A new study uses a USDA Forest Service modeling tool – the Water Supply Stress Index, or WaSSI, ecosystem services model – to explore the relationship between water use, river flows, and fish populations across the conterminous U.S.
Researchers found that in the western U.S., irrigating cattle feed crops is the greatest human-induced cause of declining river water levels. Declining water levels endanger fish and other aquatic species. In the South, river flow depletion is lower than in the West (on a percentage basis) but can exceed 20 percent in some river basins during dry years.
The study investigated the impact of temporary rotational fallowing in the Colorado River Basin. This practice of letting farmland go unused for some time – if financially incentivized for 20 percent of crops – could prevent river flow depletion in the river basin above Lake Powell without adverse economic effects on farmers or food security risks.
“Forests have and will continue to play a key role in providing a clean, stable water supply across the U.S.,” says Caldwell. “Our recent work has shown that in the South, for example, forested lands provide 44 percent of the total available water supply in the region, and ongoing work is showing that forests play an even greater role in the West.”
In addition to managing water demand, maintaining and managing forests on the landscape will be an essential component of water resource management in the future.