Freshwater ecosystems often suffer greatly at the hands of human activity, especially when there is little or no data on the potential impact of development.

But a cutting-edge software program designed by The Nature Conservancy and software developer Chuck Smythe is challenging that situation across the globe: 

• The Indicators of Hydrological Alteration (IHA) software program — which is available for free download at nature.org— is now used by nearly 2,000 water resource managers, hydrologists, ecologists, researchers and policymakers worldwide.
• IHA enables them to measure everything from the hydrological impacts of human activities to the optimum water flow of a river system.

“The IHA software is pretty much all inclusive,” says Bob Biel, a retired hydrological engineer with the U.S. Army Corps of Engineers. “By allowing for accurate comparative analysis, it’s a wonderful tool for determining the best way to manage water systems.”

Technology Meets Conservation at the Green River

This ground-breaking software proved to be a vital tool during a landmark collaborative project between the Conservancy and the Corps to conserve Kentucky’s Green River.

Stretching for 300 miles, the Green River is a national treasure of freshwater diversity. It boasts 152 fish species, 71 mussel species and numerous endemic species. It also includes portions of Mammoth Cave, the world’s largest underground cave system. 

However, the natural hydrological function of the river system has been altered by a series of locks and dams. In particular, the amount of water released from the Green River Dam and the temperature of the water created by the releases seriously impaired the natural reproductive cycle of native mussel species — jeopardizing their long-term survival.

Operating Dams for Nature and People

Concerned that the continued operation of the dam could cause irreparable harm to the river system, the Conservancy contracted Biel to assess the impact of the Green River Dam operations on the river system and determine a possible solution.

Biel used the IHA software to compare and contrast hydrologic data from before and after the dam was built and operational. He then used the software to determine the most ecologically sustainable way to operate the dam without sacrificing flood control, recreation and downstream water quality.

Based on the results of Biel’s study, the Corps implemented a plan in 2002 to change the way water is released from Green River Dam, creating more natural regimes of flow and stream temperature.

“We are very encouraged by the results of the dam re-operation,” says Richie Kessler, Green River Basin coordinator for the Conservancy. “With improved changes to stream flow and temperature, scientists are observing real differences in populations of green mussels and fish.”

The success of the Green River project led to the formation of the Sustainable Rivers Project, an ongoing national partnership between the Conservancy and the Corps to improve the health of rivers.

The Sustainable Rivers Project informs changes in the operation of Corps dams while maintaining benefits such as flood control, recreation and power generation.

An Indispensable Global Tool

Since its use on the Green River, the IHA software has proved to be an irreplaceable tool across the world in the field of freshwater conservation. For example:

• Susan Libes, a professor of marine science and chemistry at Coastal Carolina University in South Carolina, has used the IHA program to simulate hands-on exercises for graduate students in her watershed science and management course. By inputting U.S. Geological Survey data for the Waccamaw River into the IHA program, her students have learned first-hand the effects of hydrological alterations.
• The province of Manitoba, Canada (in cooperation with the federal Department of Fisheries and Oceans and University of Manitoba) are using the IHA software as a primary tool in an ongoing study to make in-stream flow recommendations for the Assiniboine River in Manitoba.
• Pan Wenbin of the College of Environment and Resources at Fuzhou University in China is planning to use the technology to research the relationship between land use activities and water resources on the Jixi River.

The latest version of IHA and its accompanying user's manual are now available at nature.org for free download.

Nature picture credits (top to bottom, left to right): Tom Barnes (Green River); Lynda Richardson (Bob Biel)