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Home My WebLink AboutWG Meeting_2021April9_DraftWorking group meeting: Sustainable Management Criteria for GW levels decline and Interconnected Surface Water April 9, 2021 Ukiah Valley Basin Groundwater Sustainability Agency Draft GOALS for today 1.Discuss strawman proposal for lowering groundwater levels and depletion of interconnected surface water: possible option and mutual impacts 2.We need to agree on the APPROACH, we can then refine the numbers ⚫How can the model help in the decision? ⚫Evaluation of preliminary scenarios will inform some of our decision 2 Draft SMC discussion: Groundwater Level Decline →OUR STRAWMAN PROPOSAL 3 Draft Hydrograph example 4 600 605 610 615 620 625 630 635 640 391730N1232108W001 GW Elevation (ft)MT PT MO Draft 5 AquiferSite_Code Well_Name Approximate Distance to Russian River (mi) Buffer (%) Max Historical DTW (ft) X% of Max Historical DTW or 10' (ft) MT (ft) PT (ft) MO (ft) PT (Spring Min) (ft) 2 392962N1232047W001392962N1232047W001 0.30 10 57.8 5.8 63.6 57.8 17.5 13.6 2 392358N1232020W001392358N1232020W001 0.14 10 88.2 8.8 97.0 88.2 53.1 88.2 2 391730N1232108W00115N12W08L001M 0.98 20 30.1 6.0 36.1 30.1 26.4 25.3 2 391096N1231677W001391096N1231677W001 0.90 20 37.3 7.5 44.8 37.3 35.0 32.3 2 391285N1231607W001Ukiah Valley-34 1.60 20 22.7 4.5 27.2 22.7 21.5 12.1 2 391918N1232003W001Ukiah Valley-1 0.08 10 40.2 4.0 44.2 40.2 38.9 35.1 2 391918N1232003W002Ukiah Valley-2 0.08 10 49.9 5.0 54.9 49.9 47.7 45.6 2 391918N1232003W003Ukiah Valley-3 0.08 10 51.0 5.1 56.1 51.0 48.7 46.6 2 391918N1232003W004Ukiah Valley-4 0.08 10 52.0 5.2 57.1 52.0 49.6 47.9 2 391174N1231836W001Ukiah Valley-28 0.40 10 22.1 2.2 24.3 22.1 20.9 19.9 2 391411N1231983W002Ukiah Valley-37 0.85 20 57.9 10.0 67.9 57.9 50.1 57.9 2 391586N1232003W002Ukiah Valley-36 0.68 20 69.9 10.0 79.9 69.9 59.1 69.9 2 391860N1232039W001Ukiah Valley-15 0.18 10 24.0 2.4 26.4 24.0 22.8 20.8 2 392455N1231977W001Ukiah Valley-16 0.25 10 48.1 4.8 53.0 48.1 46.9 44.9 2 392455N1231977W002Ukiah Valley-17 0.25 10 93.4 9.3 102.8 93.4 92.1 93.4 2 392455N1231977W003Ukiah Valley-18 0.25 10 67.1 6.7 73.8 67.1 61.2 60.0 2 392572N1231906W001Ukiah Valley-9 0.75 20 40.3 8.1 48.3 40.3 37.2 22.5 2 T0604500280T0604500280 0.12 10 -----0.0 2 Ukiah WWTP-MW1Ukiah WWTP-MW1 0.22 10 -----0.0 2 South – Central #1(a)South – Central #1(a)0.35 10 -----0.0 2 North - Redwood Valley #1North - Redwood Valley #1 0.37 10 -----0.0 1 391918N1232003W001Ukiah Valley-1 0.08 10 40.2 4.0 44.2 40.2 38.9 44.2 1 391225N1231852W001Ukiah Valley-26 0.33 10 20.0 2.0 22.0 20.0 19.7 22.0 1 390664N1231491W001Ukiah Valley-32 0.24 10 24.8 2.5 27.3 24.8 23.8 27.3 Draft 6 M i n i m u m T h r e s h o l d Me a s u r a b l e O b j e c t i v e Tr i g g e r Draft How do we reach the goal? PMAs! 7 Draft To be considered ◼How will these SMCs impact other Sustainability Indicators? And other beneficial users? Will these SMCs for GW LEVELS be protective of them? 1.Well failure →quick calculation: if we go down 20 ft, about 10% of the wells in the basin may go dry 2.GDEs →with the approach that we are suggesting GDE will not be impacted more than the 2015 conditions 3.Sustainability Indicators: Interconnected Surface Water Depletion →If yes: we move forward and agree on numbers for MT!!! →If no: we need to reconsider the approach and reevaluate the numbers ◼How can we better understand the system? ⚫USE THE MODEL ⚫EVALUATE CLIMATE CHANGE AND MANAGEMENT SCENARIOS 8 11/12/20 1. Forecasted well failure under a return to fall 2016 lows well type n active n dry domestic 276 6 agricultural 15 0 public 6 0 well type n active n dry domestic 333 10 agricultural 19 0 public 10 0 31-year retirement age 40-year retirement age ~2%~3% Land surface elevation ft AMSL 11/12/20 Forecasted well failure under a return to fall 2016 lows minus 20 feet well type n active n dry domestic 251 25 agricultural 14 1 public 6 0 well type n active n dry domestic 288 44 agricultural 18 1 public 10 0 31-year retirement age 40-year retirement age ~9%~12% Land surface