In only a few years, workers with President Franklin Roosevelt’s Civilian Conservation Corps built Coweeta’s original laboratory buildings, climatic stations, roads, and stream measurement devices. Much of their work still stands, including the stream weirs that have given SRS scientists decades of baseline data invaluable for charting the changes now taking place in the forests of the South.

Data from stream weirs gives scientists windows on a hidden world where water is an integral and integrating factor in many natural processes. The gauged weirs are equipped with instruments that measure the physical and chemical characteristics of the water that flows through them, enabling researchers to measure the interactions among factors such as nutrient cycling, acidity, vegetation changes, and natural disturbance.

The Coweeta Basin is richly endowed for forest hydrology research. Located in the Nantahala Mountain Range in western North Carolina, the 5,400-acre laboratory is made up of two adjacent, bowl-shaped basins covered with forest that contain several well-defined watersheds and more than 45 miles of stream. Ecologist Hursch picked Coweeta because of the terrain, and because the area has some of the highest annual rainfall in Eastern North America. All that rain penetrates the litter of a mixed-hardwood forest to be immediately absorbed by deep permeable soils. Under those soils there’s solid bedrock that forms a temporary water trap, making it easier for hydrologists to account for most of the rainfall that enters the basin.

For more than 7 decades, across 16 watersheds, hydrologists, technicians, and others at Coweeta (renamed the Coweeta Hydrologic Laboratory in 1948) have recorded data from rain gauges and gauges installed in streams, calculating water budgets from input and outflow, studying the hydrologic cycle of the mountains. Though some gauges are automated now, Coweeta staff once literally collected the data by hand, riding horses on a daily circuit that took them up and down the wooded basins. The records they and those following them kept constitute the longest and most accurate information in existence on rainfall and streamflow from small forested watersheds. These longterm records form the backbone of a research program that has targeted a wide range of impacts on water resources, from roads to ozone damage and the loss of foundation forest species.

The Pressure’s On

Since these data make up a continuous history, they become more valuable each year. Periods of drought in the past couple of decades have pushed concerns about water to the forefront, according to Jim Vose, ecologist and current project leader for Coweeta.

“With population across the Southeastern United States expected to grow by as much as 30 percent in the next 30 years, municipalities will rely more and more on forested watersheds to offset or mitigate the impacts of growth, while land use change and climate variability will make it increasingly difficult to keep up with the demand,” Vose says.

Coweeta research has shown that even a mile of forest makes a difference in water quality. Much of what is known about the importance of watersheds in providing clean water for human consumption and wildlife habitat comes from nearly a century of research at Coweeta on water-quality issues.

Some of Coweeta’s earliest experiments demonstrated the harmful effects of exploitive logging and improper road construction, farming on steep mountain slopes, and woodland grazing—all common practices throughout the Appalachians at that time. Hursch designed four paired watershed experiments in the 1940s that showed that it’s not cutting trees per se that causes erosion and sediment runoff, but the disturbance from roads and traditional timber practices such as building skid trails directly up steep slopes and roads right next to, sometimes in, streams.

Besides changing road-building practices, the paired watershed experiments gave scientists a basic understanding of the hydrology of the Southern Appalachian region—and how land management can be used to affect both water quality and quantity. Coweeta research went on to show that in addition to roads and road construction, the forest practices with the most potential for causing erosion and stream sedimentation are tractor skidding (as opposed to cable or aerial removal) and intensive site preparation. In 1945, Marvin Hoover, for example, found that careless skidding reduces the benefits of forest cover for watershed protection by creating channels that concentrate runoff from road surfaces. In 1977, James Douglas and Lloyd Swift published on soil and nutrient losses caused by roads, logging, mechanical site preparation, and prescribed burning.

Coweeta’s early emphasis on how land management practices affect the hydrologic cycle evolved into a broader interdisciplinary effort that began looking at a wide array of complex ecological interactions. When former project leader Swank arrived at Coweeta in 1968, he began monitoring stream chemistry to measure the effects of disturbance and long-term trends. His work and that of Swift, John Hewlett, and others established the use of stream chemistry criteria as signatures of an ecosystem response to disturbance in a watershed, allowing scientists to detect emerging threats that might otherwise have escaped notice.

Today, Coweeta soil research scientist Jennifer Knoepp and ecologist Katherine Elliot study the effects on stream chemistry of disturbances such as prescribed burning or the loss of foundation species such as American chestnut and Eastern hemlock. Ecologist Barry Clinton is looking at the effects of tree canopy loss, while Vose is investigating the effects of ozone damage. Meanwhile, ecologist Chelcey Ford is linking together tree physiology and stream chemistry data to look at the effects of tree species diversity on water quantity and quality.

Coweeta scientists take an interdisciplinary approach to understanding how watershed systems respond to natural and human disturbances. The more scientists understand about the interconnections between climate, vegetation, soils, and water the better they can be at developing management practices to deal with the consequences of disturbance, according to Vose. Because this approach requires integrating many scientific disciplines, Coweeta’s staff roster is made up of ecologists, hydrologists, soil researchers, chemists, and many others, including collaborators both regional and worldwide.

Swank, shortly after coming onboard at Coweeta, started a unique long-term collaboration with the University of Georgia (UGA) that led to the selection, in 1980, of Coweeta as one of the first sites in the National Science Foundation Long-Term Ecological Research (LTER) network. The centerpiece of continuing cooperative efforts between Coweeta and UGA, the program includes other major university cooperators. The LTER program addresses region-wide issues, with Coweeta studies focused on Southern Appalachian forests, as well as on predictive models for how land changes and population pressures will affect water quality and quantity in the South.

“It’s time to shift our focus to larger scales and to cumulative effects over longer periods of time,” says Vose. “With advances in computing technology and improved understanding of physical and biological processes, we are positioned to develop more complex models at larger scales.”

 

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