Fish, flows and irrigation: working together

Access granted: The new bypass channel around Ware and Hinds diversion dam.

By Richard van Gytenbeek

It began as a casual conversation in a Colorado River District meeting between Trout Unlimited staff and Colorado Parks and Wildlife (CPW). Now a project to restore fish passage on Elk Creek, a tributary of the Colorado River and a key spawning reach for wild trout, is a reality. After more than a century of being shut out by an irrigation diversion dam, spawning salmonids will now be able to use the new bypass channel on Elk Creek to access 3.5 miles of previously blocked upstream reaches.

The project at New Castle, Colorado, is a unique collaboration involving operational and environmental components that work together for both irrigators and fish. The Ware and Hinds diversion dam and head gate span the entire width of the channel and control the senior water right on the creek. This means that during the low flows of late summer and early fall, the creek always has water in it above the diversion. This is important in the yearly cycle of flows, fish and irrigation.

Spring runoff begins in late April, peaks at the end of May and quickly ends by late June. During this period the new bypass channel will remain open and—for the first time in almost 100 years—spawning wild rainbows from the Colorado River can move upstream to spawn. As the low flows of summer become the norm, the larger fish will return to the big river. Their progeny, however, will be protected by the senior water right, which ensures adequate flows for incubating eggs, fry and young fish during the heat of summer.

During the late summer to early fall, the ditch company exercises their legal water right and removes all the water from the creek, drying the channel bed from the diversion to the Colorado River main-stem. During this time, the bypass channel is closed. The creek above the diversion, however, continues to have adequate water to sustain the rainbow fry that have hatched.

At the end of the irrigation season in late October, the irrigation head-gate is closed and the bypass channel is reopened, allowing water to re-wet the channel down to the Colorado River. For the next two months, the wild brown trout will take their turn moving upstream to spawn. As winter deepens, low flows and ice will force the adult fish back to the main-stem, but their progeny are protected under the gravel awaiting spring and a new annual cycle.

This project is another example of how TU’s Western Water and Habitat Program staff work with local agricultural producers around the West to improve flows and habitat for fish. In the case of Elk Creek, the project would not have been possible without the cooperation of the Ware and Hinds Ditch Company and the underlying landowners of the property on which the diversion dam is located. After multiple discussions and presentations, the ditch company shareholders voted to allow the project team to construct a naturalized channel around the active portion of the diversion dam.

The ditch company and landowners stood to gain nothing except the knowledge that this would be good for the fish, good for the river and good for their community. In the end, it’s all about cooperation.

Richard van Gytenbeek is Upper Colorado River coordinator for TU’s Western Water and Habitat Program.