Man's Impact on Water Resources

ABSTRACT

The SSARR model is applied to simulate flood levels in the Mekong river delta. The Mekong and Bassac rivers which are two main rivers and the Vaico river are interlaced together with canals and floodplains with storage. The flow exchanges between these rivers, and the tidal influences in their estuarial reaches make it necessary to utilize the backwater mode of the SSARR model in the simulation. In addition to the backwater mode, the diversion algorithm of the SSARR model is also used to take into account the over bank flow conditions.

Since the river storages during the flood periods are considerable, the rivers have been divided into several storage reaches or reservoirs. The flow between these storage reaches depends on the water level differences between each pair. Moreover, the various flood plain storages are also represented by a network of interconnected storage reaches or reservoirs. The upstream boundary condition is the discharge in the Mekong river at Phnom Penh, and the downstream boundary conditions are the tides at the mouths of the three rivers. Rainfall over the study area is also considered as input to the model.

In general, very close agreement is obtained in the calibration and verification except at thte stations Can Tho and My Thuan where tidal influences are significant. However, good results are obtained for the envelope of high tides at these two stations. Sensitivity analysis is made to determine the effects of the overbank flow parameters, and the exchange flow parameters on the flow in the rivers. More data collection of delta discharges and water levels is recommended for the future to improve the existing backwater relationship for better simulation of tidal fluctuation in the estuarial reaches of the delta.