Hydrology of spring-dominated streams in the Oregon Cascades

Spring-dominated streams in the Oregon Cascades are often characterized by nearly constant discharge and by peak flows that occur in late summer or fall, several months after the annual snowmelt. A model is presented that can account for the temporal variations of discharge and the delay between snowmelt and the period of peak streamflow. Springs are assumed to be fed by an unconfined aquifer that is recharged by the annual snowmelt. Model results depend primarily on the effective permeability and the dimensions of the aquifer. Four spring-fed streams in the Deschutes River basin in the Oregon Cascades are studied. The effective permeability of the young (<2 Ma) volcanic rocks that comprise the aquifers i inferred to be O(10 -•) m 2.