Addressing the demand-supply gap in the water sector in Bangladesh

Bangladesh is renowned for its mighty rivers such as the Padma, the Meghna, the Jamuna, the Brahmaputra and their numerous tributaries that are endowed with plenty of surface water as well as the capability to recharge ground-water. 

Yet the adequate and sustainable supply of water has been identified as one of the major challenges in the Perspective Plan (2021-2041) and the Bangladesh Delta Plan 2100 which can further be compounded by future threats attributable to climate change. Therefore, a pertinent question is whether there are adequate renewable groundwater resources to meet the increasing demand. 

The main use of water in Bangladesh is irrigation. The total area equipped for irrigation in Bangladesh increased from 1,457 thousand hectares in 1969 to 5,550 thousand hectares in 2018 growing at an average annual rate of 3.05%. 

Such intensive groundwater extraction causes a gradual decline of both pre and post-monsoon groundwater tables. The dry season also affects the groundwater recharge system. In intensively irrigated areas, groundwater level fluctuates between 5 to 15 meters below ground level, in some places even up to 23 meters during the dry peak irrigation season.

Domestic and industrial use of water is also increasing. In Dhaka city, groundwater levels have fallen to 80m below ground level in the central part, as 85% of the water supply depends on groundwater. The obvious reason is the explosive growth of the number of tube wells for drinking water supply. 

Due to the depletion of groundwater, the tube wells are installed into the deeper part and more energy is needed for water extraction which not only causes a total increase in extraction cost but also increases carbon emission.

Besides irrigation, domestic and industrial use, fisheries, navigation and the environment or biodiversity conservation, evapotranspiration also creates a natural demand for water. The proportion of total water demands, as projected for 2025 in some studies, is estimated to be: in-stream-56%, agriculture-32%, environment-9% and water supply-3%. Environmental flow requirements according to IUCN should at least be 30% of the world's river flows to maintain a sustainable condition of the freshwater ecosystems. 

The current condition of the demand and supply for water was also observed by comparing the rainfall and crop evapotranspiration. The average rainfall during the critical dry months is 242 mm whereas the average crop evapotranspiration is 720 mm which indicates that the supply of water in the driest periods in the whole country is much less than demand.

Water demand for agriculture amounts to about 70% of the global withdrawal; for Bangladesh, the figure is about 80% (November to March withdrawal). Water balance, on a yearly basis, shows a clear deficit for the entire country. This deficit is even more alarming for the driest period of the year. 

A study conducted by the Master Plan Organization projected the demand and supply for March in 2018. The study found that the demand for water for agriculture is 14,290 million cubic meters whereas river supplies 11,740 million cubic meters of water. 

For navigation, environment and fisheries, the requirement is 9,910 million cubic meters of water against the supply of 6,390 million cubic meters from regional tributaries. Against the total demand of 24,270 million cubic meters of water, the total supply is 23,490 million cubic meters. The projected water supply is found to be less than demand.

Bangladesh Delta Plan 2100 has identified that domestic and industrial water demand will keep increasing over time. Given the declining groundwater tables and the ever-augmenting demand-supply gap in Bangladesh, it will be extremely difficult to exploit groundwater resources sustainably. 

Without an increase in water productivity, it will be difficult to meet the demand. A few districts have already passed the sustainable thresholds for groundwater usability including Khulna, Bogura, Pabna, Barisal, Chittagong, Kishoreganj, Kushtia and Rajshahi; as identified in the Perspective Plan (2021-41).

The demand and supply gap in the water sector must be addressed for sustainable development and to meet future demands. Water demand can be reduced by increasing water productivity or effective use of water. Otherwise, increasing demands will cause over-extraction of groundwater and, hence, lowering of groundwater table which will eventually increase the extraction cost of groundwater.

Although surface irrigation reduces the use of groundwater, it is also the primary source of misuse of available water. The relative abundance of water in the wet season in the region historically has created a cultural mindset to use water unsustainably. But we forget that unsustainable water use can cause water shortage during the dry season. The data from dry season evaporation, rainfall and groundwater indicate that abundance of water in the wet season cannot fight drought in the dry season.

Due to its geographical location, Bangladesh is the most downstream country in the region to share the Brahmaputra with China and India. Different tributaries of the Brahmaputra are also shared by Nepal and Bhutan. Though the major stream of the Ganges runs through India, its tributaries are also shared by Nepal. Therefore the supplies of water through these rivers depend on the activities and the wishes of the upstream countries. The bilateral approaches or treaties have not been found to work effectively. Therefore, the supply approach cannot solve water issues properly. Multilateral or regional approaches should be adopted to find out a solution to the sharing of transnational river water. Even then the supply approach to fighting water scarcity during the dry season may not be sufficient. Changing our water consumption practices may be the best alternative to fight water scarcity during the dry season.

Muhaiminul Hossain, Md. Al Forhad Islam and Muhammad Faruq-Uz-Zaman are a graduate student of Dhaka School of Economics, Bangladesh