When Streams Die (or at least dry up!)

February 19  Presentation: “When Streams Die (or at least dry up!), Presented by Sarah Godsey, Idaho State University.

Intermittent streams – those that occasionally are dry – make up as much as half of all streams worldwide; about one-third of U.S. households rely on these unreliable streams for at least part of their water supply. If intermittent streams are so common and so important, it might surprise you to learn that scientists cannot accurately predict when and where streams will be dry! This talk will explore what we know about stream drying, why our predictions about stream drying are wrong almost half the time, and what we’re doing to improve those predictions.

We will also review the Clean Water Rule and the proposed definitions of “jurisdictional waters” (and why that matters). We’ll discuss the science behind these definitions, including lateral, longitudinal, and vertical connections between surface waters and groundwater. New observations from the past several years, including a case study from the Intermountain West, will help us delineate how connections between the hillslope, riparian zone, and the stream itself affect stream drying. We’ll also examine how subsurface hydraulic properties control surface flows, and we’ll use arrays of real-time water quality and geophysical measurements to trace water as it flows into and out of the banks and stream beds. Finally, we’ll explore how interactions between subsurface characteristics and plants control daily expansion and contraction of the stream network.