RIVER REGIMES

RIVER REGIMES Do you know that the quantity of water flowing in a river channel is not the same throughout the year? It varies from season to season. In which season do you expect the maximum flow in Ganga and Kaveri? The pattern of flow of water in a river channel over a year is known as its regime. The north Indian rivers originating from the Himalayas are perennial as they are fed by glaciers through snow melt and also receive rainfall water during rainy season. The rivers of South India do not originate from glaciers and their flow pattern witnesses fluctuations. The flow increases considerably during monsoon rains. Thus, the regime of the rivers of South India is controlled by rainfall which also varies from one part of the Peninsular plateau to the other. The discharge is the volume of water flowing in a river measured over time. It is measured either in cusecs (cubic feet per second) or cumecs (cubic metres per second). The Ganga has its minimum flow during the January-June period. The maximum flow is attained either in August or in September. After September, there is a steady fall in the flow. The river, thus, has a monsoon regime during the rainy season. There are striking differences in the river regimes in the eastern and the western parts of the Ganga Basin. The Ganga maintains a sizeable flow in the early part of summer due to snow melt before the monsoon rains begin. The mean maximum discharge of the Ganga at Farakka is about , cusecs while the mean minimum is only , cusecs. What factors are responsible for such a large difference? The two Peninsular rivers display interesting differences in their regimes compared to the Himalayan rivers. The Narmada has a very low volume of discharge from January to July but it suddenly rises in August when the maximum flow is attained. The fall in October is as spectacular as the rise in August. The flow of water in the Narmada, as recorded at Garudeshwar, shows that the maximum flow is of the order of , cusecs, while the minimum flow is only cusecs. The Godavari has the minimum discharge in May, and the maximum in July-August. After August, there is a sharp fall in water flow although the volume of flow in October and November is higher than that in any of the months from January to May. The mean maximum discharge of the Godavari at Polavaram is , cusecs while the mean minimum flow is only cusecs. These figures give an idea of the regime of the river. EXTENT OF USABILITY OF RIVER WATER The rivers of India carry huge volumes of water Table . : Comparison between the Himalayan and the Peninsular River Sl. No. Aspects Himalayan River Peninsular River . Place of origin Peninsular plateau and central highland . Nature of flow Seasonal; dependent on monsoon rainfall . Type of drainage Super imposed, rejuvenated resulting in trellis, radial and rectangular patterns . Nature of river Smaller, fixed course with well-adjusted valleys . Catchment area Relatively smaller basin . Age of the river Old rivers with graded profile, and have almost reached their base levels Himalayan mountain covered with glaciers Perennial; receive water from glacier and rainfall Antecedent and consequent leading to dendritic pattern in plains Long course, flowing through the rugged mountains experiencing headward erosion and river capturing; In plains meandering and shifting of course Very large basins Young and youthful, active and deepening in the valleys