In 1987, lime (250 mg/L calcium carbonate or 250 mg/L calcium hydroxide) was added to four hardwater dugouts in northwestern Alberta to precipitate the phosphorus and algae and improve water quality. Calcium carbonate reduced algal biomass to 39 percent of pretreatment concentrations between June and August of 1987, but dugouts recovered to pretreatment concentrations during the next summer. Calcium hydroxide treatments reduced algal biomass to 12 percent of pretreatment concentrations and dugouts remained at that level over the following summer. Phosphorus concentrations were decreased by 80 percent in calcium hydroxide-treated dugouts but were relatively constant in calcium carbonate-treated dugouts. Calcium hydroxide treatments can improve water quality in dugouts for a chemical cost of $200–$400.