Author(s): Alexandra M. Murray; G. H. Jorgensen; P. N. Godiksen; H. Madsen; N. Balbarini; L. Comeau

Linked Author(s): H. Madsen

Keywords: Global hydrological model; Discharge forecasting; Drought; Water resources management; Data scarcity

Abstract: Global hydrological models (GHMs) provide a comprehensive view of the earth’s hydrological system by incorporating global climate datasets, rainfall-runoff modelling, and water routing components at the global scale . Most GHMs are descriptive and constructed to provide answers to specific research questions, hence they typically require large amounts of computational resources and only provide historical results. DHI has developed a GHM that not only provides historical simulations, but also functions as an operational service to provide real-time, 10-day forecast, and 9-month seasonal forecast simulations for the entire globe. DHI’s GHM is comprised of 1) a distributed rainfall-runoff model with more than 1.5 million grid cells at 0.1° resolution and 2) a routing model that routes water from grid cells to sub-basins and through the river network. The average sub-basin is 100-200 km2 and the outlet of each basin is a simulation node, resulting in over 1 million computational points. The model produces not just river discharge, but also rainfall-runoff model results, such as overland flow and soil moisture. The computational run-time is less than one hour, and thus real-time and 10-day forecast simulations are produced hourly, as often as global precipitation datasets are updated. The data provided by the operational system is valuable to governments and institutions working to mitigate flood, drought, and food security risks and to inform national-scale climate change resilience measures. Because it provides continuous, real-time information, it can support preventative measures as well as disaster relief efforts while an event is occurring. The system is invaluable for areas and projects where data and resources are scarce. The data provided by DHI’s GHM has been used in a rapid integrated assessment of water resources in northern Kenya to evaluate current and future water scarcity issues and provide recommendations for improving water security. What little local observed data is available is difficult to assemble, and the nature of the project as a rapid assessment with limited time and resources further prevented development and application of a local model. Yet local decision-makers still need to develop water resource management plans and identify and implement appropriate integrated water resources management actions in the face of increasing uncertainty and climate change. DHI’s GHM is instrumental to such work, as 40-year hindcast simulations and up-to-date forecasts are available to support the needs of these decision-makers.

DOI: https://doi.org/10.3850/IAHR-39WC2521711920221912

Year: 2022