Louisiana Lake Water Quality

Across Louisiana, 162 lakes carry an active water-quality grade spread over 43 counties. The underlying measurements come from the Louisiana Department of Environmental Quality, alongside federal programs and volunteer monitoring networks. A-grade lakes are scarce in Louisiana: about 1% of the dataset. Most lakes here sit in C or D — productive, often shallow, frequently algal in late summer.

A meaningful share of the state's monitored lakes register as hypereutrophic — heavily nutrient-loaded, frequent blooms, low summer transparency. These are usually shallow, surrounded by row-crop agriculture, with little volume to buffer the inputs. Orleans Parish ranks highest on average county grade (A). Madison Parish sits lowest. With only 43 counties in the state, the cross-county spread is narrower than the within-county spread for most lakes.