Baltimore Ecosystem Study Cary Institute of Ecosystem Studies

2012 BES Annual Meeting Presentation and Poster Abstracts

Effect of Channel Substrate Type on Storage and Transport of Solutes in Urban Storm Runoff of the Semi-Arid Southwest
meixner, Thomas
Co-Authors: Erika L. Gallo, Kathleen Lohse1, Paul Brooks, Jennifer McIntosh, Thomas Meixner

Abstract: Urbanization in arid and semi-arid regions alters the hydrologic and biogeochemical system of ephemeral washes by increasing flow frequency and inputs of solutes. The characteristics of the stormwater drainage system (SWDS) are likely to have a large effect on the overall system rainfall-runoff responses. To understand the impact of the SWDS on biogeochemical processes we characterized grass- and gravel-lined ephemeral reaches and collected urban storm runoff samples throughout the 2007 monsoon. Overall, solute concentrations in runoff decreased over the monsoon, although NO3-N increased in the grass-lined waterways. Comparisons of soil chemistry before and shortly after rainfall-runoff show significant (p < 0.05) losses of soil Cl, NH4-N, SO4-S and DOC, suggesting potential solute transformation and flushing during runoff. In contrast, soil NO3-N, significantly increased, indicating accumulation between storms and subsequent flushing during runoff (build and flush). Using a biologically inert solute (Cl) to infer source/sink dynamics during streamflow we show more conservative solute transport in gravel reaches than in grass-lined reaches. Soil CO2 efflux was elevated before and after the onset of the monsoon, pointing to high rates of biogeochemical processing. We show that stream channel characteristics play an important role on solute sourcing during rainfall-runoff, and on altering soil solute stores between rainfall events, which has large implications for the future of stormwater management and SWDS design. Implications for urban low-impact development design in both dry and more humid locations will be discussed with poster attendee’s.