Groundwater Trends in Utah

Patrick M. Lambert, U.S. Geological Survey, Utah Water Science Center2011 Utah Water Users Workshop

March 14-16, 2011St. George Utah

The groundwater resource in Utah

An aquifer can be compared to a bank account and groundwater occurring in the aquifer as money in the account

Recharge/Deposits

Storage/Savings

Discharge/Withdrawals Infiltration of

precipitation

Seepage from surface water

Percolation of irrigation water

Subsurface inflow

Discharge to streams and springs

Transpired by plants

Subsurface outflow

Artificial recharge – Injection, infiltration ponds

Withdrawal from wells

Just as a bank account must be balanced, withdrawals from an aquifer must be balanced by some combination of increased recharge, decreased discharge, or removal from storage.

Predevelopment conditions

Natural and Induced recharge

4,500 cfs

Natural and Induced recharge

13,400 cfs

Discharge to surface-water bodies, springs, ET4,500 cfs

Development conditions

Pumpage13,500 cfs

Discharge to surface-water bodies, springs, ET1,600 cfs

Rate of decrease in storage: 1,700 cfs

… withdrawals from an aquifer must be balanced

Hypothetical groundwater system

Why do we care what the balances of Utah groundwater accounts are and which way we are trending?

Development conditions

Pumpage13,500 cfs

Discharge to surface-water bodies and ET1,600 cfs

Rate of decrease in storage: 1,700 cfs

Increased pumping costs

Changes in water quality

Reduced flows to streams, lakes, springs, flowing wells

Land Subsidence

Potential negative effects of groundwater depletion

Such effects, while variable , happen to some degree with any groundwater withdrawal.

Why do we care what the balances of Utah groundwater accounts are and which way they are trending?

As with other resources, society must weigh the benefits against the consequences of groundwater use.

In order to preserve and optimize the use of critical groundwater resources, we observe and assess to provide the information necessary to make informed choices in issues that have long-term effects.

Utah Groundwater Resources

Withdrawal from the 16 areas shaded in the figure made up 87% of total withdrawal for the state in 2009 (2009 statewide withdrawals = 969,000 acre-ft)

Areas of groundwater development in Utah

From Groundwater Conditions in Utah, Spring of 2010: Utah Division of Water Resources Cooperative Investigations Report no. 51 - http://ut.water.usgs.gov/publications/GW2010.pdf

Utah Groundwater Resources

Most wells in Utah yield water from unconsolidated basin fill deposits.

Smaller percentage of withdrawal occurs from consolidated rock mainly in eastern and southern parts of the state where basin fill aquifers have limited occurrence and capacity.

2009 estimated withdrawals from wells = 969,000 acre-ft

Trends in groundwater use in Utah

(Modified from Gates, 2004, Groundwater Development in Utah and Effects on Groundwater levels and Chemical Quality: in Groundwater in Utah; Resource, Protection, and Remediation, Utah Geological Association Publication 31)

Trends in groundwater use

State wide annual total groundwater withdrawal has increased by about 740,000 acre-ft since 1939 and about 340,000 acre-ft since 1963.

Irrigation withdrawals made up over 57% of total withdrawals in 2009.

Fluctuations in irrigation withdrawals are the main cause of the fluctuations in total withdrawal.

Irrigation, and thus total annual withdrawals, fluctuate mostly in response to changes in precipitation and resulting changes in surface-water flow and its availability for irrigation.

Withdrawals of groundwater from wells in Utah, 2009

2009

From Groundwater Conditions in Utah, Spring of 2010: Utah Division of Water Resources Cooperative Investigations Report no. 51 - http://ut.water.usgs.gov/publications/GW2010.pdf

Utah Groundwater State-Wide Monitoring Network

Program began in 1962 Annual water-level

measurements in about 1,000 wells

Water-quality sampling at about 100 wells

Cooperatively funded by Utah Department of Natural Resources, Divisions of Water Rights and Water Resources and the USGS Cooperative Water Program, more recently by the UDEQ (2005)

Average declines in water levels in major groundwater basins – March 1980 to March 2010

Groundwater Trends

Depicted range of declines represents average of water-level changes at all measured wells within a basin.

