step 4. Establish current levels

Step 5. Establish reference levels

Step 6. Identify changes and interpret results

The analytic process will provide a starting point

for discussion of hydrologic issues, related

resource issues, and questions to be addressed

through ecosystem and resource management

planning. The analysis is intended to be watershed-specific, dealing only with factors associated with the specific watershed being analyzed.

It is likely that the analytic factors will differ

between watersheds, especially watersheds in

substantially different geographic settings. The

expectation, however, is that within a common

landscape unit, such as those defined by Bailey

(1995) or Maxwell et al. (1995), the suite of

important processes will likely be similar. This

means that the knowledge gained in one analysis

may be used to shape the next.
A Framework for Analyzing the Hydrologic Condition of Watersheds 3

Analysis Preparation

Delineating

Watersheds

Ecosystem analysis requires thinking about

processes and characteristics at a variety of

scales. Geographic areas are often used as the

basis for analysis. Since watersheds are hierarchical, they provide a convenient structure for

the analysis of hydrologic condition at a variety

of geographic scales (Seaber et al. 1987).

The BLM and FS follow a standardized

approach for delineating hydrologic units

(watersheds) (USDA-NRCS 1995). Working

cooperatively with the Natural Resources

Conservation Service, U.S. Geological Survey,

and other Federal and State parties, the BLM

and FS delineate hydrologic unit/watersheds

through the fifth code, and as necessary, the sixth

code, at a scale of 1:24,000. Protocols are based

on surface watershed divides. The boundaries

are coordinated across state boundaries.

Analysis of hydrologic condition at larger geographic scales, such as the subbasin (fourth-level

hydrologic unit), provides a broader view of

conditions and important processes or factors.

Analysis at larger geographic scales provides

valuable context for subsequent analyses of

smaller areas. Data used for analysis at the subbasin scale is more general than that used at

smaller scales. Patterns and the distribution of

characteristics or conditions are evident at larger

scales.

The process outlined in this document is intended to be used to assess hydrologic condition of

fifth- or sixth-level-code hydrologic units during

land and resource management planning efforts.

It is possible to complete an analysis of hydrologic condition at the watershed scale using

information that is available anywhere in the

United States (Core Hydrometeorological Data

and Information Protocols, Appendix A). The

process is intended to provide the broad context

and to point to specific data and information

needed for subsequent project investigations,

design, prescriptions, and implementation.

Analysts should resist the notion that projector site-level data is required to complete an

analysis at the watershed scale.

Developing Case

Files for Core

Hydrometeorological

Data

Core hydrometeorological data needs to be

assembled in order to gain a basic understanding

of the hydrologic cycle for a watershed (see

Appendix A). Principles and concepts of fundamental hydrologic processes and hydrometeorological facts are usually published and generic

(i.e., change in water yield due to vegetation

management). The information (e.g., annual

precipitation) is universally available for larger

basins and ecoregions containing important

watersheds located within Federal forests and

rangelands. The published principles, concepts,

and hydrometeorological facts and/or their

sources need to be identified, assessed, and

incorporated into a watershed case file so that

they can be managed on a watershed basis.

A permanent watershed case file should be

developed and maintained for each watershed.

These case files build a picture of the basic characteristics of the watershed. They should

include trip reports; studies that relate to

hydrology, geology, geomorphology, soils, or use

activities; flood or storm reports; research
Office Location:

Watershed File Number/Name:

Hydrologic Unit Code:

WATERSHED CASE FILE INDEX

Data Gaps Data Format Data Location & Data Quality Analysis

File Name Methods

METEOROLOGY

Precipitation

Air Temperature

Evaporation

Wind

SURFACE WATER

Quality

Quantity

GROUND WATER

Springs and Wells

Aquifers

DRAINAGE BASIN

CHARACTERISTICS

Watershed Morphometry

Wetlands/Riparian Areas

Soils

Geology

Vegetation

Human Influence

OTHER WATERSHEDSPECIFIC DATA

Figure 1. Watershed case file index.

4 A Framework for Analyzing the Hydrologic Condition of Watersheds

reports; and other information that would be

helpful to the analyst. The core hydrometeorological information should be included in this

file, along with the hydrologic condition analysis

when it is completed. The case file provides a

vital source of information to current and future

analysts and should be permanently maintained.

(The Forest Service File Systems Handbook recognizes this need and provides for maintaining

these permanent files).

Case files should be numbered by the hydrologic unit code and a watershed name. Each watershed case file should contain an index that

describes the contents of the file and directs the

hydrologist to additional information (e.g., large

documents, maps, and access to electronic data

files) (Figure 1). All data and analyses should be

referenced by author, date, or location. Data

collection standards and procedures should be

explained. All data and analyses should provide

a “version,” sequence identifier (e.g., date). The

files will evolve as each watershed analysis is

performed. Developing full descriptive case

files may take years or decades depending on

the level of activity in a watershed and the priorities and resources that can be devoted to

analysis.

The watershed case file will be used as a data

source to assess hydrologic changes resulting

from land management actions. The core

hydrometeorological data is intended to improve

the effectiveness of analysts as members of

interdisciplinary teams, and help them provide

credible advice and counsel to agency partners

and other interested publics in a timely manner.
A Framework for Analyzing the Hydrologic Condition of Watersheds 5

The Hydrologic Condition

Analysis Process

The following pages describe each step of the

process in detail. An example illustrating how

the process is applied and the product of each

step is included. The Rio Hominy example is

entirely hypothetical, and is intended to demonstrate the analysis process with some ideas for

the analyst to consider. The Rio Hominy watershed has been delineated as a fifth-level hydrologic

unit code watershed. This delineation was

accomplished using the Federal interagency standards, as modified (USDA-NRCS 1995). Some

of the factors are represented by numeric values,

while other factors are described in more qualitative terms. The analyst is expected to select

those factors, whether quantitative or qualitative,

that are most useful for describing hydrologic

condition.

In actual application, the availability of data, in

addition to the experience of the analyst, will

determine how each factor will ultimately be

presented. The basic characterization of the

watershed (Step 1) builds upon those data that

should be available in the case file, along with

the experience and common sense of those

preparing the analysis. Other information for

completing the remaining steps, particularly

those supporting reference levels and interpretation, must be sought from whatever sources are

available, such as research data, field data, model

simulation, and/or professional knowledge and

experience. Often, creativity may be required

to identify and select a factor that will be useful

throughout the process.

Regardless of the source of data, the analysis

must be supported and documented as necessary

to describe its applicability. The analysis process

is designed for land use planning applications.

The analysis information may be useful for

other applications. Therefore, documentation of

confidence, reliability, and assumptions is very

important.

RIO HOMINY STEP 1: Characterize the Watershed

The following is an example characterization of the Rio Hominy watershed. This step is a summary

of the hydrometeorological information provided in the Rio Hominy case file (Appendix B). Data

sources are cited in the case file. If additional information is thought to be important and is included

here, it should also be placed in the case file, which serves as the ultimate repository of information

about the watershed.

Step 1: Characterize

the Watershed

The first step in the analysis process involves an

organized documentation of what is known

about the previously delineated watershed based

on information available in the watershed case

file. Meteorological, surface- and ground-water,

physical and biological factors, and biophysical

processes in the watershed should be documented.

Documentation of past and current human use

and development and disturbance regimes should

be included. This step will provide a broad

overview of the watershed. The characterization

sets the stage for identifying the truly important

and relevant factors that directly influence flow,

quality, or timing of water in the watershed.
6 A Framework for Analyzing the Hydrologic Condition of Watersheds

METEOROLOGY

Precipitation

• Amount: Average annual precip = 7.0 inches at 3,000 feet mean sea level

• Type: Rain only, no snow

• Duration: Flashy—short-duration storms are common

• Frequency/Intensity: 2 yr.- 6 hour precip. = 2.5 inches

• Timing: 80% of annual precip. falls between April and June

Air Temperature

• Average annual temp = 76 °F

• Extremes = 30-120 °F

Evaporation—Exceeds precipitation at lower elevations; high evaporation rates observed at stock 

ponds.

Wind—40-50 mph winds (duststorms) between June and August.

SURFACE WATER

Quantity

Streams

• Avg. annual flow is 200 cfs (perennial streams)

• Annual peaks occur between April and June

• Bankfull discharge at the Grits gage (near mouth) is about 400 cfs

• Incised channel capacity at the Grits gage (near mouth) is approximately 6,000 cfs

Reservoirs and Impoundments

• Evaporation pond at mine (drainage control, 20 acre-feet)

• Stock ponds (about 50 at the 700-1,000 feet elevations, ave. size 2 acre-feet)

GROUND WATER

Springs and Wells—Major springs above mine supplying stream; water right = 2 cfs. One well at 

mine site (800 ft) and several agricultural wells in the lower watershed; numerous water rights

exist for these wells.

Aquifer—Navajo sandstone aquifer averages 0 to 300 feet below surface; ground water plays a 

significant role in providing perennial flow to some lower streams. Recharge of ground water is

derived from higher elevations and floodplains.

