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HomeMy WebLinkAboutWG Meeting_2021April9_Draft_AmirWorking group meeting: Sustainable Management Criteria for GW levels decline and Interconnected Surface Water April 9, 2021 Ukiah Valley Basin Groundwater Sustainability Agency Draft Update on Integrated Model Draft Historical output from Calibrated Model 3 Draft Historical output from Calibrated Model 4 Draft Historical output from Calibrated Model 5 Draft Historical output from Calibrated Model Draft Historical output from Calibrated Model 7 Draft GSP Water Budget Requirements 8 Historical Evaluate how past water supply availability or reliability has previously affected aquifer conditions and the ability of the local resource managers to operate the basin within sustainable yield. Use at least the most recent ten years. Current Provide an accounting of current water budget conditions to inform local resource managers and help the Department understand the existing supply, demand and change in storage under the most recent population, land use, and hydrologic conditions. Projected Use 50 years of historical precipitation, evapotranspiration, and streamflow information as the baseline condition to estimate future hydrology. Use the most recent land use, evapotranspiration, crop coefficient, and water supply information. Draft GSP Water Budget Requirements 9 1991-2018 2015-2018 20 1 8 -20 7 0 : 1 9 6 5 -20 1 8 Draft GSP Water Budget Requirements 10 Dataset/Condition Historical Current Future Baseline (without PMAs) Climate Change (without PMAs) Climate Condition Climate data from 1991-2018 Climate data from 2015-2018 Climate data from 1965-2018 Climate data from 2965-2018 multiplied by DWR climate change multipliers Hydrologic condition Known historical hydrology from 1991- 2018 Known historical hydrology from 2015- 2018 Known historical hydrology 1965-2018 Modified hydrology based on changes to climate (ex. reservoir releases) Land Use 2010 Land Use 2010 Land Use 2010 Land Use 2010 Land Use Ag Demand Estimated demand using IDC for 1991- 2018 Estimated demand using IDC for 2015- 2018 Estimated demand using IDC for 1965- 2018 Estimated demand using IDC based on climate data Municipal Demand Available historical data Available historical data 2018 demands 2018 demands Draft Hydrologic Periods 11 Historical PeriodCalibration PeriodFuture Baseline WY Type Historical Future Above Normal 9 12 Below Normal 5 6 Critical 4 9 Dry 4 8 Wet 6 15 Period Length 28 50 Draft Historical Demands 12 ◼Groundwater pumpage falls between 6,000 to 7,000 AFY with small changes in different water year types. ◼In more recent years a 1000 AFY swing can be seen from wet to dry years. Draft Historical Demands 13 ◼SW Diversion falls mostly between 17,000 to 19,000 AFY with some changes in different water year types. ◼Municipal diversions have a decreasing trend, assuming our data is complete. DraftHistorical Water Budget –Basin Boundary 14 Draft Future Seepage 15 Draft Climate Change 16 ◼DWR Climate Change Scenarios are run with the future baseline setting. ◼Reservoir outflows are assumed constant, and no change has been made to the demands. Draft Climate Change -Average Annual Budget Changes 17 ◼Water budget shrinks due to climate change impacts ◼All elements show declines (except pumpage that was assumed constant). ◼CC 2030◼Future Baseline ◼CC 2070 Draft Climate Change -Impact on Groundwater Elevations 18 ◼A general decline can be expected, between 0-10 meters. Decline may be higher in the northern area than the south. This is with the assumption that reservoir releases stay the same. ◼Maps show difference of CC-2070 and Future Baseline: Elevation=CC-2070elev-(Future baseline)elev Draft Summary 19 ◼Future Baseline ◼Basin storage is in balance and water budget dynamically resembles climatic conditions. ◼Budget is driven by the precipitation and recharge from basin area and outer watershed. ◼Basin may not provide similar seepage to the river in the future if conditions stay the same. ◼Climate change may decrease budget terms and limit the water available. ◼Climate change may decrease groundwater levels between 0-10 meters, higher declines expected in the north and lower in the south. Model uncertainty is higher in the Redwood Valley area and these results should be considered cautiously. ◼Assuming conditions stay the same, significant decline in storage is not observed. ◼Major data gaps exist, and impactful assumptions were made to run these scenario. Filling these data gaps, including demand data, will improve model performance and accuracy of scenarios. Draft Exploratory/Informational Scenarios 20 ◼No Historical Supply ⚫We turned all diversion (Ag and Municipal) and pumpage (Ag and Municipal) off. ⚫Reservoir release is assumed constant and equal to historical releases. ⚫All other model input are held constant. ◼Business as usual: ⚫Equals our historical baseline ◼2x-Pumpage: ⚫We multiplied all pumpage (Ag and municipal) by 2. ⚫All SW diversions are equal to historical baseline. ⚫Reservoir release is assumed constant and equal to historical releases. ⚫All other model input are held constant. Draft GW Elevation Difference from Historical Baseline 21 2x-Pumpage -Historical Critical WY Type 2014 Fall (September) 2x-Pumpage -Historical Above Normal WY Type 2017 Fall (September) No Supply -Historical No Supply -Historical Draft Future Seepage 22 Draft Future Seepage 23 Draft Hopland Flow 24 Draft Questions?