24 April 2013

Hydrological drought



Definition:
Hydrological drought refers to deficiencies of water in some component of the hydrologic system, such as soil moisture, streamflow or groundwater or reservoir levels. 

Examples:
In urban watersheds we observe reduced groundwater levels, especially in riparian zones due to 1) reductions in the infiltration that feeds groundwater in uplands that are covered by impervious surface and 2) incision (deepening) or stream channels by either deliberate action or erosive storm flows.

Why important:
Riparian zones have been shown to have the ability to prevent the movement of pollutants from upland land uses into streams.  Hydrologic drought reduces this ability, particularly the capacity to support denitrification, an anaerobic process (wet soils) that converts nitrate, a common pollutant in urban watersheds, into nitrogen gas.

For more information:
·         Gift, D. M., P. M. Groffman, S. S. Kaushal, and P. M. Mayer. 2010. Denitrification potential, root biomass, and organic matter in degraded and restored urban riparian zones. Restoration Ecology 18:113-120.
·         Groffman, P. M., D. J. Bain, L. E. Band, K. T. Belt, G. S. Brush, J. M. Grove, R. V. Pouyat, I. C. Yesilonis, and W. C. Zipperer. 2003. Down by the riverside: urban riparian ecology. Frontiers in Ecology and the Environment 1:315-321.
·         Groffman, P. M., N. J. Boulware, W. C. Zipperer, R. V. Pouyat, L. E. Band, and M. F. Colosimo. 2002. Soil nitrogen cycle processes in urban riparian zones. Environmental Science & Technology 36:4547-4552.
·         Groffman, P. M. and M. K. Crawford. 2003. Denitrification potential in urban riparian zones. Journal of Environmental Quality 32:1144-1149.
·         Kaushal, S. S., P. M. Groffman, P. M. Mayer, E. Striz, and A. J. Gold. 2008. Effects of stream restoration on denitrification in an urbanizing watershed. Ecological Applications 18:789-804.
·         Mayer, P. M., S. K. Reynolds, M. D. McCutchen, and T. J. Canfield. 2007. Meta-analysis of nitrogen removal in riparian buffers. Journal of Environmental Quality 36:1172-1180.

Contributed by BES Co-PI Dr. Peter Groffman

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