Evaluation of riparian forest water supply with groundwater monitoring and numerical modelling

Riparian zone forests are a special type of agro-forestry systems. As buffer zones protect stream systems against stress factors. These ecosystems are diverse so ecologically valuable, on the other hand, they are valuable (because of high productivity) from an economic viewpoint as well.

Riparian forests are very vulnerable because they strongly depend on surplus water (shallow groundwater or seasonally flooded condition). Long drought periods caused by changing climate induce lowering of the water table and shortening flooded periods. With reasonably designed water supply systems, these negative processes can be stopped, and valuable ecosystems can be preserved.

The effect of an artificial structures (new lakes and bottom thresholds) induced water supply was evaluated in Kaszó Forest (Somogy county, Hungary). Eco-Hydrological monitoring (groundwater and phenological) was conducted on 14 regular (under the effect of water supply interventions) and 4 control plots in different forest ecosystems. The impact of water supply interventions was interpreted with spatio-temporal groundwater level difference analysis and found that surplus water had a positive effect on the riparian zone water table (40-50 cm rise in the neighbourhood of new lakes) and vegetation.

A complex field monitoring (hydro-meteorological and phenological measurements) was conducted on three representative locations. 1-D Hydrus model was successfully calibrated for an alder and two common oak forest plots. Diurnal signal of groundwater levels was used for ET estimation in the model. Model results showed that groundwater uptake of forest vegetation was significantly increased (30%) regarding water supply interventions.

Acknowledgements: The research was supported by EFOP-3.6.2-16-2017-00018 in University of Sopron project.

Keywords: riparian forest, water supply, groundwater monitoring, 1-D Hydrus model