Tarboton, David G.

English

DigitalCommons@USU

Modeling the Hydrology of the Great Salt Lake: What makes the Great Salt Lake go up and downDavid Tarboton Utah State Universitydtarb@usu.edu435-797-3172Outline• Lake level fluctuations• Water Budget– Precipitation– Streamflow– Evaporation• Sensitivity• Salinity• Modeling – integrated water and total salt (not individual minerals)Area, AArea, AE x AHow a closed basin (e.g. GSL works)LevelLevelInflows IIE x AIf I > E x A level risesIf I < E x A level fallsLevel adjusts to fluctuating inputs so that on averageI = E x AI includes inflows from streams and precipitation on the lake I = Q + P x ASubject to climate variability.E is less variable, but also depends on climate and salinity, C.As C increases E decreasesEvaporation depth EEvaporation volume  E x AVolume, VSalt Load LSalt Concentration C=L/V1850 1900 1950 20004195420042054210Level (ft)South Arm USGS 10010000 Great Salt Lake at Saltair boat harbour, UTNorth Arm USGS 10010100 Great Salt Lake near Saline, UTSouth Arm water year mean16% 4195.750% 4200.884% 4205.516% 4194.950% 4198.884% 4202.2Max 4211.6 on1872-06-271986-06-23Min 4191.4 on1963-10-152014-05-03 N 4194.4 S 4195.1GSL Level Record10/1/1949 - 09/30/2013  period with complete climate and streamflow dataWater Budget• Q,  Streamflow+Groundwater– 3 major rivers. Multiple USGS gauges– Groundwater 75000 acre ft/yr (Waddell and Barton, 1980)• A, V Area and Volume– From bathymetry and level• P, Precipitation– From PRISM (Oregon State University) • E, Evaporation• Withdrawals (West desert pumping, Evaporation ponds)WnetAEAPQV -×-×+=D29%69%-96%-4%2%Bathymetry0 200000 600000 100000041704180419042004210Area (acre)Level (ft)Baskin 2005Loving 2000Baskin 2005 + Farmington Bay+MagCorp ponds0e+00 2e+05 4e+05 6e+05 8e+05 1e+0641704180419042004210Area (acre)Level (ft)Baskin 2006Loving 2000South Arm North Armthe lake bed topography that relates area to level and volume Great Salt Lake Precipitation and StreamflowBasin Area (km2)Precipitation (mm)Streamflow (acre-ft)Great Salt Lake 4713 326.7 -Bear 19262 536.4 1328023 (57%)Weber 6413 657.4 338634 (15%)Jordan/Provo 9963 563.9 509638 (22%)West Desert 14604 347.7 -Other (Davis etc) - - 135240 (6%)Total 54953 565.6 2311434 (100%)Mean Annual Values 1949-2013• Precipitation from aggregation of PRISM data over each area• Streamflow from multiple USGS gauges1950 1960 1970 1980 1990 2000 20100e+004e+068e+06Water Yearacre ftTotal Natural InputStreamflowPrecipitationGroundwaterW Desert PumpingW Desert ReturnMineral Pond WithdrawalGreat Salt Lake Inputs (1949-2013)Adjustments to GSL inputs• West Desert pumping. 2.5 MAF removed 4/87 to6/89. 27 months• 200000 AF return from West Desert. 1/90 to 6/92.30 months• Pond operations 5 months per year May – Sept withwithdrawals based on reported water use and waterrights.Precipitation 991,992 acre-ft (29%)Streamflow 2,311,435 acre-ft (69%)Groundwater 75,000 acre-ft (2%)Total Inflows 3,378,427 acre-ftNet pumping and withdrawals-132,060 acre ft (4%)0 100 200 300 4000.50.60.70.80.91.0TDS  (g/L)Ebrine/EfreshSalinity dependent evaporation(Penman evaporation equation modified for salinity based on ion activity coefficients, Mohammed and Tarboton, 2008)1950 1960 1970 1980 1990 2000 20100.40.60.81.01.21.4102030405060inchesmetersMass balance Mean = 1.06 mNorth Mean = 1.05 mSouth Mean = 1.21 mAnnual GSL EvaporationEvaporation in each arm calculated from Penman Equation with activity coefficient adjusted for salinityWhat input is the lake level most sensitive to?∆𝑉 = 𝑃% + 𝑄 + 𝐺 − 𝐸% −𝑊,-.𝜙%01 = 𝜎%01𝜎34 Sensitivity0.3 0.83 0.55Variability dominated by Q, but stabilized by EvBut how does Ev depend on area and salinity?Mohammed, I. N. and D. G. Tarboton, (2012), "An examination of the sensitivity of the Great Salt Lake to changes in inputs," Water Resour. Res., 48(11): W11511, http://dx.doi.org/10.1029/2012WR011908. How do changes in area and salinity affect evaporation volume𝐸% = 𝐴. 𝑆𝐶𝐹. 𝐸:;0.49 0.09 0.07Variability in evaporation volume is dominated by changes in area with only small effects due to changes in salinity and changes due to potential evaporation 1950 1960 1970 1980 1990 2000 2010050100200300C  (g/L)Causeway closureLVG4NMLRD2RT3ECNFB2AS2RT2RT4NLNAC3SSAC1AC2IS1IS2RT1What about salinity?NorthSouthC≈L/VCauseway ClosureData from Utah Geological Survey (Andrew Rupke 10/10/2012).  Calculation of Salt Load• z1, C1• z2, C2• z3, C3•Lake Level hℎ − (𝑧? + 𝑧@)/2ℎ − (𝑧@ + 𝑧D)/2𝑉? = 𝑉(ℎ) − 𝑉(ℎ − (𝑧? + 𝑧@)/2)𝑉@ = 𝑉(ℎ − (𝑧? + 𝑧@)/2) − 𝑉(ℎ − (𝑧@ + 𝑧D)/2)……𝐿 = 𝐶?