The response of river intermittence to projected climate change and associated anthropogenic adaptations

River intermittence is a pivotal characteristic of freshwater systems and holds substantial ecological importance. The alteration of river intermittence due to climate change has raised concerns and has been primarily studied based on changing meteorological conditions. However, the mediating effects of groundwater and the influence of anthropogenic activities induced by climate change remain insufficiently explored.

This study quantitatively assessed the changes in river intermittence under different Shared Socioeconomic Pathways (SSP126, SSP370, SSP585) through the coupling of a fully distributed hydrological model (mHM) and a groundwater model (MODFLOW) up to the 2100s. The methodology was applied to the Bode catchment (3200 km²) in central Germany, one of the driest regions of the country. We evaluated the model from 2000-2024 using the observed data. We investigated the effects of the delayed response of the groundwater table on river intermittency using the inverse Fourier transform of the recharge. Additionally, we examined the impact of increased groundwater extraction on river persistence.

The results indicate that, compared to the reference period (2000–2014), the total active river network is projected to contract by 9.6%, 6.9%, and 3.8% under the SSP585, SSP370 and SSP126 pathways, respectively, by the 2080s. Additionally, the duration when the wetted fraction falls below the mean value of the reference period is expected to increase by 48 days under the SSP126 pathway and by 101 days under the SSP585 pathway in the 2080s. The impact of groundwater recharge delay predominantly affects transient small streams, particularly those experiencing changes in river-groundwater flow direction, with the magnitude of this effect varying based on their distance to the river. While climate-induced drying poses a notable challenge, water extraction is expected to have a more pronounced effect on local stream persistence, albeit within a restricted spatial range.