San Juan Basin Regional Watershed and Groundwater Models

Transcription

1 San Juan Basin Regional Watershed and Groundwater Models Modeling Workshop July 31,

2 Overview Executive Summary Goal of Briefing Modeling Overview Basin Yield- Surface Water/Groundwater Yield Model Model Calibration Long-Term Basin Operation Simulation Repeat of Hydrology Questions/Answers/Discussion/Follow-Up 2

3 Overview Executive Summary Goal of Briefing Modeling Overview Basin Yield- Surface Water/Groundwater Yield Model Model Calibration Long-Term Basin Operation Simulation Repeat of Hydrology Questions/Answers/Discussion/Follow-Up 3

4 San Juan Basin Modeling Work Adequate tools and information were not available to analyze the Doheny Desal Project interaction with the groundwater basin. The Doheny Desal workgroup undertook the development and calibration of surface water/ground water modeling to develop the necessary tools. The model was cooperatively developed between the Doheny Desal workgroup and San Juan Basin Authority The goal was to understand the interactions between the Doheny Desal Project and the groundwater basin to support upcoming decisions; we are still in the decision-making process at this time. 4

5 Modeling Limitations Advanced Surface and Groundwater Models provide powerful analytical tools for evaluation of groundwater basin yield, recharge/discharge, groundwater level responses, solute transport, and seawater intrusion. Results are not absolute. A calibrated model provides a high degree of accuracy in prediction. Calibrated models provide an excellent tool for assessment and comparative evaluation. 5

6 Modeling/Data Refinements for the Modeling Work Interpretation of precipitation & rain gauge info and application to the surface and groundwater models; surface water model time step is daily for runoff modeling to more accurately reflect the short duration of storms and watershed response Evapotranspiration losses Geologic/lithologic structure of basin Basin bedrock elevations Stream gauging data limitations Stream infiltration rates Dry weather/urban runoff flows Pumping and water level records Multiple iterations between the surface model and the groundwater model to get acceptable results; groundwater model time step is monthly Calibration period changed to 2004 to 2010 when the basin was under higher pumping stress Calibration of upgradient creeks at boundary conditions of the model 6

7 Major Findings 1. Groundwater storage capacity is 46,000 AF, about 12% less than DWR s 1972 estimate. Actual storage in the basin in 2010 was approximately 30,000 AF. 2. Run 2h overstates basin supply due to seawater intrusion. With the salinity constraint, runs 2i/2j reduces the pumping yield to 8,040 afy and 9,150 afy in dry and average periods and results in less seawater intrusion than under run 2h. However, runs 2i/2j also overstate yield if the seawater intrusion control point is maintained at the coast. 3. Planned extractions of 11,300 AFY exceed supply. 4. Storage levels fall below 50% during extended dry periods (repeat of hydrology). 5. Seawater intrusion would impact SCWD wells in 9 to 12 years. 6. The Doheny Desal Project utilizes on average about 1,660 AF per year from the inland water sources (groundwater basin); this needs to be mitigated if the Doheny Desal Project is to move forward. 7. Additional work will be completed by both the Doheny Desal Project and the San Juan Basin Authority under the MET Foundational Actions Program 7

8 Overview Executive Summary Goal of Briefing Modeling Overview Basin Yield- Surface Water/Groundwater Yield Model Model Calibration Long-Term Basin Operation Simulation Repeat of Hydrology Questions/Answers/Discussion/Follow-Up 8

9 Goal of Briefing Accept modeling process, work and results Will be peer reviewed by the SJBA Modeling Results/Implications (with +/- ranges) o o o Basin operations without Doheny Desal Project Same with Doheny Desal Project Mitigation Options for the Doheny Desal Project 9

10 Modeling Process The scope of work was developed based on discussions at 7 meetings Participants included CSJC, SMWD, RMV, MWDOC, WEI, PACE and GEOSCIENCE. 16 project progress meetings were held during the model development Nine technical meetings (with MWDOC, WEI, Psomas, PACE and Numeric Solutions) Five Model Advisory Committee Meetings Two Technical Advisory Committee Meetings Another Peer Review will be conducted by SJBA 10

11 Surface Water Model/Groundwater Model Interface Surface Water Model Infiltration Precipitation Surface Runoff Interflow ET Deep Percolation Iterative Process Streambed Percolation Dad Daily time steps Groundwater Model Ocean Water Intrusion Rising Water Discharge to Streamflow ET Ground Water Pumping Areal Recharge & Mountain Front Runoff Recharge Streamflow Routing Streambed Percolation Monthly time steps Return Flow Subsurface Outflow to the Ocean Change in Groundwater Storage Underflow Inflow from Upgradient of San Juan, Horno, Trabuco, 11 and Oso Creeks