𝑉? + 𝐶@𝑉@ + 𝐶D𝑉D +…012345Billion tons1965 1970 1975 1980 1985 1990 1995 2000 2005 2010West Desert PumpingWest Desert Return FlowNorth Arm LoadSouth Arm LoadLVG4NMLRD2RT3ECNFB2AS2RT2RT4NLNAC3SSAC1AC2IS1IS2RT1Total LoadTotal Dissolved LoadPrecipitated Load4.807  Billion Tons 4.793  Billion Tons3.844 BillionTonsSalt LoadsInferred decline in total dissolved salt in GSLData from Utah Geological Survey (Andrew Rupke 10/10/2012).  Loads here are reported in US or short tons. 1 US ton = 0.9072 metric tons = 907.2 kg.4194 4196 4198 4200 4202 4204 4206200000300000400000500000Level (ft)Area (acre)CurrentModifiedEvaluating the impact of Mineral Evaporation Ponds on Lake Level• Input balanced by less evaporation -> Smaller Area• Bathymetry altered due to Pond occupation of part of Lake• Net effect is a difference in lake level• Time series modeling to account for variabilitySmaller AreaChange in levelPredictive Mass Balance Model• Inputs– Precipitation (N and S)– Evaporation (Historic or Calculated)– Streamflow– Initial Level• Output– Levels and volumesCnet QWAEAPQV ±-×-×+=DEvaluated separately for N and S arm with Causeway flow by USGS modelValidation1970 1980 1990 2000 201041904195420042054210levelSouthNorthSouth ModeledNorth ModeledObserved and Modeled Lake LevelValidation case driven by Mass Balance EvaporationNote:  West desert pumping salt loss reduced to 40% of reported to reconcile with load observations Validation1970 1980 1990 2000 2010050100150200250300350g/LSouthNorthObserved and Modeled ConcentrationValidation case driven by Mass Balance EvaporationNote:  West desert pumping salt loss reduced to 40% of reported to reconcile with load observations Validation1970 1980 1990 2000 2010012345billion tonsSouthNorthPrecipitateTotal DissolvedTotalObservedObserved and Modeled Salt LoadsValidation case driven by Mass Balance EvaporationFuture simulations• Water budget model with inputs P, Q, E/T resampled from historic years retaining each year as a block• Resampling used k-nearest neighbors (based on total streamflow) to group similar years together and maintain statistical dependence• Evaporation used either the historic value from mass balance, or was calculated from salinity • Pumping limits level to 4208 ft• Pond withdrawal and altered bathymetry scenario 0 1 2 3 4 5 6 7 8 9 11 13 15 17-0.20.00.20.40.60.81.0Lag yearsAnnual Total Inflow autocorrelation from knn100 resampled input simulations2010 2012 2014 2016 2018 202041854190419542004205Level (ft)Frequency4190 4195 4200 420505101520Distribution of 10 year ahead Levels10 year simulations2012 2014 2016 2018 20204180419042004210Level (ft)South Arm Level - NA100 simulated traces of South Arm Level for the no action scenario.  2012 2014 2016 2018 20204180419042004210Level (ft)South Arm Level - PA100 simulated traces of South Arm Level for the proposed action scenario  South Arm LevelQuantile 16% 50% 84%NA 4190.4 4194.1 4199.8PA 4188.1 4192.4 4199.0North Arm Concentration (g/L)Quantile 16% 50% 84%NA 263.8 337.6 343.8PA 239.8 332.1 341.7North Arm LevelQuantile 16% 50% 84%NA 4189.4 4192.8 4199.4PA 4187.0 4190.9 4198.7South Arm Concentration (g/L)Quantile 16% 50% 84%NA 86.9 118.4 153.6PA 80.8 119.5 151.5Evaluation of Expansion Pond AlternativesNote:  These simulations are from the permit request as of 2010.  The permit request has since evolved 10th year quantiles.  Net additional withdrawal 280,000 acre-ft/yrShaded colored areas give the 25th and 75th percentiles for lake level predictions under streamflow changes. Lines give the median (50th percentile) lake level predictions.Great Salt Lake level predictions time series under different streamflow input change scenariosMohammed, I. N. and D. G. Tarboton, (2012), "An examination of the sensitivity of the Great Salt Lake to changes in inputs," Water Resour. Res., 48(11): W11511, http://dx.doi.org/10.1029/2012WR011908. Conclusions• Multi-year dynamic variability with 5-10 year adjustment time scale• Streamflow is most sensitive input• Lake area is most sensitive evaporation determinant• Total dissolved salt load is declining• Integrated water and salt simulation effective for addressing questions about future management scenariosQuestions?dtarb@usu.edu

Modeling the Hydrology of the Great Salt Lake: What makes the Great Salt Lake go up and down

What makes the Great Salt Lake go up and down.  Examining the sensitivity of the Great Salt Lake to changes in inputs

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Modeling the Hydrology of the Great Salt Lake: What makes the Great Salt Lake go up and down

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