DRYP 2.0: A hydrological model for local and regional scale across aridity gradients

Abstract. The increasing demand for freshwater resources due to population growth, economic development, and climate change, requires more accurate representation and quantification of the key components of the water balance at relevant scales that goes beyond catchment domains. To address this need, we present DRYP 2.0 (DRYland water Partition model), a new version of a parsimonious, process-based, spatially distributed hydrological model (DRYP). DRYP 2.0 introduces several new capabilities, including the hydrological representation of small ephemeral ponds and large lakes, multiple interacting hydrogeological domains within a single-layer groundwater model, and vegetation canopy interception and evaporation to better capture the effects of vegetation on hydrology across different climatic gradients. Computational performance has also been enhanced through more efficient algorithms that reduce simulation time for long runs and/or over large spatial domains. We demonstrate these advances using high-resolution (1 km, 1 h) simulations over the Horn of Africa Dryland region (2,000,000 km²) as well as through various synthetic numerical tests. The results highlight the ability of the model, even without calibration, to reproduce global remote sensing data such as soil moisture, actual evapotranspiration, and total water storage, while also significantly reducing computation time. Furthermore, the explicit inclusion of multiple hydrogeological domains reveals important impacts on water table depth, with implications for improving global-scale simulations of the water balance.