Question 4 (15 marks) A water supply dam (Dam B) is fed by a nearby dam (Dam A) via a 2x3 m french drain (a gravel-filled channel) which runs along a 150 m route. The permeability factor for the french-drain is 102 m/s. A small village requires 18 000 L/d from the supply dam. Determine how long it will take until the residents of the village will need to find an alternate water source if the dam has a current accessible water volume of 150 m3 assuming the inflow from Dam A remains constant over the analysis and an evaporation rate of 10 mm/m2/d from Dam B. Note the water levels of the dams are provided in the figure below in metres above mean sea level (mamsl). V 185 mams1 Dam area: 300 m2 Outlet to Village Dam A French Drain V 179 mams1 150 m Dam B