A self contained floor standing unit consisting of a water reservoir and a tank for sand with overhead spray nozzles that simulate rainfall both stationary and moving.  It is for studying hydrology principals including rainfall, throughflow and the movement of water over land and rivers. The apparatus is a sturdy metal frame which holds a large rectangular stainless-steel tank and a reservoir tank. A jacking mechanism allows adjustment of the angle of the catchment area. Students can fill the catchment area with a granular medium to form a permeable catchment area. A valve selects all or half the nozzles. Students can use this facility to vary the lag time on a hydrograph or to simulate a moving storm. Above the catchment area is a frame that holds spray nozzles which simulate rainfall on the catchment. Students can vary the flow to the nozzles and tank. A flow meter measures the overall flow. A pump takes water from the reservoir and feeds it to the overhead nozzles and to the ends of the catchment area.