Tuesday, April 14, 2009

Despite winter rains, conservation measures still needed, researcher says

Recent heavy rains may have helped to end the exceptional drought the metro Atlanta region has faced for several years, but conservation measures are still needed to help boost the region’s water capacity during the drier summer months, according to a Georgia State University professor.

“This is no time to let go of conservation measures that are in place,” said Jordan Clayton, assistant professor of geosciences. “We need to maintain conservation levels so that we can increase storage capacity to the point where local reservoirs are mostly full.”

Typically, Atlanta’s reservoirs and streams are replenished during the winter, and then depleted during the summer due to many factors, including a process called evapotranspiration — a combination of evaporation and transpiration, or the loss of water from plants during photosynthesis.

“In metro Atlanta, we have a roughly equivalent annual rate of precipitation to evapotranspiration,” Clayton explained. “The balance is therefore sensitive because even small deviations in precipitation can result in water deficits. Conservation measures help reduce our vulnerability.”

Lake Lanier, Atlanta’s main source of water, is still several feet below full pool, despite recent heavy rains. Local aquifers, which are limited but also help to provide water, have improved, but due to metro Atlanta’s heavy runoff ratio from impermeable surfaces like concrete and asphalt, less water is stored locally than at times past, Clayton said.

Rainfall and runoff also affect local streams, their flows, and the fish and invertebrates which live there. These animals benefit from a limited range of variability of water flow, which both drought and recent heavy rains can disrupt.

When flows are low, chemicals and other items in the stream become more heavily concentrated, he said.

"This can cause problems," Clayton explained. “On the flip side, when we do get rain, our streams may clear out materials that help to regulate the flow.”

Clayton and colleagues, in conjunction with arborist Neil Norton, are working on a pilot study in Decatur to explore the impact of altered streamflow and water quality on erosion and invertebrates in Peavine and Glenn Creeks.

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