Based on data presented in Groundwater Conditions in Utah, Spring of 2010: Utah Division of Water Resources Cooperative Investigations Report no. 51 - http://ut.water.usgs.gov/publications/GW2010.pdf

Curlew and Cache Valleys Groundwater use is

predominantly for irrigation Currently, no significant

trend in annual withdrawals Moderate fluctuations

groundwater levels and storage – Generally declining water levels

Groundwater Trends – Northern Utah

Water-level change from March 1980 to March 2010

1930 2010

Cache ValleyUnless otherwise stated, water-level change maps in this and subsequent slides are from Groundwater Conditions in Utah, Spring of 2010: Utah Division of Water Resources Cooperative Investigations Report no. 51 - http://ut.water.usgs.gov/publications/GW2010.pdf

East Shore, Salt Lake Valley, Tooele Valley, Utah and Goshen Valleys

Groundwater use is predominantly for public supply

Substantial public-supply withdrawals in high-population basins – Salt Lake (137,000 acre-ft in 2009) and Utah valleys (109,000 acre-ft)

Zones of significant water-level declines including flowing well areas

Groundwater Trends – North-Central Utah

Water-level change from March 1980 to March 2010

1930

2010

1930 2010

East Shore Area

Water-level change from Feb 1980 to Feb 2010

Groundwater Trends – North-Central Utah

Salt Lake Valley

201019301930 2010

1930 2010

Northern Utah Valley

Groundwater Trends – North-Central Utah

Water level change in the principal basin-fill aquifer, 1981-2004

1930 2010

Negative values indicate water-level declines From Hydrology of Northern Utah Valley, Utah County, Utah, 1975-2005: U.S. Geological

Survey Scientific Investigations Report 2008-5197 http://pubs.usgs.gov/sir/2008/5049/

Groundwater Trends – Southwestern Utah

Pahvant, Milford, Parawan, Cedar Valley, Beryl-Enterprise, Central Virgin River

Groundwater use predominantly for irrigation

Significant increases in total withdrawals from 1940 through mid 70’s

Largest and most extensive water-level declines observed in groundwater basins with significant groundwater development

Water-level change from March 1980 to March 2010

Groundwater Trends – Southwestern Utah

Pahvant Valley

1930 2010

1930 2010

Water-level change from March 1980 to March 2010

Groundwater Trends – Southwestern Utah

Cedar Valley

1930 2010

Water-level change from March 1980 to March 2010

Groundwater Trends – Southwestern Utah

Beryl-Enterprise area

Water Quality trends are also important!

Withdrawals from aquifer zones containing good-quality water can allow adjacent poorer-quality water to migrate and degrade water quality.

Where groundwater is withdrawn from an aquifer, surface water of differing quality may be drawn into the aquifer.

Curlew Goshen Pahvant Milford Beryl-Enterprise Cedar Valley (Iron County) Salt Lake Valley

Increasing trends in dissolved-solids concentrations indicated in Utah long-term monitoring network

Areas where increases in dissolved-solids concentrations in groundwater are observed

Groundwater quality monitoring network

• Water quality sampling began in 1964.

• Sampling ended after 2001.

• Restarted in 2005, 60 wells.

• Sampled about 104 wells in 2010

• Network of about 300 wells, each sampled every 3 years.

Trends in chemical quality of groundwater

8-27

-80 9

Curlew Valley

Graphs of annual withdrawals and dissolved solids concentrations in this and subsequetn slides are from Groundwater Conditions in Utah, Spring of 2010: Utah Division of Water Resources Cooperative Investigations Report no. 51 - http://ut.water.usgs.gov/publications/GW2010.pdf

Pahvant

Trends in chemical quality of groundwater

Trends in chemical quality of groundwater

Beryl-Enterprise

Groundwater comprises about 30% of water use in the valley (most groundwater withdrawals are for public supply)

Range of water-quality results from different sources of water to the aquifer and water rock interaction

Salt Lake Valley - dissolved-solids concentrations

Distribution of dissolved-solids concentrations in the principal aquifer in Salt Lake Valley, 1998-2002

< 250 mg/l

250-500 mg/l

500-1,000 mg/l

1,000-2,000 mg/l

2,000-5,000 mg/l

> 5,000 mg/l

Decadal-Scale Changes in Dissolved-Solids Concentrations in Groundwater Used in Public Supply, Salt Lake Valley, Utah: U.S. Geological Survey Fact Sheet 2010-3073 - http://pubs.usgs.gov/fs/2010/3073/

Confining layers and upward vertical gradients inhibit vertical flow of poor quality water to confined aquifer however…

Substantial increases in TDS in the principal aquifer are occurring in some areas

Salt Lake Valley groundwater quality trends

Central and Eastern and Salt Lake Valley

• Colored zones indicate distribution of dissolved solids.

