Description
Groundwater has become one of the most precious resources of the 21st century. As climate change continues to impact surface water availability, groundwater supplies will become increasingly variable in the future. In California’s arid desert regions such as the Imperial Valley, while historically minor, groundwater is used as a primary and secondary source for both agricultural and domestic use. The area surrounding the All-American Canal just north of the US-Mexico border in Imperial Valley is a region sharing a cross boundary aquifer and is experiencing groundwater change due to groundwater pumping and a reduction in recharge. Because of excessive groundwater use and very little recharge, it is becoming overdrafted, leaving the area susceptible to water scarcity, land subsidence, and water quality concerns. Decades of ongoing legislative battles over water rights to Colorado River water has created legal, financial, and cultural implications for the neighboring countries; particularly for Mexican residents, some of whom have no surface water rights to the Colorado River. As deeper wells need to be drilled to reach the groundwater table, this may lead to financial inability for farmers in the Mexicali Valley to install and operate production wells in the near future. The objectives of this study were to determine 1) how the lining of the All-American Canal and groundwater pumping have altered the groundwater hydrology in the region, and 2) what the relative impact of the canal lining and groundwater extraction has had on the regional water balance. Current and historic data were gathered from observation and production wells throughout the study area and interpolated as groundwater elevations (Appendix A-T) and hydrographs (Figures 5-9). The pre and post-lining results were compared to data during active groundwater extraction to determine what the rate and pattern of groundwater loss in the region. Previous studies observed loss of 7 to 14 meters in the water table elevation between 2005-2014 in the vicinity of active production wells in the Lower Colorado Water Supply Project. The results of this thesis confirm an additional 5 to 20 meters of groundwater loss post-2011 through the end of 2018 in various wells throughout the region. A statistical model suggests that while both the lining of the canal and groundwater extraction are affecting the groundwater loss in the region, the lining of the canal is statistically more significant with regards to that loss and the water balance. Results from a water balance indicate a water table decline that is not sustainable for water use practices on both sides of the U.S.-Mexico border sharing this aquifer system.
