Rainy weather in recent years is being blamed in part for slow-going in efforts to reduce the amount of phosphorus flowing into Lake Champlain.
Phosphorus is washing from farms and suburban developments into the 18 rivers that drain into the lake. That in turn feeds the growth of noxious algae and aquatic weeds in the lake.
Vermont, New York and Quebec have been involved for years in efforts to reduce phosphorus by stopping it at its source.
But new figures indicate the amount of phosphorus flowing into the lake has grown by as much as 50 percent since 1991.