Fish Ladders

After the construction of the Woodbridge Dam in 1910, the new dam blocked salmon and steelhead trout from reaching their upstream spawning areas to which they return each year. When those species lose access to upper watersheds, they can't reproduce. To help fish bypass the dam and continue their natural lifecycle, a “fish ladder” was installed in 1925. (Although it’s called a “ladder,” this structure is more like a series of small waterfalls, allowing fish to jump up from pool to pool to navigate past the dam.)

The fish ladder at Woodbridge Dam is the only one along the Mokelumne River that allows fish to swim past a dam; Pardee Dam and Camanche Dam do not allow fish to cross, effectively halting their upstream journeys. The East Bay Municipal Utility District (EBMUD) now maintains the fish ladder at Woodbridge Dam and has redesigned it several times to increase effectiveness, with its latest upgrade in 2004. The new ladder has smaller steps to ease the climb, a path for fish to swim downstream, and screens to prevent them from being diverted into the Woodbridge Canal. To monitor fish migration, the dam has underwater cameras so EBMUD staff can count each fish as it passes through the ladder. 2024 saw a new record as nearly 30,000 Chinook salmon passed through the ladder!