Multidimensional hydrological modeling of a forested catchment in a German low mountain range using a modular runoff and water balance model

Abstract

Sufficient plant-available water is one of the most important requirements for vital, stable, and well-growing forest stands. In the face of climate change, there are various approaches to derive recommendations considering tree species selection based on plant-available water provided by measurements or simulations. Owing to the small-parcel management of Central European forests as well as small-spatial variation of soil and stand properties, in situ data collection for individual forest stands of large areas is not feasible, considering time and cost effort. This problem can be addressed using physically based modeling, aiming to numerically simulate the water balance. In this study, we parameterized, calibrated, and verified the hydrological multidimensional WaSiM-ETH model to assess the water balance at a spatial resolution of 30 m in a German forested catchment area (136.4 km2) for the period 2000–2021 using selected in situ data, remote sensing products, and total runoff. Based on the model output, drought-sensitive parameters, such as the difference between potential and effective stand transpiration (Tdiff) and the water balance, were deduced from the model, analyzed, and evaluated. Results show that the modeled evapotranspiration (ET) correlated significantly (R2 = 0.80) with the estimated ET using MODIS data (MOD16A2GFv006). Compared with observed daily, monthly, and annual runoff data, the model shows a good performance (R2: 0.70|0.77|0.73; Kling–Gupta efficiency: 0.59|0.62|0.83; volumetric efficiency: 0.52|0.60|0.83). The comparison with in situ data from a forest monitoring plot, established at the end of 2020, indicated good agreement between observed and simulated interception and soil water content. According to our results, WaSiM-ETH is a potential supplement for forest management, owing to its multidimensionality and the ability to model soil water balance for large areas at comparable high spatial resolution. The outputs offer, compared to non-distributed models (like LWF-Brook90), spatial differentiability, which is important for small-scale parceled forests, regarding stand structure and soil properties. Due to the spatial component offered, additional verification possibilities are feasible allowing a reliable and profound verification of the model and its parameterization.

Variations in Bedrock and Vegetation Cover Modulate Subsurface Water Flow Dynamics of a Mountainous Hillslope

“…The model was run for 10 years, with a maximum time step of one day. The first 5 years acted as spin up (Schäfer et al., 2023), where groundwater levels are increasing to constant seasonal dynamics from year 6 onward. The calculated flow velocities of years 6–10 were used to perform particle tracking, with particles being released at 0.5 m intervals across the surface of the modeling domain.…”

Variations in bedrock and vegetation cover modulate subsurface water flow dynamics of a mountainous hillslope

“…The model was run for 10 years, with a maximum time step of one day. The first 5 years acted as spin up (Schäfer et al, 2023), where groundwater levels are increasing to constant seasonal dynamics from year 6 onward. The calculated flow velocities of years 6-10 were used to perform UHLEMANN ET AL.…”

Estimating soil water content in a thorny forest ecosystem by time‐lapse electrical resistivity tomography (ERT) and HYDRUS 2D/3D simulations

“…Gridded physically based models have been applied in forestry ecosystems to cope with spatial heterogeneity (Schäfer et al, 2023).…”

“… determination by mechanistic models has been customarily applied for decades (Eitzinger et al, 2004; Skaggs et al, 2004). Gridded physically based models have been applied in forestry ecosystems to cope with spatial heterogeneity (Schäfer et al, 2023). Point‐scale simulations have been applied successfully to tropical (Casagrande et al, 2021) and temperate (Rabbel et al, 2018) forests with the HYDRUS model.…”