The hot and dry July we all experienced has quickly melted most of what remains of the snowpack from last winter. Across the State, rivers and streams are slowing down, making it possible to safely wade out to my favorite fishing spots. Unfortunately, lower flows can also mean rising water temperatures, a severe stressor to fisheries and aquatic habitats. The end of snowmelt runoff and slowing of the rivers means that base flow season is upon us. Snowmelt is no longer the major contributor to flows, and accumulated groundwater—from snow, rain, and importantly, irrigation return flows—slowly drains out into our rivers. Sporadic afternoon storms also help, but monsoon season is off to a slow start this year. While the fisherman in me loves this time of year, as a hydrologist, environmental scientist, and Colorado Water Trust Board member I also worry about the long-term sustainability of these vital resources.
Base flows are critically important to rivers and the aquatic habitats and recreational activities they support. In dry or hot years, base flows can drop to the point that aquatic species become stressed, by low flows which limit viable habitat, and by high water temperatures. And if it seems that these problematic conditions are happening more frequently, it’s not your imagination. The so-called drought that began in 2000 may in fact represent a new normal that all water users will have to adjust to.
This is the busy season for Colorado Water Trust staff. Through creative water leasing agreements, Colorado Water Trust and its partners can react to adverse stream conditions and provide additional water to rivers that would otherwise be critically low. Irrigators, cities, and other water management agencies who own these water rights play a critical role in this process. They realize the value of healthy streams and are willing to relax some of their own needs in order to restore water to rivers during critical periods. Particularly useful are lease arrangements that involve reservoir storage, because they allow Colorado Water Trust and its partners to make targeted releases during specific times of critically low flows.
In late July, for example, Colorado Water Trust and its partners began releasing water from Stagecoach reservoir to enhance flows in the Yampa River. These additional flows, available through a water supply contract with the Upper Yampa Water Conservancy District and a temporary Instream Flow Lease with the Colorado Water Conservation Board, increase the flows in the upper Yampa River above Lake Catamount by as much as 40%. These flows help avoid river closures to fishing and other recreational activities and are responsible for helping to maintain important recreational economic activities in the Steamboat Springs area.
John Carron
Board Member, Colorado Water Trust
Ph.D., Founder and Principal, Hydros Consulting