Context: Called the ‘lifeline of Gujarat', the Sardar Sarovar Narmada Dam usually has no water for irrigation during summers.

More in the news:

  • The dam is called the ‘lifeline of Gujarat’, it usually has no water for irrigation during summers.
  • For the first time in the history of the dam, as many as 35 dams and reservoirs, close to 1,200 check dams and 1000 village tanks have been filled with Narmada water this year.
  • River Narmada is a classic case of Integrated River Basin Planning, Development, and Management, with water storage available in all major, medium, and minor dams on the main river and its tributaries. 
  • It is shared amongst four party states – Gujarat, Rajasthan, Madhya Pradesh and Maharashtra — in the ratio stipulated by the 1979 award of the Narmada Water Dispute Tribunal.

Status of the Dam on 3 June 2021:

  • The dam had 122.72 metres with live storage of 1,711 million cubic metres.
  • In 2017, the dam was raised to a height of 138.68 meters (spillway level until 2017 was 121.92 meters) and 30 gates were installed.
  • The dam achieved its Full Reservoir Level (FRL) for the first time in 2019.

The water management initiatives that helped harness water

  • The strategic operation of River Bed Power House (RPBH) ensures that minimum water flows downstream into the sea and maximum water is used during the dam overflow period, which is not calculated in the annual water share.
  • These measures help in maximizing the annual allocation of a water share.
  • In the non-monsoon months, the measures for efficient use of the allocated share typically include 
    • Minimising the conventional and operational losses, 
    • Avoiding water wastage, 
    • Restricting water-intensive perennial crops, 
    • Adopting of Underground Pipelines (UGPL); 
    • Proper maintenance of canals and structures and operation of canals on a rotational basis (among member states).

How has Full Reservoir Level (FRL) helped?

  • The good rainfall in the catchment area of the dam in 2019 and 2020, ensured that it achieved FRL for two consecutive years.
  • Which helped in increasing the annual share of the water allocated to Gujarat and other catchment states.

Has the Covid-19 lockdown helped in preserving water in the basin?

  • The industrial consumption of the water from the Narmada dam is very less as compared to other uses.
  • The present utilisation of water by the industries is 0.07 per cent MAF (million acre-feet) even during full operational years in normal times
  • The lockdown or partial closure of industries has not impacted the storage levels much.

How would the summer level help in the functioning of the powerhouses during the next water year, beginning on July 1?

  • A water year is counted from July 1 to June 30.
  • A comfortable water level at the beginning of the monsoon can definitely lead to higher hydropower generation during non-summer months as experienced during the last two years.

Dam spillway operation to maximize storage in the dam reservoir and mitigate the risk of the flood as seen in 2020.

  • The operation of Dam Spillway Gates is a specialized and complex issue, involving domain expertise and experience in hydrology, flood routing, and hydraulics.
  • It is about striking a balance between the safety of the dam as well as the population and environment located downstream and the likelihood of having scarce water storage.
  • The dam has to have an adequate flood absorption capacity by maintaining cushion levels and must also harness the available flood water in order to ensure that there is no water scarcity.
  • Ideally, as a general guideline, a major dam should not be filled more than 
    • 60 per cent as of July 31, 
    • 75 per cent on August 31, and
    • 85 per cent on September 15.
  • Therefore, excess flood water received after attaining these levels is allowed to flow downstream by opening the gates.
  • Each spillway gate level is decided after duly considering: 
    • The storage and flood absorption capacity in the upstream dams, 
    • The rain forecast, flood conveyance capacity of the river downstream, and 
    • Balancing hydropower generation with power grid requirements.

Related Facts:

About Sardar Sarovar Narmada Dam:

  • It is a concrete gravity dam.
  • The Sardar Sarovar Narmada Dam is a terminal dam built on the Narmada river at Kevadia in Gujarat’s Narmada district. 
  • It is the second-largest concrete dam in the world in terms of the volume of concrete used to construct the dam (after the Grand Coulee Dam in the United States).
  • It involves a series of large irrigation and hydroelectric multi-purpose dams.
  • It was funded by the World Bank through its International Bank for Reconstruction and Development (IBRD), although it withdrew in 1994.
  • It is a part of the Narmada Valley Project, a large hydraulic engineering project involving the construction of a series of large irrigation and hydroelectric multi-purpose dams on the Narmada river.

Source: The Indian Express