A catchment area of 140 km2 received 120 cm of rainfall in a year. At the outlet of the catchment the flow in the stream draining the catchment was found to have an average rate of 2.0 m/s for 3 months, 3.0 m/s for 6 months and 5.0 m/s for 3 months. (i) What is the runoff coefficient of the catchment? (ii) If the afforestation of the catchment re- duces the runoff coefficient to 0.50, what is the increase in the abstraction from precipi- tation due to infiltration, evaporation and transpiration, for the same annual rainfall of 120 cm?

Please answer question 2

A 40-year annual series of eak river discharges with the mean equal to 15,000 cfs and standard deviation equal to 7,500 cfs approximates a normal distribution. (1) Determine the discharge woth a return period of 10 years. (2) Determine the discharge with a return period of 20 years. (3) what is the return period rhay corresponds to a discharge of period of 20 years. (3) What is the return period that corresponds to discharge of 20,000 cfs? (4) What is the probability that a discharge equal to or greater than 20,000 cfs will occur during a 5-year period?