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<br />" <br /> <br />of precipitation over most of southern Colorado. For a small region of the State on the Colorado <br /> <br />Plateau near the Utah border, autumn is the wettest time of year while late spring and early <br /> <br />summer is the driest. A few areas inbetween see precipitation that averages nearly the same <br /> <br />amount in each month of the year. Seasonal precipitation distributions not only vary from region <br /> <br />to region across the state but may also vary locally from one side of a mountain to the other or as <br /> <br />a function of elevation within a drainage basin. Some of the high mountains have a mid winter <br /> <br />precipitation maximum and some are wetter in mid summer. Most precipitation in summer in the <br /> <br />higher mountains produce little streamflow (ST) as most of the water is returned to the <br /> <br />atmosphere by evapotranspiration. <br /> <br />3.2 Elevation <br />Elevation has a large effect in the total annual precipitation as is shown in Figure 1. In this <br /> <br />study a major limitation is that very few year round precipitation measurements are made at higher <br /> <br />elevations. The seasonal distribution of precipitation varies rapidly with elevation. Denver has a <br /> <br />spring maximum but just 30 miles to the west Berthoud Pass has a mid winter maximum. In <br /> <br />western Colorado a similar shift occurs from a late summer maximum in many valley locations to <br /> <br /> <br />winter at higher elevations. This reality means that combining data from different locations in one <br /> <br /> <br />river basin has the problem of combining data from different seasonal distributions which can be <br /> <br /> <br />misleading since the various precipitation systems operating throughout the year are not well <br /> <br />correlated. <br /> <br />In the winter west of the Continental Divide the higher elevations receive more <br /> <br />precipitation in individual storms and receive a larger number of days with precipitation. Along <br /> <br />the Front Range, the higher elevations receive a larger number of days with precipitation (due to <br /> <br />9 <br />