Rain, snow carry hope for Basin irrigators

Predicted La Niña cycle means more moisture than normal expected 

By SARA HOTTMAN 

H&N Staff Reporter

December 16, 2010

  The Klamath Basin has experienced steady rain and snow the last few months, giving local farmers and ranchers hope that snow accumulation in the mountains will prevent another water shortage.

   Forecasters at the National Weather Service in Medford predict a moderate to strong La Niña cycle, which means heavier than normal precipitation is expected through the winter and spring. Last winter’s pattern was a strong El Niño, an abnormally dry weather pattern.

   Apprehension about water supply largely revolves around Upper Klamath Lake levels. The lake provides surface water for many irrigators, but also is home to fish protected by the Endangered Species Act. Under the act, federal agencies can restrict irrigation water to maintain levels deemed necessary for fish.  

   A multitude of variables play into whether the lake will meet required levels this year, but conditions are nearly mirroring those of fall 2002 and winter 2003, when the lake met mandated levels and irrigators received adequate surface water.

   Upper Klamath Lake was at 4,140.19 feet Wednesday afternoon, according to the U.S. Geological Survey. A federal biological opinion says it must be at 4,141.5 feet by February.

   Presumably if the lake hits that first target, the rest of the water year, April through September, will go smoothly, officials say.     

   Precipitation alone doesn’t necessarily have an immediate effect on lake levels, said John Risley at the U.S. Geological Survey Oregon Science Center in Portland.

   “Antecedent precipitation, whether in the form of snow or rain, can reside in upper elevation snowpack and deep aquifers for many years or decades before it enters the lake,” he said in an e-mail.

   But the moisture from a strong La Nina is still good news for water storage.  

   Risley couldn’t say exactly how much precipitation the Basin would need during the next few months to meet February’s mandate, but said Upper Klamath Lake in October 2002 was at the same level as this October — 4,138.97 feet.

   USGS data show that through the end of 2002 and beginning of 2003,   the lake exceeded mandated levels, peaking at more than 4,143 feet in May, two feet above that month’s requirement.

   From October 2002 to February 2003, the Basin received 6.59 inches of precipitation, half   an inch less than the historical norm, according to the National Weather Service. Last year over the same period, the Basin received 4.6 inches of precipitation.

   The area received 3.95 inches of precipitation   from October 2002 to December 2002. To date the Basin has had 4.11 inches — nearly at the historical norm — with rain and snow in the forecast.

   In January government agencies will start   measuring snowpack in the mountains; that measurement will determine how the Bureau of Reclamation allots water resources among stakeholders.