An interesting feature of all ancient civilisations was that its inhabitants realised the tremendous value of water in human life. Each of these civilisations was located either on the banks of rivers or within a convenient distance from fresh water sources. This was to ensure a perennial supply of water for day-to-day activities. It is indeed astonishing to realise that at the dawn of civilisation, humans understood the significance and importance of water.

Apart from its uses for cooking, personal cleanliness and hygiene, water was vital for cultivation and irrigation of crops. With further progress and development, water again became an invaluable source of food as well as trade and commerce. Demand for fresh water proportionately increased with advancements in technical, social and other spheres of humankind.

However, the flows of the world’s rivers are increasingly being modified through impoundments such as dams and weirs, abstractions for agriculture and urban water supply, return flows, maintenance of flows for navigation, and structures for flood control. These interventions have caused significant alteration of flow regimes mainly by reducing the total flow and affecting the variability and seasonality of flows. While economically and/or politically powerful users have relatively well developed methods for quantifying and justifying their water needs, this is not the case for ecosystem – the silent water user. This is a brief study report on the state of affairs of a holy river in Karnataka – Tungabhadra.

The Tungabhadra River is a composite river of two east flowing rivers, namely Tunga and Bhadra. Tunga rises at Gangamula in Gangrikal hill ranges north of Kudremukh.

Bhadra rises near Samse in the Aroli hill range of Kudremukh. Bhadra river joins Tunga at Kudli in Shimoga district to form Tungabhadra River. It flows up to 298 km through Karnataka and some parts of Andhra Pradesh and joins Krishna.

The natural flow regime in the river has changed from 1953 with the construction of Tungabhadra Dam at Munirabad and later on other dams like Bhadra Reservoir in 1962, etc. Before alterations in its natural flow regime, this basin was known for its natural resources and several kingdoms flourished on them.
Till a few decades back, the native fish population comprising Labeo, Cirrhinus, Puntius, Catfish, Murrels, etc. of the river were famous for their quality.

With the construction of various diversion schemes, presently, the catchment and command area of the river comprises of seven districts and 27 taluks and covers an area of 48,000 sq km and has contributed to significant economic and social development of the basin.

The basin has been consuming 227 TMC annually for agricultural practices and 4.49 TMC for drinking water from surface water sources.

On the other hand, alterations in flow regime in the river has directly and critically damaged the riverine ecosystem. To list a few:

* Soil fertility.
* Shift in the fish community, as native species could not adjust their life cycles to flow changes as well as competition from introduced exotic species.
* Natural regeneration of vegetation was severely curtailed and existing vegetation was exposed to severe biotic pressure.
* Reduced groundwater table recharge along the river course which was taking place originally.
* Constantly deteriorating water quality. 

Realising the importance of maintaining minimum environmental flows, several agencies like IUCN, World Bank, etc. have recommended several measures. While some developed countries like the US have already decommissioned some of the dams, countries like Australia, South Africa and France have enacted legislations to ensure minimum environmental flows in the river.

Not ensuring minimum care for ecosystem could have disastrous effects on our economy, since most of our population is ecosystem-dependent.

It is universally recommended that a minimum of 20 per cent of inflows to any reservoir should be released for the survival of downstream riverine ecosystem.

But presently, downstream releases hardly reach 5 per cent. It is time for our environmental policy makers to bring in necessary changes to ensure the survival of downstream ecosystem before it is too late.


(This paper is part of a larger study currently being carried out by the Centre for Ecological Economics and Natural Resources, ISEC, Bangalore, India.)