Rainfall variability and probability for crop planning in Solan, Himachal Pradesh

Daily rainfall data of 38 years (1971–2008) was analysed to estimate the long term averages of weekly, monthly, seasonal and annual rainfall and its variability at Solan in Himachal Pradesh. Normal annual rainfall of the area was 1163.9 mm. August received the maximum rainfall of 246.9 mm followed by July 240.3 mm. The stable rainfall period was of 14 weeks spread over 24^th to 37^th Standard Meteorological Weeks (SMW) which can be considered as an assured period for crop growth. This confirms the onset and withdrawal of South-West monsoon. Different conclusions were madeon the basis of data collected. The probability of receiving 10 and 20 mm of average weekly rainfall during 25^th to 39^th SMW exceeds 50 per cent. The chances of water stress increases in second fortnight of September for kharif crops. South-West monsoon (11–17 June to 10–18 September) has 60–90 per cent chances of receiving rainfall. The probability of 10–20 mm rainfall in rabi season (1^st SMW- 8^th SMW) is 50–70 per cent. Since the winter rainfall is uncertain and erratic, residual moisture can be recharged and is essential for the preparation of tree basins, application of fertilizers in temperate fruits and for growing early kharif season crops under rainfed conditions. Well distributed winter rains and early snowfall before January are beneficial for fruit crops and wheat under rainfed conditions. Keeping in view the rainfall pattern and its distribution in the area, suggestions have been made to modify the microclimate with respect to crop planning to increase the quality and productivity under rainfed conditions.