Federal water managers will begin spilling hundreds of thousands of gallons of water over spillways instead of through turbines during annual “spring spill” operations at U.S. Army Corps of Engineers’ dams on the lower Snake and Columbia rivers.  The operations, which primarily benefit juvenile fish, start today on the lower Snake River and next Monday on the lower Columbia River. It’s intended to decrease the time it takes juvenile salmon and steelhead to move through the system of dams to the Pacific Ocean as well as provide a non-turbine passage route past the dams.  Spill levels vary at each of the eight dams, but all projects have an upper limit that protects water quality such as total dissolved gas, or TDG.  Bonneville, McNary and Ice Harbor dams will spill up to the 125% TDG levels 24 hours per day.  The Dalles Dam will spill 40% of the river over the spillway, equivalent to 2022 spill level.  The John Day Dam will spill 16 hours per day up to the 125% TDG levels and reduce spill for up to eight hours to performance standard spill levels or 32% of the river.