Center for Climate Risk Management

“The Importance of Temporal Inequality in the Assessment & Design of BMPs”

Dr. Heather Gall, Penn State
Wednesday, 8 February, 12:00-1:15p
157 Hosler

Abstract: Inequality is an emergent property of many complex systems. For a given series of stochastic events, some events generate a disproportionately large contribution to system responses compared to other events. In catchments, such responses cause streamflow and solute loads to exhibit strong temporal inequality, with the vast majority of surface runoff occurring during short periods of time. These periods of time are commonly referred to as “hot moments” or “hot events”. Although this temporal inequality is widely recognized, there is currently no uniform metric for assessing it. My research group uses a novel application of Lorenz Inequality, a method commonly used in economics to quantify income inequality, to quantify the temporal inequality of streamflow and nutrient (nitrogen and phosphorus) loads exported to the Chesapeake Bay. Lorenz Inequality and the corresponding Gini Coefficient provide an analytical tool for quantifying inequality and identifying the “hot moments” for solute loads and corresponding flow conditions. These flow conditions can then be used as the input for designing the dimensions of structural BMPs, such as vegetated filter strips (VFSs). I will provide some stochastic modeling examples to show how ignoring the effects of temporal inequality can lead to overestimation of VFS performance. A paradigm shift is needed to understand how to best leverage temporal inequality as “windows of opportunity” that can be targeted to reach Chesapeake Bay nutrient and sediment load reduction goals.