To replenish it. I know it was made by accident but agricultural runoff kept it from drying out. Now it is full of fertilizer and pesticide residue and the farms have gotten better at using water so less flows into the Salton Sea. As it dries up toxic dust clouds are blown over the cities nearby. California is trying to stop the dust. One idea is to fill it with sea water from the Gulf of California from Mexico.

I am not saying this is a good idea, only that it is an idea.