Man's Impact on Great Salt Lake Elevations

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Man’s Impact on Great Salt Lake Elevations Eric K. Klotz, P.E. Craig W. Miller, P.E. Utah Division of Water Resources Great Salt Lake Issues Forum April, 2010

Future Water Needs Will Be Driven By Population Growth Utah's Population Millions 6.0 million in 2050 6 5 4 2.8 million in 2009

3 Population 2 1 0 1990 2000 2010 2020 2030 2040 2050 Year Source: Governors Office of Planning and Budget 2009 Population Projections Future Water Needs Will Be Driven By Population Growth GSL WatershedUtah's Population Population Millions 6.0 million in 2050 6 5 4.8 million 4 in 2050 2.8 million in 2009

3 Population 2 2.5 million in 2009 1 0 1990 2000 2010 2020 2030 2040 2050 Year Source: Governors Office of Planning and Budget 2009 Population Projections Million Ac-ft. Million Ac-ft. 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2 Future Future M&I Water Needs Existing Supply Vs. 2000 Based on 2000 per capita water use of 295 gpcd of 295 usewater percapita Based2000on Existing Existing M&IWater Supply 2010 Demand Demand with 25%Conservation GSL Watershed Demand Demand w/out Conservation 2020 Years 2030 2040 2050 acre acre 400,000 200,000 - - feet feet Utah’s Public Community System per Capita Use

Total Potable + Secondary Use Potable Use 375

370 350 345 350 325 320 320 300 310 295 285 275 285 260 250 260 260 255

240 220 225

Per Capita Water Use(gpcd) Water Capita Per 210 200 190 180 175 1970 1980 1985 1990 1995 2000 2005 2010 2020 2030 2040 2050

Years 08/21/07 Rev. Meeting Future Needs . Water Conservation . Agricultural Water Conversions . Water Development . Management Strategies Correcting Misconceptions Great Salt Lake in Local News May 9, 2002 – City Weekly “Salt Lake County’s thirsty lawns may spur an environmental casualty at the Great Salt Lake.” “…..the diversion of 250,000 acre feet, or 20 percent of the Bear River’s flow, would drop the lake’s water level anywhere from 1 to 6 feet, depending on annual precipitation. ….. consulted more than 20 academics and specialists in disciplines ranging from water and wetland management to ornithologists and environmental consultants at the United States Geological Survey before writing her report. ” Concept Diversions ≠ Depletions

The difference between what is diverted and what returns is depletion. It is water unavailable to a designated system (GSL). It is intended to represent the net water loss to a system.

However, remember the water cycle. The water that is depleted here is used by other systems downwind. Water is after all a renewable resource! Evapotranspiration (ET) Inefficient Landscape 40% Watering Return Flow Diversion 60%

Landscapes

Diversion Consumptive use Approx. 5%

Wells Great Salt Lake

Sewer Return Flow Residential, Commercial Diversion 95% & Industrial (M&I) Rivers

Diversion

Return Flow Consumptive use 50% Agriculture 50% Wells What Changes in Agricultural Conversion? Residential . About half of area is hardscaped . Turfgrass depletion somewhat less than alfalfa depletion . Indoor depletions are relatively small . Net depletions are around half. Residential Depletions Lower Than Agriculture

Rainfall on roof either enters storm sewer or shallow groundwater system

Indoor water use depletes little water Rough Salt Lake City Residential Depletion Budget (.25 acre lots) Hardscape (50%) Landscape (50%) & Indoor Usage 14.5 inches precip. x .8 23 inches depletion (turf) = 11.6 inches runoff 50 inches diversion Net depletion = 11.6”* *Less depletion (45%) compared to alfalfa (25.5”) depletion with nearly the same water diversion)

GSL: 55% more water is being received plus the runoff from hardscapes What Changes in Agricultural Conversion? Commercial  Often mostly hardscape.  Small landscaped areas.  Indoor depletions small (depending upon the business). Commercial Water Users Much Lower Than Agriculture

