Climate change will have a considerable impact on the dynamics of the river Ganga, an IISc study has found. This will directly affect a major portion of northern India, which depends on the river for meeting domestic, agricultural, and industrial water needs. The study was carried out by the researchers from the Department of Civil Engineering, Indian Institute of Science, Bangalore.
The researchers studied how the streamflow in the basin would change under changing land use pattern and climate. Though both the factors affect streamflow, the effect of climate change was much more pronounced than that of land use change. Streamflow is a measure of how much water flows in a river or a stream, and at what rate.
“Certain changes are because of Land Use and some because of Climate change. Looking into the future, with respect to water management efforts, if we conclude that Climate change has more implications, then our responses will be much different”, explains Pradeep Mujumdar, a Professor in the department of Civil Engineering, who led the study.
It's hard to imagine an India without the river Ganga, its longest river. The 2,500 km river, flowing through the states of Uttar Pradesh, Bihar, and West Bengal, touches 44% of India's population, before flowing through Bangladesh, and emptying into Bay of Bengal. Originating in the mighty Himalaya, the Ganga has a very fertile and large basin that accounts for 30% of India's cultivable land. In addition to it's social and economic relevence, it also has strong cultural presence among Indians. However, there is a dearth of efforts to understand how this massive river is responding to changes along its basin.
The researchers studied about one-eighth of the total catchment area, called the Upper Ganga Basin (which is just as large as the country of Iceland). They divided the study region, that also contained the origin of the river, into three different parts depending on the topography, altitude and land use. For them, this region is a natural choice for the study because, any changes observed in the streamflow here, is likely to be reflected in the entire river.
They studied changes in landuse through satellite imagery. Their analysis revealed that, between 1973 and 2011, area under cultivation increased by more than 20%. During the same period, the urban land had also expanded significantly, though it occupied a small area in the entire basin. They also noted an appreciable drop in the area under forest cover. Such changes are not at all surprising because, between 2001 and 2011, the population of the region has skyrocketted by 120%. Their predictions of the future climate indicated changes in rainfall pattern and rise in average minimum and maximum temperatures.
The researchers ran a well-calibrated hydrological model to predict how streamflow would change under changing land use and climate. They found that, although the streamflow was sensitive to changes in Land Use (crop land, urban area, forest cover) it was mostly affected by climatic changes. Rainfall was found to have a strong influence on the streamflow. The changing climatic conditions were predicted to cause severe changes in water availability in the Upper Ganga Basin. The researchers also found the combined effects of Land use and Climate change to be more pronounced than their individual effects.
“Climatic changes introduce a large uncertainty in future water situations. Because of this, we need to bring more resilience in our water management system – use more conservative methods. We need to base these methods on a worst-case scenario and prepare ourselves”, says Mujumdar.
This study has paved a smoother path for future research as their approach can be applied to any river basin in the country. It also stresses on the effects of climatic conditions and our efforts to manage the same.
About the authors
Prof Pradeep Mujumdar is with the Department of Civil Engineering, Indian Institute of Science, Bangalore. Ipsita Chawla is his graduate student.
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