Despite strong relations in various fields, there are a few areas of concern between the two countries. Major of them are Transborder river water management, and illegal migration from Bangladesh, and China factor.
One of the major areas of conflict between the two countries is the Sharing of Transboundary River Waters: both countries share 54 common rivers, but to date, only two treaties have been signed so far viz the Ganga Waters Treaty and The Kushiyara River Treaty. The major issue has been for sharing of water of Teesta River which is still under negotiation. Teesta River is the 4th largest river (after Ganga, Brahmaputra, and Meghna), the water which both countries share. Teesta River originates from Sikkim. Out of its total length of 414 km, the Teesta River flows for about 151 km through Sikkim, nearly 142 km through West Bengal, and the final 121 km through Bangladesh. The major population of Bangladesh and the West Bengal state of India rely on the Teesta River. In 1984 agreement was reached with Bangladesh's share at 37.5% and India’s share at 42.5% was decided by the Joint River Commission while the rest was unallocated. This was an ad-hoc agreement. In 2011, both countries were about to reach the 15-year agreement, however, water being a state subject in India, the state government of West Bengal is opposing the water-sharing agreement stating it will affect crops and irrigation in its state. Further Bangladesh has been asking 50% share of water, which is also an area of contention.
Another major area of contention is the illegal migration of the population from Bangladesh to India. This influx strains Indian border states, impacting the resources and security of India. The issue is further complicated by Rohingya’s entering India through the Bangladesh route. The migrants in question are mainly poor people, mostly Muslim, looking for livelihoods that will help them survive affecting not only resources but changing the demography of India. Further, they are used by anti-nationals for their insidious designs against India including sabotage, drug trafficking, fake currency, etc. In 2016, Kiren Rijiju, the then Minister of State for Home Affairs, told India's parliament: "According to available information, there are about 20 million illegal immigrants from Bangladesh in India." Certainly, these numbers are more than enough to put constraints on India’s resources.
The China factor is also an important issue between the two countries. India and China are known rivals and even security relations are not cordial between the two countries. Hence Bangladesh moving close to China is alarming for India. Currently, Bangladesh is an active partner in the Belt and Road Initiative (BRI) (of which India is not a part). China's increasing involvement with Bangladesh could potentially undermine India's regional standing and impede its security concerns. Further China wants to encircle India via its ‘String of Pearls’ strategy and Bangladesh is important for China in this aspect. Bangladesh also receives substantial defense support from China and was been the recipient of a Chinese Submarine in 2019 thus any bonhomie between Bangladesh and China can be risky from India’s perspective.
Despite India acting as a midwife for the birth of Bangladesh, the relations between the two countries have evolved over the years. There have been few areas where there has been very strong partnership while certain areas are there which need to be tackled with much sensibility. Both are neighboring countries and both have to live with it. As Vajpayee ji once said, ‘You can change friends but not neighbors. Hence it is in the best favor of both countries to cooperate on pending issues and set an example of friendship for the rest of the world.