Dam Safety in India
22nd Jul, 2019
More than 900 people from over 50 villages of Madhya Pradesh staged a dharna outside the Narmada Control Authority (NCA) office in Indore, fearing flooding of their villages if the Sardar Sarovar Dam was filled to its brim.
Dam is defined as a barrier built across a stream, river or estuary to confine and check the flow of water for such uses as human consumption, irrigation, flood control and electric-power generation. Lately, dams are seen more as hydropower generators with flood mitigation, irrigation and drinking water supply only being additional benefits.
However, globally about 2.2% of dams build before 1950 have failed mainly due to flooding, inadequate spillway capacity, bad workmanship etc. India ranks third globally with 5264 large dams in operation and about 437 are under construction. But, India too has had its share of dam failures. There are more than 36 reported failures cases so far.
First failure recorded in Madhya Pradesh during 1917 when the Tigra Dam failed due to overtopping. The worst dam disaster was the failure of Machu dam (Gujarat) in 1979 in which about 2000 people have died. Recently, the breach in Tiware dam in Maharashtra’s Konkan region swept away more than 20 people.
Types of dam in India
- Earth dam: Earthen dam utilizes natural materials with a minimum of processing. In India most of the dams are earthen dam.
- Gravity dam: A gravity dam is a dam constructed from concrete or stone masonry and designed to hold back water by primarily utilizing the weight of the material. Gravity dams provide some advantages over embankment dams.
- Composite dam: It is an earthen dam which is provided with a stone masonry or concrete overflow (spillway) section.
Dam Safety Framework in India
- National Committee on Dam Safety (NCDS)
- Constituted by Govt. of India in 1987.
- Chaired by Chairman, CWC and is represented by all the States having significant number of large dams and other dam owning organizations.
- Suggest ways to bring dam safety activities in line with the latest state-of-art consistent with the Indian conditions.
- Acts as a forum for exchange of views on techniques adopted for remedial measures to relieve distress in old dams.
- Central Dam Safety Organization (CDSO)
- Central Dam Safety Organization was established in CWC, in 1979
- The objective of Central DSO was to:
- Assist in identifying causes of potential distress;
- Perform a coordinative and advisory role for the State Governments;
- Lay down guidelines, compile technical literature, organize trainings, etc.; and create awareness in the states about dam safety.
- State Dam Safety Organizations (SDSO)-
- DSO/Cell established in 18 States and 5 dam owning organizations
- Routine Periodic Inspection
- Done by trained and experienced engineers from DSO
- At least twice a year : pre monsoon and post monsoon
- Examination of general health of the dam and appurtenant works
- Preparedness of dam and hydro mechanical structures for handling expected floods
- Comprehensive Dam Safety Evaluation
- Once in a 10 year
- More comprehensive examination
- Multi-disciplinary team for holistic view
- May order additional field and laboratory investigations as well as numerical simulations
Significance of Dams in India
- Dams supply the wealth of water to the parched fields of millions of farmers.
- They meet the domestic, municipal and industrial water needs of urbanized and rural areas.
- They form the backbone of India’s Power Grid Management because they generate cheap and eco-friendly hydro power across the country.
- Dams also sustain the growth of flora and fauna in many of the degraded forests.
- Dams offer a viable solution for checking unsustainable depletion of ground water, which may be inching towards tripping point under the tremendous pressure of growing population.
Need for Dam Safety in India
- Over 75% of the country’s dams are over 25 years old and about 164 dams are more than 100 years old. With the increasing number of dams becoming older and older, dam failures are more expected now.
- Ensuring Dam Safety is essential for safeguarding huge investments in infrastructure.
- It is also crucial for safeguarding human life, and properties of the people living downstream of the dams.
- Many dams have varied structural deficiencies and shortcomings in operation and monitoring facilities, while few do not meet the present design standard- both structurally and hydrologically.
- Most of the States have been failing to provide sufficient budgets for maintenance and repair of the dam. Many States also lack the institutional and technical capacities for addressing dam safety issues.
