An artificial lake created over a hundred years ago now, with it's own ecosystem that has developed around it. And rivers still flow from that downstream, like

An artificial lake created over a hundred years ago now, with it's own ecosystem that has developed around it. And rivers still flow from that downstream, likely entering the water table of a much larger area than the lake itself. Despite it being "artificial", the water still passes through it to downstream ecosystems, as it did before any dam construction. While they may be lower volume due to the drought and limited releases from the lake, replacing that with "Salt water or nothing" would still be a massive change.