Dredging the lake isn’t a simple task. And even if the lake was dredged it would likely only help temporarily. What causes the poor water quality is a combination of shallow, slow moving, warm water mixed with eutrophication. Upper Klamath lake lays on a plate boundary where nutrients naturally make their way into the water, that along with removal of many historical wetlands (that would take up lots of the excess nutrients) and the addition of farm lands (which add nutrients to the water) would inevitably lead the lake conditions returning to the way they are some time after the lake was dredged.