University Honors

The California Central Valley aquifer system relies heavily on water supply from the Sierra Nevada mountain range, including surface water inflows and groundwater recharge. This study seeks to understand the dynamics of surface water and groundwater resources in the Kaweah River and Tule watersheds, located in the southern Sierra Nevada and Central Valley, and how they respond to climate variations and human water use. We propose that large hydraulic connectivity exists between the mountain and valley aquifer systems. We performed exploratory data analysis in MATLAB to understand trends and variability in streamflow, groundwater level, precipitation, and temperature observations in the mountainous and valley regions. We fit a series of linear regression models to the time series data from publicly available monitoring stations in the two regions to assess trends and variability in groundwater and surface water resources. The Mann-Kendall Test was used to determine if there was a significant increasing or decreasing trend in groundwater levels over time. Anomaly plots were generated to visualize annual deviations from the long-term mean for the precipitation, temperature, and streamflow time series. Results indicate a significant decreasing trend in groundwater levels for seven out of the ten wells over time. This decrease worsens over periods of extended drought. Groundwater recovery post-drought is small, largely due to deeper groundwater levels and large pumping rates in the region. Streamflow experienced a strong decline over the drought period, but recovered quickly post-drought due to higher precipitation. This research has important implications for groundwater management in the region, as current groundwater decline is reaching unsustainable levels without intervention.