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HomeMy WebLinkAbout4-14-21_TACMeetingPresentationSustainable Management Criteria for GW levels decline and Interconnected Surface Water April 14, 2021 Ukiah Valley Basin Groundwater Sustainability Agency Draft Exploratory Scenarios Draft Exploratory/Informational Scenarios 3 ◼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. ◼No Lake Mendocino Releases in Dry and Critical years: ⚫Historical pumpage and diversions ⚫No releases to the East Fork in 2013-2015 WYs. Draft GW Elevation Difference from Historical Baseline 4 2x-Pumpage -Historical Critical WY Type 2014 -Fall (September) Difference in meters (~3ft) No Supply -Historical No Release –Historical Draft GW Elevation Difference from Historical Baseline 5 2x-Pumpage -Historical Above Normal WY Type 2016 -Fall (September) Difference in meters (~3ft) No Supply -Historical No Release –Historical Draft River Leakage 6 Draft River Leakage 7 Draft Hopland Flow 8 Draft GW Elevation vs. Leakage and Streamflow 9 Aug 2015 ~ 2 cfs 14 ft 13 ft 15 ft 12 ft Draft Gaining Losing Conditions of River 10 2x-Pumpage Critical WY Type 2014 -Fall (September) Difference in meters (~3ft) No Supply No ReleaseHistorical Draft Gaining Losing Conditions of River 11 Summer Below Normal WY Type 2012 Change of River Gaining/Losing Conditions in a year Winter FallSpring River Losing to Aquifer Dry River Segment River Gaining from Aquifer Draft Gaining Losing Conditions of River 12 2x-Pumpage Critical WY Type 2014 -Fall (September) No Demand No ReleaseHistorical River Losing to Aquifer Dry River Segment River Gaining from Aquifer Draft Gaining Losing Conditions of River 13 2x-Pumpage Above Normal WY Type 2016 -Fall (September) No Demand No ReleaseHistorical River Losing to Aquifer Dry River Segment River Gaining from Aquifer Draft Questions Draft GOALS for today 1.Evaluate model results and scenarios: model can help to inform decision on SMCs 2.Discuss strawman proposal for lowering groundwater levels and depletion of interconnected surface water: possible option and mutual impacts 3.We need to agree on the APPROACH, we can then refine the numbers 15 Draft Exploratory scenarios analysis ◼Business as usual (historical) ◼No pumping-no diversion ◼2X pumping and normal diversion ◼Historical with no release from Lake Mendocino in dry and critical years 16 Draft SMC discussion: Groundwater Level Decline →OUR STRAWMAN PROPOSAL based on the scenario results 17 Draft Hydrograph example 18 600 605 610 615 620 625 630 635 640 391730N1232108W001 GW Elevation (ft)MT PT MO Draft 19 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 Undesirable results ◼Undesirable results: Significant and unreasonable chronic lowering of groundwater levels occurs when such lowering threatens the long-term viability of domestic, agricultural, municipal, or environmental users of groundwater. ◼Criteria to Define Undesirable Results Significant and unreasonable Chronic Lowering of Groundwater Levels resulting from groundwater extraction occurs when more than *25%* of representative monitoring wells for groundwater levels and storage in the Basin fall below their MTs for *2* consecutive years 20 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 10 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 use model results and future PMAs (Projects and management actions) to finalize MT numbers!!! →If no: we need to reconsider the approach and reevaluate the numbers 21 Draft How do we reach the goal? PMAs! 22 Draft 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 Draft Forecasted well failure under a return to fall 2016 lows minus 10 feet well type n active n dry domestic 261 15 agricultural 14 1 public 6 0 well type n active n dry domestic 299 33 agricultural 18 1 public 10 0 31-year retirement age 40-year retirement age ~5%~9% Land surface elevation ft AMSL Draft 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 Implications for well protection measures Fall 2016: $0.23 -0.32M well replacement costs* Fall 2016 minus 10 feet: $0.42 –0.81M well replacement costs* Fall 2016 minus 20 feet: $0.67 –1.1M well replacement costs* *cost methodology based on (Pauloo et al, 2021) Draft 2. Impact to GDEs 27 Draft 3. Impact to Interconnected Surface Water Depletion 28 ◼“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 First key component of the ISW SMC… ◼We need to provide a map of the surface water that will be considered “INTERCONNECTED” ◼Based on our analysis of depth to groundwater and GDEs: the main stem of the Russian river is considered CONNECTED for SGMA management ◼The tributaries are considered disconnected as most of them are ephemeral and dry during most of summer ⚫To include tributaries as interconnected SW we need to collect more information to understand how pumping (which is what the GSA can manage) really impacts the tributaries 29 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 31 ◼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 Which METRIC can we use for ISW depletion? ◼Groundwater elevation as proxy FOR NOW ◼Streamflow and leakage estimates →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(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 32 Draft Which METRIC can we use for ISW depletion? ◼Groundwater elevation as proxy FOR NOW ◼Streamflow and leakage estimates →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(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 33 Draft Take away messages: what is reasonable? ◼The groundwater level MT leads to: ⚫No additional ISW depletion ⚫No additional loss of GDEs ⚫No land subsidence ⚫~x% well impacted (requiring rehabilitation) ◼Going lower than 2015, we need to prove that a lower MT will NOT cause significant and unreasonable impacts to: ⚫interconnected surface water ⚫groundwater dependent ecosystems ⚫land subsidence ⚫domestic wells, agricultural wells, municipal wells 34 Draft Next step ◼Start providing written approaches to the SMCs for all the Sustainability Indicators in Chapter 3: need to agree on the approach and we can continue the discussion on refining the numbers ◼Development of future climate change scenarios ◼Development of more targeted and implementable PMAs scenarios: some of them can be simulated with the model, other should just be described in Chapter 4 35 Draft Final questions? Thank You!