Abstract
Climate change is expected to exacerbate water management issues already being faced within California. This project used the combination of water chemistry and groundwater modeling to explore how climate change will affect aquifer dynamics in east Sacramento, California. Groundwater samples were collected from 17 monitoring wells on the CSUS campus and analyzed for apparent groundwater ages, isotopic composition, recharge temperatures, and major ion chemistry. Within the unconfined aquifer, apparent groundwater ages ranged from 0-12 years and isotopic compositions varied as a function of distance from the American River. Within the confined aquifer, apparent groundwater ages ranged from 11-50 years and isotopic compositions were similar to the American River. Using the water chemistry results, a groundwater model was calibrated and input data from four different climate projections was used explore how aquifer dynamics and water budgets in east Sacramento could be affected by climate change. Numerical groundwater modeling results show that with the optimistic RCP 4.5 emissions scenario there were relatively little overall impacts on water levels over the simulated timeframe. Each climate scenario produced seasonal variations in water levels which differed between 1-2 meters depending on the climate model. The minor variation in water levels could be due to the proximity to the American River and a predicted increase in average annual precipitation by each climate scenario with the exception of MIROC5, which maintained relatively consistent water levels. Over the 81-year simulation, there was a difference of about 30% and 2.6% of groundwater recharge from precipitation and the American River between the highest and lowest producing climate models, respectively. Over the next century, if CO2 emissions peak in 2040, then climate change could have a minimal effect on groundwater supply in the east Sacramento area. The results of this study could provide stake holders with valuable information on aquifer dynamics related to water resource management as well as possible economic impacts.