Abstract

                                Wide variations are seen in the occurrence of rainfall and distribution in Coimbatore district. As such arithmetic mean may not represent the average rainfall. so Thiessen-weighted average and Isohyetal average of rainfall were worked out.. The arithmetic mean (826.70 mm) was the lowest and the Thiessen weighted average value was increased by about 100 mm. The isohyetal average showed a very high value (1348.05 mm): These variations were due to the non-uniformity in the dis- tribution of rain gauges and also because of steep precipitation gradients. Isobyetal mean which seems to be more representative, should be utilised for hydrological analysis such as surface water, recharge of ground water etc.

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