• Outlines indicate areas where concentrations of dissolved solids increased by 20% or more from 1988-92 to 1998-2002.

< 250 mg/l

250-500 mg/l

500-1,000 mg/l

Decadal-Scale Changes in Dissolved-Solids Concentrations in Groundwater Used in Public Supply, Salt Lake Valley, Utah: U.S. Geological Survey Fact Sheet 2010-3073 - http://pubs.usgs.gov/fs/2010/3073/

Northern Utah Valley

Utility of basic data and groundwater flow models to understand the effects of water use on groundwater systems – an example

Goal – Information to preserve and optimize the use of critical groundwater resources

• Lower water levels (drawdown) in large areas of the aquifer

• Reduced natural discharge

Application to groundwater resource management From USGS Northern Utah Valley (NUV) Groundwater assessment and flow modeling project - Projected effect of future increased pumping in Northern Utah Valley - Test case of 2x current pumping

30 ft

25 ft

20 ft

Drawdown, comparedto 2004 water levels

(Computed drawdowns from simulated 2x 2004 pumping for 30 years) Utah

Lake

Decision Variables 47 individual wells

Constraints Maximum flow rate of

2,500 gpm per well Drawdown ≤ 20 ft Total of all withdrawal ≥

89,000 acre-ft/year

Objective Maximize Withdrawal

Simulation-Optimization modeling to assess groundwater systems - NUV Optimization Example 1: Problem design

Application of the USGS groundwater flow and optimization (Groundwater Management (GWM) process tool) models for Northern Utah Valley

• > 70 wells pumping 44,500 acre-ft/yr in 2004

• Increase to 89,000 acre-ft/yr over 30 years

Scenario to meet future groundwater demands

Existing wells in 2004 with capacity > 300 gpm

Example 1: results

19 ft

19 ft

17 ft

Example 1 Drawdown,Compared to 2004 water levels.Resulting from optimized pumping from existing wells.

• Only 86,300 acre-ft/yr could be withdrawn and still meet constraints

• Results show which wells must be pumped & how much• 27 wells versus >70 wells• 100 to 2,400 gpm• most average 500 gpm• 4 wells > 1,500 gpm• 11 wells > 1,000 gpm

• Reduced overall drawdown by 5 to 10 ft

• This result was achieved in one run of the model

(Computed drawdowns from simulated 2x 2004 pumping for 30 years)

% change (base case)

Changes in ground-water discharge

-23%-39%-15%

Utah LakeDrains, springs, & flowing wellsEvapotranspiration

30 ft

25 ft

20 ft

Drawdown,

19 ft

19 ft

17 ft

Drawdown,Ex.1

% change (Ex.1) -25%-35%-14%

Example 1: comparison2x 2004pumping

• 97% of the target withdrawal using only 27 wells (versus more than 70 wells)

• Significant improvement in drawdown

(Computed drawdowns from simulated 2x 2004 pumping for 30 years)

Groundwaterwatch.usgs.gov or NWIS Mapper

http://ut.water.usgs.gov/

References

Groundwater Conditions in Utah, Spring of 2010: Utah Division of Water Resources Cooperative Investigations Report no. 51 - http://ut.water.usgs.gov/publications/GW2010.pdf

Groundwater Development in Utah and Effects on Groundwater levels and Chemical Quality: in Groundwater in Utah; Resource, Protection, and Remediation, Utah Geological Association Publication 31

Decadal-Scale Changes in Dissolved-Solids Concentrations in Groundwater Used in Public Supply, Salt Lake Valley, Utah: U.S. Geological Survey Fact Sheet 2010-3073 - http://pubs.usgs.gov/fs/2010/3073/

Groundwater Depletion Across the Nation, U.S. Geological Survey Fact Sheet-103-03 - http://pubs.usgs.gov/fs/fs-103-03/

Hydrology of Northern Utah Valley, Utah County, Utah, 1975-2005: U.S. Geological Survey Scientific Investigations Report 2008-5197 http://pubs.usgs.gov/sir/2008/5049/

Three-Dimensional Numerical Model of Ground-Water Flow in Northern Utah Valley, Utah County, Utah - http://pubs.usgs.gov/sir/2008/5049/

Use of Simulation-Optimization Modeling to Assess Regional Groundwater Systems: U.S. Geological Survey Fact Sheet 2005-3095 - http://pubs.usgs.gov/fs/2005/3095/

O.E. MeinzerUSGS Groundwater Division Chief, 1912-1946

Questions?