According to the ‘Drought Management Manual’ released by the Ministry of Agriculture, drought is a recurrent feature of climate and occurs in all climatic regimes.
Conditions of drought appear when the rainfall is deficient in comparison to the statistical multi-year average for a region, over an extended period of a season or year, or even more.
However, there is no universally accepted standard definition of drought because of its varying characteristics and impact across different regions.
How a Drought Differs From Other Natural Disasters
Unlike other natural disasters, drought is different due to certain governing factors, some of which have been listed below:
- It is difficult to determine the beginning and end of the event.
- The duration may range from months to years.
- No single indicator or index can identify precisely the onset and severity and its potential impact.
- Multiple indicators are usually more effective.
- Spatial extent is usually much greater than that for other natural hazards.
- Impact is generally non-structural and difficult to quantify.
- Impact is cumulative and the effects magnify when events continue from one season to the next.
When is a Drought Declared?
The are four indicators that are usually applied in combination for drought declaration. They are:
- Rainfall deficiency,
- The extent of area sown,
- Normalised difference vegetation index and
- Moisture adequacy index.
The information on these indicators is available at the level of Taluka / Tehsil / Block. Drought may be declared by the state government at these levels.
Deficient Rainfall:
Rainfall is the most important indicator of drought and departure in rainfall from its long-term averages is taken as the basis for drought declaration.
The departure could be either measured for specific months or an entire season. Rainfall data are easily available and simple to apply. The rainfall data can be applied in two ways:
- The state government could consider declaring a drought if the total rainfall received during the months of June and July is less than 50 percent of the average rainfall for these two months and there is an adverse impact on vegetation and soil moisture.
- The state government could consider declaring a drought if the total rainfall for the entire duration of the rainy season of the state, from June to September (the south-west monsoon) and/or from December to March (north-east monsoon), is less than 75 percent of the average rainfall for the season and there is an adverse impact on vegetation and soil moisture.
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Area under Sowing:
Sowing is another important indicator of the spread and severity of drought.
Drought conditions could be said to exist if along with the other indicators, the total area sown by the end of July/August is less than 50% of the total cultivable area.
In case of Rabi crops, the declaration of drought could be linked to the area of sowing being less than 50% of the total cultivable area by the end of November/December along with the other indicators.
Normalized Difference Vegetation Index (NDVI):
The National Agricultural Drought Assessment and Monitoring System (NADAMS),
instituted by the National Remote Sensing Centre (NRSC), issues a bi-weekly drought bulletin and monthly reports on detailed crop and seasonal condition during the kharif season. These present the Normalized Difference Vegetation Index (NDVI) and Normalized Difference Wetness Index (NDWI). These reports provide quantitative information on sowing, surface water spread and crop condition assessment along with spatial variation in terms of maps.
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Moisture Adequacy Index (MAI) :
Moisture Adequacy Index (MAI) is based on a calculation of weekly water balance,
is equal to the ratio (expressed as a percentage) of Actual Evapo Transpiration (AET) to the Potential Evapo Transpiration (PET) following a soil–water balancing approach during a cropping season.
Impact of a Drought
Adverse impact of drought can be broadly categorised as under:
Economic: Economic impacts of drought include production losses in agriculture and other related sectors.
It causes loss of income resulting in reduction of purchasing power especially among those dependent on agriculture and living in the rural areas.It also has a multiplier effect on other sectors dependent on agriculture for raw material.
Environmental: Decreased water levels in reservoirs, canals, ponds are the primary environmental impacts. This will lead to decreased availability of drinking water and water for other needs. It will also cause loss of forest cover etc.
Social: Migration of population is the top most social impact resulting out of lack of income.
Decrease of income also leads to people withdrawing children from schools, postponement of marriages, sale of assets etc. It will also lead to inadequate food leading to malnutrition and other health hazards.
What are the Relief Measures Taken?
Various ministries of the Government of India involved in planning and implementing the relief measures are:
- Agriculture,
- Rural Development,
- Drinking Water,
- Animal Husbandry,
- Food & Public Distribution,
- Water Resources, Home Affairs,
- Finance and Railways
The state governments submit reports on drought condition with all the relevant information and the government of India extends support based on these reports.
The various relief measures include:
- Financial assistance to states
- Contingency crop planning
- Relief employment
- Food security
- Initiatives to mitigate the impact
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