12 Major Assumptions of Model Runs 2 and 3 Model Run Hydrology Streambed Percolation Rate Local Groundwater Pumping and Well Screen Pumping Level Constraint Doheny Desalination Project Model Version Run 2a Run 2b Run 2c Run 2d Run 2e Run 2f (Dry) (Average) 3 ft/day 1 ft/day 6 ft/day 3 ft/day 1 ft/day 6 ft/day Initial requested pumping using existing wells and anticipated new vertical wells with water level constraint (top of screen) September 2012 Run 2g Run 2h Run 2i Run 2j (Dry, Wet and Average) (Dry) (Average) 3 ft/day Same as Runs 2a-2f with salinity constraint for SCWD wells Requested near-term pumping (from existing wells and anticipated new vertical wells) with water level constraint of 2 ft above top of well screen Same as Runs 2h with salinity constraint for SCWD wells No Doheny Desalination Project December 2012 (recalibrated with period and revised subsurface inflow from upgradient creeks) Run 3a Run 3b (Dry, Wet and Average) 3 ft/day Same as Run 2h Near-term With Project Pumping of 30 MGD (7 Slant Wells with length of 520 ft) With Project Pumping of 30 MGD (7 Slant Wells with length of 1,000 ft) December 2012 (recalibrated with period and revised subsurface inflow from upgradient creeks) 12

13 Local Groundwater Yield (Run 2 without Doheny Desal Project) Summary of Total Lower Basin Yields (AFY) Without Doheny Desalination Project (Over range of percolation rates from 1 to 6 per day) Hydrology Dry Hydrology ( ) Run 2h Water Level Constraint, Streambed Percolation Rate = 3 ft/day Runs 2i (Dry) and 2j (Average) Water Level and Salinity Constraints, Streambed Percolation Rate = 3 ft/day 8,558 (-1,263 to +1,152) 8,038 (-1,263 to +1,152) Average Hydrology ( ) 9,382 (-1,710 to + 1,663) 9,146 (-1,710 to +1,663) Wet Hydrology ( ) 10,937 (-2,804 to +2,369) - 13

14 Summary in Local Groundwater Yield (Run 2 without Doheny Desal Project) Summary in Lower Basin Yields (AFY) Due to Change in Streambed Percolation Rate of 3 ft/day Hydrology Runs 2b and 2e Streambed Percolation Rate = 1 ft/day Runs 2c and 2f Streambed Percolation Rate = 6 ft/day Dry Hydrology ( ) Average Hydrology ( ) Wet Hydrology ( ) -1,263 (-14.8%) +1,152 (+13.5%) -1,710 (-18.2%) +1,663 (+17.7%) -2,804 (-25.6%) +2,369 (+21.7%) 14

15 Ocean Water Intrusion Impact (Run 2 without Doheny Desal Project) Without mitigation, ocean water intrusion occurs in all years and progressively moves inland. South Coast wells are impacted first as they are located closest to the ocean. Production out of the South Coast wells was reduced only under the Salinity Constraint Runs 2i (dry) and 2j (average); the production was shut down when increasing salinity reached 2,600 mg/l. Impact of Salinity Constraints on South Coast Water District Well Yields (AFY) Scenario Run 2h (Water Level Constraint) Runs 2i (dry) and 2j (average) (Water Level and Salinity Constraints) Difference Dry Hydrology 1, Average Hydrology 1, Wet Hydrology 1,

16 Basin Storage Utilization (Run 2 without Doheny Desal Project) The water rights held by SJBA requires that the cumulative storage in the basin always remain at or above 50% of the basin storage capacity now estimated at 46,000 AF. This limits the cumulative use of storage to 23,000 AF. Groundwater in storage under Run 2h conditions is generally below this limit during dry years and only rises above it in during wet years. 16

17 Precipitation, Pumping & Groundwater in Storage (Run 2h) Full Basin (46,000 acre-ft) Cumulative Departure from Mean Annual Precipitation Cumulative Decline in yr. 64 (-2,300 acre-ft) Groundwater in Storage, acre-ft Storage (30,000 acre-ft) 50% of Storage (23,000 acre-ft) Pumping Note: The area of the basin is from the model boundaries and is approximately 3,700 acres Groundwater in Storage Annual Ground Water Pumping, acre-ft

18 Storage Capacity of Model Area Area (in orange and white) Used for Storage Calculation (3,700 acres) Parameter Units GEOSCIENCE (Jan 2013) Area [acres] 3,700 Storage Capacity [acre-ft] 46,000* Groundwater in Storage 2010 [acre-ft] 30,000** * Storage capacity was calculated from land surface to the base of the aquifer **Based on water level in December

19 Comparison of Storage Capacity Parameter Units DWR (1972) WEI (Mar 2012) GEOSCIENCE (Jan 2013) Area [acres] 2,800 2,800 2,800 Storage Capacity [acre-ft] 40,850 26,539 36,000* Area Used for Storage Calculation (2,800 acres) Groundwater in Storage Fall 2010 [acre-ft] NA 20,387 25,000** * Storage capacity was calculated from land surface to the base of the aquifer **Based on water level in December

