Modélisation Koshi

The Koshi River takes its source on the Tibetan plateau in China and flows through Nepal before joining the Ganges in India. In Nepal, the Koshi is the largest hydrological basin with its 29'600 km2 and the living population is estimated to 5.2 millions people.

In the frame of a collaboration with the Laboratoire de Constructions Hydrauliques (LCH) of the École Polytechnique Fédérale de Lausanne (EPFL) and the International Center for Integrated Moutain Development (ICIMOD), a hydrological model has been developed for the Nepalese part of the Koshi river basin. The software RS MINERVE has been used with the hydrological model GSM-SOCONT.

The hydrological model, once calibrated and validated, has been used to propose a warning system based on the meteorological forecast for the coming days. This concept has showed the potential of such a system in comparison to the actual system based on the real-time monitoring of the water level in the different tributaries that allows only very little time to take action before a flood.

nepal

In the second part of the project, the hydroelectrical projects planned in the basin have been integrated in the hydrological model. Every year, the monsoon generates in the region heavy rain that result in regular floods. The mitigation potential of floods linked to these projects has been evaluated. The results of this preliminary study showed that with the planned reservoir volumes, floods might be attenuated considerably during the first part of the monsoon. However, once the reservoir are filled, this potential is strongly reduced if now preventive operations are undertaken.

 

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