Precipitation analysis conducted by the U.S. Energy Information Administration (EIA) could have mixed meanings for hydroelectric power operators and providers along America's Pacific coast in coming months.
Using studies conducted by the Northwest River Forecast Center (NWRFC) and California Department of Water Resources (CDWR), EIA said the water resources available for hydropower generation in California could be significantly higher in recent years, while resources in the Pacific Northwest region (Washington, Oregon, Idaho and western Montana) are projected to be normal to below normal through September.
According to CWDR, snowpack in the Sierra Nevada mountain range through the current water year (which begin October 1 and end September 30) is already at 94% of normal, with precipitation in December being twice the average.
This represents a "significant departure from the prior year," EIA said, which was "significantly below normal".
EIA notes that California's hydroelectric projects usually contribute between 11% and 28% -- record low and high percentages achieved in 1992 and 1995, respectively -- of the state's overall power supply, with production peaking in the spring and early summer when melting snow starts flowing through river basins.
Meanwhile, NWRFC reported that its water projects for April to September -- typically the high hydro season -- call for a normal to below-normal supply.
NWRFC made its forecast by examining precipitation that fell in a given period, snowpack held through a watershed, and subsequent runoff of snow melting in the watershed.
Using these three phases in the water cycle, NWRFC said precipitation in October 2012 was 189% of normal, but was countered by a January that was 66% of normal. Additionally, temperatures were too high in October for the extra precipitation to build snowpack, NWRFC said, meaning current snowpack levels are only about average at most measuring stations.
The Pacific Northwest is home to about 35% of the United States' hydroelectric supply, according to EIA.
EIA also noted that many of the California's hydropower generators operate on different river basins than their northern counterparts, meaning weather patterns and production can vary significantly between the two regions.