Undergraduate Thesis - Feasibility of Rainwater Harvesting in Paarden Island

The volume of rainwater is calculated per month and uses the average rainfall for that period to determine what will be the most likely estimate of rainfall that can be captured. The equation below is used to calculate the volume of rainwater collected in a month which has been modified slightly from The Texas Manual on Rainwater Harvesting to accommodate the metric system.

                                                                                                                                                                                                                                                                                                                                                                    V = 0.001CiA                                                                                                                                              [3.1]

Where: V = the volume of rainwater captured in a month (m³/kL)

                                                C = the runoff coefficient

                                                i = the average rainfall in a month (mm)

                                                A = the catchment area (m²)

                                                0.001 = the conversion factor

The groundwater infiltration for a catchment can be calculated by calculating the maximum amount of rainwater that can be captured and subtracting all the rainwater that is captured through roof and ground surface runoff. The calculated value of rainwater that remains would then either be evaporated or infiltrated into the ground. A factor is selected to estimate the amount that would be infiltrated into the ground and this value is multiplied by the remaining rainwater to calculate the amount of rainwater that infiltrates into the ground.