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A three-step interdisciplinary method to assess approaches to water shortage, water quality and flood risks is presented. This method, based on water system analysis, economics, law and public administration, seeks to create common understanding based on newly developed concepts and definitions. First, generating content knowledge about the water system and about values, principles and policy discourses. Second, providing an organizational process with sufficient stakeholder involvement, insight into the trade-off between social objectives, and attribution of responsibilities in addition to regulations and agreements. Finally, implementing the agreed service level through adequate infrastructure, enforcement and conflict resolution.

Abstract. Recent flood dynamics of the Mekong Delta have raised concerns about an increased flood risk downstream in the Vietnamese Mekong Delta. Accelerated high dike building on the floodplains of the upper delta to allow triple cropping of rice has been linked to higher river water levels in the downstream city of Can Tho. This paper assesses the hydraulic impacts of upstream dike construction on the flood hazard downstream in the Vietnamese Mekong Delta. We combined the existing one-dimensional (1-D) Mekong Delta hydrodynamic model with a quasi-two-dimensional (2-D) approach. First we calibrated and validated the model using flood data from 2011 and 2013. We then applied the model to explore the downstream water dynamics under various scenarios of high dike construction in An Giang Province and the Long Xuyen Quadrangle. Calculations of water balances allowed us to trace the propagation and distribution of flood volumes over the delta under the different scenarios. Model results indicate that extensive construction of high dikes on the upstream floodplains has had limited effect on peak river water levels downstream in Can Tho. Instead, the model shows that the impacts of dike construction, in terms of peak river water levels, are concentrated and amplified in the upstream reaches of the delta. According to our water balance analysis, river water levels in Can Tho have remained relatively stable, as greater volumes of floodwater have been diverted away from the Long Xuyen Quadrangle than the retention volume lost due to dike construction. Our findings expand on previous work on the impacts of water control infrastructure on flood risk and floodwater regimes across the delta.

Major changes are occurring with far reaching implications for the existing equilibria or disequilibria in the water-energy-food-environment interface. The increased demand of energy worldwide will reflect directly and indirectly on water-dependent systems. Direct implications will come from higher energy prices, which make extraction and conveyance of water more costly. Indirect implications will be in the form of demand for alternative energy sources. It triggers demand for hydropower and remains a major driver—along with some environmental policies—for biofuel expansion. The key question is how these effects may alter water allocation and influence food security, rural poverty and environmental sustainability. This paper sets the background and context of this special issue by highlighting some of the major water-related policy issues related to the subject and provides an overview and synthesis of the papers in this special issue. Besides offering insight into how these papers address these questions in the practical context of few selected countries and basins, this paper also indicates some key areas for future research on the subject.