Rivers need water—a fact that may seem ridiculously obvious, but in times of increasing water development, drought, and climate change, the quantity of natural streamflow that remains in river channels is coming into question, especially in the Colorado River basin. Newly published research poses a tough question in these days of falling reservoir levels and high-stakes urban development: Whether the continued development of rivers for water supply can be balanced with fish conservation.
The Colorado River basin is historically a highly dynamic river with a wide range of streamflow during the year, a wide range of river temperatures, and large sediment loads in some seasons. Native fish evolved through periods of wet and dry cycles when the total flow was relatively large or relatively small. But water-supply development has further depleted the flow of many rivers in the Upper and Lower Colorado River basins, and today’s river habitats are increasingly decoupled from that natural cycle of spring snowmelt and monsoon season floods and intervening low flows in favor of depleting the natural flow and stocking nonnative sports fish in some places.
The health and recovery of native fish species now depends largely on the public’s willingness to protect those rivers that retain some semblance of a natural flow regime as freshwater conservation areas, say authors Casey Pennock, Phaedra Budy, Wally Macfarlane and Jack Schmidt of the Watershed Sciences Department in the S. J. and Jessie E. Quinney College of Natural Resources and colleagues Matthew Breen of the Utah Division of Wildlife Resources and Justin Jimenez of the U.S. Bureau of Land Management.