Thursday, May 15, 2014

Water supply forecast as varied as this winter’s weather

The latest Water Supply Report issued by the Natural Resources Conservation Service shows variable precipitation and snow pack conditions across Idaho this winter leading to a wide range of water supply forecasts.

“Depending where you are in the state the conditions can be thin low-elevation snow or near record high snow pack with concerns for drought conditions or floods,” said Ron Abramovich, Water Supply Specialist with the Idaho Natural Resources Conservation Service. “Some areas have too little water and water supplies will be short; some areas may have too much water and high runoff is a concern. Yet other areas seem to have about the right amount of water.”

The snow pack in north Idaho’s Lochsa River basin shows winter has not loosened its grip. Numerous storms provided the Clearwater basin with 120% of the normal April precipitation, the third straight month with well above average amounts. The already deep snow pack continued to increase and is now at its peak for the season.

NRCS Hydrologist Karl Wetlaufer and Lynn Reese from US Army Corps of Engineers measured 11 feet of snow depth with 57.4 inches of water content, the second highest May measurement since records began in 1955, at the Fish Lake Airstrip snow course in the Selway-Bitterroot Wilderness.

The deep snow pack in this region foretells a plentiful runoff season to come. River runners heading to the Selway and Lochsa this summer can expect some of the biggest whitewater in years. The stream flow volume forecast for the May to July period is currently 145 to 150% of average, highest in the state. Peak stream flow timing and magnitude depends on spring temperatures and precipitation.

Other areas across central, southern and eastern Idaho experienced a range of conditions in April, but only the upper Snake region had above normal precipitation.

Reservoir storage also varies around the state. The Owyhee and Salmon Falls reservoirs have low storage and very low projected inflows. Magic, Little Wood and Mackay reservoirs are 50-80% full but users will have short water supplies. Other reservoirs are near full or scheduled to fill after the peak stream flows occur.

“Hang on! We may not be done with this rollercoaster weather ride yet,” Abramovich said. “The increase in variable weather we saw this season keeps our job as hydrologists, forecasters and water managers interesting each year. Having weather that was even close to normal would make water management and planning decisions much easier.”

There will be one more 2014 water supply report issued in June.

No comments:

Post a Comment