An aerial view of Matilija Dam and reservoir.

To make that possible, the Nelson Dam needs to come down first. The eight-foot high irrigation diversion dam on the Naches River sits just upstream of the City of Yakima on the largest tributary of the Yakima River, which flows into the Columbia River. Built in the 1920s, the now unneeded dam blocks the movement of salmon through the area, choking off the ecosystem’s lifeline.
But once the dam is taken out—by 2020, proponents of the removal hope—it will allow fish and nutrients to flow downstream. It will also reduce the risk of flooding in the area. (Learn more about the rapid restoration of a river after dam removal.)
And perhaps surprisingly, removal of the dam will actually increase the water and climate resilience of the area, says Michael Scott, acting director of the environment program of the William and Flora Hewlett Foundation. That’s because pooling water in a reservoir leads to …