Ogden Valley is a fault trough bounded on both the east and west by faults that dip toward the middle of the valley. This fault trough contains unconsolidated deposits of clay, sand, and gravel, whose thickness is more than 600 feet. These materials are stream and lake deposits and in places are well sorted and stratified. The lake sediments were laid down in a small lake that occupied Ogden Valley and that was connected with glacial Lake Bonneville at its high stage by an arm of water that occupied Ogden Canyon. During this stage of Lake Bonneville the Ogden Valley was completely filled with lake sediments up to an altitude of about 4,900 feet. These sediments include about 70 feet of clay, sand, and gravel in alternating layers, below which is a bed of varved clay whose maximum thickness is about 70 feet. This clay is continuous under the lower parts of the valley and is the confining bed that produces the artesian conditions. Below the varved clay is a deposit of silt, sand, and gravel of unknown thickness, most of which is believed to be pre-Bonneville alluvium.
In most summers the streams entering Ogden Valley are diverted for irrigation, and the upper parts of their channels are generally dry during the irrigation season. Lower down in the valley seepage water appears in the channels, and below these points there is continuous flow. The flow of the Ogden River increases as it passes through Ogden Canyon. This gain in flow is believed to be derived chiefly from ground-water seepage from the canyon walls, although there is probably some groundwater underflow from Ogden Valley at the head of Ogden Canyon. Some of the gain is also due to leakage from pipe lines in the canyon.
Of the 146 wells whose records are given in this report, 70 are flowing wells.
