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The pattern of the seasonal flow of water in any river is called its regime. Differences in climate are the main cause of the differences in the flow patterns of rivers of Himalayan and peninsular origin. The Himalayan Rivers are perennial and their regimes depend upon both rainfall and snow.
Thus, the regimes of the Himalayan Rivers are both monsoonal and glacial. On the other hand, the regimes of the Peninsular Rivers are only monsoonal as they are influenced only by rainfall. There also exist the intra-peninsular differences in the river regimes. This is due to differences in the seasonal distribution of rainfall in various parts of the plateau.
The regimes of the two Himalayan (Ganga and Jhelum) and the two peninsular (Narmada and Godavari) rivers may be called examples of the river regimes.
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The Ganga has its minimum flow in the period January-June. The maximum is attained either in August or September. There is a steady fall in the flow of water after September. The river has a typical monsoonal regime.
The Jhelum attains the maximum water flow in June, or even in May, since its flow is mainly caused by the snow-melt from the Himalayas. The range of variation between the regimes of the Ganga and the Jhelum Rivers is shorter in the case of the former.
The two peninsular rivers display interesting differences in their regimes from the Himalayan Rivers. The Narmada attains its maximum water flow in August, while it has a very low volume of discharge from January to July. The Godavari flows at a low level until May. It attains maximum water flow twice—one in May-June and the other in July-August.