1.Sketch out the structure of confined aquifer and unconfined aquifer, on your sketch, label a) water table or potentiometric surface, and b) aquifer (permeable layer) or aquitard (impermeable layer). Note: you may complete this question on paper and upload it as your answer.

2.According to the IDF curve given below, predict the precipitation intensity for a rainfall event with a return period of 25 years and a duration of 45 minutes.

TI 46T 200 RETURN 106 PERIOD 9 898 25 YEARSY 48 RAINFALL INTENSITY ( MILLIMETRES / HOUR ) 35 20 RAINFALL INTENSITY - DURATION - FREQUENCY CURVES FOR SINGAPORE ISLAND 15 460 506 635 709 850 9501560 5 6 7 8 9 10 0 50 60 70 80 40 1018 200 2 3 TIME ( MINUTES )TI 46T 200 RETURN 106 PERIOD 9 898 25 YEARSY 48 RAINFALL INTENSITY ( MILLIMETRES / HOUR ) 35 20 RAINFALL INTENSITY - DURATION - FREQUENCY CURVES FOR SINGAPORE ISLAND 15 460 506 635 709 850 9501560 5 6 7 8 9 10 0 50 60 70 80 40 1018 200 2 3 TIME ( MINUTES )