Abstract:
Spring-dominated streams in the Oregon Cascades
are often characterized by nearly constant
discharge, and by peak flows which occur in late summer or fall,
several months after the annual snowmelt. A model
is presented which can account for the temporal variations of discharge
and the delay between snowmelt and the period of peak
stream flow. Springs are assumed to be
fed by an unconfined aquifer which 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 (<2Ma)
volcanic rocks which comprise the
aquifers is inferred to be O(10^-11) m^2.