20 Impact on Local Groundwater Yield from Doheny Desalination Project (Run 3) Summary of Total Lower Basin Yields (AFY) with and without Doheny Desalination Project Scenario Dry Hydrology ( ) Average Hydrology ( ) Wet Hydrology ( ) Run 2h (No Doheny Desal Project with Water Level Constraint) Runs 2i and 2j (No Doheny Desal Project with Water Level and Salinity Constraints) Run 3a (Doheny Desal Project with Water Level Constraint) Doheny Desal Project Impact Compared to Run 2h Compared to Runs 2i and 2j 8,558 8,038 6,545-2,013-1,493 9,382 9,146 7,326-2,056-1,820 10,937-9,142-1,795 - Doheny Desal Impact = 1,660 AFY 20

21 Ocean Water Intrusion Protection (Run 3 with Doheny Desal Project) SCWD Well Stonehill Model-Calculated TDS Concentration, mg/l 35,000 30,000 25,000 20,000 15,000 10,000 5,000 Doheny Desalination Project will benefit the local purveyors, providing an ocean water intrusion barrier. Run 3b (with Doheny Desal Project) Run 2h (without Doheny Desal Project)

22 Overview Executive Summary Goal of Briefing Modeling Overview Basin Yield- Surface Water/Groundwater Yield Model Model Calibration Long-Term Basin Operation Simulation Repeat of Hydrology Questions/Answers/Discussion/Follow-Up 22

23 Modeling Overview Assumptions Source of Data Confidence Level / Model Limitations Model Sensitivity Boundary Conditions 23

24 Major Model Assumptions Hydrologic Period: A 64-year period from January 1947 through December 2010 was selected for the hydrologic period for the model simulation. This hydrologic period covers wet ( ), dry ( ), and average ( ) hydrologic cycles. 24

25 Assumption for Hydrologic Period Annual Precipitation, inches Cumulative Departure from Mean Annual Precipitation Annual Precipitation* Dry Hydrology (Ave Precipitation = 10.7 in/yr) Average Hydrology (Ave, Precipitation = 12.4 in/yr) Wet Hydrology (Average Precipitation = 19.0 in/yr) 12.3 in/yr Cumulative Departure from Mean Annual Precipitation, inches *Laguna Beach No. 2 Station Calendar Year 25

26 Major Model Assumptions (Cont.) Streambed Percolation Rate: A total of three streambed percolation rates were used for the model predictive scenarios. The values of 1 ft/day, 3 ft/day, and 6 ft/day were assumed to represent estimated minimum, average and maximum, streambed percolation rates within the SJB, respectively. Summary of Total Lower Basin Yields (AFY) Sensitivity on Percolation Rate (ft/day) Scenario 1 foot per day 3 feet per day 6 feet per day Dry Hydrology 8,093 9,356 10,508 Average Hydrology 8,436 10,146 11,809 Wet Hydrology 8,710 11,514 13,883 26

27 Major Model Assumptions (Cont.) Local Groundwater Pumping: SJB local groundwater pumping (including initial requested pumping of 15,487 acre-ft/yr and requested near-term pumping of 11,216 acre-ft/yr) was provided by the CSJS and SCWD. 27

28 Assumptions for Local Groundwater Pumping City's GWRP Wells City's Other Wells SCWD Wells Initial Requested Groundwater Pumping Requested Near-Term Groundwater Pumping [acre-ft/yr] [acre-ft/yr] Kinoshita Tirador 1, SJBA No. 4 1,381 1,230 SJBA No CVWD No. 1 1,381 1,230 Dance Hall 1,243 1,110 Eastern Well-So Cooks 1, Eastern Well-WS#5 1, So Well-Rosan Ranch #2 1,105 0 So Well-Rosan Ranch #1 1,105 0 Subtotal 10,907 7,758 Rosenbaum No North Open Space Hollywood 2A Mission St. 0 0 Subtotal 1,330 1,023 Stonehill 1, New No. 2 1, Subtotal 2,000 1,585 Private Wells 1, Total 15,487 11,216

29 Major Model Assumptions (Cont.) Water Level Constraint: During the model simulation, groundwater levels within the existing and anticipated CSJC and SCWD vertical wells were constrained in order to maintain water levels at 2 ft above the screened intervals. This constraint was set to prevent cascading aerated water from entering the wells. These constraints were achieved by using the USGS (2002) Drawdown-Limited Multi-Node Well Package, which adjusted the pumping rates during each model predictive scenario. 29

30 Wells Susceptible to Water Level Constraint Wells (shown as yellow) Kinoshita, Dance Hall, Eastern Well So. Cooks, and Eastern Well WS #5 are most susceptible to the water level constraint due to the top of screens being too high. 30

31 Major Model Assumptions (Cont.) Water Quality Constraint Run: For the water quality constraint run, the pumping from SCWD wells was stopped when the model-predicted TDS concentration at the SCWD s wells exceeded a threshold (i.e., TDS at 2,600 mg/l, maximum TDS for Groundwater Recovery Facility listed in the CDPH permit), and stayed off for the remainder of the model predictive period. 31

