Drought is defined as a deficiency in precipitation over an extended period, usually a season or more, resulting in a water shortage causing adverse impacts on vegetation, animals, and/or people. It is a normal, recurrent feature of climate that occurs in virtually all climate zones, from very wet to very dry. A temporary aberration from normal climatic conditions, a drought can vary significantly from one region to another. Drought is different from aridity, which is a permanent feature of climate in regions where low precipitation is the norm, as in a desert.
When is a drought declared?
The Indian Meteorological Department (IMD) defines a drought year as one in which the overall rainfall deficiency is more than 10 per cent of the long period average and more than 20 per cent of the agricultural area is affected. Because of the interplay between a natural drought event and various human factors, drought means different things to different people. Drought can be of various types (Fig. 2):
- A meteorological drought is based on the degree of dryness (in comparison to ‘normal; or average dryness) and the duration of the dry period. A drought generally follows a meteorological drought.
- An agricultural drought links various characteristics of a meteorological (or hydrological) drought to an impact on agriculture, with precipitation shortages, soil water deficit, reduced ground water or reservoir levels needed for irrigation, and so forth.
- Hydrological drought usually occurs following periods of extended precipitation shortfalls that impact water supply (stream flow, reservoir and lake levels, ground water), potentially resulting in significant societal impacts.
Why does it happen?
The most common cause for drought is the failure of rains. Consequently, there is not enough water available through hand pumps, wells and other traditional sources that depend on underground reserves of water.
Apart from scanty rainfall, a number of other factors also adversely affect the magnitude of droughts. Depletion of green cover is one such factor. Rainwater falling over barren land is washed away into rivulets and thereon, into the sea. Underground reserves, hence, fail to get recharged and agricultural and hydrological drought follows.
Unlike earthquakes or cyclones, droughts can be predicted well in advance. Natural phenomena such as flowering of bamboo, intense flowering of the Moringa tree, and the multiplying of the rodent population are indicators of drought. Besides, advanced instruments and technical know how can help meteorological scientists predict the quantity and duration of rainfall with a fair degree of accuracy.
Monitoring of drought through early warning systems
Since 1992, the India Meteorological Department (IMD)’s Earth System Science Organisation (ESSO-IMD) monitors the rainfall situation throughout the year in different spatial scales (districts/states/meteorological subdivisions and all India) on daily, weekly/monthly/seasonal scales. Based on this data, ESSO-IMD prepares rainfall reports for the use of different state/central government agencies. Until 2012, ESSO-IMD was monitoring drought using two most important drought indices viz. per cent deviation of rainfall from normal and aridity anomaly index (AAI). Since 2013, ESSO-IMD has started using the standardized precipitation index (SPI) to monitor drought in various Indian districts of India on a monthly scale, in accordance with guidelines issued by the World Meteorological Organization (WMO).
Besides standard monthly and cumulative SPI, four weekly district SPI maps are computed and prepared every week to monitor progress, starting or ending of agricultural drought. In addition to the SPI and AAI, the normalized difference vegetation index (NDVI) is also used in drought monitoring. The Central Water Commission, National Centre for Medium Range Weather Forecasting, National Remote Sensing Centre and National Rain-fed Area Authority are other key agencies that provide early warning on drought.
Since 1967, the Drought Research Unit of the ESSO-IMD conducts studies on various aspects of droughts in India, in collaboration with the Indian Council of Agricultural Research (ICAR), and provides medium range weather forecast based agro-advisories at district levels through its Agro-Meteorological Field Units (AMFUs)(GoI 2010). In addition, the National Agricultural Drought Assessment and Monitoring System (NADAMS) project provides near real-time information on prevalence, severity level and persistence of agricultural drought at state/district/sub-district levels in 13 drought prone states.
The 2015 drought in India
After a promising, forecast-defying start in June and good rainfall in July, resulting in a better-than-average sowing, the monsoon weakened end-July 2015 owing to a strong El Niño phenomenon that disrupted international weather patterns. By mid-September, the rainfall deficit had widened to as much as 16 per cent, with the prolonged dry patch making it the worst monsoon in three decades, barring the drought years of 2002 and 2009, as per reports in The Economic Times, September 14, 2015. The deficit was as high as 40 per cent in the agriculturally-rich northern states of Punjab, Haryana and Uttar Pradesh, raising concerns regarding soil moisture and hence, the health of the winter crops.
As per IMD data, India received 6 per cent lower rainfall than usual, but in some areas, the deficit was as high as 57 per cent. Meanwhile, the southernmost and north-eastern regions received adequate to very heavy rains resulting in massive floods. Thus, the country was faced with contradictory weather patterns spanning two extremes.
Uttar Pradesh declared 44 of its 75 districts ‘drought-hit’ and sought INR 6,000 crore as central assistance for relief, having suffered a 60 per cent deficit in rainfall. Haryana declared a drought on September 2 and sought INR 4,830 crore in central assistance, since it faced an overall rain deficit of 54 per cent, with 10 out of its 21 districts being drought hit. According to the Central Ground Water Board(CGWB), Haryana has been overexploiting its groundwater reserves by over 9 per cent. Gujarat faced a deficit ranging between 8-60 per cent except for a couple of districts in north Gujarat and one in Saurashtra. As on September 9, 2015, water storage stood at 16,262 million cubic meters (MCM) in 203 irrigation schemes including Sardar Sarovar, down 154 MCM from corresponding levels last year.
The Andhra Pradesh government declared 196 mandals in seven districts drought affected. The majority of the drought hit mandals are in Rayalaseema, with some in the coastal districts of Srikakulam, Prakasam and Nellore. The State suffered a 5.4 per cent deficit in rainfall in 2015. About 700 farmers committed suicide in Telangana amid mounting debts and poor production of paddy, maize and cotton. With drastic reduction in water levels, farmer bodies pressed the panic button. Madhya Pradesh declared 35 out of 51 districts in the State as drought affected and sought an initial central assistance of INR 2,400 crore. The State also sought an additional INR 300 crore for drinking water supply and INR 750 crore for waiving off interest payments on loans. Overall, the State recorded a 12 per cent rainfall deficit, according to the IMD, affecting 4.4 million hectares of farmland, and estimated crop losses amounting to INR 13, 846 crore.
In Maharashtra, for the first time in a hundred years, farmers were unable to sow the Rabi (winter) crop, thanks to the region’s worst dry spell in the period. The Marathwada region received just a third of its average rainfall until September, according to IMD reports. Latur was the worst affected district, followed by Parbhani, Osmananabad, Jalna, Beed, and Aurangabad. Odisha faced a 13 per cent deficit in rainfall until August 31, 2015, with six out of its 30 districts facing a deficit as high as 40 per cent. Bolangir, Koraput, Kandhamal, Khorad, Nayagarh and Puri were the worst-affected. Karnataka too was faced with a 34 per cent deficit in rainfall in 27 out its 30 districts and demanded INR 3050 crore in central assistance from the National Disaster Response Fund.