Location: Water Management Research
Project Number: 2034-13000-013-004-S
Project Type: Non-Assistance Cooperative Agreement
Start Date: Nov 15, 2019
End Date: May 31, 2024
Objective:
1. Determine groundwater recharge at the mountain front.
2. Assess impacts of farmland irrigation management practices on groundwater recharge.
Approach:
For Objective 1, we will implement the integrated groundwater-land surface watershed model, ParFlow.CLM using historic meteorological data to estimate groundwater recharge at the mountain front, just below Lake Kaweah, where Kaweah River reaches the valley floor. Model calibration will be made using streamflow and groundwater level observations from the United States Geological Survey (USGS) and state water agencies. Transducers will be installed at selected existing wells in the watershed above mountain front to monitor groundwater levels. Data will be collected periodically and used, along with recent streamflow, groundwater and evapotranspiration observations, for model validation. Mountain front recharge estimates are required to accurately close the basin water budget. For Objective 2, ParFlow.CLM model will also be used to estimate groundwater recharge on the agricultural lands below Lake Kaweah under real life and simulated irrigation and recharge practices. Deficit irrigation is a potential means of water conservation, especially for permanent crops in water-starved arid and semi-arid regions such as the San Joaquin Valley (SJV) of California. For crop water use, irrigation at 100% crop evapotranspiration (ETc), which is a real-life situation, and a simulated deficit irrigation scenario at 75% ETc will be used for model estimation of aquifer recharge. It is hypothesized that crops under deficit irrigation would use less water thus less water lost through plant transpiration. This would have an impact on water budget at the basin scale because majority of the agricultural lands are planted with crops. Approximately 50% of the crop land immediately below Lake Kaweah is citrus. Real time ETc will be determined using in-situ instrumentation in citrus orchards. Additional simulation may include on-farm recharge using irrigation during the winter wet season when deciduous crops (not citrus) are in dormancy. Infiltration or retention ponds are considered one of the useful methods for groundwater recharge, which has been adopted by some farmers in the SJV. Farmers with delivered water may temporarily store the water in retention ponds before applying it to the field through pressurized irrigation systems. To assess the impacts of recharge from these ponds, two scenarios will be used in model simulation: A) recharge from existing infiltration ponds, B) existing plus 30% additional infiltration ponds as model input.