32 Major Model Assumptions (Cont.) Doheny Desalination Project: For the local yield run (Run 2), it was assumed that no Doheny Desalination Project pumping occurred during the entire model predictive period. Run 3a assumed the Doheny Desalination Project slant wells produced 30 MGD during the 64-year predictive period using seven (7) slant wells with a total length of 520 ft each. 32

33 Major Assumptions of Model Runs 2 and 3 Model Run Hydrology Streambed Percolation Rate Local Groundwater Pumping and Well Screen Pumping Level Constraint Doheny Desalination Project Model Version Run 2a Run 2b Run 2c Run 2d Run 2e Run 2f (Dry) (Average) 3 ft/day 1 ft/day 6 ft/day 3 ft/day 1 ft/day 6 ft/day Initial requested pumping using existing wells and anticipated new vertical wells with water level constraint (top of screen) September 2012 Run 2g Run 2h Run 2i Run 2j (Dry, Wet and Average) (Dry) (Average) 3 ft/day Same as Runs 2a-2f with salinity constraint for SCWD wells Requested near-term pumping (from existing wells and anticipated new vertical wells) with water level constraint of 2 ft above top of well screen Same as Runs 2h with salinity constraint for SCWD wells No Doheny Desalination Project December 2012 (recalibrated with period and revised subsurface inflow from upgradient creeks) Run 3a Run 3b (Dry, Wet and Average) 3 ft/day Same as Run 2h Near-term With Project Pumping of 30 MGD (7 Slant Wells with length of 520 ft) With Project Pumping of 30 MGD (7 Slant Wells with length of 1,000 ft) December 2012 (recalibrated with period and revised subsurface inflow from upgradient creeks) 33

34 Sources of Data Groundwater levels, groundwater pumping, groundwater quality, pumping test and lithologic logs: CSJC, SCWD, MWDOC, CSWRCB, PSOMAS and WEI. Land use: Southern California Association of Governments. Soil types: Soil Survey Geographic (SSURGO) Database. Streamflow: USGS. Land surface elevations: USGS. Precipitation: Western Regional Climate Center. Evaporation: CIMIS. Land Use Soil Type 34

35 Confidence Level/Model Limitations The San Juan Basin Regional Groundwater Model has been improved through the additional modeling work including: Integration with a basin-wide surface water model, Incorporated results from a 3D-litholoigc model, Recalibration to a more recent period ( ), which has higher groundwater pumping than other historical conditions, Recalibration against portion of the Phase 3 extended slant well pumping test, Reevaluation of the subsurface inflow from the upgradient creeks 35

36 Confidence Level /Model Limitations (Cont.) The San Juan Basin Model is a simplified approximation of a complex hydrogeologic system and has been designed with certain built-in assumptions. The accuracy of the predictions made by the model is highly dependent on the simplifying assumptions used. The predictive ability of the model will improve if the model is recalibrated on a regular basis as new data is collected. The modeling results are not absolutes, but are indications that will need to be confirmed by actual operations, monitoring and refinement through an adaptive management process. 36

37 Surface Water Model Sensitivity Analysis Varied model parameters +/- 50% of the calibrated values Compared Relative Error of Streamflow at La Novia and Trabuco Gages Parameters Varied Length of Overland Flow Plane Average Slope of Overland Flow Plane Manning s Coefficient of Overland Flow Streambed Infiltration ET for Baseflow ET for Lower Zone ET for Ground Water Mean Infiltration Rate Ratio of Maximum and Mean Soil Infiltration Rates Fraction of Surface Detention Storage to Become Interflow Exponent Affecting Infiltration Rate by Lower Zone Storage Fraction of Infiltrated Water Lost to Deep Aquifer Interception Storage Upper Zone Storage Lower Zone Storage Groundwater Recession Rate The most sensitive model parameters are: Lower Zone Storage ET for Lower Zone Streambed Infiltration Upper Zone Storage Mean Soil Infiltration Rate Exponent Affecting Infiltration Rate by Lower Zone Storage Groundwater Recession Rate 37

38 Groundwater Model Sensitivity Varied model parameters +/- 50% of the calibrated values Compared Relative Error of Water Levels Parameters Varied Horizontal Hydraulic Conductivity Vertical Hydraulic Conductivity Specific Yield Streambed Percolation Groundwater Pumping The most sensitive model parameters are: Groundwater Pumping Streambed Percolation Horizontal Hydraulic Conductivity x 1.5 Horizontal Hydraulic Conductivity x 0.5 Normalized Sensitivity of Selected Model Parameters Normalized sensitivity is the difference between the sum of squared residuals from the sensitivity run and the calibration run, divided by the sum of squared residuals of the calibration run. The greater the normalized sensitivity value, the more Specific Yield x Specific Yield x Vertical Hydraulic Conductivity x 1.5 Vertical Hydraulic Conductivity x 0.5 Streambed Percolation, Areal Recharge, Recharge from Mountain Front Runoff and Return Flow x 1.5 Streambed Percolation, Areal Recharge, Recharge from Mountain Front Runoff and Return Flow x 0.5 Groundwater Groundwater Pumping x 1.5 Pumping x

