What is the basis for Ecology’s general assumption that ground water used by wells will affect streams?
When evaluating WRIA 17, Ecology found that each of the interior sub-basins (generally those with rivers or large creeks) functions largely as an independent system. Over the long-term, the amount of water entering these systems (mainly through rain and snow) is equal to the amount of water leaving (through surface water runoff and groundwater discharge to marine waters). If consumptive use within any of these sub-basins increases over time, the amount of water leaving the sub-basins will decrease. This conclusion is based on the law of conservation of mass. To some extent new consumptive uses could also reduce the amount of ground water stored in a sub-basin and this could result in declining ground water levels over time. However, in the long run our understanding of the hydrogeology tells us that if new well use within any of these sub-basins increases over time, this will result in decreased surface water flow or a combination of storage loss and decreased surface water flow. The C
