TY - Generic T1 - Percent Bias Assessment of Water-Supply Outlooks in the Colorado River Basin T2 - 82nd Annual Western Snow Conference Y1 - 2014 A1 - Brent Harrison A1 - Roger Bales KW - bias KW - Colorado River KW - forecast KW - forecast skill KW - runoff AB -

Water-supply forecasts on various watersheds are intended to predict the April through July (snowmelt) runoff and assist in estimating the total water-year runoff, and are thus are very important to users of water from those watersheds. Water-supply outlooks, a type of forecast, are made on major contributing watersheds of the Colorado River. This study reviewed the characteristics of twenty-eight watersheds on the Colorado River. During that review, a strong linear relationship was found between watershed elevation and yield. As elevation increased, the runoff yield increased in a linear fashion. When studying the relationship between runoff and area, it was found that there was a non-linear relationship between increasing area and increasing runoff. The skill level of April to July forecasts was examined using percent bias as a representative summary measure of forecast skill. Review of percent bias of forecasts during dry, near normal and wet years indicates that in dry years the forecasts have a positive bias while those in wet years have a negative bias. Forecasts for near normal runoff years show limited or no bias toward over or under prediction. Seventy percent of the values for the absolute value of percent bias for individual forecasts were 40 percent or less.

JF - 82nd Annual Western Snow Conference T3 - Proceedings of the Western Snow Conference CY - Durango, Colorado UR - sites/westernsnowconference.org/PDFs/2014Harrison.pdf ER -