39 Groundwater Model Boundary Conditions Specified flux: Subsurface inflow from upgradient creeks (including San Juan, Oso, Trabuco and Horno creeks) was calculated by the San Juan Creek Watershed Model, and averages 2,700 acre-ft/yr. The total subsurface inflow is consistent with the subsurface inflow of 2,600 acre-ft/yr reported in the Order No of the SWRCB (1978). No flow: assigned to bedrock portion of model area Constant head: assigned to ocean 39

40 Subsurface Inflow from Upgradient Creeks Estimated Subsurface Trabuco Creek Upgradie nt Creek Groundwater Recharge from Watershed Estimated Groundwater Production Inflow used for Groundwater Model [acre-ft/yr] Model Oso Creek Horno Creek San Juan Creek San Juan Creek Horno Creek [acre-ft/yr] [acre-ft/yr] 3,670 2,500* 1, Oso Creek Trabuco Creek Total 5,200 2,500 2,700 *WEI, oral communication,

41 Overview Executive Summary Goal of Briefing Modeling Overview Basin Yield- Surface Water/Groundwater Yield Model Model Calibration Long-Term Basin Operation Simulation Repeat of Hydrology Questions/Answers/Discussion/Follow-Up 41

42 Previous Groundwater Models Phase 2A 2007 Model Purpose Slant wellfield capacity and source yield Limitations Very limited offshore data required several assumptions. Onshore model was limited to two layers due to limited data. Not a regional groundwater model CSJC 2009 Model Purpose Potential impact on CSJC s water supply from the contaminant plumes Limitations It s a one layer model and only covers the area to the coastline and is not able to simulate the Doheny Desal Project. Phase 2B Regional Groundwater Model Purpose Groundwater basin water yield and drawdown impacts Limitations Surface water daily flow model was not part of scope of work. Monthly streamflow constraint overestimated GW basin supply Upper basin pumping data was not available. 42

43 Overestimation of Basin Yield by the 2010 Model One of the limitations of 2010 model is that it did not include a surface watershed/streamflow model and had to rely on a monthly time step approximation, which resulted in an overestimation of basin yield. Precipitation does not occur in average amounts, some of the major storms last 2 hours, some 8 hours or longer. Representing the input to the basin in smaller time increment (e.g. daily) is critical to estimate the streambed percolation. 43

44 Surface Water Model/Groundwater Model Interface Surface Water Model Infiltration Precipitation Surface Runoff Interflow ET Deep Percolation Iterative Process Streambed Percolation Dad Daily time steps Groundwater Model Seawater Intrusion Rising Water Discharge to Streamflow ET Ground Water Pumping Areal Recharge & Mountain Front Runoff Recharge Streamflow Routing Streambed Percolation Monthly time steps Return Flow Subsurface Outflow to the Ocean Change in Groundwater Storage Underflow Inflow from Upgradient of San Juan, Horno, Trabuco, 44 and Oso Creeks

45 Schematic Diagram of Surface Water Model (HSPF) Precipitation ET Gravity Drainage Infiltration Deep Percolation Streambed Percolation Surface Runoff Interflow Surface Water Model HSPF (Hydrological Simulation Program FORTRAN) is a model evolved from the Stanford Watershed Model. It continues to undergo refinement and enhancement of its capabilities along with user support and code maintenance activities under joint sponsorship of both the 45 EPA and USGS.

46 Delineation of Sub-Watershed 36 sub-watersheds were delineated. Each element consists of Reach segment, Pervious land segment, and Impervious land segment. They were delineated based on: Topography Drainage Patterns Types of stream channels, and Location of gaging stations and basins 46

47 1 1 Groundwater Model Grid j-direction 50 ft 50 ft 524 PUMPING & RECHARGE i-direction INFLOW/OUTFLOW 1,012 Groundwater Model 1,012 x 524 Cells/Layer X 3 layers* (1,590,864 cells in total) *For the on-shore area, the model is two layers. One additional model layer was added to the offshore area to simulate the percolation of ocean water. 47

48 Basement of Aquifer Systems Basement of Basin Fill Non-water Bearing Layer 2 Layer 3 Stonehill Well 48

49 Lithologic Model Cross Section A-A A A B-3 MW-1 SL-1 MW-1 BH-6 BH-5 Layer 2 Layer 3 A A Bedrock (unweathered) Bedrock (weathered) Organics High Plasticity Clay Clay Silt Equal Coarse / Fine-Grained Clayey Sand Silty Sand Sand with Silt or Clay Clean Sand Gravel with Clay Gravel with Silt Clean Gravel Clean Gravel / Cobble 49

