In 1969, a study of the water resources of Alaska's Arctic was initiated in response to the area's large scale petroleum exploration and extraction activities. A summary of the work is presented through a discussion of the basic features of the hydrologic system; the physical system, climatic input, and hydrologic output, with particular emphasis given to the Kuparuk, the Sagavanirktok, and the Putuligayuk Rivers. Precipitation acts as the controlling input function for the overall system. It occurs as snowfall in the eight winter months and as rainfall in June, July, August, and most of September. Comparison of precipitation records are made for Barrow, Barter Island and Prudhoe Bay.