U.S. Department of the InteriorU.S. Geological Survey

Sustainability of Ground-Water Use in the San Pedro River

Basin, Cochise County, Arizona

James Leenhouts, Ph.D.

IAEA/GEF IW Learn/USGS Aquifer Exchange

April 19, 2007

The Upper San Pedro Basin

San Pedro River flows north from near Cananea, Mexico to Gila River

4,480 km2 area above Tombstone gage 1,810 km2 in

Mexico 2,670 km2 in U.S.

Fort Huachuca

The Problem: Competing Assets

The San Pedro’s riparian system (SPRNCA) Federally protected in 1988 One of shrinking number of free-

flowing perennial rivers in the Southwest

The human community National asset: Fort Huachuca Growing population Great climate, beautiful environs

Streamflow at Charleston

Total uses

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1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000YEAR

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Pumping

Streamflow

Fort Huachuca

Zero flow at Charleston, Summer 2005

June-July 2005 Charleston Streamflow

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6/1/05 6/16/05 7/1/05 7/16/05 7/31/05

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Investigations

Geohydrologic studies Improve the conceptual model Detailed investigation of physical system Synthesis in ground-water model

Riparian water needs studies Multidisciplinary study Related hydrologic variables to riparian condition Quantified riparian ET

Geohydrologic Studies

Water levels

Streamflow

Aquifer storage change - microgravity

Geophysical exploration

Unsaturated zone flow

Stream temperature monitoring

Lacoste and Romberg Model D

Relative-gravity meter

Investigations Network

WE

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BEDROCK

ETET

RECHARGE

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CURRENT CONCEPTUAL CURRENT CONCEPTUAL GROUND-WATER FLOW GROUND-WATER FLOW

SYSTEM SYSTEM

Spring

limestone

EPHEMERALSTREAM

RECHARGE

EPHEMERALSTREAM

RECHARGE

EAST WEST

WE

TL

AN

DS

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BEDROCK

SCHEMATIC SCHEMATIC REPRESENTATION OF REPRESENTATION OF

GROUND-WATER FLOW GROUND-WATER FLOW MODELMODEL

BEDROCK

LAYER 3

RECHARGE

RE

CH

AR

GE

ETET

EAST WEST

EPHEMERALSTREAM

RECHARGE

EPHEMERALSTREAM

RECHARGE

RE

CH

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GE

RE

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LAYER 5LAYER 4

LAYER 2

LAYER 1

Riparian Water Needs Investigation

Three components

Hydrology

Ecology

Evapotranspiration

Riparian Condition Class Relates

hydrology to ecology

Provides science to inform policy

The Mandate: Sustainable Yield

Stipulated by Congress

Not safe yield --> pumping = recharge

Sustainable Ground-Water Yield “…the development and use of ground water in a

manner that can be maintained for an indefinite time without causing unacceptable environmental, economic, or social consequences.”

The Players

Upper San Pedro Partnership 21 local, state, federal, and non-

governmental agencies Goal is to identify and implement

solutions to assure reasonable water supply for the river and the people

AZ congressional delegation

Other groups

Reservoir Analogy

No Pumping

Safe Yield

Sustainable Yield

Initial Criteria for Sustainability

Unacceptable consequences:

The riparian system ceases to function

Unavailability of water causes Fort Huachuca to close

Sustainable yield

How much water: Do the people need? Does the riparian system

need? Temporal effects Spatial effects Climatic effects

Ground-Water Budget

Sustainable yield – initial goalAn Aquifer-Storage Approach

Sustainability – defined spatially

Define indicators and thresholds Indicators – variables that inform status Thresholds – markers beyond which sustainability

fails

Environment SocioeconomicIndicator Threshold Indicator Threshold

Ground-water levels – regional aquifer ? ? ?Streamflow ? ? ?Spring discharge ? ? ?Ground-water levels – alluvial aquifer

Defined by water-needs study ? ?

Assessing Progress = Monitoring

Water budget aspects

Tabulation of pumping Continued refinement of

inflow and outflow values

System-response aspects

Water levels Microgravity Spring and stream

discharge Vertical gradients

Sustainable Yield – Adaptive Management

Iterative interaction

Management Action

Monitoring

Analysis

Science Informing Policy

Spatial definition of ground-water management

“Capture map”

Semiarid: Only half of the residents drive camels

Questions?

Reaching the Goal

Broad categories of water management measures:

Conservation Growing population

Recharge Needs source of water

Importation Potential legal issues

PerennialIntermittent

Stream gage

Who, What, Where, When, How?

June-July 2005 Charleston Streamflow

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Interaction of Multiple Factors

Summer (June) 7-Day Low Flow at Charleston, 1936-2005

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June 7-day low flow

5-year average

2005 streamflow data not yet verified.

Annual Section 321 Reports

See the 2004 Section 321 report at:http://water.usgs.gov/Section321.2004_050705.pdf

Sustainability: “…the development and use of ground water in a

manner that can be maintained for an indefinite time without causing unacceptable environmental, economic, or social consequences.”

Outline

Introduction to basin – talk about SPRNCA – usual superlatives, Fort, Cities The issues – declining streamflows, zero flow. Discussion of the players Capture Description of work done – model, water needs. Sustainable yield goal – Section 321 Status of water budget – include reservoir analogy to sustainable yield Science to policy section

Section 321 reports Capture maps Level change maps Gravity maps