Revival of Innovative systems for reservoir operation and flood forecasting

Most reservoirs in Sri Lanka are agriculture and hydropower dominated.

- By G.T. DHARMASENA FORMER DIRECTOR GENERAL OF IRRIGATION

Reservoir operators are often unwilling to acknowledge the flood detention capability of major reservoirs during the onset of monsoons.Deviating from the traditional priority for food production and hydropower development, it is time to reorient the operational approach of major reservoir operators under extreme events, where flood control becomes a vital function. While admitting that total elimination of flood impacts is not technically feasible, the impacts can be reduced by the efficient operation of reservoirs and effective early warning systems.

At the very outset, I would like to mention that the contents in this article are based on my personal experience in the Irrigation Department (ID), and there is no intention to disrespect their contributions during the most recent flood event. The objective is to improve the efficiency and the capability of the human resources available in the ID and other relevant institutions to better respond to future flood disasters.

Reservoir operation and flood forecasting

Reservoir management is an important aspect of water management, as water storage and release are crucial for managing floods and droughts. Several numerical models and guidelines have already been introduced to the ID and MASL during numerous training programs for reservoir management and forecasting of inflows.

B. Adherence to Reservoir Standing Orders

According to the standing orders of the ID, water levels in major reservoirs must be kept below the Full Supply Level (FSL) during the Northeast (NE) monsoon season (from October to March) until the end of December. According to my recollection, this operational height is 1.0m below the FSL.

Therefore, maintaining a reservoir below the FSL during this period is not a new practice; it explicitly serves the dual purpose of dam safety and flood detention for the downstream areas.

C. Gate Operation Methodology