50 Total Annual Recharge, acre-feet Model Calculated Total Annual Recharge 30,000 27,000 24,000 21,000 18,000 15,000 12,000 9,000 6,000 3,000 (Run 2h, streambed Percolation = 3ft/day) Cumulative Departure from Mean Annual Precipitation Dry Hydrology (Ave Recharge = 8,640 afy) Ocean Water Intrusion Total Annual Recharge Average Hydrology (Av Recharge = 10,320 afy) Wet Hydrology (Average Recharge = 15,480 afy) Calendar Year Cumulative Departure from Mean Annual Precipitation, inches

51 200,000 Streamflow Discharge to the Ocean (Run 2h, Streambed Percolation = 3 ft/day) 180, ,000 Average Hydrology Median Outflow = 8,300 acre-ft/yr Surface Runoff Outflow to Ocean, acre-ft 140, , ,000 80,000 60,000 Dry Hydrology Median Outflow = 6,800 acre-ft/yr Wet Hydrology Median Outflow = 35,800 acre-ft/yr 40,000 20,

52 Overview Executive Summary Goal of Briefing Modeling Overview Basin Yield- Surface Water/Groundwater Yield Model Model Calibration Long-Term Basin Operation Simulation Repeat of Hydrology Questions/Answers/Discussion/Follow-Up 52

53 Surface Water Model Calibration Criteria Graphic Comparisons Time series plots of observed and simulated values for streamflow Observed and simulated scatter plots for streamflow Statistical Tests Residual statistics: mean residual, absolute mean residual and relative error Correlation test: correlation coefficient (R) and goodness-of-fit (R 2 )

54 Statistical Measure of Model Calibration Type of Flow Data Goodness-of-Fit (R 2 ) Calibration Performance R 2 < 0.60 Poor Daily Flow 0.60 < R 2 <0.70 Fair 0.70 < R 2 < 0.80 Good R 2 > 0.80 R 2 < 0.65 Very Good Poor Monthly Flow 0.65 < R 2 <0.75 Fair 0.75 < R 2 < 0.85 Good R 2 > 0.85 Very Good Source: AQUA TERRA Consultants (EPA HSPF maintenance contractor)

55 Hydrograph of Monthly Flow (1989 to 1999) SJC at La Novia Model-Calculated Observed Trabuco Ck at San Juan Capistrano

56 Scatter Plot of Monthly Flow (1989 to 1999) R 2 = 0.93 SJC at La Novia Very Good Trabuco Ck at San Juan Capistrano R 2 = 0.89 Very Good

57 Scatter Plot of Daily Flow (1989 to 1999) R 2 = 0.73 SJC at La Novia Good Trabuco Ck at San Juan Capistrano R 2 = 0.70 Good

58 Groundwater Model Calibration Procedure Model calibration was performed to compare model-simulated water levels to field-measured values using the history matching technique along with Visual PEST (Parameter ESTimation). PEST optimizes aquifer parameters based on observed water levels over time. Ranges of acceptable values for each parameter are set. Through a nonlinear estimation technique known as the Gauss-Marquardt-Levenberg method, PEST adjusts the parameter values to reduce the residual error at wells across the model area. 58

59 Histogram of Water Level Residuals in the Vicinity of the City Wellfield Transient Model Calibration (January 2004 through December 2010) 100% 80% Frequency 60% 40% 70.7% This histogram shows a bell shape with over 70% of the water level residuals found in the range of +/- 5 ft, indicating a reasonable good model calibration. 20% 13.8% 15.1% 0% 0.0% 0.3% 0.2% 0.0% < to to -5-5 to 5 5 to to 25 > 25 Water Level Residuals (Measured Less Model-Calculated), ft 59

60 Calibrated Hydrographs near City Wellfield 60

61 Basin Yield Sensitivity The groundwater model sensitivity analysis shows that the model is most sensitive to changes in recharge terms (in turn affected by changes in precipitation and streambed percolation rate). 61

62 Sensitivity of Basin Yield to Precipitation Change in Lower Basin Yields (AFY) Due to Change in Precipitation from Average Hydrology Conditions ( ) Hydrology Change in Yield from Average Hydrology ( ) Dry Hydrology ( ) -824 Wet Hydrology ( ) +1,555 62

63 Sensitivity of Basin Yield to Streambed Percolation Rate Change in Lower Basin Yields (AFY) Due to Change in Streambed Percolation Rate of 3 ft/day Hydrology Streambed Percolation Rate = 1 ft/day Streambed Percolation Rate = 6 ft/day Dry Hydrology ( ) Average Hydrology ( ) Wet Hydrology ( ) -1,263 +1,152-1,710 +1,663-2,804 +2,369 63

64 Overview Executive Summary Goal of Briefing Modeling Overview Basin Yield- Surface Water/Groundwater Yield Model Model Calibration Long-Term Basin Operation Simulation Repeat of Hydrology Questions/Answers/Discussion/Follow-Up 64

