Bangladesh will be back to square one regarding the Ganges water sharing in 2026 when its 30-year sharing agreement with India, signed in 1996, expires.
The treaty was signed based on an inaccurate projection of future flow and the obligation of allocating guaranteed flow to lower riparian Bangladesh in what water experts consider an endless water sharing dispute.
The two neighbours share the Ganges waters based on, what water experts think, inaccurate statistics about water availability at Farakka in India and Hardinge Bridge in Bangladesh.
The provision of guaranteed minimal flow alternately to India and Bangladesh during critical periods leads to frequent low-flow controversies.
The treaty underestimated the impact of climate variability on lower riparian Bangladesh due to increasing water withdrawals by India from the upstream.
While reviewing thewater sharing of the Ganges from 1997 to 2016, water experts have found that during most of the critical dry periods Bangladesh did not receive its part as agreed under the Ganges treaty.
Experts called for finding out reliable water availability using a combination of modelling and improved observation of river flows to ensure the just share of Bangladesh for the preservation of its ecosystem and production of food and energy, flood mitigation and pollution control.
They said that Bangladesh cannot ignore its growing need for fresh water to address the adverse impact of climate change.
The problem arises for Bangladesh, they think, due to undeclared excess withdrawal of Ganges waters by India from the upstream in the absence of a transboundary institutional mechanism.
The resultant water scarcity in lower riparian Bangladesh creates an adverse impact on its ecosystems and livelihoods.
The dispute between Bangladesh and India over the Ganges-Brahmaputra-Meghna provides an example of a lack of a fair and acceptable institutional arrangement on sharing the world's third-largest freshwater outlet to the ocean.
When India unilaterally commissioned the Farakka Barrage in 1975, the dry season flow of the Ganges in Bangladesh fell sharply, resulting in a dispute over sharing the waters of the common river.
Water experts called for both qualitative and quantitative analysis of the 1996 treaty by examining its performance in the matters of water sharing during the leanest periods. This is necessary to evaluate the efficacy and failure of the treaty by identifying its relevant features and also to find out the barriers to its proper implementation.
The 2,600 km-long Ganges originates in the Central Himalayas at an altitude of 7010 metres and passes through the alluvial Gangetic Plains before draining into the Bay of Bengal.
Its 108,700 square km basin spreads across China, Nepal, India and Bangladesh.
The Ganges basin's hydrological cycle and water resources, marked by the southwest monsoon, high temperatures, heavy rainfall with strong seasonal variations cause flooding during June to October and water scarcity between November and May, identified as the dry season.
The insufficient supply of water in overpopulated downstream Bangladesh during the dry season causes severe adverse socio-economic impact by disrupting its agriculture, fisheries, forestry, navigation as well as ecology.
On April 21, 1975, India unilaterally commissioned its Farakka Barrage disregarding an agreement with Bangladesh that allowed the upper riparian neighbour to test run the barrage for 41 days until May 31.
The result was an acute shortage of water in lower riparian Bangladesh in dry months.
India built its 2,240 metre-long Farakka Barrage approximately 18 km above the Indo-Bangladesh border to divert Ganges waters to flush the Calcutta Port.
The dispute forced Bangladesh to take the issue to the United Nations before a 5-year agreement was signed in November 1977, stipulating Ganges waters sharing during the dry season from January to May, split into 10-day periods, based on 75 per cent water availability at Farakka in India according to historical flows recorded between 1948 and 1973.
The 1977 agreement had a guarantee clause stipulating, under no circumstances, Bangladesh's share would fall below 80 per cent of its share specified in the agreement.
After the expiry of the 1977 agreement in 1982, India refused to renew it and after some difficult negotiations signed two Memoranda of Understanding (MoUs) between 1983 and 1988 by dropping the guarantee clause.
From 1989 to 1996, there was no arrangement in place to share the Ganges waters.
On December 12, 1996, the two neighours signed a new treaty to share the Ganges waters for 30 years.
Under it, sharing takes place from January to May, split into fifteen 10-day periods based on an indicative historic flow at Farakka between 1949 and 1988.
According to the 1996 treaty each country would receive a guaranteed share of 35,000 cusecs, equivalent to 991 m3/s of the flow in alternate 10-day periods during the most critical dry periods between March 11 and May 10.
There were differences between the two agreements concerning the estimates of water availability at Farakka, share distribution, sharing arrangement in critical months. The guarantee clause for Bangladesh was also dropped.
Water experts listed the inaccurate projection of future availability of Ganges flow at Farakka in India, exclusion of the guarantee clause for Bangladesh, inadequate projection of flow at Hardinge Bridge and failure to take into consideration the impact on climate and economy of the lower riparian as the main shortcomings of the 1996 Ganges water-sharing treaty.
India's irrigation canals, dams and barrages on the Ganges for unspecified and increased water withdrawals above Farakka reduced the actual flow to lower to the indicative flows mentioned in the treaty, calling for a thorough investigation to ensure reliable flows at Farakka.
The treaty's new sharing formula allowed flexibility to divide the 10-day average flows to each country, irrespective of how much water was available at Farakka.
The flows at Hardinge Bridge should be higher than the flows released to Bangladesh at Farakka because of the water coming from the tributary Mahananda. But it does not happen, said experts.
Bangladesh is being deprived of its guaranteed minimum flow during the most critical periods of the dry season, they said. The average flow at Hardinge Bridge was much lower compared to what presumably was released from Farakka.
In 1961, India and Pakistan signed the Indus Treaty, with the UN and the World Bank standing as guarantors.
The Indus Treaty survived two wars India and Pakistan fought since 1965.
Indian prime minister Pandit Jawaharlal Nehru and Pakistan President Ayub Khan signed the Indus Treaty in Karachi, then Pakistan's capital.
Jehangir Hussain is a senior journalist.