Idaho Budget Includes Island Park Dam Extension

Idaho Budget Includes Island Park Dam Extension

In his annual budget address on January 6, Idaho Governor C.L. “Butch” Otter proposed $15 million in the fiscal 2015 budget to fund water-supply projects, two of which have the potential to affect stream flows in the Henry’s Fork. The governor pledged $2.5 million toward a proposal that would expand the storage capacity of Island Park Reservoir by about 20 percent over its current capacity. He also pledged $4 million to ongoing efforts to recharge the Eastern Snake Plain Aquifer; water diverted from the Henry’s Fork in the St. Anthony area provides some of this recharge.

Although Otter’s speech brought the proposed Island Park Reservoir expansion public attention that it has not received until now, this project is one of several alternatives that have been discussed in the Henry’s Fork Basin Study process over the past three years. The Henry’s Fork Watershed Council, co-facilitated by the Henry’s Fork Foundation and Fremont-Madison Irrigation District (FMID), has served as the stakeholder work group for the Basin Study, which is scheduled for completion this spring and is being funded by the Idaho Water Resources Board and the U.S. Bureau of Reclamation.

HFF has been intimately involved in the Basin Study since its inception, providing leadership via its co-facilitation of the Watershed Council, extensive comments on Study documents, and technical input in the form of hydrologic modeling and analysis.

Analysis of the Island Park Reservoir expansion shows that because the water rights associated with the new storage will be junior to all other water rights in the upper Snake River system, filling this additional storage will negatively affect winter flows below the dam in only a small fraction of water years. The Island Park Drought Management Planning process, which has improved winter flows and trout populations in recent years, will remain in place, further limiting the potential for negative effects of additional Island Park storage on fisheries, and perhaps even revealing some benefits. For example, in most years, additional storage in Island Park will result in higher reservoir levels at the end of the irrigation season and will also reduce the need for delivery of large amounts of storage water from Henry’s Lake.

Both of these possibilities would improve water quality in the Henry’s Fork both upstream and downstream of Island Park Reservoir. However, a formal federal environmental review process and additional engineering studies will be required before any additional water can be stored in Island Park Reservoir, and these processes will require funding beyond the governor’s pledge and many years to complete. HFF will continue to be an active contributor to these processes.

Because stream flow is critical to maintaining the fisheries of the Henry’s Fork, an important component of HFF’s work is proactive collaboration with water management agencies, water resources scientists, conservation groups, and local irrigators to ensure that the stream flow needs of wild trout are met. In addition, HFF constantly monitors legal and procedural activities related to water management and intervenes as needed on behalf of the Henry’s Fork and its wild trout. For example, in January 2013, HFF protested Fremont-Madison’s application for the rights to store additional water in Island Park Reservoir. 

HFF also protested applications to divert water from the Henry’s Fork to recharge the aquifer—applications from the Idaho Water Resources Board in 1998 and from FMID in 2012. Through this work, HFF gives the river and its wild trout a seat at the negotiating table.

For more information, email Rob Van Kirk, Senior Scientist.