Simulated Changes in Seasonal and Low Flows with Climate Change for Irish Catchments

Abstract

We assess changes in the seasonal mean and annual low flows (Q95) for 37 catchments across the Republic of Ireland. Two hydrological models (SMART and GR4J) are trained and evaluated for their ability to capture key hydrological signatures from observations before being forced with bias corrected outputs from 12 Earth System Models from the CMIP6 ensemble. Projected changes are derived for three shared socio-economic pathways (SSP126, SSP370 and SSP585) for the 2020s, 2050s, and 2080s. The results show a wide range of change in all metrics across the catchment sample. While even the direction of change is highly uncertain in spring and autumn, there is a tendency towards increased flows in winter and reduced flows in summer, together with large reductions in annual low flows. Under SSP370, the median reduction in summer flows across catchments for the 2080s simulated by GR4J is −21.3 percent (90 percent CI: 4.8 to −36.9 percent). For Q95, for the 2080s, GR4J returns a median reduction of −20.9 percent (90 percent CI: −2.5 to −38.2 percent), while SMART suggests a median reduction of −21.2 percent (90 percent CI: −6.0 to −36.9 percent). Such changes would pose significant challenges for water management, requiring significant adaptation. Notably, for low flows in particular, significant reductions in emissions under SSP126 result in more moderate future changes, indicating the importance of both adaptation and mitigation to sustainable water management.