Development of conjunctive use model for lower Gandak basin – A Research Report by National Institute of Hydrology

The study attempts to develop a conjunctive use model involving judicious use of surface and groundwater for the Habibpur region of Gandak command in Bihar. The area is characterized by insufficient surface water during rabi and summer seasons and excess surface water in the kharif season.

The study area falls in the Gandak command and lies between the river Gandak and Vaishali Branch Canal (VBC), one of the branches of the Gandak canal system. The Habibpur sub-distributary from VBC conveys water to the study area. The canal system provides water during the kharif season and for 35-45 days during the rabi season. Water is not provided for irrigation from the canal during the summer season when it is most needed. This uneven availability of surface water in different seasons results in waterlogging and poor agricultural output from the region.

As groundwater potential in the area is yet to be fully explored, it is proposed to use groundwater resources in the region and this would provide two fold advantages to the region -

• Increase the irrigation water availability for summer and rabi crops and
• Subsequent replenishment of groundwater in kharif seasons.

This would not only improve the waterlogging conditions but also bring more cultivable area under agricultural practices. Increasing the cropped area in different seasons would also improve waterlogging conditions in addition to increasing agricultural productivity of the area.

A groundwater flow model has been developed for the region to simulate the groundwater behavior taking into account the surface water and groundwater interaction under various external stresses. The calibrated model has been used to predict the waterlogging conditions under increased crop area coverage.

The model has also been used to forecast the extent of waterlogged areas on utilizing the groundwater resources of the area. The model results clearly show positive impacts on reducing the waterlogged area if more area is brought under cultivation apart from an increased agricultural productivity in the region.

Download the report here: