Attachment 5 - Work Plan – San Jacinto Groundwater Compliance Management Tool Project (MTP)
1. INTRODUCTION
This scope of work outlines the required tasks to refine the construction of Eastern Municipal Water District’s (EMWD’s) Regional Groundwater Model for the San Jacinto Watershed (Model). To clarify the difference between the existing Model and refined Model, the refined Model will hereinafter be referred to as the “MTP.” EMWD’s current Model simulates groundwater flow and solute transport (total dissolved solids and nitrates) using MODFLOW, a finite difference flow model developed by the United States Geological Survey (USGS). The initial model configuration, calibration, and simulation results are documented in a report entitled “Regional Groundwater Model for the San Jacinto Watershed” dated December 2002
Both the Model and the MTP cover an area of approximately 300 square miles in the western portion of Riverside County known as the San Jacinto Basin (8-5, Bulletin 118). The San Jacinto Basin is encompassed by the Santa Margarita Watershed to the south, the San Jacinto Mountains to the east, and hills around the remainder of the perimeter. This area was delineated by the Santa Ana Regional Water Quality Control Board into eight groundwater management zones (GMZs) in the Santa Ana River Watershed Basin Plan.
The San Jacinto Basin is managed as defined by the Hemet/San Jacinto Groundwater Management Area Water Management Plan and the West San Jacinto Groundwater Basin Groundwater Management Plan (figure 1). EMWD oversees and administers the groundwater monitoring programs for each groundwater management plan (GWMP), and is also the designated monitoring entity of the San Jacinto Basin for the California Statewide Groundwater Elevation Monitoring (CASGEM) program.
EMWD has just completed an update of Model data in the San Jacinto Basin based on data gathered since the 2002 model was completed. Since that time, water levels in the basin have dropped significantly (on the order of up to 400 feet) in some areas of the basin while other areas have remained steady or have increased due to changes in groundwater production (figure 2).
The MTP scope of work will include:
o Task 1 - Establishment of a model advisory panel to provide peer review
o Task 2 - Model Configuration Refinement Review with Advisory Panel
§ Physical construction
§ Aquifer parameters
§ Recharge parameters
o Task 3 - MPT Calibration
§ Define Model Calibration Targets
§ Input Data Preparation
§ Update Water Balance
§ Update Model Calibration
o Task 4 - Final Simulations
§ Baseline
§ Minimized Recycled Water Discharge from the Basin
§ Drought Reliability
§ Local Groundwater Reservoir Optimization
§ Salt Mitigation
o Task 5 - Reporting
§ Final Report - Document in a new report the model refinements and updated calibration.
2. TASK DESCRIPTIONS
Task 1 – Establishment of a model advisory panel to provide peer review
In order to provide a peer-reviewed groundwater model update, a model advisory panel (Panel) will be established. The Panel will be comprised of up to 5 members including stakeholders and model experts. Agencies to recruit Panel members from will include: California Department of Water Resources; Santa Ana Regional Water Quality Control Board; Cities of Hemet, Moreno Valley, Menifee, and Perris; California Department of Public Health; and other local water agencies. The peer review of MTP will give EMWD a management tool capable of predicting project impacts to the groundwater of the San Jacinto Basin that is widely recognized by local stakeholders. It therefore provides a basis for efforts to implement groundwater management plan (GWMP) goals such as ensuring a reliable water supply, providing for planned urban growth and addressing pumping overdraft concerns. Successful implementation of these GWMP objectives will also allow EMWD to develop a cost effective water supply, as rising water levels and improving water quality will lower pumping and treatment costs. In addition, the Panel’s recommendations may highlight areas where existing monitoring for water supply and water quality could be enhanced. A consultant shall be retained to perform the MTP calibration.
Task 2 – Model Configuration Refinement Review with Advisory Panel (Panel)
2.1 Physical construction
The consultant and EMWD will review the physical construction of the Model with the Panel. Based on the recommendations received from the Panel, the consultant will make revisions to the conceptual model as deemed necessary. The physical reconstruction of the Model may include the model extent, the model grid (cell size, orientation, etc.), and the model layering. Defining the physical construction of the MTP supports the GWMP goal of providing adequate monitoring for water supply and water quality by identifying areas where current monitoring is not representative of true aquifer conditions.
2.2 Aquifer parameters
The consultant and EMWD will review the estimates of various aquifer parameters defined in the MTP with the Panel. Aquifer parameters for review may include conductivity/transmissivity, hydraulic head and storativity/specific storage. A review of historic geologic structure in the area along with input from the Panel and EMWD personnel will be used by the consultant to refine the estimated aquifer parameters to a reasonable and acceptable range for validation during calibration. Accurate estimation of aquifer parameters significantly impacts the results of groundwater flow calculations that are part of the input into the calculation of long term solute concentrations, which are part of the GWMP objective to protect and enhance water quality.
2.3 Recharge parameters
The consultant and EMWD will review the estimates of various recharge parameters defined in the MTP with the Panel. Recharge parameters for review may include mountain front recharge, the areal extent of various recharge components, the magnitude of recharge components and the percolation potential of the recharge components. Input from the Panel and EMWD personnel will be used by the consultant to refine the estimated recharge parameters to a reasonable and acceptable range for validation during calibration. The estimation of recharge parameters supports GWMP goals of addressing pumping overdraft and maximizing the use of local supplies by providing input into the effort of quantifying the safe yield of the groundwater basin.
