International Day to Combat Desertification and Drought 2025: India’s arid landscape now receives more rains and floods
The north-western part of India, especially the western part of Rajasthan has been experiencing significant changes in rainfall pattern, aeolian terrain and demography. Comprising 12 districts of Rajasthan and geographically situated between the Aravalli range in the east (with an aridity index value of -66 per cent) and the Indus riverbed in the extreme west (with an aridity index of -85 per cent), the region represents India’s desert ecosystem. About 27 million people (as per 2011 Census) and 26 million livestock (as per 2019 livestock census) live in western Rajasthan, thus it is considered as the most densely populated desert of the world.
The terrain of the Thar Desert is unique in nature. It is an assemblage of landforms, which have been described as polygenic, being associated with various geomorphic processes. Sand dunes with spectacular morphology and various types occur in about 48 per cent area. These may be old dunes and very high (12 to 50 m) or new and low dunes (less than 6 m). The Thar desert is also known for palaeo-channels of the Saraswati river and several others and there are many inland Ranns and playa lakes. The origin of all these landforms is linked to dry and wetter climatic regimes in the past. The region is still described as a dryland where climate is hot and dry during the summer months and cold during the winter months. Annual amount of rainfall in the region is scanty and drought occurs every two to three years. However, the scenario has been changing for last few decades. More rains, lesser sand dunes, more irrigated croplands, more vegetation cover, more floods, less droughts, less dust storms are the common features of the present arid landscape of the western Rajasthan.
Increasing rainfall trend
Maximum and minimum rainfall data, as per the State Flood Action Plan 2024 of Rajasthan, indicates that all the 12 districts of western Rajasthan received not only more rainfall in 2023 than the normal rainfall but also experienced significantly higher rainfall during this period. At the Central Arid Zone Research Institute (CAZRI), under the Indian Council of Agricultural Research, 64-year (1957-2020) rainfall data of 62 stations located in the Thar desert were analysed through box-whisker plots and geospatial modelling, which revealed that the mean annual rainfall is the lowest (<200 mm) in the western parts and highest (>500 mm) in the eastern and southern parts of arid region. A distinct gradient of the annual rainfall is discernible from southeast to northwest direction. The highest temporal variability of rainfall (with coefficient of variation or CV>75 per cent) was observed in the western and the lowest (CV ~35-40 per cent) in the eastern portion. The trend analysis of annual rainfall using Mann-Kendall test revealed increasing trend of rainfall at 54 of total 62 stations with statistically significant trend (p-value <0.05) at four stations.
Rainfall data of 2023 and 2024 evidenced the unprecedented rainfall occurrence and a different kind of situation than the earlier period. During 2023, the southwest Rajasthan was hit by the remnant of cyclone Biparjoy—a tropical storm that resulted in widespread pre-monsoon rains in the state. During June 17-19, 2023, as many as 112 stations recorded very heavy rainfall (>115.6 mm in one day). One station in Pali recorded 530 mm rainfall on June 19, two stations in Jalore district recorded 471 and 456 mm rainfall on June 18, as many as 15 stations received 300-400 mm rains and 35 stations recorded 200-300 mm rainfall during June 17-19. Rainfall activities continued after the arrival of monsoon on June 25 and the monsoon was fairly active in Rajasthan during July as well. During 2024, seasonal increase in rainfall is evident that varied from minimum of 322 mm in Hanumangarh district to maximum of 737 mm in Pali district. The departure from normal values was the maximum in Jaisalmer district (145 per cent) followed by 2-81 per cent in all other desert districts. Overall, the rainfall in the Thar desert has been rising in the recent times mainly due to increase in rainfall intensity, which may be advantageous to solve the prevailing water scarcity problems.
Floods in the Thar desert
The term “flood” denotes both the discharge of a river under condition of excessive rainfall and the inundation of low-lying areas. Flood characteristics in desert areas are different from humid and coastal ecosystems. Floods in desert are caused when rainfall of ~300 mm or more is recorded in two to three consecutive days. Though, the Thar desert experiences flood-causing rainfall in two to three years in a decade, a maximum of five flood-causing rainfall years in a decade were recorded during the 1950s, 1970s and the 1990s. The most severe eight flood years, observed from the annual rainfall recorded at more than 25 per cent rainfall stations, were 1975, 1976, 1977, 1983, 1997, 2010, 2015 and 2019. Thus, most frequent flood occurrences appeared during three decades—1971-1980 (five years), 1991-2000 (four years) and 2011-2020 (six years).
During 1979 and 2006, some parts of western Rajasthan experienced flood-oriented geomorphic events. In July 1979, an intense rainfall of 514-773 mm in the upper Luni river basin in five days (July 15-19) resulted in flood in the Luni and its major tributaries. About 6,850 sq km area in Jodhpur-Pali-Pachpadra tract was affected. During 2006, two stations (Kawas and Malwa) in the northern part of Barmer district and adjoining part of Jaisalmer district received rainfall of 300-400 mm during August 17-24, causing a flash flood. The above information indicates that occurrence of floods at a few places may not be a common phenomenon in the water-scarce region of the Thar desert but its frequency is slightly increasing over the recent years.