Rainfall on roof either enters storm detention & shallow groundwater system or storm sewer

Indoor water use depletes little water

Small landscaped areas=small evapotranspiration

Hardscape evaporates little water. Runoff may feed directly into storm sewers and then into a water body. Rough Salt Lake City Commercial Water Use Budget Hardscape (80%) Landscape (20%) & Indoor Usage 14.5 inches precip. x 23 inches depletion (turf) .8 = 11.6 inches Diversion depends upon runoff business type Net depletion = 4.7”* *Less depletion (18%) as compared to alfalfa (25.5”)

GSL: 82% more water is being received plus runoff from hardscapes What Changes in Agricultural Conversion?

Institutional (includes parks, schools, churches, public buildings) . Large landscaped areas . Large hardscaped areas . Indoor depletions relatively small Institutional Depletions Somewhat Lower Than Agriculture

Rainfall on roof either enters storm sewer or shallow groundwater system

Lawn evapotranspiration lower than alfalfa Indoor water use depletes little water Rough Salt Lake City Institutional Depletion Budget Hardscape (20%) Landscape (80%) & Indoor Usage 14.5 inches precip. x 23 inches depletion (turf) .8 = 11.6 inches Diversion dependent upon runoff institution Net depletion = 18.5”* *Less depletion (72%) compared to alfalfa (25.5”)

GSL: 28% more water is received plus runoff from hardscapes Agricultural Depletions by Basin (Acre-Feet) Years GSL Watershed 2000 2050 Bear 540,000 510,000 Jordan 40,000 0 Utah Lake 260,000 180,000 Weber 160,000 70,000 West Desert 110,000 100,000 Total 1,110,000 860,000 GSL Gains: +250,000 Acft Municipal and Industrial Depletions by Basin (Acre-Feet) Years GSL Watershed 2000 2050 Bear 20,000 50,000 Jordan 190,000 270,000 Utah Lake 60,000 170,000 Weber 90,000 160,000 West Desert 10,000 20,000 Total 370,000 670,000 GSL Loses: -300,000 Acft GSL Basin Imports (Acre-Feet)

Years GSL Watershed 2000 2050 Colorado 120,500 189,950 River Basin Total 120,500 189,950

GSL Gains: +70,000 Acft AFFECT ON GSL! Gain: 250,000 AF Agricultural Depletions Decrease: 300,000 AF M&I Depletions Gain: 70,000 AF CUP Depletions In 2050: 20,000 More AF/Year To the Great Salt Lake! 4201.0’ – Historical SA average elevation 4198.4’ – Present modified average elevation 2.6’ – Difference Terminal lake stage difference model

Volume Difference {

Additional depletion Difference in evaporation

At Equilibrium Difference in Inflow = Difference in Area x Net Evaporation Rule of thumb for Great Salt Lake 100,000 AF of long term additional inflow or depletion yields ~ .75 feet elevation difference With and Without Modern Depletions Great Salt Lake Elevations 4220 Natural South Arm Present modified Present Modified South Arm average south arm Historic South Arm lake elevation about 2’ 4215 below current average.

7.3’ – Average lake elevation difference caused by man

4210

4205

4200 Elevation (feet abv msl) abv (feet Elevation

4195

4190 1870 1890 1910 1930 1950 1970 1990 2010 Year Latest GSL Photo 4195.4

28 What affects lake elevation?

. Basin yield minus man’s depletions . Lake evaporation (salinity and lake bathymetry influence this) . Rainfall on Great Salt Lake’s surface Great Salt Lake Inflows

