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. 4218 segregated within the project service area - two irrigable and two nonirrigable. These classes are listed and described in Table 111-2. These standards are based on the general performance of irrigated lands in this and other areas, supplemented by appli- cation of accepted agronomic principles and by results from field and laboratory investigations. 5. Hydrology a. Surface Water . Streamflow in the Project development area is greatly affected by snowmelt. The primary source of streamflow in both the Roaring Fork (Fryingpan River and Hunter Creek) and the Arkansas River Basins is the snowpack that accumulates at high altitudes during the winter months. With. the onset of spring, the snow- pack melts and the rate of runoff is greatly increased. The annual hydrograph or pattern of stream discharge in this area, as in other areas where snowmelt is a primary source of water, shows the highest streamflows occur in the late spring and early summer months. During the winter months the area's streams flow at their lowest rates. The fact that a large part of the annual runoff occurs in a short period in the spring is germane to the concept of the Fryingpan-Arkansas Project. In the Colorado River Basin, well over 50 percent of the annual runoff occurs in May, June, and July. During this period, the water supply is much greater than the local demand. The surplus water is utilized by allowing it to remain in the river for use farther downstream, storing it, or tr90sporting it out of the bag;n -fnT I1c:.P ;11 other_areas which have inadequate water supplies. As in most mountainous areas, snowpack on the western slope increases with altitude. For example, the drainage areas above the Fryingpan River near Ivanhoe Lake gage, elevation 9892, yield an average of 24.8 inches of snowmelt runoff annually. The drainage area above the Fryingpan River gage at Norrie, Colorado, elevation 8410, yields an average of 18.4 inches of runoff; and the area above Fryingpan River at Meredith gage, elevation 7780, yields an average of 14.6 inches annually. It is because of this high yield at the upper elevations that a collection system covering a relatively small drainage area can be feasible. Streamflows in primarily from the upper Arkansas River Basin are also derived snowmelt, though the yield per square mile on . III-30