MEASUREMENT OF RAINFALL
- Rainfall is the principal source of all waters.
- It is expresse as the depth of water in centimetres which falls on a pucca, impermeable levelled surface.
- The rainfall is measured with help of rain-gauges.
- Rain-gauges may be automatic or nonautomatic.
- Govt of India has approved use of non-automatic rain gauges at all the rain-gauge stations.
- Following are different types of rain-gauges.
- Simon’s rain-gauge.
- Weighing bucket rain-gauge.
- Float type rain-gauge.
- Tipping bucket rain-gauge.
1. Simon’s Rain-gauge.
- A typical Simon’s rain gauge is shown in Fig. It is also known as non-recording type of rain-gauge, as it does not record the rate of
- rainfall at any moment but only collects rain water.
- It consists of a funnel fixed at the top of a receiving bottle.
- The receiving bottle is about 8 to 10 cm in diameter and is encased in the metal casing.
- This bottle is fixed in the ground slightly below the ground level.
- The rain water enters the bottle through the funnel and gets collected in the bottle.
- The bottle can collect about 10 cm to 12 cm of rain.
- Rainfall is recorded daily at 8 A.M.
- by a man deputed for this purpose.
- If the rain fall is too much and is likely to exceed the capacity of the bottle,
- Then two or three intermediate readings are taken and their sum is recorded as the total rainfall during past 24 hours.
2. Float Type Rain-gauge.
- It is a type of automatic rain-gauge.
- The instrument consists of a funnel and a rectangular container.
- The container consists of a float which remains connected to a pointer.
- The pointer moves on a recording drum which is kept moving at such a rate that drum completes exactly one revolution in 24 hours.
3. Weighing Bucket Rain-gauge.
This rain-gauge consist receiver