From Baskin, et al., 2002 Some Great Salt Lake Precipitation Facts GSL Basin GSL Basin Great Salt Depletions (without Lake GSL Inflow GSL) Precipitation 29,700,000 AF 900,000 AF GSL Basin Percent of total 97% 3% Precipitation GSL Inflow (% 6.4% of basin precipitation) Depletions Salt Lake City 15.62” NWFSO average annual precipitation (inches) Standard deviation 22.6% Maximum recorded 24.26” Minimum recorded 8.70” Years of record 62 30-year Mean Annual Precipitation

Precipitation grid from University of Oregon PRISM data 32 Small shifts in use or precipitation can produce large GSL elevation responses Wet year Normal year Dry year Runoff } Runoff }

} Runoff

Precipitation

Consumptive Use Consumptive

Consumptive Use Consumptive Consumptive Use Consumptive GSL Basin VegetationSource: Randy Julander 2004 GSL Basin Cloud Seeding Cloud Seeding Runoff Augmentation Great Salt Lake Basin Area Increase 2005 (af) Cache County 50,000 West Box Elder 9,000 County Tooele County 9,400 Western Uinta’s 13,200 Basin Totals 81,600 GSL in Drought GSL and Drought GSL Basin Man-Caused Depletions Farming and Agriculture Crops at peak growth stages can deplete as much water as a water surface. 80% of Utah water diversions supply agriculture. Irrigated Agriculture in GSL Basin

Each irrigated acre converted to dry farming could potentially save about an acre-foot of water. Impoundments Approximately 55,000 net af annual evaporation from reservoirs upstream. Over 116,000 acres of diked wetlands exist around the Great Salt Lake. Existing solar evaporation ponds are found in the north and south arms as well as Bear River Bay. GSL Elevation and Impoundments Man involved in changing lake

Bear River Bay Sedimentation over ~30 years Elevation Waddell, et. al., 1972 BioWest, 2010 Perhaps ½ of sediment load is caused by man. (feet) Area (acres) Volume (acre- Area (acres) Volume (acre- feet) feet)

4192 0 0 0 0 4192.5 210 109 0 0 4193 438 218 0 0 4193.5 900 553 0 0 4,194.00 1,419 1,133 0 0 4,194.50 2,100 2,013 0 0 4,195.00 3,026 3,294 0 0 4,195.50 4,100 5,076 0 0 4196 5,593 7,589 0 0 4196.5 9,000 11,327 0 0 4197 12,614 16,731 1,546 393 4197.5 16,500 24,010 3,364 1,614 4198 21,592 33,533 4,969 3,727 4198.5 26,000 45,431 5,713 6,410 Old diking plans for declining lake Dikes for flood protection Inundation map

47 48 Natural and Historical Great Salt Lake Elevation 4220 14

Historical South Arm Natural South Arm 12 4215 Elevation Difference

10 4210

4205

4200

Elevation DifferenceElevation (feet) South Arm (feet) Elevation

4195 2

4190 0 1840 1860 1880 1900 1920 1940 1960 1980 2000 Year 49 Conclusions and Observations • Man has and will continue to affect the level of the lake. • Lake level can be affected or controlled. • Development through 2050 will have a subtle effect upon lake elevations. • Climate can produce large elevation changes.

50 2007 Salinity

GSL Area Salinity (%) South Arm 12.6% Upper layer (96% fresh water evap) South Arm 15.2% Lower (93% fresh Layer water evap) North Arm 25.4% (75% Fresh water evap) GSL Salinity

Figure 2. Dissolved and precipitated salt load in Great Salt Lake, Utah

6 290- ft wide Breach Breach Depth 4200 ft depth 4198 ft 4193 ft

Total salt load in Great Loss to 5 Salt Lake West Pond

4 Total dissolved salt load of south and north parts

Dissolved load, south part

SALT LOAD, IN BILLIONS OF TONS OF BILLIONS SALT IN LOAD, Dissolved load, north Part

Precipitated load, north part 0 1962 1966 1970 1974 1978 1982 1986 1990 1994 1998 2002 2006 2010

Waddell, 2009

If We Each Save a Little, We All Save A lot!