||Emigration Canyon is situated in the portion of the Wasatch Mountains that are in the eastern part of Salt Lake County in north central Utah. A significant amount of ground-water development has taken place in the canyon in recent years to satisfy domestic water needs. This hydrologic investigation was undertaken to learn more about the ground-water aquifers in the canyon and their interrelationship so that the effects of past and future water development can be better understood. The area under study comprises about 29 square miles in the Rocky Mountain physiographic province and ranges in altitude from 4,870 feet to 8,954 feet. The rocks in the canyon have been folded into the Emigration Canyon syncline. The axis of the syncline is near to the stream channel and roughly parallel to it. The syncline plunges to the northeast, which is opposite to the direction of flow of Emigration Creek. More than half of the nearly 120 drilled wells in the canyon divert water from bedrock formations; others divert water from the alluvial, valley-fill material overlying the bedrock. The bedrock aquifers in the canyon are almost entirely in the Twin Creek Limestone, the Preuss Sandstone, and the Kelvin Formation. For this ground-water study, the area is referred to as the Emigration Canyon district of Salt Lake County and divided into four sub-districts--the Twin Creek, Preuss, Kelvin, and the Pinecrest. There are about 37 drilled wells in the Twin Creek sub-district, 12 in the Preuss sub-district, 65 in the Kelvin sub-district, and 4 in the Pinecrest sub-district. The water in the aquifers is under artesian pressures, and the pressures fluctuate annually as does the stream flow. The wells generally produce only a few gallons per minute, and their specific capacities are low. The rights to divert water from the stream date back as early as 1847, but most of the well rights have been established within the last 20 years. The majority of the estimated 660 persons that live in the canyon on a fu11- or part-time basis depend on drilled wells for their water supply. Over the past 65 years the stream flow of Emigration Creek has averaged about 4,350 acre-feet of water annually and has ranged from 13,500 acre-feet to 234 acre-feet. A thick alluvial cover over most of the canyon absorbs a large amount of the 20 to 35 inches of annual precipitation and influences the total annual stream flow. A seepage run, which was conducted in the late summer of 1965, indicates that some reaches of the stream are effluent, while other reaches are influent. The chemical quality of the stream and all but two of the wells sampled is of a calcium bicarbonate type. The water is very hard, but it is suitable for culinary use. Two wells sampled produce waters that are very high in total dissolved solids and are unfit for culinary use. The stream is highly contaminated with coliform bacteria. Coliform bacterial contamination was found in the shallow ground water, but tests indicate that deeper sources are probably uncontaminated. During the period of study, stream temperatures varied almost 30 degrees, while temperatures of water from individual wells varied only 3 or 4 degrees and remained near the average annual air temperature of the canyon. The annual ground-water pumpage is about 100 acre-feet of water, which is only about one-fortieth of the average annual flow of the stream. It is unlikely that present ground-water development has influenced surface- or ground-water rights, and additional drilling of small culinary wells could probably be allowed. Large wells or additional surface-water development could influence already established surface- and ground-water rights in both quantity and quality.