Water Budget
SECTION 4. WATER BUDGET
The water budget of the Santa Ana Canyon Management Area is dominated by surface flows of the Santa Ana River with a minor contribution of subsurface inflow, return flows from irrigation, and a small amount of groundwater production. Table 1-2 presents the water budget for the Santa Ana Canyon Management Area for the last five years. Additional water budget information was presented in the 2017 Alternative. The water budget contains both surface water and groundwater components and is not used to analyze change in groundwater storage. The purpose of presenting this water budget is to show the relative contributions of different sources in the Santa Ana Canyon Management Area. Groundwater level data suggest that groundwater conditions in the Santa Ana Canyon Management Area are essentially at steady state conditions with inflow equaling outflow and no change in groundwater storage. Inflow to the shallow alluvial aquifer includes subsurface inflow and infiltrated Santa Ana River water. Outflow includes evapotranspiration, groundwater production and subsurface outflow. Table 4-1 presents the groundwater budget for the Santa Ana Canyon Management Area.
Table 4-1: Groundwater Budget, 5-Year Average (2016-21)
5-Yr Avg: 2016-21 (afy)
Flow Component
INFLOW Subsurface Inflow (1)
6,000
Infiltrated Santa Ana River Flow (2)
740
TOTAL INFLOW
6,740
OUTFLOW
Evapotranspiration (3)
740
Groundwater Production
1,000
Subsurface Outflow to OCWD Management Area (4)
5,000
TOTAL OUTFLOW
6,740
NET CHANGE
0
(1) Subsurface inflow is estimated and includes irrigation return flow and areal recharge from precipitation. (2) Estimated infiltration of Santa Ana River flow to balance outflow. (3) Evapotranspiration is based on 370 acres of riparian habitat and a usage rate of 2 afy/acre of habitat per Santa Ana River Watermaster Reports. (4) Subsurface outflow is based on OCWD’s cali brated groundwater flow model.
4.1 BUDGET COMPONENTS
The components of the groundwater budget are described below.
BASIN 8-1 ALTERNATIVE 2022 UPDATE
4-1
Appendix F - 257
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