Impacts of Plant Water Use on Streamflow at Daily, Storm, and Event Scales

Abstract:

The science of runoff generation describes the processes by which catchments lose water by drainage during high flow periods. For many ecohydrological problems, however, we are more interested in how water is retained during low flow periods. For example, fish habitat in the relatively dry catchments of the semiarid mountain west depends on how low streamflow is metered through the summer. Additionally, upland plants survive by the soils ability to retain water in opposition to runoff generation. Here, I discuss the impacts of soil water retention and vegetation on low flow in seasonally dry, semiarid catchments. I present evidence showing 1) low flows are getting lower, 2) plants and streams receive water from different co-existing sources, and 3) transpiration perturbs streamflow at daily, storm and seasonal scales. The simultaneous occurrence of points 2 and 3 point to conflict emerging in recent hydrologic literature: How can plants use water that is seemingly disconnected from streams while simultaneously impacting streamflow?