RHU Rainfall Hydrographs Unit



The Rainfall Hydrographs Unit, "RHU", is a self-contained unit designed to demonstrate some of the physical processes found in hydrology and fluvial geomorphology, such as rainfall hydrographs for variable permeability catchment areas, dewatering groundwater using drainages, with or without surface recharge by rain, etc.




The main element of the Rainfall Hydrographs Unit,"RHU", is a tank mounted on a frame. The tank can be filled with sand. There are removable curtains to prevent splashing.

There are two square pattern spray nozzles at the top that supply water to the sand. Water, before being sprayed, passes through a flow control valve, a flowmeter and a solenoid valve controlled with the electronic console.

The drainage of the system is driven towards one end of the tank, through which water leaves towards a collection and measurement system, mounted on another frame. The collection system consists of a vessel divided internally into 17 storage compartments and a central drainage channel. Its frame includes a drive motor that allows its displacement to a controlled velocity under the tank outlet, thus enabling an immediate visualization of the hydrograph. The motion time of the system is measured and visualized in the console to be able to obtain an immediate hydrograph of the drainage in function of time.

The unit includes several accessories to analyze the surface retention, the storage effect in depressions and land drainage.



  1. Recording of hydrographs.
  2. Study of hydrographs from one or more storms.
  3. Calculation of the concentration time for a short storm.
  4. Study of storm hydrographs from a variable permeability catchment area.
  5. Study of storm hydrographs from an impermeable catchment area.
  6. Analysis of the influence of a moving storm on a flood hydrograph.
  7. Analysis of the influence of reservoir storage on a flood hydrograph.
  8. Analysis of the influence of land drains on a flood hydrograph.