Use of distributed hydrological model and field investigation for efficient water management decision making in the Mekong Basin.

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Initially, using the available spatially distributed information, hydrology of the Mekong basin was modeled using a distributed hydrological model. The model predictions were compared with the observed stream flow data which showed the need to vastly improve existing data to make reliable impact assessment for alternative development scenarios. The bulk of the remaining part of the project focused on the collection of hydro meteorological and catchment physical data. As a result, the whole Mekong basin data set was improved and data were compiled from 90 discharge gauges and 99 rain gauges that can be used in the numerical simulations. The land cover, elevation, soil data has been compiled and tested. Especially the elevation data set was tested by computing and comparing Horton parameters for the drainage network for various drainage density networks.The flow regime and changes were analyzed, especially the flow characteristic changes over a period of two decades were analyzed. It was found that the river flows are affected profoundly by the water infrastructure development in the basin. River low flows in general have been increasing while the flood flows are decreasing. Even though the general characteristics are such, in extreme weather conditions, very low river base flows and extreme high flows that exceed historical records can be seen. Further more, the flow variation over time are not even along the main river. Some parts of the basin has shown increased water consumption, making a negative overall contribution to the mainstream flow.In addition to data compilation research methodologies have been developed to improve flood inundation modeling and loss estimates. One of the major obstacles in assessing future water demand is the lack of adequate information on water infrastructure. An email based data collection system was developed for collecting water infrastructure data to address this issue.