Combined Use of Local and Global Hydro Meteorological Data with Hydrological Models for Water Resources Management in the Magdalena - Cauca Macro Basin – Colombia

Reanalysis and earth observation data have enormous potential to support water resources management, particularly in river basins where data availability is poor or where available stations are unequally distributed. Despite this potential, these datasets continue to be underused around the world. In this article, we combine a recently established global water resources reanalysis that was developed within the EartH2Observe research project, and in-situ data in the Magdalena Cauca Macrobasin in Colombia. Through rigorous hydrological modelling we evaluate the contribution of this new information to the derivation of water availability indices used to support water policy and management. Results confirm the complementarity of the reanalysis, with water management indices derived from the reanalysis data showing good comparison to values obtained using in-situ data only. Indeed, the estimation of simple indices such as an Aridity Index and a Water Regulation Index show to be a suitable method for assessing and comparing the different reanalysis datasets. We also explore the value of the reanalysis and earth observations datasets in the study of climate and land use change scenarios in the basin. While considering the associated uncertainties, results show that on average rainfall is projected to increase in the basin and thus available water resources. Deforestation will increase the water balance due to lower evapotranspiration. However, reduced fog deposition in deforested cloud forest areas will lead to a decrease in the water balance. The promising results of the comparison have bolstered the confidence of the national hydro-meteorological agency to include the evaluated reanalysis datasets in the national water resources evaluation, complementing available in-situ datasets.