Monthly climatic water balance at selected locations in India

Abstract

Meteorological data (1971-2000) for twenty seven (27) well distributed locations in India, have been utilized to compute average monthly rainfall (RF) and potential evapotranspiration (PET). In the present study, potential evapotranspiration (PET) has been calculated by using FAO recommended Penman-Monteith equation. An attempt has been made to identify the months of water deficit / surplus and these have been discussed in relation to crop planning for both seasons Monsoon or Kharif (June to September) and Rabi (October to February).
In northwest, west and central zone, water deficit is observed at several stations in Kharif and all stations in Rabi. The average RF/PET ratio in this zone is 0.53 indicating that except in Pantnagar and Adhartal (0.94), crop selection and planning do not favour crops requiring more water. During Kharif season RF/PET ratio of several stations, except Hissar and Jodhpur, is more than 1, suggesting successful cropping with rainfall. In east and northeast zone, water surplus is observed at all the stations in Kharif. Water deficit in Rabi occurred at most of the places during December, January and February. RF/PET ratio during Kharif season ranges between 1.44 and 5.93 suggesting none of the stations undergo water deficit during the crop growing period. For the stations selected in south zone, water deficit in Kharif occurred at many places in the months of June, July and August. Water deficit in Rabi occurred at many places during January and February. During Kharif RF/PET ratio is less than 1 except for Rajamundry and Pattambi. This emphasizes the need for proper crop selection for successful cropping with limited moisture.