DRAINAGE BASIN CHARACTERISTICS

Watershed Morphometry (see USDA, Ecomap, 1996 for possible factors)

• Elevation range = 700 to 5,000 feet mean sea level

• Average watershed slope = 2%; slope range = 1-45%

• Watershed aspect is southwest

• 12 miles of perennial channels between 1,000 and 5,000 feet elevation

• 150 miles of intermittent/ephemeral channel, 80% of which is below 1,000 ft.

• Dendritic drainage pattern

• Watershed size = 100,000 acres
A Framework for Analyzing the Hydrologic Condition of Watersheds 7

• 80% of watershed is lower than 1,000 feet; 20% is higher than 1,000 feet

• Upper stream reach gradients are between 0.5 and 1.5%, lower watershed reach gradients are <

0.5%

• 80% of the streams in the watershed are G channel type (Rosgen, 1995), 15% are C channel

types, and the remainder are A channel types

• Stream channel erosion is common in the watershed

• Sheet erosion is the dominant surface erosion process

Wetlands/Riparian Areas—All wetlands are associated with streams in upper reaches and those 

associated with springs from the intersection of the channels and ground water. Generally, these 

areas are functioning at-risk, and could be improved with more establishment of deeper rooted 

shrubs and trees. They are classified in the National Wetland Inventory as:

• Upper Reaches

Palustrine Scrub Shrub (80%) 

Palustrine Forested (5%)

Palustrine Emergent (15%)

• Spring Areas

Palustrine Scrub Shrub (80%)

Palustrine Emergent (20%)

Soils

• Low precipitation at lower elevations results in poor soil moisture conditions.

• Soils primarily in upland areas are shallow and have low infiltration rates which cause higher

amounts of runoff from these sites.

Geology—Marine sediments with inclusions of Navajo sandstone; Flagstaff limestone; volcanic peaks.

Vegetation

• Ground cover = 40%; lowland shrubs (rabbitbrush, creosote) represent 80% of existing ground

cover; the remaining 20% are mesquite and palo verde

• Mesquite and palo verde trees are common in draws

• Vegetation is stagnant...old; not much carrying capacity for fire

• This is a thermally dominated system, which causes hydrophobic soil conditions and precludes

extensive ground cover due to high evapotranspiration

Human Influence

• No urban development

• Cattle graze throughout the watershed

• High elevation mining; calcite exploration

• 2 active, exploratory copper mines

• 170 miles of dirt road accessing stock ponds

• Expansion of agricultural areas is beginning to impact ground water.

• 75 miles of pioneer roads to mines

Step 2: Rate Factors

The purpose of this step is to identify the truly

influential factors for a given watershed. Factors

displayed in Step 1 are carried into this step to

be rated based on their relative influence on

flow, quality, and/or timing. All factors in

the characterization can, and probably do,

affect flow, quality, and/or timing, but to

varying degrees. The factors used in the

characterization should be tabulated, and
Table 1. Relative importance scale.

Rating Relative Influence on Flow, Quality, or Timing

1 High

2 Moderate

3 Slight/none

8 A Framework for Analyzing the Hydrologic Condition of Watersheds

RIO HOMINY STEP 2: Rate Factors

Table H-1 represents the characterization factors and their relative importance in influencing flow,

quality, or timing for the Rio Hominy watershed. The decisions about these factors were made with

the assistance of the fisheries biologist, wetland ecologist, geologist, and U.S. Geological Survey

hydrologist. The factors and their ratings should be amended by the analyst to reflect locally important watershed factors that influence water flow, quality, and timing in the watershed. The rationale

for the ratings follows the table.

each factor’s potential to influence flow, quality,

and timing should be documented by rating its

relative importance for the particular watershed

using the scale in Table 1.

The subjective ratings are established based on

professional judgment and knowledge of the

physical and biological systems within the

watershed. The rating will gain strength and

value if the analyst consults with other disciplines

during the rating.

The ratings are relative. Factors are rated in

relationship to each other. For example, all

meteorological factors affect flow, quality, and/or

timing—some may have a large effect and some

may have only a slight effect. The same is true

for water quality and quantity and other groups

of factors.

The relative ratings of influence are used to help

condense the wide array of possible factors into

a more refined list containing only the key or

controlling factors. The rationale for each rating

should be documented because subsequent steps

will rely on the information. The documentation

also provides tracks for future analysis and

facilitates response to third-party inquiries.
A Framework for Analyzing the Hydrologic Condition of Watersheds 9

Table H-1. Ratings of factors that characterize the watershed (from the data in Step 1). These factors can be amended as

needed to include locally relevant factors influencing flow, quality, or timing or water.

Factors Flow Quality Timing

METEOROLOGY

Precipitation

Rain

Amount 1 1 1

Duration 1 1 1

Frequency/Intensity 1 1 1

Air Temperature

Monthly, Daily, Hourly

Maximum 1 1 1

Minimum 3 3 3

Evaporation 213

Wind 313

SURFACE WATER

Quantity

Streams

Floods 1 1 1

Reservoirs and Impoundments

Natural 3 3 3

Constructed (stock ponds) 2 2 2

DRAINAGE BASIN CHARACTERISTICS

Watershed Morphometry

Channel Geometry (cross section) 1 2 1

Topography (slope, aspect, drainage density) 3 3 2

Wetlands/Riparian Areas 212

Soils

Depth 1 3 1

Infiltration 1 1 1

Geology (lithology) 1 1 1

Vegetation (upland) 2 3 2

Human Influence

Domestic Stock 2 1 3

Mining 3 1 3

Roads 2 3 2

Agriculture

Ground-Water Extraction 1 3 3

Urban/Residential 3 3 3

Rationale for the subjective ratings in Table H-1:

METEOROLOGY

Precipitation

Rain

Amount The total quantity of rainfall is directly related to the amount of streamflow

produced by the watershed. Rainfall in the area is chemically neutral—a

characteristic that influences the overall pH of the streams in the area.

Runoff responds to rainfall directly due to the flashy nature of the watershed.

Rainfall amount does affect water quality of the surface runoff as the result of

surface erosion in the area during high-intensity storms.
10 A Framework for Analyzing the Hydrologic Condition of Watersheds

Duration The duration of rainfall is important because runoff in the Rio Hominy is

flashy and responds to short-duration storm events. The amount of runoff is

directly related to the duration of the storms since there is limited soil storage

capacity. The short-duration storms of the area typically create a rapid

response in runoff and often exceed infiltration capacity of the soils. Surface

erosion and channel erosion products both influence water quality of the Rio

Hominy watershed.

Frequency/ High-intensity rainfall occurs infrequently and is associated with convective

Intensity storms during the hot summer months. This high-intensity rainfall often

exceeds local infiltration rates and is directly related to the amount of runoff

and the rapid response of the streamflow (flashy). Local surface erosion and

channel erosion directly affect the water quality of the surface runoff.

Air Temperature

Maximum The maximum air temperature of the area (120 °F) directly influences evapotranspiration rates in the area—high levels of evaporation from standing water

(stock ponds) and strong demand for water from local vegetation. Streamflow

tends to be low in the area as the result of the high ET levels. The evaporative

rates also affect the total dissolved solids (TDS) of the surface water in the

Rio Hominy in the immediate vicinity of the stock ponds.

Minimum Minimum temperatures are not a controlling factor for hydrologic processes

in the area.

Evaporation Evaporation directly influences the amount of surface runoff during the hot

summer months. The loss of water from the Rio Hominy due to evaporation

is slight, however, due to the relatively low amount of stored surface water in

the watershed. The amount of evaporation is also insignificant in terms of its

ability to alter flow timing. As described above (temperature/maximum),

evaporation also influences the chemical and physical water quality

characteristics of the area.

Wind Wind does not play any role in production or timing of surface runoff. It is

not a major factor affecting snow distribution (no snow) and is not a major

factor influencing evaporation rates. High winds do create some dust, which

appears as turbidity in the runoff of the area for short periods each year.

SURFACE WATER

Quantity

Streams

Floods Infrequent, major flood events do occur as the result of major convective cells

with sufficient development and duration to impact this watershed. When

they occur, the floods have a serious and direct effect on water yield, quality,

and timing.

Reservoirs &

Impoundments

Natural There are no natural lakes in the area.
A Framework for Analyzing the Hydrologic Condition of Watersheds 11

Constructed Stock ponds in the area have a moderate effect on the amount of water yield

from the Rio Hominy. This is due to the fact that, at the watershed scale, evaporation from the ponds is insignificant. The stock ponds have slight influence on

water quality (TDS) as the result of evaporation. These effects are local and do

not travel downstream in significant amounts. The stock ponds have a moderate

influence on the discharge of sediment from the watershed since they offer a

limited storage capacity. Temporary storage of water in the stock ponds during

high-runoff periods has a moderate influence on the overall timing of water

yield. Stock ponds are, however, subject to periodic overtopping and failure.

DRAINAGE BASIN CHARACTERISTICS

Watershed Morphometry

Channel The broad channels in the lower elevations (C channels) are characterized by

Geometry a net loss of surface runoff from the area (ground-water recharge). The G

channel types tend to be unstable and produce sediment by bank erosion during flashy runoff periods. The G and A channels provide an efficient network

to route water from the area during high-intensity precipitation periods.

Topography The slopes and aspects of the Rio Hominy watershed, in combination with

the geology and soils of the area, regulate the type and extent of channel network development. Overall, the topography of the area does not influence

the amount of water produced or the quality of the water. Topography does

have a moderate effect on the timing of yield as a result of the drainage

density of the watershed.

