Agricultural production in the Ganges River basin is affected by the water shortage in the dry months, while the excess water during the rainy season causes floods in the downstream. Annual total surface runoff generated in the basin is about 298 ± 99 Bm3, and runoff in the monsoon months contributes up to 80 % of this total runoff. Comparison of sub-basin-wise surface runoff with the estimated unmet water demand indicated that capturing only a portion of the wet-season runoff would be sufficient.