Recycling water within the local ground-water system is an effective means to increase quantity and control water temperature of the water supply and to control or avoid environmental pollution. A fish-rearing facility, operated for 15 months, returned water to the local ground-water system through an infiltration pond and recycled 83 percent of its water supply. For each 100 gallons pumped the net stress on the aquifer was equivalent to withdrawing 17 gallons. Despite recycling, nutrient content and temperature of the water supply were acceptable throughout the study period. The rearing-facility nutrient output ranged from 1 to 2 pounds of nitrate-nitrogen per day, but nitrate-nitrogen levels in the water supply remained below 4 mg/1. The water temperature ranged from 7°C to 14°C. Mathematical relations developed show that acceptable nitrate-nitrogen levels and water temperatures nearly optimum for salmonid rearing could be maintained during full-scale hatchery operation.