Wetlands/Riparian Riparian vegetation in the Rio Hominy has a moderate influence on water

Areas yield due to evapotranspiration rates associated with the riparian species.

Since evapotranspiration rates are highest during times when the highest

runoff rates occur, the effect of the riparian vegetation on the timing of water

yield is only moderate. Riparian vegetation is extremely important for control

of sediment from upslope sources during high runoff/surface erosion periods.

Riparian vegetation is also important because it provides localized bank

stability along many of the G and C channels in the area.

Soils

Depth Shallow soils in the area have little water storage capacity, thereby directly

influencing the runoff potential and timing. The shallow soils of the area do

not have sufficient development to influence water quality through leaching

or exchange.

Infiltration Infiltration rates of the shallow soils in the Rio Hominy are often exceeded by

rainfall intensity. This results in a direct influence on runoff amount and timing as described above. The high-intensity rainfall rates in excess of the infiltration rates drive surface erosion processes that influence local water quality

(sediment and turbidity).

Geology (lithology) Ground water from large springs is a significant component of the water yield

from the Rio Hominy. This ground water also has a significant effect on the

chemical water quality of the area. In addition, the springs of the area create relatively stable flow conditions during base flow periods. These are very important

factors for interpreting downstream water yield, quality, and timing of flows.
12 A Framework for Analyzing the Hydrologic Condition of Watersheds

Vegetation (upland) The Rio Hominy watershed is sparsely occupied by rabbitbrush, creosote,

mesquite, and palo verde. These species are phreatophytic and tend to have a

high consumption of water. The old age of the vegetation, the relatively

sparse density, and the lack of extensive vertical structure reduce the overall

influence of the vegetation on ET rates in the watershed. At best, the density

of this vegetation only has a moderate effect on the amount of water yield or

timing of yield. Other than surface erosion and resultant sedimentation, there

are no obvious effects of the vegetation on water quality.

Human Influence

Domestic Stock Cattle grazing in the riparian areas is having a significant effect on water quality (bacteria and nutrients). Cattle are also trampling streambanks. This creates localized erosion and sedimentation as well as a direct change in channel

form. Flow is moderately affected by localized soil compaction. Timing of

flows is not affected by domestic stock.

Mining Mines in the area are having a direct and significant influence on water quality as the result of their operations. Heavy metals are being introduced into

surface waters. The mining operations do not have a discernable influence on

the amount of water yield or the timing of water. Water quality problems are

generated during the periods of high runoff as the result of overburden and

waste disposal practices.

Roads Due to the relatively low density of roads in the area, there are only moderate

influences on water yield or timing. Effects of the roads on runoff during

high-intensity storms are obvious, but can only be considered as moderate relative to the amount of water produced from direct runoff from the hillslopes

of the Rio Hominy. Roads are not producing major effects on sediment production. This is because the low road density, location, and low gradients of

most roads.

Agriculture

Ground-Water Increasing agriculture in the lowlands of the Rio Hominy is placing an

Extraction increased demand on ground water. Since the Rio Hominy is a system that

loses surface water in the low elevations, the increased demand on ground

water tends to increase the demand for ground-water recharge. The net

result is a loss of surface water. The enhanced ground-water recharge has a

significant influence on water yield and a very limited effect on timing and

water quality of surface waters.

Urban/Residential There are no urban or residential developments in the Rio Hominy

watershed.

Step 3: Identify

Important Factors

After rating the factors that characterize a

watershed, the analyst will identify and focus on

factors for further analysis. It is anticipated that

the factors used to evaluate hydrologic condition

will vary from watershed to watershed. The

intent is to identify the primary factors that are

directly influencing flow, quality, or timing of

water in the watershed being analyzed.

In addition to identifying the primary factors

influencing flow, quality, and/or timing, the

analyst needs to decide how to best measure or

describe each factor. There are many ways to
A Framework for Analyzing the Hydrologic Condition of Watersheds 13

express hydrologic condition factors (e.g., flow

can be represented as average annual flow,

instantaneous peak flow, or as a probability estimate associated with a specific return period).

The analyst needs to select a measure and metric that does the best job of relating the factor

to changes in flow, quality, or timing. Ideally,

the selected measure of the factor would be the

one that is easiest to understand and evaluate

and that best describes the factor. For example,

rather than trying to evaluate all water quality

variables that could be affected by grazing, the

analyst might choose to describe water quality

using concentrations of coliform bacteria or

nutrients as the measures of water quality. The

analyst may decide that these are the best measures of water quality effects associated with

grazing in this watershed. The metrics chosen

for coliform bacteria or nutrients might then be

colonies per 100 mL and mg/L, respectively.

Where specific factors are identified that have

limited or no information, the analyst should

select a surrogate factor for which information

exists (e.g., road density as a surrogate for infiltration reduction), collect information, or use

simulation models or extrapolative techniques.

The decision about which approach to take will

depend on the time, funding, and resources

available to do the analysis. The relative sensitivity or importance of a factor, or the measure

chosen to represent it, should be considered

when making a decision about how much time

or energy to spend preparing the data.

Credibility and reliability of the analysis will be

affected by the approach selected. Confidence

and reliability of the analysis should be documented.

When selecting the primary factors for the

remaining steps of the analysis, it is important to

consider factors that:

• Directly link to and greatly influence flow,

quality, and timing

• Are influenced by management

• Are obtainable (quantifiable and/or qualifiable)

• Reflect the dominant biophysical processes

• Have a definable reference or range of variation over time

These considerations help the analyst to focus

on how a factor was first identified and how it

will be used in Steps 4, 5, and 6, but they are

not meant to be used to reject a factor. They

help document the logic and professional judgement used in selecting the primary factors.

Any factor in the rating table (Step 2) that has a

rating of 1 for flow, quality, and/or timing

should be included. Other factors with ratings

of 2 or 3, or any combination thereof, may be

brought forward into the analysis at the analyst’s

discretion. Decisions to carry forward a factor

rated 2 or 3 should be based on the need for that

data to analyze or interpret another factor or to

support findings.
14 A Framework for Analyzing the Hydrologic Condition of Watersheds

RIO HOMINY STEP 3: Identify Important Factors

Table H-1 was completed based on information from the characterization to show the relative

importance of the meteorological, surface-water, ground-water, and drainage basin factors to flow,

quality, and/or timing of water in the watershed. Considering the relative ratings in Table 1, several

factors have been identified as the most important for the watershed.

Factors with ratings of 1 for flow, quality, and timing of water:

• Rain amount, duration, and frequency/intensity

• Maximum temperature

• Floods

• Infiltration

• Geology

Factors with ratings of 1 for flow, quality, or timing of water:

• Evaporation

• Wind

• Channel geometry

• Wetlands/riparian areas

• Soil depth

• Domestic stock

• Mining

• Ground-water extraction (agriculture)

Factors with ratings other than 1 and that the analyst has determined are relevant to the analysis:

• Constructed impoundments - Capacity and number of stock ponds are needed to support analysis of evaporation and riparian vegetation. Stock ponds are subject to failure and management

influence.

Of the factors selected, the following cannot be influenced by management, but will be important

descriptors to supplement and support conclusions about hydrologic conditions. Quantification of

the following factors will not be necessary. Without human influence there is no variation between

current and reference levels (Steps 4 and 5) that allow interpretation (Step 6):

• Rain amount, duration, frequency, and intensity

• Maximum temperature

• Floods

• Geology

• Wind

Factors that management will affect include:

• Evaporation - Stock ponds and vegetation use

• Constructed impoundments - Stock ponds

• Channel geometry - Stock trampling/chiseling of streambanks

• Wetlands/riparian areas - Grazing allotments and permits

• Soil depth - Soil compaction/erosion, stock, roads

• Infiltration - Soil compaction, roads, stock use

• Domestic stock - Grazing allotments and permits

• Copper mines - Operating plans

• Ground-water extraction - Pumping for agriculture

Table H-2 displays the measures and metrics for the factors that are influenced by management.
Table H-2. Summary of important hydrologic condition factors and selected measures.

Factor Flow Quality Timing

Evaporation Not significant TDS (mg/L) Not significant

Constructed Total yield (ac-ft) Sediment yield Time to peak (hr)

impoundments Peak flow (cfs) (tons/yr)

Channel geometry Bankfull discharge (cfs) Not significant Time to peak (hr)

Bankfull width/depth ratio

Average depth (ft)

Wetlands/riparian areas Not significant Sediment yield (tons/yr) Not significant

Soil depth Total yield (ac-ft) Not significant Time to peak (hr)

Infiltration Total yield (ac-ft) Sediment yield Time to peak (hr)

Peak flow (cfs) (tons/yr) Duration of min. flow

Minimum flow (cfs) (days)

Domestic stock Not significant Coliform bacteria Not significant

(#/100 mL)

Nutrients (mg/L)

Mines Not significant Heavy metals (mg/L) Not significant

Ground-water extraction Total yield at mouth (ac-ft) Not significant Not significant

Table H-2 shows the measures of the factors to be analyzed and sources of data. Identical items in

Table H-2 are grouped below.

Flow

• Total water yield (ac-ft) - The watershed is equipped with gaging stations, making this factor relatively simple to document, but its usefulness as a short-term monitoring factor is questionable.

