Modern computer models provide a powerful means of integrating and exploring information

   The use of modern computer simulation modeling provides powerful tools for first understanding the dynamics of the water cycle of the Mekong basin, and then to analyze potential consequences of different outcomes. Johnston and Kummu (2011) provide the following summary of the major issues, and the different models brought to bear:

“The debate around water resources development in the Mekong can be framed, in its simplest terms, as a debate about allocation of water and water-related benefits between sectors and users, explicitly including subsistence livelihoods and the environment. The degree to which such allocations can be considered as “fair” or otherwise can only be determined by a comprehensive analysis and comparison of the impacts of development. The impacts of water resources development will be felt in five main domains, which must be approached more or less sequentially:

• Hydrological: flow volume and distribution, river water level, river connectivity, flood dynamics, water quality, sediment and nutrients
• Ecological: habitat quality, wetland functioning, fish migration, aquatic organisms
• Livelihood: water availability for agricultural and aquacultural production, availability of fish and other aquatic products, vulnerability to floods and droughts
• Economic: economic costs and benefits of different water use options
• Social: migration, gender relations, family structure, public health.

   Coherent assessment frameworks must be developed in each of these domains in order to characterise impacts comprehensively. Because of the importance of Mekong inland fishery, and the large proportion of subsistence and semi-subsistence users who depend on it, realistic assessment of the impact of changes in flow on aquatic ecology is of particular significance.

   In the context of water management in large basins, both the drivers and impacts of hydrological change act over a wide range of spatial and temporal scales resulting in a very complex set of interactions, with cumulative impacts across both sectors and scales (Kummu 2008). Impact assessments in the Mekong Basin can be grouped into four main groups:

• Basin-scale assessment of changes due to projected broadly-based WR development or climate change (usually scenario-based) (e.g. World Bank 2004; Costa-Cabral et al. 2007; Eastham et al. 2008; ICEM 2010; MRC 2011).
• Basin-scale assessment of the impact of a specific large-scale development [e.g. Nam Theun 2 CIA (ADB 2004), Nam Ngum 3 CIA (ADB 2008)]
• Local assessment of impacts of basin-scale changes including climate change (e.g.
Friend et al. 2006; Kummu and Sarkkula 2008)
• Local assessment of impacts of specific developments (environmental impact assess- ments) (Hoanh et al. 2009b).

Johnston, R. and M. Kummu. 2011. Water Resource Models in the Mekong Basin: A Review. Water Resour Manage. DOI 10.1007/s11269-011-9925-8