It describes a situation where there is a reduction in rainfall for a specific period (days, months, seasons or year) below a specific amount (long term average for a specific time). The Indian Meteorological Department (IMD) has defined drought as a situation occurring in any area when the mean annual rainfall is less than 75% of the normal rainfall. IMD has further classified droughts into the broad categories viz., a severe drought when the deficiency of rainfall exceeds 50% of the normal rainfall and moderate drought when the deficiency of rainfall is between 25 and 50% of the normal rainfall.
Hydrological drought is associated with reduction of water. A meteorological drought often leads to hydrological drought. Generally it takes two successive meteorological droughts before the hydrological drought sets in.
There are two types of hydrological droughts viz. (i) surface water drought and (ii) ground water drought.
(i) Surface-water Drought:
It is concerned with drying up of surface water resources such as rivers, streams, lakes, ponds, tanks, reservoirs etc.
(ii) Ground-water Drought:
Ground-water drought is associated with the fall in the ground water level. This happens due to excessive pumping of ground water without compensatory replenishment and creates more or less irreversible ground water drought even in normal rainfall conditions.
Agricultural drought is concerned with the impact of meteorological/hydrological drought on crop yield. When soil moisture and rainfall conditions are not adequate enough to support a healthy crop growth to maturity thereby causing extreme moisture stress and wilting of major crop area, it leads to agricultural drought.
Agricultural drought may occur even when there is no meteorological drought and vice-versa. It is worth noting that agricultural drought is a relative category, depending upon the value of plant and soil. What could be a drought condition for the cultivation of rice could well be a suitable condition for wheat and a condition of excess soil moisture for dry crops like bajra or jowar.
Soil Moisture Drought:
This is a situation of inadequate soil moisture particularly in rainfed areas which may not support crop growth. This happens in the event of a meteorological drought when the water supply to soil is less and water loss by evaporation is more.
It reflects the reduction of availability of food and income loss on account of crop failures endangering food and social security of the people in the affected areas.
A famine occurs when large scale collapse of access to food occurs which, without intervention, can lead to mass starvation.
Ecological drought takes place when the productivity of a natural eco-system fails significantly as a consequence of distress induced environmental damage.
Who declares drought in India?
The India Meteorological Department (IMD) has officially expunged the word “drought” from its vocabulary.
According to the department the move is part of a decision to do away with or re-define terms that are not scientifically precise. From 2016, for instance, if India’s monsoon rainfall were to dip below 10 per cent of the normal and span between 20 and 40 per cent of the country’s area, it would be called a “deficient” year instead of an “All India Drought Year” as the IMD’s older manuals would say. A more severe instance, where the deficit exceeds 40 per cent and would have been called an “All India Severe Drought Year,” will now be a “Large Deficient Year”.
It is because declaring droughts is the prerogative of States. Declaring a drought has never been the IMD’s mandate and, in fact, not even that of the Central government.
Tamil Nadu declared a drought. The agrarian crisis in the state is a fallout of a weather vagary that hasn’t received much notice. The northeast monsoon — critical to the southern peninsula, particularly Tamil Nadu — has been a failure, with overall rainfall between October and December 45.2 per cent below normal. This is the worst since the 48.3 per cent deficit recorded in 2011. At present South India’s combined reservoir levels were 22 percentage points less than the average water availability over the past 10 years.
Implications of the deficit in North-East Monsoon
It will affect crops like paddy and coconut and will impact milk and sugar production, especially in Karnataka.
It will have implications for the economy.
It may also accentuate inter-state river disputes, especially the sharing of Cauvery waters.
Sowing area of crop is likely to decrease and thus crop production.