Introduction

This EIFFEL project pilot is focusing on water shortages / droughts and soil carbon in the river catchment of Aa of Weerijs. This medium-sized catchment (346 km²) is transboundary. The upstream part is located in Belgium (199 km²) and the downstream part, which is the focus of this pilot, is located in the Netherlands (147 km²). The brook system of the West-Brabant river Aa of Weerijs is degraded in its capacity for water retention and biodiversity because of former sub-soil drainage and canalisation works. These interventions have been implemented in the past for purposes of flood protection and for enabling agricultural activities. Agricultural lands currently make up about 65% of the Dutch part of the catchment, while natural areas are covering about 23%. The remaining part (12%) of the area is covered by urbanized zones, with buildings and infrastructure.

In recent years, summer droughts have become more severe due to climate change (CC), and the anthropogenic water use in the catchment is highly under pressure. At the same time, agricultural water use is increasing by a rapidly growing tree-nursery export sector. Hot and dry summers, combined with sandy soils that are low in water retention and soil carbon, have led to an increase of water use for irrigation. These pressures are next to high demands for protected and dedicated nature and recreation areas by citizens of Breda, Zundert and Roosendaal. In such conditions, this pilot aims to support the co-design of climate adaptation strategies with Nature-Based Solutions (NBSs), primarily aimed at more water retention in the basin. These strategies will also be tested for their contribution to soil carbon retention. Support for development of the strategies is provided by a hydrological and a soil carbon model. These tools are basis for analyzing future coinditions under selected CC scenarios. The same models are then used to design and compare different adaptation strategies, using selected Key performance Indicators (KPIs).