Patrick M. Lambert, U.S. Geological Survey, Utah Water Science Center 2011 Utah Water Users Workshop March 14-16, 2011 St. 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, ET 4,500 cfs Development conditions Pumpage 13,500 cfs Discharge to surface- water bodies, springs, ET 1,600 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 Pumpage 13,500 cfs Discharge to surface- water bodies and ET 1,600 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.

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

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 (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)

State wide annual total groundwater withdrawal has increased by about 740,000 acre-ft since 1939 and about 340,000 acre-ft since Irrigation withdrawals made up over 57% of total withdrawals in 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, From Groundwater Conditions in Utah, Spring of 2010: Utah Division of Water Resources Cooperative Investigations Report no

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 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

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 Water-level change from March 1980 to March Cache Valley Unless 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 pdf 10.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 Water-level change from March 1980 to March East Shore Area

Water-level change from Feb 1980 to Feb 2010 Salt Lake Valley

Northern Utah Valley Water level change in the principal basin-fill aquifer, Negative values indicate water-level declines From Hydrology of Northern Utah Valley, Utah County, Utah, : U.S. Geological Survey Scientific Investigations Report

Pahvant, Milford, Parawan, Cedar Valley, Beryl-Enterprise, Central Virgin River Groundwater use predominantly for irrigation Significant increases in total withdrawals from 1940 through mid 70s Largest and most extensive water-level declines observed in groundwater basins with significant groundwater development

Water-level change from March 1980 to March 2010 Pahvant Valley

Water-level change from March 1980 to March 2010 Cedar Valley

Water-level change from March 1980 to March 2010 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

Water quality sampling began in Sampling ended after Restarted in 2005, 60 wells. Sampled about 104 wells in 2010 Network of about 300 wells, each sampled every 3 years.

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

Pahvant

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, < 250 mg/l mg/l ,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

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 to < 250 mg/l mg/l ,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

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, compared to 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 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 Lake Drains, springs, & flowing wells Evapotranspiration 30 ft 25 ft 20 ft Drawdown, 19 ft 17 ft Drawdown, Ex.1 % change (Ex.1) -25% -35% -14% Example 1: comparison 2x 2004 pumping 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 MapperNWIS Mapper

Groundwater Conditions in Utah, Spring of 2010: Utah Division of Water Resources Cooperative Investigations Report no 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 Groundwater Depletion Across the Nation, U.S. Geological Survey Fact Sheet Hydrology of Northern Utah Valley, Utah County, Utah, : U.S. Geological Survey Scientific Investigations Report Three-Dimensional Numerical Model of Ground-Water Flow in Northern Utah Valley, Utah County, Utah - Use of Simulation-Optimization Modeling to Assess Regional Groundwater Systems: U.S. Geological Survey Fact Sheet

O.E. Meinzer USGS Groundwater Division Chief, Questions?