5 points5ave Answer QUESTION 3 Consider a 5.5km 2 catchment which contalns a wet

Question

5 points5ave Answer QUESTION 3 Consider a 5.5km 2 catchment which contalns a wetland with an area of 1.9km*2 situated at the catchment outlet (see fgure). The wetland area recelves 65MLy of effluent and discharges 120MLtyr In environmental flows. The mean annual ralnfall Is 980mm the mean annual potential evaporation rate is 1210mm. Estimate the runoff coefficient for the catchment area surrounding the wedand area using a steady state water balance. Provide your answer acurate to 2 decimal places

Explanation / Answer

Given,

mean annual rainfall = 980 mm = 0.98 m

mean annual potential evaporation = 1210 mm = 0.121 m

Catchment area = 5.5 Km2 = 5.5 * 106 m2

Wetland area = 1.8 Km2 = 1.8 * 106 m2

Inflows = 65 ML/yr = 65 * 103 m3/yr

Outflows = 120 ML/yr = 120 * 103 m3/yr

Change in Volume = Precipitation - Evaporation + Surface Inflows - Surface Outflows

= 0.980 - 0.1210 + (65 * 103 *1)/(1.8 * 106) - (120 * 103 *1)/(1.8 * 106) = 0.98 - 0.121 + 0.036 - 0.067 = - 0.828 m = - 828 mm

Here, negative (-) indicates runoff i.e., outflows

Runoff Coefficient = (amount of runoff / amount of precipitation) = (828/980) = 0.845

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