Report on the Platte River Basin, Nebraska Level B Study

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Figure 8 ALTERNATE SOURCES OF GROUND WATER Brule Formation. Mostly a thick sequence of clay, claystone, ® Niobrara Formation. Mostly cream - colored to gray chalk, Climate Weather in the basin is typical of the interior of a large land mass in the temperate zone — variable. Rapid weather changes are caused by invasions of large masses of warm, moist air from the Gulf of Mexico; hot, dry air from the southwest; cool, dry air from the Pacific Ocean; and cold, dry air from Canada. PRECIPITATION The period 1941 -1970 is presently considered by the U. S. Weather Service to represent a "normal" Precipitation period. Figure 9 shows how the average annual precipitation for that period varied. It decreased fairly uniformly from about 32 inches in the most easterly part of the basin to less than 14 inches in the western part. The amount of rainfall at any location generally varies considerably from year to year. The figure also shows the annual variation at several stations across the basin. Intense thunderstorms are common although they are generally localized in extent, seldom cov- ering large areas of the basin. 17 silt, and siltstone. Cracks-and fractures in the uppermost part shaley limestone, and limey shale. Yields water to wells in areas yield water to wells in Lodgepole and Pumpkin Creek valleys where the formation has been exposed to long periods of and in parts of the North and South Platte River valleys. weathering. Source of limited supplies of water where directly by saturated sands and gravels in the Pleistocene .overlain Chadron Formation. Basal deposits of sand and gravelly sand deposits or the Ogallala Formation. overlain by clay and claystone. Basal sand and gravelly'sand is a source of water to some domestic and stock wells in the ■ Dakota Formation. Sandstone, with clay, claystone, siltstone, western part of the Upper Platte Subbasin. and sandy silt. Capable of yielding water to wells and is used as ❑a Lance and Foxhills Formations. Sandstones with interbedded source of supply for municipal, stock, and domestic supplies in some parts of the Lower Platte Subbasin. clay and shale. Potential source for limited supplies of water. Climate Weather in the basin is typical of the interior of a large land mass in the temperate zone — variable. Rapid weather changes are caused by invasions of large masses of warm, moist air from the Gulf of Mexico; hot, dry air from the southwest; cool, dry air from the Pacific Ocean; and cold, dry air from Canada. PRECIPITATION The period 1941 -1970 is presently considered by the U. S. Weather Service to represent a "normal" Precipitation period. Figure 9 shows how the average annual precipitation for that period varied. It decreased fairly uniformly from about 32 inches in the most easterly part of the basin to less than 14 inches in the western part. The amount of rainfall at any location generally varies considerably from year to year. The figure also shows the annual variation at several stations across the basin. Intense thunderstorms are common although they are generally localized in extent, seldom cov- ering large areas of the basin. 17