In arid, semi-arid and marginal areas there is a probability of drought incidence once in ten years. It is important for those responsible for planning of land-use, including agricultural programmes, to seek expert climatological advice regarding rainfall expectations. Drought impact is the result of the interaction of human pattern of land use and the rainfall regimes, ttere is thus an urgent need for a detailed examination of rainfall records of these regions. Agricultural planning and practices need to be worked out with consideration to the overall water requirements within an individual agroclimatic zone. Crops which need a short duration to ma-
ture and require relativelylittle water, need to be encouraged in drought prone areas. Irrigation, through canals and groundwater resources, needs to be monitored with optimum utilization avoiding soil salinity and excessive evaporation loss. A food reserve is needed to meet the emergency requirements of up to two consecutive droughts. A variety of policy decisions on farming, human migration, population dynamics, livestock survival, ecology etc. must be formulated. Sustainable strategies must be developed to alleviate the impact of drought on crop productivity.
Sustainable strategies to alleviate the impact ofdrought
In areas of recurring drought, one of the best strategies for alleviating drought is varietal manipulation, through which drought can be avoided or its effects can be minimised by adopting varieties that are drought-resistant at different growth stages. If drought occurs during the middle of a growing season, corrective measures can be adopted; these vary from reducing plant population to fertilization or weed management. Rainfall can be harvested in either farm ponds or in village tanks and can be recycled for lifesaving irrigation during a prolonged dry spell, tte remaining water can also be used to provide irrigation for a second crop with a lower water requirement, such as chickpea.
Immediately after the passage of a western disturbance (WD), a lot of moisture is available in the atmosphere and the regional and synoptic scale conditions provide the trigger for the formation of fog. Even though this phenomenon is not directly related to the extreme weather events it has an effect in all forms of transport and in particular aviation, ttis has an indirect effect on the economy of aircraft operations and air passenger inconvenience.
De and Dandekar (2001) studied the visibility trends during winter season for 25 aerodromes over a period of 21 to 31 years and concluded that most of the north Indian airports show a significant increasing trend in the poor visibility days (due to fog) amounting to 90% i.e. almost everyday, tte airports in south India show only 20 to 30% days with poor visibility.
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