Have you ever wondered what the age of our rivers is? For instance, did you know that the rivers that flow in Karnataka are older than the mighty Himalayas?
Karnataka is bestowed with seven critical river systems that are the lifelines of the state: Godavari, Krishna, Cauvery, North Pennar, South Pennar, Palar, and collectively all the west-flowing rivers. The Cauvery is the largest river in Karnataka and originates from Talacauvery in Kodagu’s Madikeri District. Although many rivers flow to the west and join the Arabian Sea, they account for a meagre 12.73% of the water that drains in Karnataka. The majority—a whopping 87.27% of Karnataka’s drainage area—is a result of the six mighty east-flowing rivers. Why this stark imbalance, you wonder? There is a bit of a geological history to this, and the story starts with the history of the Western Ghats, where most of Karnataka’s rivers originate from.
The Chronicles of the Western Ghats
Over 180 million years ago (mya), the present-day landmass (most continents) was merged together as a supercontinent called Gondwanaland. During that period, due to a certain geological event, the landmass split; one of them was the peninsular Indian plate that drifted northwards for about 100 mya to eventually hit the Asian plate about 45 mya, which resulted in the formation of the Himalayan mountain range. That is why the mighty Himalayas are considered one of the youngest mountain ranges.
During its movement, the peninsular Indian plate passed through the present-day Reunion Islands, which had a volcanic centre in the earth’s lithosphere, over 200-300 km across. As it passed through this region, it generated basaltic magma resulting in the uplift of what is now the Western Ghats, and tilted the Indian plate in the easterly direction. Thus, the Western Ghats are not true mountains but the faulted edge of a raised plateau.
By the time peninsular India ended its northward drift and collided with the Asian mainland (between 45 and 65 mya), the Western Ghats was very much in place. All these events had permanently cast the drainage pattern. Thus, in Karnataka, most of the rivers originate in the Western Ghats and drain into the Bay of Bengal.
Ecology and Biodiversity
With such distinguished history to their origins, it is little surprise that the rivers of the Western Ghats have nurtured a unique ecosystem. The Western Ghats’ mountain ranges comprise of high-altitude grasslands, sholas, wet evergreen forests, semi-evergreen, moist deciduous and dry deciduous forests.
As one moves eastwards towards the plains, a bulk of the plateau is scrub-grasslands, with occasional dry-deciduous forests. Yet, these regions form the catchment area and are part of the river hydrology, responsible for capturing the incident rainwater and draining them off. Most of the west-flowing rivers are perennial while the east-flowing rivers depend on the monsoons.
During all these cycles, life in various forms is nurtured and supported. These unique landscapes are home to several species of plants like the Neelakurinji, which blooms once in 12 years, and animals like the endangered Lion-tailed Macaque, which is found nowhere else on earth.
Historically, rivers are known to harbour life; thus, most civilisations have emerged around rivers. Consequently, rivers have played a key role in human social organisation. Several key cities have evolved around rivers, and so did some of the erstwhile capitals of kingdoms. Srirangapatna and Hampi are glowing examples, with the rivers Cauvery and Tungabhadra flowing past these cities respectively.
India, an agriculture-dominated country, has over 70% of its population directly or indirectly dependent on rivers for food and livelihood. In Karnataka, the rivers originating in the forests of the Western Ghats provide food and power security for the entire southern peninsular India. These east-flowing rivers, which flow for thousands of kilometres before joining the Bay of Bengal, support livelihoods in hundreds of towns and villages on their downstream journey. Massive irrigation projects on rivers like Cauvery, Krishna and Godavari serve the region known as the granary of the Deccan Plateau. Apart from household consumption and irrigation, these rivers also provide water for the generation of electricity.
The west-flowing rivers mostly contribute to the production of electricity to power Bengaluru’s IT hub and other parts of Karnataka. The Karnataka Power Corporation Limited has 34 dams on its rivers and 24 hydropower stations across the state.
Fisheries also form a substantial means of livelihood for those who live on the banks of these rivers and their tributaries. The means to livelihoods for tribes and other locals also largely depend on these river systems.
Rivers for Development
Since the east-flowing rivers are vital sources of water for drinking and irrigation, large dams have been built in the past to cater to these needs. With the generation of hydroelectricity gaining momentum in the last century, several hydroelectric projects came up along the Western Ghats. A series of dams have been built along the west-flowing Sharavathi River, which has reduced the natural flow of the 140 km long river to a mere 8 km! The ecological impact of dams has been irreparable. For instance, several species of stream fishes are unable to move across the stream for breeding, since they are now confined to one side of the dam. Some species, which swim upstream for reproduction, are also now restricted.
The construction spree of these massive dams took a break in the 1970s after a protest by locals against building a dam across River Bedthi. However, in the past decade, there has been a resurgence of small dams instead of large ones, and some water diversion projects taking afoot as well.
The recent floods in several parts of North Karnataka ring a warning bell for pursuing any alterations to the ecology of the Western Ghats and rivers in particular. Understanding river hydrology and floodplains, which form diverse habitats for flora and fauna, can go a long way in arriving at sustainable solutions. Time and again, ecologists have raised concerns against river linking and the threats it can cause to larger ecosystems. Development goals should be evolved locally, and the water demands should be assessed at watershed levels. Mini-hydel and water diversion projects may need to be evaluated using these lenses. It is crucial that policymakers apply integrated water resources management towards achieving sustainable development.