Tuesday, August 4, 2009 - 2:50 PM

OOS 18-5: The impacts of droughts and floods on southeastern rivers and reservoirs: Managing water supplies to sustain biodiversity

Alan P. Covich, University of Georgia and John C. Bergstrom, University of Georgia.


Freshwater ecosystems provide numerous values to society such as clean drinking water, irrigation, hydropower, industrial cooling water, aquaculture, recreational and commercial fishing. However, climatologists predict that droughts and floods in the southeastern states will become more frequent and intense in the coming decades, resulting in extremely uncertain supplies of clean water.  Individuals and organized groups are developing new means to sustain water supplies in response to this highly variable precipitation.  Although the supply of clean water varies greatly from one year to the next depending on uncertain spatial and temporal distributions of rainfall in each sub-basin, the demand for water to provide seasonal uses for  ecosystem services is increasing. Evaluating the impacts on the biodiversity of fishes, turtles, mussels and crayfishes requires integrated analyses relative to plans for future water allocations.  How water is stored either at, or below, the surface during wet and dry years can alter the biodiversity of flowing rivers, ponds and lakes.   We expect that Eugene Odum was right 40 years ago in concluding that, ‘the safest landscape to live in is one containing a…mixture of communities of different ecological ages…Vast made-made lakes solve some problems, at least temporarily, but may not be the best device for storing water. It might better be stored in the watershed or underground in aquifers.”  


Recent studies have estimated the storage capacity and possible impacts of 60,000 water bodies relative to flood control, drought storage and the importance of their locations within stream drainage networks in the coastal plain of Georgia.  The effects of differently sized reservoirs on flows within stream networks during periods of extreme low and high levels of precipitation on biodiversity are becoming clear.  However, study of cumulative impacts of these changes is needed to determine how effective additional storage ponds and reservoirs will be in different drainage basins as climate changes and increased demands for freshwater are intensifying.  Alternative tradeoffs among different types and locations of water storage are being examined to determine how the species-rich biota of the southeastern region can be sustained.  Economic analyses of demand for irrigation waters provide insights regarding the incentives needed to postpone regional use of groundwater during extreme droughts that can increase levels of environmental flows of spring-fed streams and rivers needed to protect the high diversity of native southeastern species while reducing chances for spread of non-native, invasive species.