Abstract
Rainfall information as a system input is very important to control water systematically by main irrigation and drainage facilities, and its accuracy depends on the suitability of rain gauge networks. Those networks, however, have been set up empirically and techniques of its optimal network design has not yet been developed.
The aim of this paper is to examine the optimal selection of rain gauge stations by applying the Kriging theory to spatial rainfall patterns in basins.
Three basins were selected and heavy rainfall events were used to determine the pattern of variograms for the watershed concerned. The Kriging theory was then applied to estimate the weight of each gauge location, which was, in turn, used to calculate the areal rainfall. Finally, the theory was applied to determine the variance of the rainfall estimate at each rain gauge station. The method thus applied proved useful to provide the following information for the design of rain gauge networks:
1. The major rain gauge station is selected successively out of all stations, based on numerically evaluated values. Hypothetical points can be included in it. The index obtained can be used for the inclusion or elimination of gauge stations.
2. When priority of investment for rain gauges, such as equipment of telemetric system, is considered, the above method guides us in deciding which combination of gauge stations should be selected. The combination number (n) of gauges can be chosen arbitrarily.
3. In installing a new gauge station, the correction of error is evaluated by moving a newly added hypothetical point in the basin, and the equi-line of its correction is drawn to specify the points.
