U.S. Water News Online
LA JOLLA, Calif. -- This year's La Niña spring could
bring increased streamflows to the Pacific Northwest and Appalachia,
but lower streamflows in the Southwest and in parts of the Northeast
and center of the nation, according to a new report by the U.S.
Geological Survey and its partners.
The new report, by the USGS, the Scripps Institution of
Oceanography in La Jolla, Ca., and the Western Regional Climate
Center in Reno, Nev., shows areas of the country where it is more
likely that streamflows will be high -- including flooding -- and
areas where streamflows will be low -- which could spell drought. The
new maps are actually a statistical survey that identifies areas
where during past La Niña years very high flows, floods, and
very low flows have occurred.
The new maps complement other long-range predictions for this
winter and spring from other agencies and institutions that forecast
temperature and precipitation based on global conditions, said USGS
hydrologist Michael D. Dettinger, one of the report's authors.
"Because streamflow has its own unique variations apart from those
of precipitation and temperatures," he said, "We went back 50 to 100
years and looked at historic streamflow data to make these
predictions. Increases in precipitation do not always produce
flooding, so we've focused directly on the streamflow connections to
La Niña. We've looked at La Niña years and determined
where there's a higher chance of having unusually high flows and
where there's a higher chance of having low flows.
"Because the earth's water system is more complicated and has a
longer 'memory' than simply precipitation, because of additional
features such as hydrogeology, soil moisture and snow pack,
streamflows respond to climate variations for a longer period of
time," Dettinger said. "This allows flow predictions that are useful
for several months longer than we can expect than when simply
He said the report is aimed at assisting emergency managers and
water-use managers in their planning for this year's La Niña,
a subject of intense interest to water managers, who want to extend
the lead time for important allocation decisions (especially in the
"We can't control precipitation. Either it comes or it doesn't.
But we can manage water," he said. "We can decide now to intervene
and make changes to reservoirs or divert water long before an
emergency happens if we know the likelihood of having a problem is
increased. So the streamflow forecasts are of special interest."
The USGS operates a network of more than 7,000 streamflow gages
across the United States. Data from the active stations, as well as
from discontinued stations, are stored in a computer database that
currently holds mean daily-discharge data for about 18,500 locations
and more than 400,000 station-years of record. Near real-time
streamflow information is available online at http://water.usgs.gov
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