Then came the floods in 2023 and 2024. During August and September of 2024, a total of 11 unusual high-intensity rainy storms occurred in Jodhpur, precipitating more than 500 mm rainfall and resulting in runoff water flow at high velocity. The duration of the storms varied from 27 to 221 minutes with rainfall amount of 11 to 72 mm and average intensity of 5.5-43.7 mm per hour. Runoff is generated when rainfall intensity exceeds the soil’s basic infiltration rate, which is 30 mm per hour in the Thar desert. However, during August 2024, a small storm of 15 mm rainfall could generate runoff due to favourable antecedent moisture condition (AMC) and saturated soil pores. The peak intensity of rainfall was more than 80 mm per hour in five of the 11 storms in 2024. Using remote sensing images captured by synthetic aperture radar (SAR) during monsoon seasons of 2023 and 2024, flood inundated alluvial plains of Pali and Jodhpur districts and sand dune/inter-dune areas in Jaisalmer and Barmer districts were mapped by scientists of ICAR-CAZRI, Jodhpur.
Changing agricultural scenario
The changing climatic characteristics especially that of occurrence of high rainfalls, has definitely increased the water availability in India’s arid zone and using various sources of irrigation, farmers are expanding their croplands. However, tubewell irrigated area has always surpassed the canal water irrigation. Between 2010 and 2020, area irrigated by tubewells has increased by 8 per cent. At present, almost 50 per cent area is covered by tubewell irrigation. Two major canal systems, Indira Gandhi Nahar Pariyojana (IGNP) and Narmada Canal Project (NCP) have brought water in the desert region and resulted in significant changes in the irrigated agriculture in about 23.05 per cent area. Area irrigated through tanks and open wells has decreased (-60 per cent and -7.45 per cent, respectively during 2010-11 and 2020-21).
Salient points on changes occurring in agriculture (2010-11 to 2020-21) in the extremely arid part of Rajasthan that comprises five desert districts (Barmer, Jaisalmer, Bikaner, Churu and Jodhpur), is depicted. It was found that net irrigated area in all these five desert districts has increased (280,000 ha or 102.43 per cent in Bikaner, 263,000 ha or 99 per cent in Jodhpur, 136,000 ha or 82.8 per cent in Barmer, 129,000 ha or 151.42 per cent in Churu and 83,000 ha or 82.54 per cent in Jaisalmer). In wasteland category, culturable waste has decreased in Bikaner district (123,000 ha, 4.07 per cent) and Jaisalmer (273,000 ha, 7.11 per cent). All these changes are possible when water is available and utilised rationally. Remote sensing-based vegetation map prepared for western Rajasthan by CAZRI found increase in vegetation cover from 13.54 per cent to 21.11 per cent between 2010 and 2020. Thus, assessments are indicating an increase in vegetation cover and greenery (due to agriculture) in western Rajasthan. Tree cover also has increased, as, about 400,000 ha land in sand dune areas has been put to afforestation as a part of sand dune stabilisation process. Vegetation has also increased due to spread of weeds and shrubs like Prosopis juliflora in many parts of Rajasthan, especially in Pali, Jaisalmer, Jodhpur, Nagaur and on false colour composites (FCC) of satellite images, such areas also appear in dark red tone due to healthy vegetation.
Canal water management through farm ponds
In recent decades, in four desert districts of Rajasthan (Jaisalmer, Bikaner, Ganganagar and Hanumangarh), small farm pond structures, locally called as diggi, have been constructed in large number. It is an interesting observation that number of diggi structures in Jaisalmer district has increased from merely 400 in 2005 to 535 in 2010, and 10,496 in 2021. These diggis store canal water or groundwater and the stored water is utilised for irrigation as and when required to deal with problems of soil moisture deficit and untimely canal water supply. The impact is clear: the irrigated crop area has increased from 19,631 ha in 2010 to 80,514 ha in 2021, and cropping pattern has also changed, as irrigated crops have replaced traditional rainfed crops.
Impact and issues
Rainfall pattern and temperatures have shown changes during past four to five decades in arid Rajasthan. Rainfall, especially high intensity rain events have increased and the region is witnessing more frequent floods providing scope for bringing more area under rabi crops, and simultaneously, other vegetation cover is also increasing. The impacts are visible in terms of changes in cropping patterns in different parts of the state with introduction of more remunerative irrigated crops, improved varieties, irrigation facilities, market demands.
One of the major issues for arid Rajasthan will be the management and utilisation of excess rainwater received during high rainfall events similar to monsoons of 2023 and 2024.
The planning for efficient management of the surplus rainwater is essential for its subsequent utilisation in domestic, agricultural (for example, in khadins) and industrial sectors in this water-scarce and dry region.
Due to improvements in vegetation cover and with intensive cultivation practices, sand dunes and sandy undulating areas are put to agriculture, thus, sand dune area is reducing. Severity of wind erosion has reduced mainly in irrigated regions. This has a direct impact on the present status of desertification. Rajasthan has the maximum area under desertification (21.23 m ha) but area under desertification in the state with respect to country’s total geographical area has shown a decreasing trend (from 6.58 per cent in 2003-05 to 6.55 per cent in 2011-13 and 6.46 per cent in 2018-19).
In comparison to desertification status in all the states having arid regions (Rajasthan, Gujarat, Haryana, Punjab, Andhra Pradesh and Karnataka), Rajasthan is the only state where area undergoing process of land degradation has decreased by 387,000 ha area since 2003-05.
Thus, the arid regions of Rajasthan are undergoing a noticeable change, a transformation from sandy terrain to a cropland production system.
P C Moharana, Priyabrata Santra, Deepesh Machiwal and D V Singh are scientists with Indian Council of Agricultural Reasearch-Central Arid Zone Research Institute, Jodhpur
This article was originally published in the State of India’s Environment 2025