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Rainfall is the primary component of the hydrological cycle and its measurement is very important for estimating groundwater recharge in any area. Its importance is further enhanced in arid and semi arid regions. This is one of the directly measurable parameter but its variability is very high and erratic both in space and time. Rainfall is generally measured using a rain gauge either manual or self-recording and hence a modest technology and cost are involved.
In a small watershed of about 55 km2 in a semi-arid region of southern India one rain gauge has been installed and maintained by the Andhra Pradesh Groundwater Department, Hyderabad, India that provides the daily measurement of rainfall. However, it has been observed that even in the small area, the rainfall varied a lot. People participation and partnership was thought and after a few rounds of awareness program and explaining the importance of rainfall measurement, about 25 volunteers from the local public were registered to measure rainfall in the vicinity of the residence using a simple plastic container and a scale. In this program volunteers are measuring the rainfall height with that scale. Its not calibrated. The plastic container height is 25cm and approximately uniform diameter. Based on this container height and diameter we developed one formula for converting rainfall height to actual rainfall.
The distribution of the measuring locations provides an ideal set of measuring locations to calculate the variogram using the theory of regionalized variables, i.e., a few clusters of many points in each village for the small scale variability and then inter-village points for medium and large scale variability. The measurements also follow the norms set by the Meterological departments for measurement of the rainfall as well as they provide an important set of data on rainfall. The data set is thus used in estimation of rainfall over the grids of the aquifer model using the adequate variability and it was found that such an input has provided useful comparison of field and model water levels.
This has provided a clear concept of water resources and the hydrological cycle to the local public and a sense of responsibility to the stakeholders as well as a good set of data for scientific analyses. The success of this experiment can be justified from the fact that the measurement from the last three years have been gathered now.
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