In 1978, the U.S. Geological Survey, in cooperation with the State of Washington Department of Ecology, investigated the hydrology of the Sagebrush Flat area as it relates to Rattlesnake Springs.
Rattlesnake Springs and all known wells on Sagebrush Flat obtain water from basalt aquifers. The wells tap aquifers at or below the altitude of the spring discharge.
Water levels in some wells on Sagebrush Flat, and in a well 27 miles to the northeast in an area of no ground-water development, show slight fluctuations that may correspond to annual variations in precipitation. However, hydrographs of most wells on Sagebrush Flat show water-level declines and rises that correspond with the beginning and end of the pumping season. The discharge of Rattlesnake Springs started to decrease at about the beginning of the 1978 pumping season and did not start to increase until after most pumping was stopped.
The water level in deep aquifers beneath Sagebrush Flat is at a lower altitude than in shallow aquifers, and water moves down well boreholes from shallow aquifers to deeper aquifers. This downward movement of water diverts ground water that is moving toward natural discharge points such as Rattlesnake Springs, thereby decreasing the discharge at these points.
