La Habra-Brea Management Area
SECTION 4. WATER BUDGET
4.1 BUDGET COMPONENTS
The components of the water budget generally include recharge from precipitation and runoff, recharge from subsurface inflow, subsurface outflow, and groundwater production. Recharge components of the water budget consist of mountain front and streamflow recharge and deep percolation of precipitation. Various hydrogeologic studies show that annual natural recharge ranges from 3,300 AFY to 3,900 AFY. No measurable subsurface inflow occurs into the La Habra- Brea Management Area. Additionally, no artificial recharge occurs in the La Habra-Brea Management Area at this time. Outflow components of the water budget consist of groundwater production and subsurface outflow. Groundwater production in La Habra-Brea Management Area has ranged from approximately 2,000 AFY to 4,200 AFY in recent years (See Table 3-1). Subsurface flow out of the groundwater basin occurs westerly near Coyote and La Mirada Creeks into the Coastal Plain of Los Angeles (Central Basin), and southerly at the gap between the East and West Coyote Hills into the main Coastal Plain of Orange County (Stetson, 2014). Subsurface outflow ranges from 2,200 to 5,500 AFY (OCWD 2015).
4.2 CHANGES IN GROUNDWATER STORAGE
Based on water level measurements the water budget appears to be in balance over the past ten years. Changes in groundwater storage are monitored through the monitoring of groundwater elevations which have shown rising trends since the 1970s. Available groundwater level data indicate groundwater levels have generally increased or remained stable over the last five years. See Section 3.2.3. These conditions indicate groundwater storage changes in the La Habra Groundwater Basin are within an acceptable range and undesirable results are not present.
4.3 WATER YEAR TYPE
The estimated water budget is based on normal/average water year type. However, historical hydrographs indicate stable or rising groundwater levels, even during dry and prolonged drought years, indicating that the water year type has little impact on the water budget.
4.4 ESTIMATE OF SUSTAINABLE YIELD
Groundwater production within the La Habra-Brea Management Area is managed by the establishment of a safe yield so that the groundwater levels and storage capacity in the La Habra Groundwater Basin will be maintained.
2017 BASIN 8-1 ALTERNATIVE
4-1
Appendix F - 32
Powered by FlippingBook