65 Annual Groundwater Budgets (Runs 2i and 2j) No Doheny Desal But Assumes Salinity Constraint Ocean Water Intrusion Rising Water Discharge to Streamflow ET Ground Water Pumping Areal Recharge & Mountain Front Runoff Recharge Return Flow Streambed Percolation ,040 9, ,150 6,790 Dry ( ) Average ( ) Subsurface Outflow to the Ocean Change in Groundwater Storage Subsurface Inflow from Upgradient of San Juan, Horno, Trabuco, and Oso Creeks 2,700 2,700 Note: Ocean water intrusion is occurring Units in acre-ft/yr 65

66 Annual Groundwater Budgets (Run 3) With Doheny Desal Pumping From Ocean Doheny Desal Project Total Pumping Rising Water Discharge to Streamflow ET Ground Water Pumping Areal Recharge & Mountain Front Runoff Recharge Return Flow Streambed Percolation 31,820 31,800 31,410 33,730 33,730 33, ,550 7,330 9, ,150 6,790 11,780 Dry ( ) Average ( ) Wet ( ) Subsurface Outflow to the Ocean ,340 Change in Groundwater Storage Subsurface Inflow from Upgradient of San Juan, Horno, Trabuco, and Oso Creeks 2,700 2,700 2,700 Note: No ocean water intrusion Units in acre-ft/yr 66

67 Groundwater Yield by Wells - Dry Hydrology ( ) City's GWRP Wells City's Other Wells SCWD Well Requested Near-Term Pumping Run 2h (without Doheny Desal Project) Run 3 a (with Doheny Desal Project) Streambed Percolation = 3 ft/day Doheny Desal Project Impact [acre-ft/yr] [acre-ft/yr] [acre-ft/yr] [acre-ft/yr] Kinoshita Tirador SJBA No. 4 1,230 1,230 1,230 0 SJBA No CVWD No. 1 1,230 1,230 1,230 0 Dance Hall 1, Eastern Well-So Cooks Eastern Well-WS# Subtotal 7,758 5,419 4, Rosenbaum No North Open Space Hollywood 2A Mission St Subtotal 1, City Subtotal 8,781 6,225 5, Stonehill New No SCWD Subtotal 1,585 1, ,424 Private Wells Total 11,216 8,558 6,545-2,013 67

68 Groundwater Yield by Wells - Average Hydrology ( ) City's GWRP Wells City's Other Wells SCWD Well Requested Near-Term Pumping Run 2h (without Doheny Desal Project) Run 3a (with Doheny Desal Project) Streambed Percolation = 3 ft/day Doheny Desal Project Impact [acre-ft/yr] [acre-ft/yr] [acre-ft/yr] [acre-ft/yr] Kinoshita Tirador SJBA No. 4 1,230 1,230 1,230 0 SJBA No CVWD No. 1 1,230 1,230 1,230 0 Dance Hall 1, Eastern Well-So Cooks Eastern Well-WS# Subtotal 7,758 6,082 5, Rosenbaum No North Open Space Hollywood 2A Mission St Subtotal 1, City Subtotal 8,781 7,019 6, Stonehill New No SCWD Subtotal 1,585 1, ,495 Private Wells Total 11,216 9,382 7,326-2,056

69 Groundwater Yield by Wells - Wet Hydrology ( ) City's GWRP Wells City's Other Wells SCWD Well Requested Near-Term Pumping Run 2h (without Doheny Desal Project) Run 3a (with Doheny Desal Project) Streambed Percolation = 3 ft/day Doheny Desal Project Impact [acre-ft/yr] [acre-ft/yr] [acre-ft/yr] [acre-ft/yr] Kinoshita Tirador SJBA No. 4 1,230 1,230 1,230 0 SJBA No CVWD No. 1 1,230 1,230 1,230 0 Dance Hall 1,110 1, Eastern Well-So Cooks Eastern Well-WS# Subtotal 7,758 7,479 7, Rosenbaum No North Open Space Hollywood 2A Mission St Subtotal 1,023 1,023 1,023 0 City Subtotal 8,781 8,502 8, Stonehill New No SCWD Subtotal 1,585 1, Private Wells Total 11,216 10,937 9,142-1,795

70 Groundwater Level Impact from the Doheny Desal Project After 31 Years (End of the Long 31 Year Dry Period) Doheny Desal Project (Runs 3a) minus Base Case (Run 2h) After 64 Years (End of the Model Simulation) Doheny Desal Project (Runs 3a) minus Base Case 70 (Run 2h)

71 80 Hydrograph for SJC Well Kinoshita Model Runs 2h and 3a Hydrology Land Surface Water Level (Run 2h) 400 Groundwater Elevation, NAVD 88 FT Screen Interval Wet Water Level (Run 3a) Monthly Groundwater Pumping, acre-ft -60 Dry Average

72 80 Hydrograph for SJC Well Dance Hall Model Runs 2h and 3a Hydrology Land Surface Water Level (Run 2h) Water Level (Run 3a) Groundwater Elevation, NAVD 88 FT Dry Average Wet Screen Interval Monthly Groundwater Pumping, acre-ft

