Dam construction and planning in mainland Southeast Asia has increased substantially in recent years. Majority of these dams have the potential to generate significant value in-terms of electricity production, drought and flood risk reduction, and improved crop production opportunities. However, they are also responsible for extensive regional impacts including alterations to water regimes, loss and degradation of natural forests and biodiversity, and reductions in soil and water quality.
There exists a need to use state of the art GIS technology to model these impacts for better planning and management. However, the regional water resource management organizations, NGOs, river basin planning organizations, regional disaster management organizations, and conservation societies in Mekong region lack the required GIS skills and resources to carry out the modeling of these dams. SERVIR-Mekong has addressed this regional need by developing an online tool, called Reservoir Mapping Tool, for modeling the inundation of proposed dams.
The tool is designed in ArcGIS Desktop 10.5 ModelBuilder, with dam point location, digital elevation model (SRTM-30m) and estimated dam height data as the primary inputs. The output of the model is an estimated inundated area for a particular dam.
The model consumes the Esri premium watershed service, which is used in a custom toolbox with 30m SRTM DEM to generate a watershed DEM. Raster calculator then uses the dam height value to delineate an inundation surface area and volume. The model is published as Geoprocessing Service in ArcGIS Server 10.5. The Web AppBuilder for ArcGIS (Developer Edition) Version 2.6 is used to consume the service and also to create and customize the application interface and functionalities.
The tool is available in the public domain (Reservoir Mapping Tool | SERVIR-Mekong ) and is currently being used by partner agencies to compile the first comprehensive collection of dam inundation areas on transboundary rivers in the Lower Mekong Region. That data product will include both the areas of existing and proposed dams. In future, the tool is expected to be used for evaluating cumulative impacts of dams on land cover and carbon emissions, preliminary alternative scenario analyses for planned dams, and application in the risk assessment contexts mentioned above.
