Guwahati: Soil erosion is a global problem, leading to the destruction of agricultural outcomes, soil fertility, landslides, and water resource systems. Unplanned land use for infrastructural development and increasing population have reduced forest cover, accelerating soil erosion.
A study conducted at Hydrosense Lab, Indian Institute of Technology (IIT) Delhi, led by Ravi Raj and Manabendra Saharia, has resulted in the creation of the Indian Water Erosion Dataset (IWED), a pan-India assessment of water erosion using gridded datasets at a composite resolution of 250 meters. This system will enable the planning and implementation of soil conservation strategies locally and nationally.
The team has also developed the Indian Soil Loss Maps (ISLM), a user-friendly web-based application to visualize and interact with maps associated with soil loss and its major contributing factors in India.
The assessment revealed that more than 78 million hectares of agricultural land in India experience an average productivity loss of eight percent.
The annual potential soil loss (PSL) for India is calculated at 21 tons per hectare per year, resulting in a total possible loss of 1408 million tons annually. According to the mean annual PSL, nine of the twenty most erodible districts are located in Assam, three each in Meghalaya, Himachal Pradesh, and Jammu-Kashmir, and two in West Bengal.
“Meghalaya and Assam are the top two states that have the highest average PSL values (78.16 and 77 tons/hectare/year). The national mean PSL value is 21 tons/hectare/year, and the mean PSL of Assam and Meghalaya is approximately four times the national average,” said Ravi Raj, a research scholar at the Civil Engineering Department, IIT Delhi.
He added that the total soil loss in Assam is 107.83 million tons per year, which is 7.6% of the total national surface soil loss (1408 million tons annually). “Considering the geographical area of Assam, it covers only 2.4% of the national area,” he said.
Out of 630 districts, about 266 have an annual potential soil loss greater than the national average potential soil loss of 21 tons per hectare per year.
“The prevailing soil texture classes in Assam and Meghalaya are predominantly loamy, clay loamy, silt loam, and sandy clay loamy. These soil types exhibit insufficient resistance to water-induced soil erosion. Additionally, a significant proportion of these regions are characterized by slopes, which require proper soil conservation measures in agricultural practices, but such measures are lacking,” the study stated.
“Rainfall erosivity, one of the major contributors to soil loss, has the highest values in Assam and Meghalaya,” the authors noted.
The study further explained that continuous flooding in the Brahmaputra River also contributes to the higher soil loss values in these regions. Every year, the river brings new soil deposits to agricultural lands, which do not have proper resistance against water-induced erosion.
“These districts of Assam and Meghalaya also exhibit some of the highest values of rainfall erosivity,” the authors emphasized in their study published in the reputed journal, CATENA.
The assessment revealed that approximately 5% of the nation’s land area, primarily covering the majority of Assam, along with portions of Meghalaya and Himachal Pradesh, falls within the E6 (Catastrophic) erosion class, denoting Potential Soil Loss (PSL) values exceeding 100 tons per hectare per year. This reflects the possible severity to damage roads, fences, and buildings.
“Based on this recommendation and the erosion severity classes, it is also concluded that more than 78 million hectares of farmland lose an average of 8% of their yearly productivity due to the E3 through E6 severity classes every year,” the study said.
Among the water basins, the Brahmaputra basin has the maximum potential soil erosion of 47.64 tons/hectare/year, followed by the East Flowing Mahanadi with 28.42 tons/hectare/year and the Ganga basin with 25.07 tons/hectare/year. “The main reason for higher potential soil loss values in the Brahmaputra and Ganga basin is due to the new soil layer formation every year due to flooding. This new soil layer has very little capacity to withstand erosive forces raised due to rainfall and runoff,” the study concluded.
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