Abstract
In a tropical country like India, instability in agricultural production stems from vagaries of rainfall. A complete and quantitative understanding of spatial and temporal variation of this resource is, therefore, required to increase and stabilize food production. The use of average seasonal or monthly rainfall does not seem to be appropriate for planning purposes as it does not cover the risk factor. A detailed probability analysis can bring out the amount of rainfall expected at different probability levels which in turn can give the number of years of adequate, deficient and excess rainfall.
Keeping in mind the above aspects, the present paper studies probabilistic rainfall scenario over the Vidarbha region which, despite having tremendous agricultural potential, could not develop to its full potential.
The study reveals that dynamic influence (mainly lows and depressions moving over the area) is the main cause of rainfall over Vidarbha. Accumulated Assured Rainfall (AAR) analysis, by fitting incomplete Gamma Distribution Model at different probability levels, indicates that it is maximum in the eastern part of Bhandara and northern part of Gadchiroli districts while it is minimum over western Vidarbha covering northern parts of Buldhana, Akola and adjoining Amravati districts. Weekly assured rainfall analysis reveals that in seventy per cent of the years, the eastern most districts of the region get at least 25 mm of rainfall per week continuously for 13 weeks during mid – June to first half of September. Based on AAR analysis at 70% probability level the entire study region has been divided into five homogeneous rainfall zones (namely A, B, C, D and E). The region to the west of 79°E (A, B, and C zones) receives lower rainfall compared to that to the east of 79°E (D and E zones). This could be attributed to the fact that Vidarbha mainly gets rainfall from lows/depressions formed over Bay of Bengal and move in a westerly/ northwesterly direction and sheds much of its rainwater over the eastern D and E zones, while A, B and C zones get rainfall when these systems pass their heyday. In each of these zones the amount of peak rainfall and when the peak is received has also been found out. This type of rainfall information at different probability levels could serve as basic input of planning for agriculture, land use, drainage requirements and water resources development. Coupled with soil information these will help deciding crop types that could be raised to increase and stabilize production.
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