- Dam Rehabilitation and Improvement Project (DRIP)
- Ministry of Water Resources, River Development & Ganga Rejuvenation through Central Water Commission, in 2012, launched the six year Dam Rehabilitation and Improvement Project (DRIP) with World Bank with an objective to improve safety and operational performance of selected dams, along with institutional strengthening with system wide management approach.
- In 2018, the government approved the extension of DRIP Project for two more years with the revised scheduled closure June 2020.
- Presently 198 dam projects are being rehabilitated under the DRIP Project.
- Dam Safety Bill
- Union Cabinet in June 2018 approved proposal for enactment of Dam Safety Bill, 2018.
- The Bill provides for the surveillance, inspection, operation, and maintenance of specified dams across the country.
- The Bill also provides for the institutional mechanism to ensure the safety of such dams.
- Dam Health And Rehabilitation Monitoring Application (DHARMA)
- It is web-based software package to support the effective collection and management of Dam Safety data in respect of all large dams of India.
- The software is designed for users at Central, State and Dam level, with user permission rights governed by their respective licenses.
- Seismic Hazard Mapping along with development of Seismic Hazard Assessment Information System (SHAISYS)
- It is also web based interactive application tool being developed in CWC under Dam Safety Organisation (DSO) to estimate the seismic hazard at any point in Indian region.
- The SHAISYS shall be capable of estimating seismic hazard using the deterministic as well as probabilistic approach.
- Other Initiatives – Other important activities include Design Flood Review, publication of important Guidelines as well as Manuals dealing with Dam Safety Management, preparation of O&M Manuals, Emergency Action Plans.
- Current legal framework does not have any provision for penalizing the owner in case of a dam failure causing a disaster in the upstream or downstream of the dam.
- Lack of systematic assessment and monitoring coupled with inadequate resources is the primary cause of poor maintenance of dams and appurtenant works.
- Real time inflow forecasting systems are not in place even in important reservoirs. Such systems can add to dam safety measures besides improving operational efficiencies.
- The procedure requires that revision study of dam hydrology needs to be completed much in advance of any rehabilitation exercise but this not being the case has led to delays in DRIP implementation
- Dam design drawings or drawings as constructed are not available with project authorities in many cases.
- Dam Safety Organizations (DSO) in states is short of adequate man power and need to be strengthened.
- Siltation of reservoir is a serious issue, though in most cases the extent of siltation continues to remain unknown. De-siltation of reservoir is difficult in many a cases owing to environmental concerns related to sediment disposal.
- Appropriate Interventions for Sediment Management is not available in most cases. In few cases river sluices are available in dams, but they have not been operated for long periods, and are no more functional.
Dam Safety Bill, 2018 - Key Provisions:
- Dam Safety Bill 2018 will empower the dam safety institutional set-ups in both the Centre and States
- It will help in standardizing and improving dam safety practices across the country.
- It will address all issues concerning dam safety including regular inspection of dams, Emergency Action Plan, comprehensive dam safety review, adequate repair and maintenance funds for dam safety, Instrumentation and Safety Manuals.
- The bill will constitute National Committee on Dam Safety (NCDS), National Dam Safety Authority (NDSA), and State Dam Safety Organization (SDSO) with well defied duties and functions.
- The Bill provides for comprehensive safety evaluation (CSE) by independent panel of expert. First CSE within 5 years, and thereafter at regular intervals specified by NCDS.
- Comprehensive Safety Evaluation would be compulsory in case of major modification to structure or design criteria; discovery of unusual condition at dam or reservoir rim; an extreme hydrological or seismic event.
- The Bill provides for punishment / penalty if the dam safety provisions are not followed
- The Bill provides for an emergency action plan to combat any disaster arising out of dam failures.
- A Standing Committee Report has recommended that a penal provision for dam failures should be incorporated in the law and compensation should be provided to the affected families.
- Latest technologies should be adopted not only at the time of constructing the dam, but also during periodic review of the dams.
- Institutional Capacity building is needed in design flood estimation and flood routing for most of the states.
- A well planned monitoring system based on data collection and evaluation using modern instrumentation is the key to early detection of defects and ageing scenarios.
- Rehabilitation of old dams using the latest materials and technologies can enhance the life of a dam for many more decades.