At least one gage has data prior to 1900.

• Peak flow (cfs) - The gaging station will provide good documentation for this factor.

• Bankfull discharge (cfs) - Data can be generated from several gaging station records. USGS has

conducted a stream geometry study on several streams in the watershed.

• Bankfull width/depth ratio - This measure can also be used as a surrogate for flow. Other factors

that may prove to be useful include bankfull width and depth, as separate factors, or perhaps

flood-prone area as it relates to potential recharge during flood events.

• Average depth (ft) - This is the depth of water typically found in the channel under average

annual flow conditions. It is expected to be a valuable measure for fishery considerations.

• Minimum flow (cfs) - Gaging records are available from 1900 on one gage. Old photos, journals,

and newspapers provide descriptions of the channel going dry.

Quality

Water quality data from 1969 to present is available from agency monitoring programs and university

studies (except heavy metals as noted below). There is little water quality data available prior to 1969.

However, several streams in the region have good records and have been studied by the university, which

enables development of reference data. Therefore, five factors will be useful in developing the analysis:

• TDS (mg/L)

• Sediment yield (tons/year)

A Framework for Analyzing the Hydrologic Condition of Watersheds 15
16 A Framework for Analyzing the Hydrologic Condition of Watersheds

• Coliform bacteria (#/100 mL)

• Nutrients (mg/L)

• Heavy metals - copper (mg/L) - mining company’s permit monitoring records

Timing

• Time to peak (hr) - This data is available from streamgage record interpretations.

• Duration of minimum flow (days) - Data is currently available on several gaging stations and

there is a historical record to 1900. Some descriptions are available from photos, journals, survey

records, newspapers, and other accounts.

Step 4: Establish

Current Levels

The next step in the process is to quantify the

current range and status of the primary factors

influencing flow, quality, or timing of water

identified in Step 3. This is accomplished by

documenting the current range of variability for

each specific factor identified in Step 3. The

current range of variability is considered to be

the range of values that occurs during a normal

cycle for the factor or process being analyzed.

For most hydrologic variables or processes, this

is approximately 10-15 years. Sources of information, assumptions, and the level of confidence

or reliability of the current values should be

documented.

RIO HOMINY STEP 4: Establish Current Levels

The numbers in Table H-3 represent a range based on hydrologic conditions over the last 10 years.

Information was taken from historic records and available inventories.

Table H-3. Current range of variability for primary factors.

Factor Value Reliability*

Flow

Total water yield 30,000-35,000 ac-ft High

Peak flow (annual) 4,000-5,200 cfs High

Bankfull discharge 4,000 cfs Moderate

Bankfull width/depth ratio 16 Moderate

Average depth 0.3 ft High

Minimum flow (7 day-10 yr) 0-5 cfs High

Quality

TDS 2,500-3,000 mg/L High

Sediment yield 4-6 million tons/year Moderate

Coliform bacteria 1,000-10,000 colonies/100 mL High

Nutrients 10-30 mg/L High

Heavy metals 1-5 mg/L High

Timing

Time to peak 4 hours High

Duration of minimum flow 35-50 days High

* Reliability is rated “high” when the values are taken from published records and/or measured data. “Moderate” ratings

are used for calculated or modeled values. “Low” ratings are used when values are extrapolated, are based on broad

regional relationships, or are based on assumptions or approximations.
A Framework for Analyzing the Hydrologic Condition of Watersheds 17

Sources of Information and Assumptions

All flow values (with the exception of bankfull discharge and width/depth ratio) are taken from

published gaging records for the Grits gage at the mouth. Bankfull discharge is calculated using

regional rating tables and field measurements of channel cross sections. The width/depth ratio was

determined in 1982 using field surveys at miscellaneous random sites.

All quality values are based on measured values obtained by standard lab analyses (standard methods).

Data sources include agency monitoring programs, university surveys, and the mining company’s

permit monitoring.

Timing values are derived from published USGS gaging records for the Grits gage.

Step 5: Establish

Reference Levels

In order to be able to determine the rate, direction, or magnitude of change, a reference level

must be established. References serve as the

benchmark from which change is determined

and provide a basis for comparison. A reference

level is needed to explain changes in the selected

factors over time as the result of human influence

and natural disturbances.

Reference levels are used for comparative purposes

only. They do not imply that conditions can or

should move to the reference level. Reference

levels are not necessarily “desired” conditions—

they are simply the conditions that would be

expected if the system were operating without

significant human influence.

Sources of information, assumptions, and the

level of confidence or reliability of the reference

values should be documented. Possible sources

of information about reference levels include

(but are not limited to): models or simulations,

extrapolation, historic records or journals, and

records or studies of other areas or least disturbed areas (e.g., wilderness areas, National

Parks).

RIO HOMINY STEP 5: Establish Reference Levels

The same quantifiable factors as those in step 4 are documented to allow comparison and interpretation of the change that has occurred. Examples of reference values are shown in Table H-4.
Table 2. Relative significance scale.

Rating Relative Significance

1 Significant difference

2 Moderate difference

3 Slight/no difference

18 A Framework for Analyzing the Hydrologic Condition of Watersheds

Table H-4. Reference value quantification for each selected factor.

Factor Value Reliability*

Flow

Total water yield 25,000-30,000 ac-ft Moderate

Peak flow (annual) 1,700-2,500 cfs Moderate

Bankfull discharge 2,000 cfs Low

Bankfull width/depth ratio 8 Low

Average depth 0.9 ft Moderate

Minimum flow (7 day-10 yr) 5-10 cfs Moderate

Quality

TDS 2,000-2,300 mg/L Low

Sediment yield 2-4 million tons/year Low

Coliform bacteria 100-500 colonies/100 mL Low

Nutrients (nitrogen) 0.1-0.5 mg/L Low

Heavy metals (copper) Not detectable Low

Timing

Time to peak 6 hours Moderate

Duration of minimum flow 70-90 days Low

* Reliability is rated “high” when the values are taken from published records and/or measured data. “Moderate” ratings

are used for calculated or modeled values. “Low” ratings are used when values are extrapolated, are based on broad

regional relationships, or are based on assumptions or approximations.

Sources of Information and Assumptions

Reference values for many of the flow measures were developed using the longer term historical

record at the Grits gaging station. Additional measures were estimated using watershed modeling

techniques provided by USGS. Cross sections were located based on three photographs taken in

1987. Measurements of these cross sections confirmed a channel geometry similar to that expected

from peak flow near 2,000 cfs, which is within the range of the values found for the Grits gaging

station. Average depth values were generated using average flow data extrapolated to the channel

using Manning’s equation. Water quality reference values were taken from similar streams in the

area that have been studied by EPA.

Step 6: Identify

Changes and

Interpret Results

Once the current range of values and the corresponding reference level of each specific factor

has been documented, the significance and

causes of any observed differences between the

two sets of information and the potential for

recovery can be evaluated.

Significance

Significance is an interpretation by the analyst

based on an evaluation of the magnitude, direction, and rate of change between current and

reference values (Table 2). Ratings assigned by

the analyst are subjective and are based on

professional judgment and knowledge of the

watershed.
of social, economic, and technical feasibility and

the need for recovery (Table 3). Not all change

is adverse or requires correction.

A description of the logic used to arrive at the

subjective ratings in Table 3 is very important.

This narrative should explain how the ratings

were derived, as well as explain any assumptions.

The narrative is the place to document the

professional understanding of the physical

processes that are primarily responsible for the

hydrologic condition of the watershed. The logic

should be documented and retained for future

use.

A Framework for Analyzing the Hydrologic Condition of Watersheds 19

Recovery

The analyst can also project the potential for

recovery of the hydrologic system when the

cause-effect relationship for the differences

between current and reference levels are understood. Statements of cause-effect relationships

need to be documented prior to rating the

recovery potential. Typical “causes” of change

include construction of roads, development of

mining, stock use, vegetation removal or

conversion, fire, insect and disease outbreaks,

agricultural development, and urbanization.

These causes impact the following processes:

infiltration, evapotranspiration, interception, and

erosion/sedimentation. Typical “effects” are

increased runoff, decreased water quality,

changes in streamflow timing, and alteration of

channel morphology.

Ratings of recovery potential are based on

knowledge of physical capability of the watershed

to respond when considered within the context

RIO HOMINY STEP 6: Identify Changes and Interpret Results

Cause-Effect Relationships

Presence of domestic stock has doubled the width-depth ratio through trampling/chiseling and caving

of streambanks, increased peak flows through compaction, and added significant nutrient and coliform

loading to the system. Roads have significant local effects on peak flows due to compaction and have

decreased the time to peak flow by increasing runoff efficiency. The change in channel geometry

caused by domestic stock, coupled with the increased peak flows, has resulted in sediment yield

increases from channel scour, increased bankfull discharge, and reduced average depths. Continued

erosion and loss of soil, coupled with increased compacted surfaces, has reduced the watershed’s ability

to infiltrate and store water to support base flows. Hence, the duration of minimum flows in the

channels has been reduced. Stock ponds serve as minimal sediment traps. Ponds have slightly

reduced water yield through increased evaporation, but the primary effect of evaporation has been

increased levels of TDS. Mines have directly introduced heavy metals into the streams.

