Conclusion

This bachelor thesis researched the impact of climate change on groundwater recharge in the Sonoran Desert. The PCR-GlobWB model was used to simulate both historical and future (approximated) groundwater recharge. The simulated data were analysed using boxplots and diagrams stating the change of approximated groundwater recharge.

The findings indicate the optimistic climate scenario, SSP1-2.5, projects the smallest change in approximated groundwater recharge, \(-2.9 \%\). This represents a slight reduction in the amount recharge compared to the ERA5 baseline. The intermediate scenario, SSP2-4.5, demonstrates the largest change in approximated recharge, -6.2%. This indicates a significant reduction in groundwater recharge. The worst case scenario, SSP5-8.5, simulates a comparable decrease at \(-5.6 \%\), reflecting a substantial reduction in groundwater recharge.

Efforts to mitigate the decline in groundwater recharge have already been initiated by institutions in Arizona, California and Mexico through implementation of strict water regulations. However, additional measures need to be taken, to further reduce the negative impacts. For instance, sustainable water management and restoration of natural water flow are critical.

Sustainable water management involves promoting efficient water use across all sectors, particularly in agriculture, which the largest consumer of groundwater resources. Implementing sustainable irrigation techniques and leveraging innovative technologies could significantly reduce water consumption.

Existing policies, such as the Groundwater Management Code in Arizona and the Law of the Nation’s Water in Mexico, focus on replenishing the current confined and unconfined aquifers (Tenney, 2021; Cruz-Ayala & Megdal, 2020). These initiatives contribute to groundwater resource replenishment and help maintain riparian zones, which plays a crucial role in stabilizing groundwater levels (Hester & Fox, 2020). These policies should be sustained and expanded, to enhance water security and environmental sustainability further.

In conclusion, to answer the research question: “How will climate change influence groundwater recharge in the Gila River basin in the Sonoran Desert over the 21st century?”. The results simulated with the PCR-GlobWB model suggest that climate change will lead to a decrease in groundwater recharge. While the optimistic scenario indicates a relatively minor decline over the 21st century, the moderate and worst-case scenario foresees a significant decrease, possibly underscoring the need for effective water management strategies to mitigate the impacts of climate change in the future.