TR(BR)-135 : Development of a weighing type rain gauge (WRG)

Abstract

For proper management of the available water resources, and for timely forecasting of the natural hazards like floods, droughts, etc., automation in the existing hydrological measurement systems is desired. It is obviously hoped that with these new techniques, the accuracy of observations as well as their time and resolution will increase.

Rainfall measurement is the core of all hydrological measurements. For automated recording of rainfall data, tipping bucket rain gauges are generally used. It has been reported that the tipping bucket mechanism of such rain gauges frequently malfunctions and gives erroneous data, especially during high intensity rainstorms. Weighing type rain gauges are considered worldwide as accurate and reliable.

For the first time in India, an attempt was made to develop a weighing type rain gauge using components and systems available indigenously. A load cell is used to weigh the accumulated rainfall. A collector rim of 205mm dia is used on an outer container from which the water is collected through a funnel into an inner container. The inner container rests on the load cell and is designed to store 10 cm of rainfall. The accumulated rain water, after reaching a preset level, is drained out using a solenoid valve. A microcontroller based data logger controls the sampling and data storage frequency, the operation of the solenoid valve, and stores the measured data alongwith other information in an on-board memory.

The rainfall data from the reported Weighing type Rain Gauge (WRG) and non-recording type rain gauge (ORG) was compared at a site in Roorkee. Results of the initial field testing were encouraging, and are presented in this report.