Summary Table

The information about current and reference conditions, as well as the estimated significance of these

values and the recovery potential, can be easily summarized in a single table. Table H-5 organizes the

data and documents the analyst’s interpretation of the significance of the differences between current

and reference conditions. The estimated recovery potential is also recorded in the table.

Table 3. Recovery potential scale.

Rating Recovery Potential

1 High potential

2 Moderate potential

3 Slight/no potential
20 A Framework for Analyzing the Hydrologic Condition of Watersheds

Table H-5. Summary of current and reference conditions and ratings of significance and recovery.

Factor Current Reference Significance Recovery

(1-3) Potential

(1-3)

Total water yield 30,000-35,000 ac-ft 25,000-30,000 ac-ft 2 2

Peak flow 4,000-5,200 cfs 1,700-2,500 cfs 1 2

Bankfull discharge 4000 cfs 2000 cfs 1 3

Bankfull width/ 16 8 1 3

depth ratio

Average depth 0.3 ft 0.9 ft 1 2

Minimum flow 

(7 day-10 yr.) 0-5 cfs 5-10 cfs 1 3

TDS 2,500-3,000 mg/L 2,000-2,300 mg/L 3 2

Sediment yield 4-6 million t/yr 2-4 million t/yr 1 3

Coliform bacteria 1,000-10,000 100-500 1 2

colonies/100mL colonies/100 mL

Nutrients 10-30 mg/L 0.1-0.5 mg/L 1 2

Heavy metals 1-5 mg/L ND 1 1

Time to peak 4 hours 6 hours 3 3

Duration of min. flow 35-50 days 70-90 days 1 3

Logic for Subjective Ratings

Total Water Yield

Vegetation cover is currently 40% and the range specialists believe this can be increased to 50%

with appropriate changes in allotment management. An increase in vegetation will tend to lower

total water yield from the area due to increased evapotranspiration. A 10% increase in vegetation

will result in an insignificant reduction of total water yield from the area.

The stock ponds trap runoff when they are in good repair, exposing the trapped water to evaporation loss. Eliminating the stock ponds would provide an insignificant amount of additional water

yield. Removing the stock ponds is probably unrealistic until alternative water sources are developed for livestock or season of use changes are made. Recovery, therefore, rests with the manager’s

capability to implement changes in livestock management.

Peak Flow

Peak flows are increased by runoff from roads and by stock ponds that intermittently fail during

flooding events. The ponds effectively store water until their poor design and construction results in a

breach. Poor ground cover results in rapid runoff of rain and delivery to the stream system.

Successive stock pond failures could result in a large increase in peak flow. The reduction in peak

flows with removal (or proper design and construction of the stock ponds) is almost certain. The

impact of the vegetation change (prior to 1950 the vegetative cover was near 50%) is clear in the

gaging records, as is the impact from the stock ponds that were constructed from about 1975 on.

Recovery is a function of economic incentive to repair and stabilize stock ponds, or to develop off-site

water sources and remove stock ponds, or to alter livestock use by changing allotment management.

Bankfull Discharge

Channel degradation has resulted in bankfull discharge being contained within the incised channel.

Time will allow the floodplain to become reestablished at a lower position (compared to the reference
A Framework for Analyzing the Hydrologic Condition of Watersheds 21

condition). Figure H-1 contains regional

curves showing reference and current relationships between the bankfull flow and

the drainage area. Alternatives to reconfiguring the incised channels are to make

extremely expensive structural changes

that allow the stream to be narrowed and

raised in position, or to restore the channel

by constructing it to its reference pattern,

profile, and dimensions. A site-specific

analysis of the channel and its watershed

will be needed in order to determine the

needed treatments. Potentially, increases in

vegetation alone could result in aggradation significant enough to raise the floodplain to the most

recent terrace. This technique has proven to be successful on other streams in the region. The

prognosis for recovery in less than 10 years is poor.

Bankfull Width/Depth Ratio

The concentration of livestock along channels for water and riparian vegetation feed has contributed to severely altered channel geometry resulting in a twofold increase in the width-depth

ratio. Channel geometry has also been altered by increased peak flows from road runoff, stock

pond failures, soil compaction, and vegetation reduction. Excluding livestock use to eliminate

chronic bank disturbance and increase vegetative cover, coupled with mechanically reconfiguring

the channel, would decrease the width-depth ratio. The recovery has social implications in that

the allotment has been held by the Navajo Indians for the past 50 years. Mechanical treatments,

though probably limited in scope, would be very expensive.

Average Depth

The average depth is regulated by the amount of available flow and channel geometry. The existing channel has incised due to increases in peak flow and widened from livestock trampling and

chiseling to the extent that normal flows are only one-third the depth of reference conditions.

With modification in range use and resulting increased vegetation, stream channel geometry can

be changed over time; however, the change will be slow. The average annual depth will be one of

the first measures showing some short-term improvement. Establishment of vegetation, alteration

of grazing practices, and limiting the failure of the stock ponds would allow streambanks to narrow

and average depth to increase.

Minimum Flow

The current 7-day, 10-year low flow is less than 5 cfs. Increasing watershed cover, removing stock

ponds, and improving riparian conditions would likely increase minimum flow by as much as

100%. The Grits gaging records show a relatively stable summer minimum flow until season-long

grazing was implemented in 1947. Old photos, newspapers, and journal records indicate that

much of the lower reaches of the Rio Hominy had perennial water, confirming the Grits gaging

records. The reduction in vegetative cover and the widening of the channel has changed the ability of the watershed to store available precipitation and sustain a base flow. This has been very

apparent since severe gullying has taken place, resulting in the conversion of the once active floodplains to terraces. This change has reduced the near-stream recharge from flood events, also

impacting the timing and amount of low flow. The minimum flow can be changed in much the

same way as the peak flow, with additional costs of channel system reconfiguration to reclaim

abandoned floodplain use for recharge.

1

1 10 100 1000

acres

10000 100000

Current

Reference 10

100

bankfull discharge (cfs) 1000

10000

Figure H-1. Regional curves.
22 A Framework for Analyzing the Hydrologic Condition of Watersheds

Total Dissolved Solids

The marginal increase in TDS due to stock pond evaporation and incidental inputs from mining is

locally confined in the watershed. TDS could be reduced a small amount through better management of the mines; however, high evapotranspiration rates makes the stock-pond-related TDS

loading difficult to manage.

Sediment Yield

Sediment yield is limiting water quality on all streams. Improving cover from 40-50%, improving

maintenance procedures of stock ponds to reduce peak flows, improving mining practices, closing

roads, improving road maintenance, and stabilizing the stream channels could result in significant

sediment reduction. It is uncertain if these changes, if implemented, would alter the State of

Arizona’s report on water quality limited segments per the Clean Water Act, Section 303d. The

composite remediation effort would be extremely expensive and the benefit to the listed water

segments uncertain. Site-specific analysis and monitoring of the effectiveness of the practices

would be required.

Coliform Bacteria

Large increases in coliform bacteria levels are attributed to season-long, unconfined grazing practices. Removing livestock or limiting livestock from the stream could significantly reduce the coliform bacteria levels. Coliform levels in ungrazed reference sites near this watershed are below

500; the coliform at these sites is attributed to wildlife and instream growth. Removing livestock

has related social implications and exclusion fencing would be expensive. Adjusting the allotment

to reduce the number of stock and limit the season of use would reduce coliform bacteria levels,

though not as dramatically as removing stock or fencing streamside areas.

Nutrients

The agency monitoring program and university studies suggest that nutrient levels will be high in

warm, low-gradient streams. Observation has confirmed that much of the lower stream segment

contains algae. Removal of livestock or limiting livestock access to the streams could reduce the

nutrient load. Removing livestock has related social implications and exclusion fencing would be

expensive. Adjusting the allotment to reduce the number of stock and limit the season of use would

reduce nutrient levels, though not as dramatically as removing stock or fencing streamside areas.

Heavy Metals

The mining company’s permit records indicate copper at elevated levels in the water below the

mine. Agency and university data show there are no metals in waters above the mine. Improving

mining practices could eliminate this problem. Adjustments in the mine operating plan regarding

overburden and waste disposal sites would reduce heavy metal loading in an economic and

technically feasible manner.

Time to Peak

Change in watershed cover and changes in stock pond operation may influence the time to peak.

The 2-hour increase in time to peak is not considered significant as the watershed is naturally a

high-intensity storm, rapid-runoff system. Remediation to alter time to peak is unwarranted.

Duration of Minimum Flow

See the discussion under Minimum Flow.
A Framework for Analyzing the Hydrologic Condition of Watersheds 23

Findings and Discussion

There are 13 factors in the Rio Hominy watershed where deviation from reference to current

values is affecting hydrologic condition. Ten of the 13 factors exhibit a significant departure.

The watershed disturbance for the significant departures has been primarily tied to livestock

utilization within the watershed. Reduction in vegetation resulting in accelerated erosion and

increased runoff, modification of channel geometry, and constructed ponds are the primary causal

agents with livestock use. Other incidental contributory disturbances include road development

and mining activity.

Identified remediation opportunities include: change in grazing practices through revision of

allotment management plans and permits, exclusion of stock from streambank areas with

fencing and off-site water supplies, removal or reconstruction of stock ponds, mechanical

configuration of channel systems, and/or elimination of livestock use within the watershed.

