The Citizen Potawatomi Nation Tribal Jurisdictional Area, consisting of approximately 960 square miles in parts of three counties in central Oklahoma, has an abundance of water resources, being underlain by three principal aquifers (alluvial/terrace, Central Oklahoma, and Vamoosa-Ada), bordered by two major rivers (North Canadian and Canadian), and has several smaller drainages. The Central Oklahoma aquifer (also referred to as the Garber-Wellington aquifer) underlies approximately 3,000 square miles in central Oklahoma in parts of Cleveland, Logan, Lincoln, Oklahoma, and Pottawatomie Counties and much of the tribal jurisdictional area. Water from these aquifers is used for municipal, industrial, commercial, agricultural, and domestic supplies. The approximately 115,000 people living in this area used an estimated 4.41 million gallons of fresh groundwater, 12.12 million gallons of fresh surface water, and 8.15 million gallons of saline groundwater per day in 2005. Approximately 8.48, 2.65, 2.24, 1.55, 0.83, and 0.81 million gallons per day of that water were used for domestic, livestock, commercial, industrial, crop irrigation, and thermoelectric purposes, respectively. Approximately one-third of the water used in 2005 was saline water produced during petroleum production. Future changes in use of freshwater in this area will be affected primarily by changes in population and agricultural practices. Future changes in saline water use will be affected substantially by changes in petroleum production. Parts of the area periodically are subject to flooding and severe droughts that can limit available water resources, particularly during summers, when water use increases and streamflows substantially decrease. Most of the area is characterized by rural types of land cover such as grassland, pasture/hay fields, and deciduous forest, which may limit negative effects on water quality by human activities because of lesser emissions of man-made chemicals on such areas than in more urbanized areas. Much of the water in the area is of good quality, though some parts of this area have water quality impaired by very hard surface water and groundwater; large chloride concentrations in some smaller streams; relatively large concentrations of nutrients and counts of fecal-indicator bacteria in the North Canadian River; and chloride, iron, manganese, and uranium concentrations that exceed primary or secondary drinking-water standards in water samples collected from small numbers of wells. Substantial amounts of hydrologic and water-quality data have been collected in much of this area, but there are gaps in those data caused by relatively few streamflow-gaging stations, uneven distribution of surface-water quality sampling sites, lack of surface-water quality sampling at high-flow and low-flow conditions, and lack of a regularly measured and sampled groundwater network. This report summarizes existing water-use, climatic, geographic, hydrologic, and water-quality data and describes several means of filling gaps in hydrologic data for this area.