ANALYZING THE RESPONSE OF SOUTHWESTERN ARIZONA’S RIVERS TO ANTHROPOGENIC PRESSURES

Water management in the Southwest is of paramount importance given the desert climate and rapidly growing population. The Salt River Project, the primary provider of water in Central Arizona states that, “SRP protects every precious drop...Water is our most valuable resource, and we’re working to ensure its resiliency for years to come.” Although every drop may be accounted for, there are countless gallons of water that have been misallocated due to outdated hydrologic engineering. The surface waters in the Gila Watershed are discontinuous within systems that were once perennial, as a result of water diversions and dam construction. Taking into consideration that these rivers naturally develop discontinuity given the dry climate, we plan to analyze changes in the amount of river fragmentation as a result of human modification and dams. River Fragmentation is the interruption of a river’s natural streamflow cycle and can be an indicator of the degree of anthropogenic influence (Revenga et al. 2000). By controlling for seasonality and using normalized difference water index filters and normalized difference vegetation index filters, we can qualitatively and quantitatively monitor trends in the extent of water and vegetation within the rivers of the Gila Watershed over the last eight years. Using Sentinel-2 satellite imagery, we seek to quantify the impact of climate human-created hydrologic infrastructure on the Gila River watershed, specifically the Salt, Gila, and Agua Fria Rivers. By examining areas of interest upstream and downstream of the Theodore Roosevelt Dam and attributing numerical values to the corresponding river fragmentation, we can quantitatively compare how dam management practices have impacted these rivers over time, if at all. We have constructed maps of local river fragmentation, which allow us to quantify how river connectedness varies in space and time. This analysis offers insight not only on the shifting flow of these rivers but also on the health of the aquatic ecosystems that depend on them.