Exploring impacts of forest management strategies on water partitioning in a drought-sensitive catchment using a tracer-aided ecohydrological framework

Abstract

Land use strongly influences water partitioning, water availability, and ecohydrological resilience in droughtsensitive regions. Forest management plays a critical role through its effects on water use, which depends on forest type, forest density, root water uptake, yet the ecohydrological consequences of different forest management strategies-particularly in terms of blue and green water fluxes-remain poorly quantified. Here, we develop and apply a parsimonious, tracer-aided forest management scenario framework using the conceptual ecohydrological model EcoPlot-iso, designed to isolate the dominant vegetation-structural controls on long-term water partitioning. We investigated how variations in generic forest type (e.g., broadleaf vs. conifer), forest density, and root distribution influence water partitioning and ecohydrological resilience under different wetness conditions in the drought-sensitive lowland Demnitzer Millcreek catchment (DMC), northeastern Germany. Baseline simulations for the period 2000–2024 were conducted at three forest sites and used to develop forest-type–specific reference conditions for comparison with alternative forest management scenarios. A key innovation in this version of EcoPlot-iso was the integration of a depth-dependent root water uptake function, allowing simulation of transpiration across soil layers under contrasting rooting distributions corresponding to different stand ages. The model was calibrated and validated using seven years of soil moisture and three years of soil water isotope (δ2H) data through a multi-criteria approach. Results showed that, on average, evapotranspiration was highest under conifers, exceeding broadleaf forests and agroforestry by 7 % and 11 %, respectively, while agroforestry exhibited the greatest groundwater recharge. Significant differences in water partitioning between dry and wet years were observed across management scenarios. Conifer forests showed stronger transpiration contrasts than broadleaf forests in early spring, while the wet–dry-year contrast between the two forest types was largest in late spring. Our findings highlight the potential of agroforestry, such as crop–tree mixtures, to mitigate drought impacts on soil water availability and groundwater recharge. Overall, this study demonstrates how a parsimonious, tracer-aided scenario framework can be used as a decision-support tool to quantify and visualize the effects of land use change on water availability in data-limited regions, supporting more informed decision-making and enhanced ecohydrological resilience under increasing drought pressure.