Our feeling is that the DWP's initial plans for the reservoirs were extraordinarily insensitive to the environment, historical and cultural contributions open reservoirs give to (Los Angeles).
The covering for the northern lake was really for the filtration plant that they wanted to build at lakeside. At other areas, the DWP feels there are particular water problems by having reservoirs open to air, dust and other wind-borne factors. But, according to the U.S. Environmental Protection Agency and the Department of Health Services of the state, Los Angeles' water--including water from open reservoirs--meets or exceeds all health standards.
There are two alternatives: one is non-lakeside filtration plants and the other is simply not doing anything if the water easily exceeds health standards.
If a kid asked me why I want to keep the lake the way it is, I'd tell the kid so that his kids can walk around the lake and see the beautiful open water.