Indus River Basin (IRB) region of South Asia is severely water-stressed with irrigation receiving 90–95% of total surface water allocations and depletion of fossil groundwater reserves of more than 30 km3/year. Simultaneously, many supply-driven hydropower reservoirs, are planned in the basin. The reservoirs constructed upstream inflict severe environmental damages and reduce water availability for irrigation downstream. Policymakers promote smart technologies as a demand-based solution to reduce water consumption in irrigation. However, the effects of such technologies are not yet well understood, and unintended consequences (such as irrigation efficiency paradox and other nexus externalities) have recently begun to appear. Therefore, we use an integrated assessment model to analyze the proliferation of smart technologies in the IRB. The analysis suggests that if the Indus countries adopt a demand-based approach and irrigate their land completely using smart technologies, surface and groundwater withdrawals are indeed reduced. However, this reduction comes with a 33% increase in total expenditures, an increase in consumption across water and energy sectors, and higher withdrawals from fossil groundwater reserves. On the other hand, we find that if the countries were to balance their investments between smart and hydropower technologies it would not only reduce the increment in expenditure to 28%, but would also conserve irrigation water while avoiding the increased multi-sectoral consumption and environmental degradation. Thus, balancing investments between smart irrigation and hydropower projects can significantly reduce the economic and environmental (including conservation of water resources, meeting environmental flow targets, among others) costs of multi-sector water conservation in the IRB.