Planning & Management
Large storage systems play a key role for securing water, energy, and food, and thus increasing socioeconomic development and reducing poverty worldwide. This is leading many developing countries and international agencies to undertake major investments in dam construction, primarily to produce hydropower. Globally, about 3,700 new major dams are planned or under construction. Despite dams generate many potential benefits, they can also create substantial negative environmental externalities that are commonly underestimated in the dam planning process.
In this work, we contribute a robust, strategic dam planning approach to i) quantify the tradeoff between hydropower production and associated impact on sediment deliveries and ii) to develop lower-impact dam portfolios under the uncertainty associated with basin-scale sediment yield. The Mekong River basin is used to demonstrate the proposed approach.
To quantify the vulnerability of the Mekong Delta to future scenarios of hydropower development under uncertain sediment yields, we first generated a large ensemble of sediment yields from the basin’s distinct geomorphic regions. This ensemble represents plausible changes in sediment supply to the rivers. We used the ensemble of sediment yields together with estimates of sediment trapping within the CASCADE framework. We then analyzed the delta’s sediment budget for the ensemble of sediment yields under two different futures, considering the planned sequence of dams as well as a sequence derived with a multi-objective evolutionary algorithm to reduce conflicts between power generation and sediment trapping.
Results show that major shifts of the sediment budget of the Mekong Delta are likely even under deeply uncertain future sediment yields and that strategic dam sequencing provides a robust option to minimize reduction of sediment delivery if hydropower is to be expanded. Results support energy planning policies, improve predictions of consequent land loss, and inform development of adaptation measures for the Mekong Delta.