Study for Shift towards Weather Forecast based Dams’ Operation in India

November 9, 2026 SANDRP

A new study has again emphasized on why dam operations in India need to move from routine schedules to weather forecast based management. The study analyzed 223 dams across the country over 23 years by comparing river flows with and without the dams. Most importantly, the study has highlighted the limitations of dams in controlling successive floods. It found that about 74% of the dams were more than 90% full on the day of a high-flood event. Thus, leaving very little space to hold the next heavy rainfall spell and control resultant floods.

The study has also found that dams increased low river flows during March–May months at about 84% of the locations it studied. However, low-flow days became less frequent at more than one-third of the sites, showing that higher low-flow levels do not necessarily mean more continuous river flows.

Notably, the study has not specified the exact calendar years covered by its 23 year analysis. Its findings are based on hydrological modelling and not on the actual records of dam-operations. The researchers have used generalized operating rules rather than dam-specific practices and have not factored in irrigation withdrawals and return flows. Lack of data has limited the assessment for the two major river basins Ganga and Brahmaputra. Moreover, the study does not establish how the identified benefits and risks vary across individual dams and river basins. The limitations are indeed very significant.

The study has recommended that dams regulations must move away from volume-centric systems, towards a weather forecast-informed management especially during the monsoon. The study also signifies a need to make actual dam storage and release data publicly available to assess whether dams are reducing flood risks and supporting river flows or creating problems downstream.

Impact of Reservoirs on Streamflow Extremes in India While India has a vast network of reservoirs, we lack a clear understanding how these structures collectively alter naturalized streamflow. We induct 223 reservoirs in a combined land surface hydrologic model framework over 23 years. The study reveals that reservoirs reduce the intensity of monsoon high inflows by nearly half (46.1%) and triple (235%) the low flow magnitude during dry season. Large reservoirs (≥1000 MCM) dominate the magnitude control of extreme events. But smaller (<1000 MCM) reservoirs are the primary controllers of lag in these extreme signals (1–3 days). Most concerningly, 74% of reservoirs hit near-full capacity immediately next day after a monsoon high inflow. This leaves a vulnerable room for sequential high flow events. These findings emphasize that India must move toward weather-forecast-driven dam operations. – South Asia Network on Dams, Rivers and People.