The Farakka Barrage, located on the Ganges River in India, was constructed with the primary objective of controlling the flow of water into Bangladesh. However, it served multiple purposes, including checking the silting of Kolkata Port and preventing erosion of the port. The only purpose it did not serve was facilitating navigation in the Ganga river.

1. Checking water flowing into Bangladesh:
The construction of the Farakka Barrage was primarily aimed at controlling the flow of water into Bangladesh. The Ganges River, which originates in the Himalayas and flows through India and Bangladesh, provides water to both countries. However, during the dry season, India was concerned about getting an adequate water supply for irrigation and navigation in the upstream regions. The Farakka Barrage was built to divert water from the Ganges River towards the Bhagirathi River, which flows into India, reducing the flow into Bangladesh. This purpose was highly controversial and led to tensions between India and Bangladesh.

2. Checking silting of Kolkata Port:
The Farakka Barrage also played a role in checking the silting of Kolkata Port. The Barrage was constructed near the point where the Ganges River splits into the Hooghly River, which flows towards Kolkata. The diversion of water through the barrage helped maintain a minimum flow in the Hooghly River, preventing excessive silting of the port. This was essential for maintaining navigability and preventing the port from becoming shallow due to sedimentation.

3. Preventing erosion of Kolkata Port:
Another purpose of the Farakka Barrage was to prevent erosion of the Kolkata Port. The diversion of water through the barrage helped maintain a steady flow in the Hooghly River, which acted as a natural barrier against erosion. Without the barrage, the reduced flow of water during the dry season would have made the river more prone to erosion, threatening the stability of the port infrastructure.

4. Facilitating navigation in the Ganga river:
Contrary to the other purposes, facilitating navigation in the Ganga river was not a primary objective of the Farakka Barrage. Although the barrage did have some impact on maintaining a minimum flow in the Hooghly River, its main focus was on controlling the flow of water into Bangladesh and preventing silting and erosion of Kolkata Port. The navigation aspect was not a significant factor in the decision to construct the Farakka Barrage.

In conclusion, the Farakka Barrage was built primarily to control the water flow into Bangladesh, as well as to check the silting of Kolkata Port and prevent erosion. Facilitating navigation in the Ganga river was not a primary purpose of the barrage.