Streamflow change with urban development
Aditi Bhaskar is an Associate Professor of Hydrology, Water Resources & Environmental Fluid Mechanics at the University of Colorado, Boulder.
Abstract: This research presents an analysis of the changes to streamflow with urban development using trends in flow duration curves of 53 watersheds across the U.S. Then we focus on the Denver, Colorado region where we examine (1) contributors to stream baseflow, and in particular water supply pipe leakage and lawn irrigation return flow and (2) an analysis of changes in streamflow response to rainfall events with urbanization. To estimate contributions to stream baseflow, we used water-stable isotope analysis of surface water, tap water, and precipitation. Thirteen urban streams and two grassland streams were selected for sampling. An isotope mixing analysis using tap and precipitation end-members estimated that tap water contributed a mean of 80% of urban baseflow on specific days in late summer. For changes to streamflow response to rainfall events, we used eight years of instantaneous streamflow data in 21 watersheds ranging in size from 1 to 90 km2 with impervious areas ranging from 1% to 47%. Using a semi-automated method we identified 2,877 streamflow events. We found that more impervious watersheds had perennial or nearly perennial flow, unlike the least impervious watersheds which usually were dry. Streamflow events were shorter in duration and had higher peak flow in watersheds with more impervious surface cover. Together, these changes point to the importance of water infrastructure systems in modifying streamflow in urban settings and the need for locally adapted management to mitigate the effects of streamflow changes with urbanization.
About: Aditi Bhaskar is an Associate Professor in the Department of Civil, Environmental, and Architectural Engineering at the University of Colorado Boulder. Dr. Bhaskar specializes in changes to water resources that accompany urban development with a focus on interactions between streams, groundwater, stormwater, and urban irrigation. Dr. Bhaskar received a Sc.B. in Geology-Physics/Math from Brown University and a Ph.D. in Environmental Engineering from University of Maryland, Baltimore County. Then, Dr. Bhaskar was an National Science Foundation Earth Sciences Postdoctoral Fellow, which took her to the U.S. Geological Survey in Reston, Virginia. Dr. Bhaskar was a faculty member at Colorado State University in the Department of Civil and Environmental Engineering for 6 years before joining CU Boulder in 2023.