WASHINGTON — According to USDA’s Natural Resources Conservation Service, the final snow survey water supply forecast for 2013 confirms most of the West will have reduced water supply from snowmelt, likely to cause drier streams and scarcer water resources.
June’s data shows snowpack was below normal in most areas, and fell further behind each month since January.
The last of six monthly forecasts for the year, the forecast compares the current level of water content in snowpack in 13 Western states with historical data to help the region’s farmers, ranchers, water managers, communities and other stakeholders make informed decisions about water use and future availability.
“Most of the West is way behind average,” NRCS meteorologist Jan Curtis said. “We have unprecedented dryness in California and the southern and middle Cascades.”
Even a snow surge in April did not make up the deficit.
“California, southern and eastern Oregon, Nevada, southern Utah, southern Colorado and especially New Mexico will experience major water shortages due to sustained drought conditions and low reservoir storage,” said NRCS hydrologist Tom Perkins.
“The soil in the southern half of the West is like a dry sponge that will absorb and hold water as it melts from the snowpack,” he said. “Only when the soil is sufficiently saturated will it allow water to flow to the streams.”
On color-coded maps for water supply forecasts, black symbols indicate areas of extreme dryness — areas predicted to receive less than 20 percent normal runoff.
“I started forecasting in 1983, and I don’t think I’ve ever seen a black symbol before,” Perkins said. “This year we have several black symbols in New Mexico.”
Agriculture Secretary Tom Vilsack designated many counties in Western states as eligible for USDA drought assistance. Western states should prepare for potentially increased vulnerability to forest and rangeland fires and mandatory water restrictions.
There are a few exceptions to the dry conditions. The northern Cascades, western Montana and the headwaters of the Missouri and Columbia rivers are near normal.
“For the rest of the West, there is no silver lining,” Perkins said. “I think it’s going to be a long, hot, dry summer.”
NRCS’ National Water and Climate Center monitors soil moisture with its SNOw system and Soil Climate Analysis Network. These sensors gather soil data that helps NRCS better monitor drought development.
“Although NRCS’ streamflow forecasts do not predict drought, they provide valuable information about future water supply in states where snowmelt accounts for the majority of seasonal runoff,” Perkins said.
In the West, in addition to precipitation, streamflow consists largely of accumulated mountain snow that melts and flows into streams as temperatures warm into spring and summer. NRCS scientists analyze the snowfall, air temperature, soil moisture and other measurements taken from remote sites to develop the water supply forecasts.