Drought Management in semi-arid tropical regions through horticultural crops

Abstract

Rainfall is the ultimate source of water, affecting production of crops and other biomass by direct falling on the fields as well as supporting surface and ground water irrigation. However, possibilities of drought occurrence in India vary from once in 2 years in Western Rajasthan to once in 15 years in Assam. The frequency and intensity of extreme weather events like droughts, floods, heat/cold waves, cyclones, delayed or early onset, long dry spells, early withdrawal, floods in drought frequented areas and droughts in flood afflicted areas have increased during the last two decades due to global warming. The Indian sub-continent is predominantly characterized by a tropical monsoon climate and entire regime is distinguished mainly by the differences in rainfall both in quantity and distribution. The most important feature is the regional and temporal alteration of atmospheric flow patterns associated with monsoon. There are two monsoon systems operating in the region (a) the southwest or summer monsoon and (b) the northeast or the winter monsoon. The summer monsoon accounts for 70 to 80% of the annual rainfall over major parts of south Asia. There is a large variability in the monsoon rainfall on both space and time scales. Consequently the Indian regions experience drought or flood in some parts of the country or the other almost every year during the monsoon period between June-September. Out of 44 (1965-2009) years, Orissa witnessed droughts in 19 years, floods for 17 years and cyclones for 7 years. In the past, India has experienced twenty two large scale droughts in 1891, 1896, 1899, 1905, 1911, 1915, 1918, 1920, 1941, 1951, 1965, 1966, 1972, 1974, 1979, 1982, 1986, 1987, 1988, 1999, 2000 and 2002 with increasing frequencies during the periods 1891-1920, 1965-1990 and 1999-2002. Droughts in the Indian region are mainly due to various kinds of failures of rains from southwest monsoon. Also there seems to be some association between El Nino and La Nina events and weak monsoons. Over more than hundred years period between 1871-1988, 11 of the 21 drought years were El Nino years. During the 90 years period between 1901-1990 rainfall was sufficient in all 7 strong El Nino cases. The El Nino phase of the Southern Oscillations (ENSO) has direct impact on drought in India which causes weak or enhanced summer monsoon.