Task 3 – MTP Calibration
Completion of the model calibration gives EMWD a working groundwater model, a tool that would support the implementation of many GWMP objectives. The model can be used to predict the impact of management decisions and capital facilities on the groundwater basin, allowing EMWD to evaluate various recharge programs designed to address pumping overdraft and declining groundwater levels. Restoring the health of the groundwater basin in the San Jacinto Watershed increases the reliability of the water supply by reducing EMWD’s dependence on imported water and reducing the propagation of poor quality water. Likewise, the model calibration allows EMWD to identify areas where existing monitoring of water levels and water quality is not sufficiently representative of local groundwater conditions, information that can be used as a basis for bolstering EMWD’s GWMP mandated monitoring program.
3.1 Define model calibration targets
The consultant will select calibration wells whose water level readings are deemed to be representative of the aquifer system in a given area. Water level readings from these calibration wells are to be compiled for each model stress period from the Model deliverables provided by EMWD. The consultant will then establish an acceptable variance of the model predicted heads from the measured water levels of these well sites with input from the Panel and EMWD based on ASTM standards for model calibration. Setting stringent calibration target criteria for the MTP allows EMWD to accurately evaluate the effects of programs aimed at fulfilling the GWMP goals of addressing pumping overdraft, ensuring a reliable water supply and enhancing water quality.
3.2 Input data preparation
The consultant will format the Model deliverables from EMWD for input into a pre- and post-processing application compatible with the USGS MODFLOW finite difference flow model. Based on the recommendations of the Panel, the consultant will also review and make revisions to the Model deliverables from EMWD as deemed necessary. The input of the Model deliverables into the pre- and post-processing application allows the consultant to verify the accuracy of the MTP prepared by EMWD during model calibration. It also allows EMWD the flexibility of performing future simulation runs as additional data becomes available This supports EMWD’s effort to meet the GWMP goal of monitoring and developing a cost-effective reliable water supply, since the potential benefits of proposed EMWD projects to recharge the groundwater basin can be estimated through model simulation runs. These results can be used to maximize project benefits relative to their costs.
3.3 Update water balance
The consultant will prepare water balances for the model area to validate the range of aquifer and recharge parameters. Boundary fluxes such as mountain front recharge will be estimated based on apparent incongruities between total inflows and outflows of the groundwater basin. Preparing these water balances assists EMWD’s efforts to meet the GWMP goals of providing for planned urban growth and addressing pumping overdraft by helping to quantify the extent of the current overdraft conditions.
3.4 Update model calibration
The consultant will calibrate a numerical flow model based on the results of the MTP and the water balances. Additional physical construction, such as no-flow or constant head boundaries may be implemented during calibration. The MTP calibration will be validated based on the calibration targets set in task 3.1. Completion of the MTP calibration assures EMWD of the relative accuracy of future simulation runs of the model. This assists EMWD’s planning efforts to meet its GWMP objectives of addressing pumping overdraft, ensuring a reliable water supply, providing for planned urban growth and protecting and enhancing the water quality within the San Jacinto Watershed. By meeting these goals, EMWD will also be able to develop cost effective water supplies, as reducing overdraft and enhancing water quality will lower pumping and treatment costs for local groundwater production. Finally, the calibrated MTP will allow EMWD to meet the GWMP goal of providing for the Soboba Tribe water rights, as the model will provide input into the optimal areas of recharge into the watershed.
Task 4 – Final Simulations
4.1 Baseline
The baseline MTP simulation will provide a reference (a metric) against which subsequent combinations of pumping and recharge projects (scenarios) will be compared. These scenario runs will allow not only EMWD to test a wide range of projects but also allow for local, regional, or State agencies to also provide input and see the expected results of projects that claim a regional benefit.
4.2 Minimize recycled water discharge from the basin
Minimization of discharge from the basin will help enhance local groundwater supplies and reduce reliance on imported water supplies from the Bay Delta and Colorado River. The model will be used to test a recommended recharge and withdrawal scenario based on current project work in the Hemet/ San Jacinto area. On average, EMWD is discharging approximately 5,000 Ac-ft annually to the Santa Ana River outside the District.
4.3 Drought reliability
Full utilization of local groundwater resources will help increase drought reliability for the region. Through modeling efforts, a greater understanding of the overall groundwater basin will ensue and provided potential for additional groundwater production well locations. The groundwater model will then be used to test the potential yield and effect to the regional basin to help determine viability of additional wells in a given area. A potential of up to 25,000 Ac-ft may be available in drought years through proper basin utilization.
4.4 Local groundwater reservoir optimization
The MTP will be used to identify and validate areas suitable for recharge and withdrawal through water banking, which will help enhance local groundwater supplies and increase drought reliability for the region. Water would be stored as groundwater, as opposed to surface water, which would reduce the potential for losses. Up to 75,000 Ac-ft of additional storage may be available in properly located and constructed recharge areas.
4.5 Salt mitigation
The MTP will be used to identify and validate areas suitable for additional desalter wells for the Perris II Desalter, which will enhance local groundwater supplies and reduce reliance on imported water supplies from the Bay Delta and Colorado River, as well as inhibit the migration of degraded groundwater into areas of potable groundwater. The desalters will remove at least 40,000 tons of salt annually from the basin.
Task 5 – Reporting
The consultant will provide EMWD with monthly performance reports documenting tasks accomplished during the previous month, as well as tasks to be accomplished in the next month. The consultant will identify any issues that will affect the schedule and/or budget.
EMWD will complete and submit quarterly performance reports to DWR documenting tasks accomplished during the previous quarter, tasks to be accomplished in the next quarter, and any changes to the schedule and/or budget.
The consultant will document the results of the MTP, the MTP calibration, and the final simulations into a Draft Final Report. This Draft Final Report will be submitted to the Panel for review and comments, which the consultant will then revise as deemed necessary with input from EMWD. A Final Report will then be submitted to DWR for review and comments.
Management decisions to facilitate the achievement of GWMP objectives may be recommended based on the results of the final simulation runs.