Ephemeral Streams (SERDP)

Structure and Function of Ephemeral Streams in the Arid and Semiarid Southwest: Implications for Conservation and Management

Building on their work in the SAHRA river systems macro-theme, ASU/SAHRA researcher Juliet Stromberg is lead PI and UA/SAHRA researcher Tom Meixner is a Co-PI on this project that was recently funded by the US Department of Defense's Strategic Environmental Research and Development Program (SERDP).  Ephemeral streams and their riparian biota are an important but little studied resource in the American Southwest.  Many agents of change affect these ecosystems, from local factors such as freshwater withdrawals to regional factors including climate change. However, the impacts of abiotic controls on ecosystem end points such as biodiversity are not well understood.  Projected climate change, including increased aridity, likely will exert significant impacts on the hydrology of these systems and thus their biota.   Local anthropogenic effects, including the withdrawal of groundwater pose a key threat to the diversity and productivity of perennial dryland rivers and may do the same for ephemeral streams although relationships between hydrology and biota of ephemeral streams is poorly understood.  Understanding how specific land and water uses affect ephemeral stream ecosystems is critical for making informed management decisions.

The goal of this series of studies is to increase understanding of linkages between abiotic processes (including flows of water and nutrients) and biotic communities (plants and invertebrate animals) of ephemeral streams of the southwestern USA.  These studies will enable assessment of how diversity, productivity, composition and limiting factors are influenced by hydroclimatology and human land and water use.  The overall objective of this project is to increase understanding of the hydroclimatic processes that influence these ecosystems.  The  specific objectives are to 1) quantify the responses to, and dependence upon, groundwater by riparian biota; 2) quantify biotic responses to seasonal water pulses and document spatio-temporal patterns of variation; 3) assess how ephemeral stream attributes are influenced by catchment size and position within a stream network;  and 4) provide an integrated assessment of regional variability of ephemeral stream ecosystems and of the processes that influence their structure and function.