With the exception of reduction in heavy metals from mining, the potential to implement

remediation measures is moderate to none at all. Recovery potential is constrained by high

costs, social acceptability, uncertainty of end results, and questionable need for initiating

recovery.

A Framework for Analyzing the Hydrologic Condition of Watersheds 25

Appendix A: Core

Hydrometeorological Data

and Information Protocols

The following tables present the data needed,

how it should be displayed, and the procedures

and/or sources that allow the display to be prepared. The tables present protocols for assessing

four categories of core hydrometeorological

data/information. These categories are: meteorology, surface water, ground water, and drainage

basin characteristics. Other data types may be

assembled, but are not considered core. Some

data listed under drainage basin characteristics may be provided by other disciplines.

The basic unit for storing hydrologic

data/information is the watershed case file.

Data/information needs to be stored in an

accessible and useable format that can be

easily updated.

METEOROLOGY

DATA/INFORMATION DISPLAY SOURCE/PROCEDURE 1/

Precipitation

(Rain and Snow)

Amount Map showing average annual PRIMARY SOURCE: National Oceanic and 

precipitation. Atmospheric Administration—National Weather

Service climatological data.

Table and/or graph showing average monthly SUPPLEMENTAL SOURCES: State climatologist,

precipitation (rain and snow if applicable) for SNOTEL, barometer watershed, research,

applicable climatic stations. Narrative or table universities, communities, schools, U.S. Forest

for each station showing period of record, Service and BLM files, and files from other

operator, frequency of sampling, Universal governmental agencies (e.g., USGS, Bureau

Transverse Mercator (UTM) coordinates, station of Reclamation, NRCS).

identification number, elevation, and methods

used for collection.

Table showing average maximum and 

minimum precipitation by month (rain and s

applicable).

Frequency and Intensity Rainfall event intensity-frequency maps. PRIMARY SOURCE: National Oceanic and

Atmospheric Administration—National

Weather Service Precipitation Frequency Atlas

for applicable state.

Snow Survey Snow pack depth and water equivalent by PRIMARY SOURCE: USDA—Natural Resources

month for the snow season. Conservation Service SNOTEL climate station

summaries.
METEOROLOGY (cont.)

DATA/INFORMATION DISPLAY SOURCE/PROCEDURE 1/

Narrative or table for each station showing

period of record, operator, frequency of SUPPLEMENTAL SOURCES: State snow

sampling, UTM coordinates, station identification survey publications.

number, and elevation.

Air Temperature Table or graph showing monthly minimum, PRIMARY SOURCE: National Oceanic and 

maximum, and average air temperature for Atmospheric Administration—National 

applicable climatic stations. Weather Service climatological data.

Narrative or table for each station showing SUPPLEMENTAL SOURCES: State climatologist,

period of record, operator, frequency of SNOTEL, barometer watershed, research,

sampling, UTM coordinates, station identification universities, communities, schools, U.S. Forest

number, and elevation. Service and BLM files, and files from other

governmental agencies (e.g., State, USGS,

Bureau of Reclamation, NRCS).

Evaporation Map of isoevaporation lines. PRIMARY SOURCE: National Oceanic and

• Annual Atmospheric Administration—National Weather

• Seasonal Service Climatological Data and Evaporation

Atlas.

SUPPLEMENTAL SOURCES: State climatologist,

barometer watershed, research, universities,

communities, schools, U.S. Forest Service and

BLM files, and files from other governmental

agencies (e.g., USGS, Bureau of Reclamation).

SURFACE WATER

Quality

State Water Quality Maps, tables, and/or narratives from State PRIMARY SOURCE: State Water Quality

Classification Designations, water quality classification designations and Agency or US-EPA, for the following: State

Standards, Beneficial Uses standards water quality classifications designations and

& Criteria, Water Quality standards, 303 (d) and 305(b) reports as 

Limited Waters required by the Clean Water Act.

Surface Water Quality Table showing summary of available water PRIMARY SOURCE: USGS, WATSTORE

Data quality information to include: station location, database.

period of record, water quality parameters

measured. SUPPLEMENTAL SOURCES: Barometer watershed,

research, universities, communities, schools,

U.S. Forest Service and BLM files, and files

from other Federal and State agencies (e.g.,

USGS, Bureau of Reclamation).

Quantity

Streams Table or hydrograph showing mean monthly PRIMARY SOURCE: USGS water resource data.

flow, and narrative describing low flow, high

flow, extremes for period of record, station SUPPLEMENTAL SOURCES: Streamflow records

location information, and water diversions by other Federal and State agencies and water

within the watershed. users. Narrative interpretation of hydrograph

using basin characteristics, location and

Narrative or table for each station showing quantification of water imports, exports, and 

period of record, operator, frequency of diversions. Where data is not available,

sampling, UTM coordinates, station identification published regional relationships should be

number, and elevation. used.

Reservoirs and Map showing location and surface area. State water rights inventories, dam engineer's

Impoundments inventory, and State water plan.

26 A Framework for Analyzing the Hydrologic Condition of Watersheds
GROUND WATER

DATA/INFORMATION DISPLAY SOURCE/PROCEDURE 1/

Springs and Wells Map of location. PRIMARY SOURCES: Agency files for range,

recreation, and administrative sites. USGS

WATSTORE database.

SUPPLEMENTAL SOURCES:

• State water planning maps

• Water users

• State Engineer's office

• USGS 1:24000 quads

• Office of Surface Mining, etc.

• Mining plans

• Color infrared and other aerial photographs

Aquifers Narrative - general description of intermediate PRIMARY SOURCE: USGS published reports.

and regional scale aquifer, noting aerial extent,

depth, geologic characteristics (depth, dip, SUPPLEMENTAL SOURCES: Office of Surface

thickness, etc.) and water quality and quantity Mining, universities, State agencies, etc.

characteristics. (Option: Develop on a local

basis with available data).

DRAINAGE BASIN CHARACTERISTICS

Watershed Map showing fifth- and sixth-level watershed PRIMARY SOURCE: USDA—Natural Resources

Morphometry units. Conservation Service (1996) Mapping and

Digitizing Watershed and Subwatershed

Hydrologic Unit Boundaries. National

Instruction No. 170-304 (1995, revised 1996).

Federal Classification Maps, tables, and/or narratives from Federal PRIMARY SOURCES: Maps, tables, and/or

of Water classifications of water, including Wild and narratives for Federal classifications of water

Scenic Rivers designations, Outstanding from agencies such as the Forest Service, BLM,

National Resource Water designations, EPA, USGS, etc.

municipal watershed boundaries.

Wetlands/Riparian Map showing wetland and riparian areas, and PRIMARY SOURCE: National wetlands inventory.

Areas narrative-description of each unit.

SUPPLEMENTAL SOURCES: Local information

for soils, vegetation, and water inventories.

Soils Maps showing soil mapping units and PRIMARY SOURCES: NRCS soil survey

corresponding tables showing: reports.

• Hydrologic soil group

• K factor/erosion hazard SUPPLEMENTAL SOURCES: Forest Service,

• Water-holding capacity BLM soil survey reports.

• Growing season

• Depth to ground-water table within 60

inches of surface hydric soils

Geology Maps and associated narratives for: PRIMARY SOURCES: Statewide geologic map.

• Structure 

• Surface rock SUPPLEMENTAL SOURCES: USGS and State

• Lithology publications, soil survey reports.

• Mass stability hazards

• Landforms

A Framework for Analyzing the Hydrologic Condition of Watersheds 27
DRAINAGE BASIN CHARACTERISTICS (cont.)

DATA/INFORMATION DISPLAY SOURCE/PROCEDURE 1/

Vegetation

Cover Type Maps and tables or narratives of the following: PRIMARY SOURCES: USDA Forest Service 

• Existing (1977) Forest and Range Ecosystems of the 

• Historical U.S. Local maps and reports showing

• Potential natural vegetation types and species. Rangeland 

Reform EIS. Landsat imagery, aerial

photography.

SUPPLEMENTAL SOURCES: Local maps, limited

area project maps, and botanical studies.

Human Influence Maps and associated narratives of roads, PRIMARY SOURCE: BLM and Forest Service

facilities, and urbanization. surface management maps.

Map showing locations of climatological, PRIMARY SOURCE: See primary source under

streamflow, ground-water, and water qualtiy specific data type.

stations applicable to the watershed.

1/Specific sources/procedures are determined by the practitioners implementing the protocol.

28 A Framework for Analyzing the Hydrologic Condition of Watersheds
A Framework for Analyzing the Hydrologic Condition of Watersheds 29

Appendix B: Watershed

Case File

METEOROLOGY

Precipitation

Amounts:

Table A-1. Calcite Station: precipitation.

Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep Total

In. 0.18 0.15 0.10 0.35 0.14 0.15 1.50 2.50 1.60 0.25 0.08 0.00 7.00

% 2.57 2.14 1.43 5.00 2.00 2.14 21.43 35.71 22.86 3.57 1.14 0.00 100.00

Type: Rain only, no snow.

Station: Calcite Station, elevation 3,000 feet. Temperature and precipitation record 1956 to 1997.

