Friday, January 13, 2006

Exercise caution in using water models

Guest opinion by Trish Klahr


Klahr is executive director of The Nature Conservancy in Idaho, based in Hailey.


Many in the Wood River Valley attended the water meeting held in the Blaine County Courthouse on Dec. 14, 2005, and heard from three local hydrologists, Bruce Lium, Lee Brown and Wendy Pabich, about the challenges of managing the changes in water use and water quality in the Wood River Valley. Kudos to these three for keeping our attention focused on our valuable water resources.

We heard a pitch for a $700,000 study that would purportedly be useful to planners in helping address concerns about population growth and proposed subdivision development on the valley's water supplies.

I am afraid a comment I made might have been misconstrued. I was trying to warn people that water models make it look like subdividing is "favorable" over continued agricultural practices because agriculture is factored in as using more water. These water models will suggest that rural subdivisions will have the least impact on water use, as subdivisions consume less water than farming. The University of Idaho reached this same conclusion in a comprehensive hydrologic study of the Big Wood and Silver Creek watersheds funded by The Nature Conservancy in 1999. To quote the executive summary: "Additional rural subdivision development from irrigated lands will have the least impact on consumptive water use if the building density is high."

I wanted folks to understand this as they consider whether or not to fund another $700,000 study in hopes of this being a tool that will help planners decide where residential development might occur. If we care about protecting our ranches and farms in the south county, this might not be the tool folks need to help make the tough decisions about development.

The state agency with the legal mandate to adjudicate our water is the Idaho Department of Water Resources. Not only will they legally sort out and determine all water rights in the valley, they will enforce the results of their adjudication. The anticipated date of release of the Director's Report for the Big Wood River Basin (Basin 37) above Magic Reservoir is June 2006. Why not wait to see this legally mandated and technically comprehensive document before deciding to fund any additional data collection?

I would also encourage folks to review the existing hydrologic studies, "Hydrologic Evaluation of the Big Wood River and Silver Creek Watersheds Phase I (1994) and Phase II (1999)," which are available online at

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