Unequal water future: Study reveals how climate change is widening scarcity in some regions while easing it in others
The global distribution of water resources is uneven, leading to varying levels of water scarcity. Climate change and global warming are expected to exacerbate this disparity, necessitating different adaptation strategies for different countries, according to a recent study published in the journal Nature.
Due to varying hydrology and terrains, the impacts of climate change would be different. Countries like India would witness widening water gaps or scarcities, while others like Nigeria and Sudan would see improvements owing to change in precipitation patterns. However, the trend may change over the years for the same basins.
These widening water gaps in some regions would mean increasing conflicts and regional tensions, especially in politically sensitive zones. This concern was also addressed in a United Nations Convention to Combat Desertification (UNCCD) report that talked about escalating conflicts when pressure on resources increases. The report also highlighted the varying effects, underscoring the necessity for region-specific policies and planning.
Addressing and planning for these issues would be challenging without quantified data. For instance, 93-95 per cent of employment in Nature-Based Solutions aimed at combating water security and addressing land degradation are being implemented in the Asia-Pacific region, with the majority in India through the Mahatma Gandhi National Rural Employment Guarantee Scheme (MGNREGS), according to a report by UNCCD launched at the 16th Conference of Parties in Riyadh.
This indicates that significant efforts are being made in India towards water conservation, but is it sufficient? Despite quantifying its groundwater and surface water supplies, stories of water scarcity in various Indian cities are well known. So, what is missing?
The study co-authored by Lorenzo Rosa and Matteo Sangiorgio in Nature brought forth the fact and need to quantify and predict the future scenarios to be able to plan better and more systematically. They mention that data is available on quantification of available groundwater and reduction in environmental flows. However, there still is a need to evaluate the past and future scenarios and quantify the water gaps to make “informed decisions and effective adaptation to water scarcities admist uncertainities”, they wrote in the report.
Water gap means the available water for use is less than the demand and consumption. The deficit may vary from region to region. The study expresses the deficit volumes in cubic kilometres, assessed at the major hydrological basin and country scale by summing the water gaps in each pixel within the country and the basin.
The research employs a multi-model and multi-scenario approach to evaluate past and future conditions while considering the requirements of all ecosystems, including surface water, groundwater, and environmental flows.
Multiple scenarios and probable outcomes have been simulated for baseline and future conditions, using five distinct climate models from the Coupled Model Intercomparison Project (CMIP6) archives. Such studies on region-based mathematical simulation of model scenarios help address policy gaps and issues with specific need-based solutions.
The study quantifies water gaps at 30-arc minute resolution (50 km at the equator) (this means that the study divides the earth into grids of 0.5 degree of size (55*55 sq Km per grid cell) which would give global and detailed understanding of water gaps in different scenarios-much better than 1 degree resolution (111 km per grid cell).
The study compares the global temperatures at baseline scenarios (2001-2010, which is 0.6°C warmer than the preindustrial era), 1.5°C (expected to be reached in 2010–2035) and 3°C (expected to be reached in 2039–2068), warming scenarios compared to the pre-industrial era, said the study lead author Rosa, principal investigator at Carnegie Science and assistant professor at Stanford University.
The study showed that global warming is increasing the water gaps in California’s Central Valley, the US High Plains, Central Chile, the Iberian Peninsula, Saudi Arabia, the Tigris-Euphrates River system, the Aral Sea Basin, the Indo-Gangetic Plains of India and Pakistan, the North China Plain and Australia’s Murray-Darling Basin. The outcome gets worse at 3°C warming in the eastern US, Chile, the Mediterranean region, South and East India and the North China Plain.
Certain areas that are unaffected in the baseline scenario, including Italy, Madagascar, North Carolina, Virginia, Wisconsin, Minnesota and Illinois, are expected to face deteriorating conditions under the 1.5°C scenario. Meanwhile, nations like Saudi Arabia are predicted to encounter reduced scarcity at 1.5°C warming, but significant increases under a 3°C warming scenario.
Country-wise water gap values under different warming scenarios
Rosa told Down to Earth that India seems to be in much greater danger than the other parts of the world. Since India has the largest irrigation water use, the water gaps are higher than in China, he said. In comparison to China, the southern region also experiences a humid climate, resulting in less water scarcity.
The simulations showed: India will see an additional water deficit of 11.1 cubic km / year at 1.5°C scenario, which is 4.1 cubic km / yr in case of China, which is the the second highest. While in 3°C scenario Pakistan replaces China in the second position. This is because of the regional differences in hydroclimate responses, mainly precipitation patterns, the expert added.
Water gap values for major hydrological basins under different warming scenarios
South Asia comes across as the most affected region, where India, Pakistan and Bangladesh seem to be most affected, falling under the Ganges-Brahmaputra, Indus, Godavari, Sabarmati. This suggests that countries such as India, which have experienced success with programmes like the Mahatma Gandhi National Rural Employment Guarantee Scheme, should continue to expand these initiatives because.
By doing so, they can create jobs and livelihoods for women and vulnerable populations, prevent migration, build resilience to climate change, ensure water security, meet global targets and set examples for other regions.
As these areas continue to be the most impacted in all three scenarios, it would lead to a further reduction in groundwater reserves and heightened conflicts over surface water resources in southern India if appropriate measures are not implemented.
The basin needs to adopt sustainable agricultural practices, build on more water harvesting and storage structures to reduce dependency on groundwater reserves, focus strategically more on treated wasterwater reuse and thus reduce dependency on fresh water resources.
The study projected that countries like Philippines, and Vietnam in southeast Asia (Mekong, coastal basins) to have improved water availability. The countries should look into the opportunities of receiving more water. More rain may cause floods if appropriate actions are not intercepted with-offsetting the opportunities.
The Middle East and North Africa (MENA region: Tigris-Euphrates and Nile Basins) and Europe (Mediterranean river system basin) to see increasing water stress and crisis should look into similar solutions as South Asia to avoid entering the water-scarce phase, while North America (Mississippi-Missouri, Colorado, Columbia basins ) and Africa (Niger, Lake Chad basins) would have mixed effects with improvements in some places.
This means they should start looking at sustainable use of available resources, leverage opportunities of improving agricultural resources, ensure the surface and groundwater resources are not contaminated with faulty sanitation practices. They should also look into harvesting water to slowly reduce on dependency on groundwater reserves.
The research acknowledges the limitations of the models used due to unpredictable rainfall patterns and recommends that future studies include more detailed monitoring and data validation.