Source: Climatological data for Arizona. Year, Month. National Oceanic and Atmospheric Administration, National

Climatic Data Center, Asheville, NC.

Frequency and Intensity:

Table A-2. Storm frequency.

Recurrence Interval (yrs) Storm Duration (hrs) Precip. Amount (inches)

2 6 2.50

5 6 2.60

10 6 2.80

25 6 3.20

50 6 3.60

100 6 3.80

500 6 4.20

2 24 2.70

5 24 2.80

10 24 2.90

25 24 3.50

50 24 3.80

100 24 4.00

500 24 4.50

Source: Miller, J.F., R.H. Fredrick, and R.J. Tracy. 1973. Precipitation Frequency Atlas of the Western United States.

Volume VI, Arizona. NOAA Atlas 2. U.S. Department of Commerce, National Oceanic and Atmospheric

Administration, National Weather Service, Silver Spring, MD.

Following is an example of the core hydrometeorological data for the Rio Hominy watershed; itwould comprise the minimal amount of data for

a respective watershed case file.
30 A Framework for Analyzing the Hydrologic Condition of Watersheds

Air Temperature

Table A-3. Calcite Station: temperature (°F).

Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep Ave

Max 90 85 79 80 75 85 90 105 110 120 110 100 95

Min 57 50 37 35 30 45 60 70 78 82 70 69 57

Ave 74 68 58 58 53 65 75 88 94 101 90 85 76

Station and Source: See Table 1 above.

Evaporation

Display is Statewide (Arizona) evaporation map located in office library. Evaporation rates generally exceed precipitation

at lower elevations. High evaporation rates have been observed at stock ponds.

Source: Jeppson, et al., 1968. Hydrologic Atlas of Arizona. Report wg 351. Arizona Water Resources Laboratory,

Arizona State University, Phoenix, AZ. Evaporation Map page 53.

Wind

High winds occur June through August: 40-50 mph.

Station and Source: See Table 1 above.

SURFACE WATER

Quality

State Water Quality Classification, Standards, etc.:

The waters of the state are classed by beneficial use, and numeric standards for each class are listed. The Rio Hominy is

classed for cold-water biota in the upper reach and for warm-water biota in the lower reach. Beneficial uses identified for

the Rio Hominy are: cold- and warm-water fisheries (e.g., resident brown trout, speckled dace, pupfish, woundfin minnows), stock watering, mining, and wildlife (e.g., bighorn sheep, desert reptiles, turtles, coyotes). Water quality limited

waters list (303d list of waters that do not attain the State water quality standards) is revised and published every 3 years.

The upper reach of the Rio Hominy is limited due to existence of heavy metals, high concentrations of sediment and bacteria, and high temperatures. The lower reach of the Rio Hominy is limited due to existence of heavy metals and high

concentrations of sediment and bacteria.

Source: State Water Quality Standards for Arizona.

Quantity

Streams:

Table A-4. Monthly streamflow (cfs).

Month Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep

Max 120 90 60 105 75 110 2,500 8,000 3,200 375 150 83

Avg 40 30 20 25 15 19 350 1,100 425 185 120 68

Min 15 12 10 15 13 14 150 200 180 70 30 714

Station: Grits River Gage No. 09378200. Location Section 25, T. 15 N., R. 17 W., Straight Line Base and Meridian.

Period of Record: 1924-1997.

Source: Water Resources Data, Arizona, Water Year 1996. U.S. Geological Survey Water Data Report AZ - 1996 - 1

Bankfull Discharge: Grits Gage = 400 cfs.

Source: BLM files.
A Framework for Analyzing the Hydrologic Condition of Watersheds 31

Incised Channel Capacity: Grits gage = 6,000 cfs.

Source: BLM files.

Reservoirs and Impoundments:

Within the watershed there are 50 stock ponds ranging from 700-1,000 feet in elevation and averaging 2 acre-feet in surface area, and an evaporation pond at the mine used for drainage control with surface area equaling approximately 20

acre-feet.

Source: State water rights files.

GROUND WATER

Spring and Wells

There are major springs above the mine supplying the streams. There is one well at the mine site (at 800 feet in elevation)

with water rights for 2 cfs, and agricultural wells in the lower watershed. Many water rights exist for the agricultural wells;

see local watermaster for data.

Source: State water rights files.

Aquifers

The Navajo sandstone aquifer averages 0-300 feet below the surface. Ground water plays a significant role in providing

perennial flow to some lower streams. Recharge of ground water is derived from higher elevations and floodplains.

Source: State of Arizona USGS surface geology map.

DRAINAGE BASIN CHARACTERISTICS

Watershed Morphometry

Accounting Code: 14120208

Area: 100,000 acres 

Elevation Range: 700-5,000 feet

Watershed Aspect: southwest

Streams and Drainage:

• 12 miles of perennial channels between 1,000 and 5,000 feet in elevation

• 150 miles of intermittent/ephemeral channel; 80% of which is below 1,000 feet

• Dendritic drainage pattern - 7 miles of stream per square mile of channel

• The upper stream reach gradients are between 0.5 and 1.5%, lower stream reach gradients are <.5%

• 80% of the streams in the watershed are G channel type, 15% are C channel types, and the remainder are A channel

types (channel classification procedures—Rosgen, 1995)

• Stream channel and sheet erosion common throughout watershed; channels are incised

• Average watershed slope = 2%; slope range = 1-45%

Sources:

• Forest/Ranger District: Shining National Forest/Stumpfield District

• Watersheds delineated to fifth and sixth level units are in District GIS database and hard-copy map is located in

office library

• USGS topographic maps: entire watershed is covered by seven topographic maps at a scale of 1:24,000, as follows:

• Honey Mountain

• Bad Dog Peak

• Desert Flat

• Nasty Crack

• Grits

• Peak-a-Boo Hills

• Bad Luck Mountain

Federal Classification of Water: None
32 A Framework for Analyzing the Hydrologic Condition of Watersheds

Wetlands/Riparian Areas

All wetlands are associated with streams in upper reaches and those associated with springs from the intersection of the

channels and ground water. Generally, these areas are functioning at-risk and could be improved with more establishment

of deeper rooted shrubs and trees. These are classified in the National Wetland Inventory as:

Upper Reaches

Palustrine Scrub Shrub (80%)

Palustrine Forested (5%)

Palustrine Emergent (15%)

Spring Areas 

Palustrine Scrub Shrub (80%)

Palustrine Emergent (20%)

Source: Forest Service/BLM inventory data.

Soils

There is a completed soil survey for the watershed. The data is digitized. Upland soils are generally shallow with moderate to low infiltration rates. Low precipitation at lower elevations results in poor soil moisture conditions. See the Forest

Soil Scientist for more specific information.

Source: USDA county soil survey report.

Geology

Marine sediments (Navajo sandstone inclusions); Flagstaff limestone; volcanic peaks.

Source: State of Arizona USGS surface geology map.

Vegetation

Cover Types: Ground cover = 40%; lowland shrubs (rabbitbrush, creosote) represent 80% of the existing ground cover; the

remaining 20% are trees (mesquite and palo verde). Mesquite and palo verde are common in draws.

Vegetation is stagnant...old; not much carrying capacity for fire. This is a thermally dominated system, which

causes hydrophobic soil conditions and precludes extensive ground cover due to high evapotranspiration.

Range Data: There are two range allotments with a total of 2,000 AUMS on the watershed. Navajo Indians are the permit holders. There is year-round range use. There are 50 stock ponds between 700-1,000 ft; approximately

2 ac-ft each.

Source: District Range Conservationist’s vegetation database.

Timber Inventory: There is a timber inventory completed in 1967.

Source: District Forester’s timber inventory and maps.

Human Influence

• There is no urban development

• Cattle graze throughout the watershed

• High elevation mining and calcite exploration; there are 2 active/exploratory copper mines (1,000-5,000 ft) with

surface-disturbing activities covering about 15 acres

• 170 miles of native surface road accessing stock ponds

• 75 miles of pioneer roads to mines

• Expansion of agricultural areas are beginning to impact ground water
A Framework for Analyzing the Hydrologic Condition of Watersheds 33

Appendix C: Interdisciplinary

Team Planning—Using

the Results

Hydrologic condition analysis offers a logical

process for analysts to become effective members of an interdisciplinary land management

planning team by providing information on:

• Current status of factors influencing flow,

quality, or timing

• Reference values of the factors influencing

flow, quality, or timing

• The factors relating to the potential change

in flow, quality, or timing that will serve as

an aid to defining potentials for waterdependent resources

• Management actions that affect water flow,

quality, or timing; hence, information on

management opportunities

This information, when combined with other

resource information in an interdisciplinary

team setting, will initiate the planning process

leading to the formulation of alternatives, land

allocation, and development of standards and

guidelines.

Following is one more example of how

analysis and interpretation might occur in an

interdisciplinary setting.

Analysis

Current: A rated staff gage at bankfull flows

indicates a flow of approximately 200 cfs.

Estimated reliability of this flow value is high

(±10%). For this watershed, bankfull flows are

roughly equivalent to average annual flow

(Tr = 2.3 years).

Reference: Long-term climatic characteristics of

the watershed were derived from regional dendrochronology records. Based on this climatic

pattern and modeled streamflow, average annual

flows were historically 100 cfs. Estimated

reliability of this flow value is low (±50%)

This reference value serves as a basis for comparison with current values. The comparison

allows the determination of changes.

