The square watershed (basin) has four rain gages. During a storm, these gages receive rainfall(precipitation) as indicated in the figure below. Contour lines show the elevations at different heights withinthe

watershed in meters. Each square within the watershed is 1 km?. a) Find the average rainfall using arithmetic mean. ) Find the average rainfall using the Thiessen (Voronoi) polygon method. c) Assuming that 50% of the basin's area is a park and 50% of the basin's area is light residential, computethe peak flow for a 50-year return period using the Rational Method. Use an intensity l= 0.55 in/hr. Reportthe peak flow in cfs. Note that 1km? =247.105 Acres. the peak TIOW in cts. Note that 1kme = 247.105 Acres.d) The basin's storm discharge system is directed to a waterway. Assuming that 1% of the peak flow forthe 50-year return period in part c) above is drained into the waterway, calculate the diameter of the stormdrain (pipe) that conveys stormwater to this waterway. Use the following data: Pipe's slope S = 1%,Manning's n = 0.014. Assume the pipe is 75% full. Standard internal diameters in the US are 12", 15", 18",21", 24", 27", 30", 33", 36", 42", 48", 54"..