University Lake is a reservoir with a surface area of 8 acres and an average depth of 10 feet. The volume of the lakes is 222.2 acre-ft. University Lake receives water from stream inflow at a rate of 302 acre-ft/year with phosphorus (P) concentration of 0.045 mg P/L. Direct precipitation to the lake totals 80 cm/year and has a phosphorus (P) concentration of 0.011 mg/L. Estimated lake evaporation is 1888 m3/year. The stream outflow from the lake is 297 acre-ft/year. You can assume that the evaporation is pure water and carries no other chemicals with it. (There are 1233.5 m3 in 1 acre-ft)
1. Determine the average residence time of the lake in days.
2. What is the surface area of the lake in meters squared?
3. What is the concentration of phosphorus in the lake? (report in µg/L, assume that the concentration associated with the out flow equals the concentration in the lake)
4. How would increasing the stream inflow by 30% affect the concentration in the lake water? (repeat number 4 but multiply the inflow by 1.3)
5. How would increasing the outflow by 25% affect the concentration of the lake? (repeat number 4 but multiply the outflow by 1.25)