elevation ft AMSL Draft 2. Impact to GDEs 11 Draft 3. Impact to Interconnected Surface Water Depletion 12 ◼“Significant depletions of interconnected surface waters” means reductions in flow or levels of surface water that is hydrologically connected to the basin such that the reduced surface water flow or levels have a significant and unreasonable adverse impact on beneficial uses of the surface water. Draft Interconnected Surface Waters ◼23 CCR §351(o) “Interconnected surface water” refers to surface water that is hydraulically connected at any point by a continuous saturated zone to the underlying aquifer and the overlying surface water is not completely depleted. Gaining Losing disconnected Losing connected Draft Depletion of Interconnected Surface Water 14 ◼Russian River is connected to the groundwater system. ◼Establishing groundwater inputs vs. surface water inputs is challenging. ◼Effects of groundwater capture from pumping and surface water diversions on the river flow increases complexity. ◼Lack of high-quality data to establish thresholds. ◼Should we consider an adaptive approach for SMCs? Management Action Trigger to avoid the MT VOLUME OF STREAM DEPLETION THAT Leads to Undesirable Result Ideal operating range Draft Russian River reaches used as RMP’s water balance calculations as monitoring type ◼We propose to calculate the impaired baseflow contributions for segments of rivers in the Ukiah Watershed. ◼Impaired baseflow contribution is defined as the amount of groundwater contribution between East Fork and Hopland considering releases, diversions, and pumping. ⚫This is more a watershed objective: the GSA has control on PUMPING and with the available data it is difficult to “discern” the contribution coming from pumping ◼Measurement locations will begin where there is data to establish thresholds and be refined during the 5 -, 10-, and 15-year check-ins. ◼Utilizes monitoring locations already in place for better historical estimates. 15 Draft RMP logistics and assumptions ◼Russian River is highly dependent on inflow from Mendocino and groundwater inputs late in the irrigation season. ◼Accurate August measurements will provide estimates of groundwater contribution to the river. ◼Spatial aggregation means we can see changes in the system rather then seeing changes in individual springs. 16 𝐼𝑙𝑙𝑎𝑖𝑟𝑑𝑑𝑎𝑎𝑟𝑑𝑑𝑙𝑙𝑟= 𝐼𝑙𝑑𝑙𝑙𝑟−𝑂𝑟𝑟𝑑𝑙𝑙𝑟−𝑑𝑖𝑟𝑑𝑟𝑟𝑖𝑙𝑙𝑟 Draft RMP Example calculation 17 diversion diversion diversion Inflow Outflow Lots of Uncertainty in the diversions! Draft Assumptions to this approach ◼Estimates done in August and September to minimize impacts of surface water flows, most of the tributaries become disconnected during the summer. ◼Estimates includes the groundwater capture from pumping, this is the impaired baseflow. ◼Evaluation of project and managements actions better represented by the model at the scale of this SMC. ◼Uncertainties in the diversion estimates 18 Draft Which METRIC can we use for ISW depletion? ◼Groundwater elevation as proxy ◼Streamflow measurements →we will have the transect data in 5 years! ◼Modified groundwater elevation proxy through gradient approach (EDF, 2018) ◼Volume of depletion calculated by the model: need better data to refine this ◼THIS IS THE APPROACH THAT WE SUGGEST: ISW SMC= f(GWL) + f(impaired baseflow) + f(Measured/Modelled GW contribution to the stream from transect data) →ADAPTIVE SMC →transect data and therefore a new SMC will be available for the 5 years update 19 Draft Which METRIC can we use for ISW depletion? ◼Groundwater elevation as proxy ◼Streamflow measurements →we will have the transect data in 5 years! ◼Modified groundwater elevation proxy through gradient approach (EDF, 2018) ◼Volume of depletion calculated by the model: need better data to refine this ◼THIS IS THE APPROACH THAT WE SUGGEST: ISW SMC= f(GWL) + f(impaired baseflow ) + f(Measured/Modelled GW contribution to the stream from transect data) →ADAPTIVE SMC →transect data and therefore a new SMC will be available for the 5 years update 20 Draft Questions concerning the approach?