Question

Problem 1 (10 credits) A lake has an area of 10 km². During a specific month the lake evaporation was 90 mm. During the same month the inflow to the lake from a river was on average 1.2 m/s and the outflow from the lake via another river was on average 1.1 m/s. Also, for the same month a water level increase of 100 mm for the lake was observed. a) What was the precipitation in mm during that month? (6p). b) What assumption is important for your answer in a)? (1p). c) The concentration of phosphorus in inflow river water was 1.0 mg/L and outflow river water 0.8 mg/L during the month. What was the change of stored phosphorus (kg) in the lake during the month? (3p).

please my teachers

Answer 1

2-28 1 X10 mg no Imonth= (60x60x24 X30) seconds a) AQ = in flow- out flow' = 1.2-1-1=001 m/s 0.1 x660X 60X 24x30) m?/month in depth Orl X 60X60X24 X 3D 6 10XID' = 0.02592 m 25.92 mm de-Evaporation =90mm increase = 100mm. IDO -90+25.92 +P se toQ+ P P = 164.08 mm.) month b) There is no loss by seapage. 1000Lsim 3 1 4 month Img/L in in flow in flow = 12m3/s 1200x60X60X24x30). in flow=1200L/S = 3:1104410 9/month phosphorus inflow 1X3.1104x109 3.1104 X10% Kg 3110.4kg out flow lo1m3/s 1100LS = 1100 x C60x60 X24x30 X 2430) = 2.8512 X109 L/month 0.8 mg / phosphorus out flow total phosphorus out flow 2.8512x10 9 xo.8 - = 2281 kg change in stored phosphorus 3110.4 -2281 = 829.41%

sir,hope this helped u

sir,please give a rating