How does urbanization influence stream hydrology in a desert city? Insights on high and low flows from Phoenix, Arizona

Abstract:

There is broad consensus that urbanization results in dramatic changes in stream hydrology, such as higher peak flows and greater flashiness, as well as changes to baseflow. In general, these patterns have been studied much more extensively in humid systems as opposed to arid urban regions. Here we present insight from the Phoenix metropolitan region in central Arizona USA. In 19 watersheds in central Arizona, USA, we evaluated influences on streamflow regime metrics calculated from daily and subdaily flow data. We find that flashiness, coefficient of variation, zero‐flow days, and hydrograph rise and fall rates decreased with extent of imperviousness—the opposite pattern to that observed in previous studies primarily in humid regions. Engineered retention basins are one explanation for this observation though novel urban sources of dry weather flows are also playing a role. We further examine patterns in dry weather flows from several storm drains in Phoenix and explore potential drivers such as watershed area and land use. Overall, we find that the urban stream syndrome manifests differently in this arid system: Urbanization increases water retention and leads to less variable and more consistent presence of flow in stream ecosystems.