Rainfall Hydrograph Technical Description The is used to demonstrate the hydrological phenomena of rainfall. It shows the relationships between rainfall and the seepage of rainwater. A stainless steel tank filled with gravel acts as the ground. The water can be drained from the ground using a drainage tube or a filter. A time-controlled motorised water drain distributes the leakage water to 17 transparent measuring tanks. This allows a chronological profile of the discharge of water from the ground to be identified. The ground sample is irrigated by 2 nozzles that can be separately selected using ball valves. A solenoid valve releases the rain. The quantity of rain is adjusted using a control valve and a flow meter. 3 electronic time switches control the irrigation time, the delay time and the measuring time. The unit includes an extra cleaning connection for cleaning the tubes. A tarpaulin is supplied for experiments including a non-permeable layer. Plastic containers that can be inserted in the tank act as rain storage reservoirs.