Statistical Analysis of Dam Failures and Ensuring Dam Safety at Koldam

Dam Safety has been a domain of universal interest with multi-disciplinary expertise, however, recent revised and stringent regulations with multi-level monitoring have further highlighted its importance. This paper summarizes comparative statistical analysis of dam failure data across the globe. The Dam failure history analyzed and recorded in terms of data were compared with the parameters prevailing e.g. most of the dam failures had occurred in the first two years after construction. Based on this information, it can be said that Koldam is on the safer side as it has crossed the critical years and completed 10 years of age. Several such comparisons for Koldam were performed with the statistical data regarding type of dam, age of dam, height and storage capacity of dam, Spillway capacity and modernization in dam design philosophy etc.

In recent past, the frequency of dam failure related incidents due to inadequate spillway capacity and mal-functioning of hydro-mechanical equipment has been reported from across the world. Few such unwarranted failures have occurred in India also which led to huge loss of men, material and money. At Koldam, due care has been taken in designing the spillway capacity after detailed hydraulic and hydrological studies. Scheduled maintenance and testing of HM equipment is ensured to avoid any such untoward event. Effect of GLOF has also been analyzed and it was observed that due to sufficient distance of dam from nearest glaciers and presence of upstream dam projects, the spillway is safe from GLOF considerations.

Koldam Hydro Power Station is NTPC's flagship installation in the hydro sector situated on river Satluj in district Bilaspur, Himachal Pradesh, India. The dam safety compliances are being followed rigorously at Koldam HPS which are also elaborated in the paper. It concludes safe dam condition for Koldam from the analysis of previous dam failure data.

Koldam HPS (2x 400MW) is managing its operation and maintenance activities along with the compliances of Dam Safety Act 2021 with optimal man-megawatt ratio. In fulfilment of provisions of Dam Safety Act 2021, Dam Safety Unit at Kodam HPS is implementing the dam safety related assignment in true sense. A muti-disciplinary dam safety committee with diversified experienced minds has been set up for holistic examination and resolution of dam safety related issues at site level. Detailed Pre and Post Monsoon inspections are being carried out with a systematic approach in a time-bound manner and as per CWC guidelines. Apart from Pre and Post monsoon inspections, inspection of dam and appurtenant structures is being carried out on monthly basis in Monsson season and bi-monthly in lean period. An SOP has been framed and implemented for regulating the frequency, magnitude and intensity of various inspections. Inspection of all components of dam complex and reservoir rim is carried out after every critical eventuality e.g., high floods and earthquakes etc.

Proactive measures for safety of lives and property, that may be required due to dam incidents, such as information sharing with people downstream of dam, awareness measures for EAP/DMP, mock drill for safe evacuation, marking of danger water levels, displays at entry points along the river etc. are also summarized in the paper. Important dam safety components such as Automatic Weather Station (AWS), Early Warning System (EWS), river inflow and flood forecasting system, hydro-meteorological stations etc. are fully functional. Reservoir siltation study, bathymetry, river depth survey, analysis of instrumentation data etc. are being undertaken regularly. Based on the Statistical analysis of dam failure data as well as compliance patterns of Dam Safety Act 2021, it can be concluded that Koldam is truly safe in all the aspects.