Dryland streams in the Great Plains host several warm-water native fish species that have adapted over time to harsh conditions, according to Falke, who is with the Department of Fisheries and Wildlife at Oregon State University. Brassy minnows, orange-throat darters and other species can withstand water temperatures reaching 90 degrees, as well as low levels of dissolved oxygen, but the increasing fragmentation of their habitats may impede their life cycle, limiting the ability of the fish to recolonize.
"The Arikaree River and most dryland streams are shallow, with a sandy bottom, and often silty," Falke said. "The water can be waist-deep, and when parts of the river dry up from the pumping of groundwater, it is these deeper areas that become refuge pools. But they are becoming scarcer, and farther apart each year."
Falke said the changing hydrology of the system has implications beyond the native fishes. The aquifer-fed stream influences the entire riparian area, where cottonwood trees form their own ecosystem and groundwater-dependent grasses support the grazing of livestock and other animals.
Pumping of regional aquifers is done almost entirely for agriculture, Falke said, with about 90 percent of the irrigation aimed at corn production, with some alfalfa and wheat.
"The impact goes well beyond the Arikaree River," Falke said. "Declines in streamflow are widespread across the western Great Plains, including all 11 headwaters of the Republican River. Ultimately, the species inhabiting these drainages will decline in range and abundance, and become more imperiled as ground
|Contact: Jeff Falke|
Oregon State University