 From the uplands to the west, rivers and streams cut channels in a generally west to east or southeast direction.Erosion of the Rockies provided alluvial and aeolian sediment that filled the ancient channels and eventually covered the entire area of the present-day aquifer, forming the water-bearing Ogallala Formation.In that respect, the process is similar to those currently prevailing in other modern rivers of the area, such as the Kansas River and its tributaries.