Reprofiling watercourses to increase groundwater levels and mitigate drought

Abstract

Increasing temperatures and changing precipitation patterns due to climate change are affecting the fresh water availability and causing drought issues globally. The increased drought severity is affecting the livelihoods of people and causing significant economic damage. The elevated sandy soils of The Netherlands are especially affected by the increased drought issues due to the soil composition, elevation, climate and little fresh water inflow. The increased pressure on the fresh water availability due to the changing climate results in declining groundwater levels affecting nature and agricultural areas. The current body of literature on modelling drought mitigation measures is however limited. Therefore this thesis is focused on analysing the effect of drought mitigation measures, in specific reprofiling watercourses, on groundwater levels.

The effect of reprofiling watercourses in the elevated sandy soils of The Netherlands was analysed by applying the groundwater model Amigo on the study area Winterswijk. The effect of reprofiling primary or secondary watercourses were analysed as well as the combined effect of reprofiling both watercourses. Additionally, an analysis has been performed on the effect it has on the agricultural and nature areas. The effect of reprofiling watercourses were analysed based on groundwater characteristics in order to quantify the impact. Raising the river bed and water level of primary watercourses was shown to be most effective in the whole area of Winterswijk but also specifically in the agricultural and nature area. Raising the river bed and water level of both primary and secondary watercourses simultaneously was shown to be overall most effective. The effectiveness of reprofiling either primary or secondary watercourses depend on the water system. A shallow water system dominated with secondary watercourses experiences more effect from reprofiling secondary watercourses. All in all raising the river bed and water level of watercourses while maintaining the same drainage volume resulted in a significant increase of groundwater levels and great contribution to drought mitigation.

While groundwater models are mere a simplification of reality, the results were supported by literature and provided valuable insights for future water management strategies. Nevertheless, reprofiling measures can mitigate drought but also increase nuisance. Therefore, further research is required on different reprofiling measures to find a balance between drought mitigation and preventing nuisance.