73 Make-up Water from Doheny Desal Project Production (AFY) (Based on Runs 2i and 2j with Salinity Constraint) Scenario Groundwater Yield Runs 2i and 2j (No Doheny Desal Project with Water Level and Salinity Constraints) Groundwater Yield Run 3a (Doheny Desal Project with Water Level Constraint) Make-up Water from Doheny Desal Project Dry Hydrology ( ) Average Hydrology ( ) Wet Hydrology ( ) 8,038 6,545 1,493 9,146 7,326 1,820-9,142 - Doheny Desal Impact = 1,660 AFY 73

74 Groundwater Basin Mitigation Approaches Doheny Desal Impact (1,660 AFY) APPROACH RESULT Smaller Project Decreases impact Injection of New Water Provide basin make-up water and reduces drawdown impact Replace w/desal Supply Reassign Desal yield to the impacted user by an equivalent amount 74

75 Mitigation Options for the Doheny Desal Project Enhanced Well Production (well modifications and radial wells) Enhanced Stormwater Spreading (with seasonal construction of T sand bars to spread storm flows) Enhanced Recycled Water Spreading and Injection Make-up water (1,660 afy) provided to CSJC and SCWD from Doheny Desal Project production (reduces Doheny Desal yield to 14,340 afy) 75

76 50000 Precipitation, Pumping & Groundwater in Storage (Run 2h) Full Basin (46,000 acre-ft) Cumulative Departure from Mean Annual Precipitation Cumulative Decline in yr. 64 (-2,300 acre-ft) Groundwater in Storage, acre-ft Storage (30,000 acre-ft) 50% of Storage (23,000 acre-ft) Pumping Groundwater in Storage Annual Ground Water Pumping, acre-ft Note: The area of the basin is from the model boundaries and is approximately 3,700 acres. Ocean water intrusion included in storage (approx. 22,000 acre-ft) 76

77 Annual and Cumulative Ocean Water Intrusion Model Run 2h Cumulative Ocean Water Intrusion, acre-ft Cumulative Ocean Water Intrusion in yr. 64 (21,700 acre-ft) Cumulative Ocean Water Intrusion Annual Ocean Water Intrusion Annual Ocean Water Intrusion, acre-ft

78 Cumulative Change in Groundwater Storage, acre-ft Precipitation, Pumping & Groundwater in Storage (Run 3) Full Basin (46,000 acre-ft) Cumulative Departure from Mean Annual Precipitation 2010 Storage (30,000 acre-ft) 50% of Storage (23,000 acre-ft) Groundwater in Storage Note: The area of the basin is from the model boundaries and is approximately 3,700 acres. Cumulative Decline in yr. 64 (-14,000 acre-ft) Pumping Annual Ground Water Pumping, acre-ft

79 35,000 Model-Calculated TDS Concentration for SCWD Well Stonehill Hydrology ,000 25,000 TDS Concentration, mg/l 20,000 15,000 10,000 Model Run 2h (without Doheny Desal Project) 5,000 TDS would exceed 2,600 mg/l in approx. 9 years Model Run 3a (with Doheny Desal Project)

80 35,000 Model-Calculated TDS Concentration for SCWD Well New No. 2 Hydrology ,000 TDS Concentration, mg/l 25,000 20,000 15,000 10,000 5,000 TDS would exceed 2,600 mg/l in approx. 16 years Model Run 3a (with Doheny Desal Project) Model Run 2h (without Doheny Desal Project)

81 Groundwater Groundwater and Pre-Development Ocean Desalination Development Development With Vertical Slant No Sea Without Well Water Extraction Control Intrusion Control Production Well Land Surface Slant Vertical Well Well Controlling Controlling Intrusion Intrusion Sea Level Freshwater Freshwater Freshwater Saltwater Saltwater Saltwater Saltwater Sea Floor 81 DEW 6-Feb-13

82 Overview Executive Summary Goal of Briefing Modeling Overview Basin Yield- Surface Water/Groundwater Yield Model Model Calibration Long-Term Basin Operation Simulation Repeat of Hydrology Questions/Answers/Discussion/Follow-Up 82

83 Future Doheny Desal Work (1) Detailed Coastal GW Model Coastal model needed to assess lagoon drawdown impacts and injection barrier effectiveness Needed for evaluation of seawater intrusion and control by aquifer layer and well screened interval Geochemical module needed to predict slant well water quality vs time and time to pump out the old marine groundwater Additional work is proposed under the MET Foundational Action Program Offshore Geophysics and Borings Needed for offshore model and slant well layout 83

84 Future Doheny Desal Work (2) Environmental Baseline Monitoring not yet begun More detailed work in the following areas: We have initial information on all issues noted below; if the group wants to move forward with the project, more detailed information is required. Preliminary Engineering and Cost Opinion Energy Supply, Costs and Regulatory Issues Brine Disposal Regulations, Compliance Analysis and Costs Product Water Quality Criteria specifics System Integration specifics 84

85 Model File Transfer All the model input files for the surface water and groundwater models will be included in the final report. 85