Columbia River Basin Water Supply Forecast: Record lows in the north, above normal in the south

Runoff from snowpack in the mountains feeds the streams in the Columbia River Basin, so the annual water supply forecast is a critical component of managing the hydrosystem and fisheries operations.

At its May meeting, Amy Burke, senior hydrologist with the Northwest River Forecast Center, NOAA briefed the Council on the basin’s seasonal water supply. The center provides both 10-day and seasonal forecasts for the basin and coastal waterways that inform regional and local decisions about water management, hydropower, public safety, drought planning, river navigation, and species protection.

The key takeaway: Snowpack levels (measured as inches of water in the snowpack) are below normal in the north and above normal in the south. The runoff and water supply forecast is well below normal in the north—the Canada portion of the basin—while in the south the forecast is above normal.

“For the water year, which is from October 1 through September 30, the seasonal precipitation in southern Idaho has been higher than normal; Oregon has done okay, but the eastern Washington Cascades, northern Idaho, and western Montana aren’t doing as well,” said Burke.

As a map of the basin shows, there is a clear demarcation between water supply levels.

“Looking at snowpack, we have record lows in northern portions of the Canadian domain and we had some record lows in western Washington, the Idaho panhandle, as well as in the northern Cascades of Washington,” noted Burke.

“We are essentially forecasting the lowest 10 percentile in a lot of this northern area and down into northern Oregon,” said Burke.

“All told, the current forecast at The Dalles is expected to be the lowest on record.”

For more information visit the Northwest River Forecast Center.