A Groundwater Extraction

Total Groundwater Extractions (AF)

Water Use Sectors

Banking Recovery, exchanges and pumpins

B Groundwater Extraction Methods

Meters

Meters and comparable measuring devices operated by local water agencies, water purveyors and city water departments in compliance with AWWA and other relevant standards

These data were collected from well meters by experienced water agency staff following monitoring protocols for urban and agricultural water supply.  Meters are considered to be well-maintained and tested; therefore, reported data meet high accuracy levels in compliance with AWWA and other relevant standards. In accordance with these standards for water supply, meter accuracy is assumed to range between 0% and 5%.  

Electrical Records

Land Use

IWFM Demand Calculator (IDC) in C2VSimFG-Kern

Estimated groundwater extractions is based on simulation results of the IDC tool within C2VSimFG-Kern model.  The water balance accuracy of the groundwater model is considered to be medium, approximately ranging between 10% and 20%.  Input data based on metered data is assumed to have an accuracy of 0% to 5%.  The agricultural pumping, which is the largest component of groundwater extraction, are estimated using the ITRC-METRIC based ET Rates.  ITRC (2020) lists the accuracy of the ET measurements as ranging from 7% to 10%. Land use is based on Kern County Agricultural Commissioner annual land use data including crop type.  Soil properties are assumed are based on local soil survey data which have a higher level of uncertainty.  Applying a weighted average of these inputs to the overall water budget produces a relative accuracy for the land use calculation for agricultural groundwater extractions ranging between 10% and 20%. 

Groundwater Model

Other

C Surface Water Supply

Total Surface Water Supply (AF)

Methods Used to Determine

Reported data by local water agencies

Water Source Types

Tailwater Recovery

D Total Water Use

Water Source Types

Water Use Sectors

Banking Recovery, exchanges and pumpins

E Change in Storage

Method used to calculate change in storage

The Kern County Subbasin Coordination Agreement refers to the local groundwater-surface water model (C2VSimFG-Kern) as the agreed upon method for generating coordinated water budgets for the Kern County Subbasin. C2VSimFG-Kern uses comparable data sets and methodologies over the entire Subbasin that meets numerous technical requirements for basin-wide coordination in §357.4.  C2VSimFG-Kern is based on the C2VSim Fine Grid Public Beta model (C2VSimFG-Beta) that was released by DWR for SGMA support in May 2018.  C2VSimFG-Beta input files were revised to incorporate locally derived managed water supply and demand data to better represent the local water budgets for the Kern County Subbasin. Appendices 2 and 4 of the Kern County Subbasin Coordination Agreement documents the development and application of C2VSimFG-Kern for GSP purposes.  

For the 2021 Annual Report model update, new data for WY2021 were requested and provided by the local agencies through their respective GSA.  Monthly data for surface water, recharge operations, measured groundwater pumping, stream inflows and other locally important conditions were updated.  In addition, regional data sets for precipitation and evapotranspiration were also updated to provide climatic data sets for the C2VSimFG-Kern update.  These data were added to the existing C2VSimFG-Kern data structure and model input files following the same procedures used for model development presented in the Kern County Subbasin GSPs and Coordination Agreement.  In addition, new recovery wells and recharge operations that became operational during the update period were added to the model input.  The change is the sum of the total change in groundwater in storage for each element and model layer in the Kern County Subbasin for WY 2021.  

F Monitoring Network Module

G PMA Module