Critics of a plan to divert river water to support a proposed nuclear reactor in Emery County say any diversion should be put on hold until a new study of the Colorado River's water supplies is completed.

Additionally, they say Utah's water engineer should hold off until their protests are formally heard in the spring of 2010.

At issue is the transfer of 24,000 acre-feet of water from the San Juan River to the Green River in support of Blue Castle Holdings' nuclear reactor at an industrial park.

Another 29,600 acre-feet of water is pending for lease from the Kane County Water Conservancy District in support of the project's development.

Both applications for the water transfers from the Green and San Juan rivers are scheduled for hearings next year before the state engineer within the Utah Division of Water Rights. Both rivers are part of the Colorado River tributary system.

John Weisheit, conservation director with Living Rivers, an advocacy group for the protection of the Colorado River, said too much is unknown about the impacts of the project for it to proceed.

Any reduction in water quantity in the Green River, for example, could imperil three species of already threatened fish and have detrimental effects on other wildlife, he said. "It does not seem like wise and prudent water management," he said.

Weisheit also points to a $1 million study authorized by the U.S. Bureau of Reclamation that will look at the water demands on the 1,450-mile river. The study will tap the efforts of the seven states in the Colorado River Basin, including Utah, to examine storage and delivery of water, improving water quality, generation and sale of electric power and improving fish and wildlife conditions, among other things.

The study is also intended to render a blueprint of a regional water plan.

Blue Castle Holdings counters that Utah has 400,000 acre-feet each year of unused water in the Upper Colorado River Basin, much of which is held by conservancy districts that want to put the water to use to hang onto water rights. According to its Web site, 29,000 acre-feet of water was leased by Blue Castle in support of a coal-fired plant in the region. The plant was never built and the water remains unused.