Interpretation

Management Implications: Where current values

are determined to be significantly different from

reference values, the cause(s) for the deviation

needs to be identified. Once the cause(s) for

the deviation has been identified, management

opportunity(s) has been identified to alter the

magnitude, direction, or rate of the deviation.

Characterization of the watershed indicated that

past management activities, including fires, grazing, road construction, and mining, may have

affected streamflow. Reviews of research papers

and journal articles indicate that road construction is the primary activity that may have

influenced flow in this watershed. Road density

has increased fourfold in the watershed. It is

believed that an increased runoff efficiency of

surface water from road surfaces, ditches, and
34 A Framework for Analyzing the Hydrologic Condition of Watersheds

culverts caused an increase in the average annual

flow of approximately 100 cfs. The reliability of

this estimate is low (±50%).

Discussion: In an interdisciplinary team setting,

the analysis results and management implications

of the increased average annual flow are

described for personnel with knowledge of

surface-water-dependent resources to consider

in regard to their resource values/needs.

The 100-cfs increase in annual flow has

provided more energy to transport sediment

through the system. Based on observed conditions in similar watersheds, it is believed that the

increase will, over time, create straight, wide,

and shallow water channels. Where increased

sediment transport capacity and wide, straight,

shallow channels are found by the

interdisciplinary team to be desirable, a management opportunity would be to build more

roads; i.e., encourage further increased average

annual flow discharges. Where such channel

conditions are found by the interdisciplinary

team to be undesirable, the management option

would be to reduce existing road density.

Potential: The potential flow, quality, or timing

conditions are established by identifying the

ability to alter the magnitude, direction, and rate

of deviation between reference and current conditions. The extent of alteration feasible from

the current condition defines the potential.

A transportation analysis available to the

interdisciplinary team (health/safety/access and

egress needs) indicates that 30% of the existing

roads can be obliterated. Runoff modeling indicates that obliteration of 30% of the roads will

reduce the average annual flow by 40 cfs; i.e.,

from 200 cfs to 160 cfs. Reliability of the 40 cfs

is low due to model coefficients. The actual

value could be ±40% different. Hence, the

potential becomes an average annual flow of

160 cfs. The decision space/operational range is

from the existing 200 cfs to a potential of 160

cfs.

Upon completing the six steps of hydrologic

condition analysis, the analyst is prepared to

interact in an interdisciplinary team discussion

with the following information:

• The reference average annual flow is 100 cfs,

with ±50% reliability

• The current average annual flow is 200 cfs,

with ±10% reliability

• The potential average annual flow is 160 cfs,

with ±50% reliability

• Roading with more sediment transport capability is causing wide, straight, and shallow

channels

The stage is set to discuss the effects of the

current 200 cfs average annual flow, a further

increase in the average annual flow, and/or the

potential 160 cfs average annual flow in regard

to water-dependent resources. Discussing the

pros and cons will shape viable alternative management actions to be considered throughout

the planning process. The discussion includes

disclosure of the reliability of the information

presented.
A Framework for Analyzing the Hydrologic Condition of Watersheds 35

Appendix D: Glossary

NOTE: The following descriptions are intended to

illustrate how various terms were used in the

development of the analytic process. They are not

formal definitions, but are provided to show use

and interpretation by the team that developed the

process.

Analyst - The person in charge of completing

the hydrologic condition process. This person

is expected to possess the technical competency

to interpret hydrologic processes and conditions.

The analyst must have sufficient knowledge of

the area being analyzed and be competent in

utilizing hydrologic tools and making judgments regarding hydrologic processes. The

analyst is expected to utilize any information,

particularly from other disciplines, that will

lead to a successful analysis. The analyst is

expected to develop rationale supporting

professional judgment.

Analytic Factor - The meteorological; surface- or

ground-water; physical, biological, biophysical;

and/or human and natural disturbance regimen

variable(s) that influences the flow, quality,

and/or timing of water in a watershed.

Characterization - The observable, dominant

processes and biophysical factors that describe

the hydrologic character of a watershed.

Examples include channel density, climatic

setting (e.g., snow-dominated, arid), and

drainage pattern. Aspects of water quality

(e.g., “quick to clear after a storm,” highly turbid, orange color) are also descriptive characterizations of the water resource in a watershed. Characterization could be achieved by

asking, “What physiographic or aquatic features

of the watershed are observable during a flight

over the watershed at 10,000 feet above the

highest terrain feature?”

Geomorphology - A natural physical process

that is responsible for the movement and

deposition of organic and inorganic materials

through a watershed under the influence of

gravity or water (either on the hillslope or in a

channel).

Hydrologic Condition - The current state of the

processes controlling the yield, timing, and

quality of water in a watershed. Each physical

and biologic process that regulates or influences streamflow and ground-water character

has a range of variability associated with the

rate or magnitude of energy and mass

exchange. At any point in time, each of these

processes can be defined by their current rate

or magnitude relative to the range of variability associated with each process. Integration of

all processes at one time represents hydrologic

condition.

Hydrologic Unit - A level of a hierarchical system to describe geographic areas (Seaber, et

al., 1987). Hydrologic units are used for the

collection and organization of hydrologic data.

Potential - The difference between current factor values and the capability to adjust toward

reference condition values is the potential.

Also referred to as operating range or

management decision space.

Professional Judgment - Intuitive conclusions

and predictions dependent upon an analyst's

training; interpretation of facts, information,

and observations; and personal knowledge of

the watershed being analyzed.

Reference - The range of a factor that is representative of its recent historical values prior to

significant alteration of its environment. The

reference could represent conditions found in

a relic site or a site having had little significant

disturbances, but does not necessarily represent
36 A Framework for Analyzing the Hydrologic Condition of Watersheds

conditions that are attainable. The purpose of

references are to establish a basis for comparing what currently exists to what has existed

in recent history. References can be obtained

through actual data, such as paired watersheds, well-managed watersheds, or extrapolated techniques such as modeling. Sources of

information include inventory and records,

General Land Office and territorial surveys,

settlers’ and explorers’ journals, ethnographic

records, local knowledge, and newspapers.

Reliability - A statistical value for the quality of

a measurement process.

Surrogate Factor - Proxies that are indicative of

specific factors influencing water flow, quality,

or timing for which there is limited or no

data/information. For example, in the absence

of water quality data, road density or stream

crossing density may be an appropriate

expression of water quality factors.

Watershed - A geomorphic area of land and

water within the confines of a drainage divide.

The total area above a given point on a stream

that contributes flow at that point.

Watershed Function - See Hydrologic

Condition.
A Framework for Analyzing the Hydrologic Condition of Watersheds 37

Literature Cited

Bailey, R.G. 1995. Description of the Ecoregions

of the United States. U.S. Department of

Agriculture. Washington, DC.

Maxwell, J.R., C.J. Edwards, M.E. Jensen, S.J.

Paustian, H. Parrott, D.M. Hill. 1995. A

Hierarchical Framework of Aquatic Ecological

Units in North America (Nearctic Zone). U.S.

Department of Agriculture, Forest Service,

GTR NC-176.

Rosgen, D. 1996. Applied River Morphology.

Wildland Hydrology. Pagosa Springs, CO.

Seaber, P.R., F.P. Kapinos, and G.L. Knapp.

1987. Hydrologic Unit Maps, U.S.

Geological Survey, WSP 2294.

U.S. Department of Agriculture, Natural

Resources Conservation Service. 1995

(Revised 1996). National Instruction No.

170-304, Mapping and Digitizing

Watershed and Subwatershed Hydrologic

Unit Boundaries. Washington, DC.

REPORT DOCUMENTATION PAGE Form Approved

OMB No. 0704-0188

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Prescribed by ANSI Std. Z39-18

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maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of infromation,

including suggestions for reducing this burden, to Washington Headquarters Services, Directorate for Information Operations and Reports, 1215 Jefferson Davis Highway, Suite 1204, Arlington,

VA 22202-4302, and to the Office of Management and Budget, Paperwork Reduction Project (0704-0188), Washington, DC 20503.

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June 1998 Final

A Framework for Analyzing the Hydrologic Condition of Watersheds

Bruce McCammon, John Rector, and Karl Gebhardt

U.S. Department of the Interior

Bureau of Land Management

National Applied Resource Sciences Center

P.O. Box 25047

Denver, CO 80225-0047

BLM/RS/ST-98/004+7210

The Bureau of Land Management and the USDA Forest Service have developed a national

framework for comprehensive interdisciplinary watershed analysis. Hydrologic condition

analysis requires, among other things, obtaining information about precipitation, ground cover,

vegetation, soils, geology, runoff, channels, floodplains, and riparian areas for each watershed.

The analysis results in an understanding of the interrelationships among meteorological, surface- and ground-water, and physical and biological factors that influence the flow, quality,

and/or timing of water. This guidance outlines a process for identifying the essential factors

needed to describe hydrologic condition, while still providing the flexibility to address sitespecific characteristics.

Watersheds

Hydrologic condition

Core hydrometeorological data 

Unclassified Unclassified Unclassified UL

48 including covers

For document tracking purposes, this document is also known as BLM Technical Note 405.