Problems of utilizing ground water in the West-Side Business District of Portland, Oregon

Abstract

The withdrawal of ground water for industrial uses and for the heating and cooling of buildings in the west-side business district of Portland has increased greatly since 1955. As a result of this increased withdrawal, groundwater levels apparently are declining progressively, even though some of the water withdrawn is returned to the groundwater bodies by means of artificial recharge. Temperature and chemical quality of the ground water also are changing at places, due to the increased pumping and the practice of artificial recharging with water of different temperature and chemical composition from the natural ground waters. The west-side business district is underlain, in downward succession, by alluvium of Recent age, fluviolacustrine deposits of late Pleistocene age, the Troutdale formation of early Pliocene age, the Sandy River mudstone, of early (?) Pliocene age, the Columbia River basalt of Miocene and Pliocene (?) age, and marine sedimentary rocks of early Tertiary age. Sand and gravel layers in the Troutdale formation and interflow zones in the Columbia River basalt are water bearing and yield water of good to fair chemical quality to several dozen industrial wells in the area. The underlying marine sedimentary rocks contain saline water, which apparently is migrating upward and mixing with water in the basalt aquifers. The data presently available indicate that with continued uncoordinated increases in pumped withdrawal and artificial recharge the problems of declining levels and changes in the temperature and chemical quality of the ground water probably will increase. A comprehensive plan for the development and management of the groundwater resources is needed to insure maximum benefits from the ground water and to minimize the effects of the problems now developing. Additional information on the changes in temperature, chemical quality, and levels of the ground water, and on the amounts of ground water pumped and recharged artificially is needed to serve as a basis for such a comprehensive plan.