Scenario analysis on impacts of climate change on flow and nutrient loads in the Mediterranean Onkaparinga catchment, South Australia: Coupling global climate models with SWAT

摘要

Water limited catchments of Mediterranean regions including South Australia experience already high seasonal variability alternating between dry and wet periods, and are particularly vulnerable to global climate change. Long-term assessments of waterresources of South Australian catchments under the projected climate changes are required as a prerequisite for sustainable water resources management.In this study, the SWAT (Soil and Water Assessment Tool) model is driven by meteorological forecasts of six global climate models (GCM) to assess impacts on flow, total nitrogen (TN) and phosphorus (TP) loads of the Mediterranean Onkaparinga catchment inSouth Australia for 50 years ahead. The GCM focus on two representative concentration pathways (RCPs) that describe possible future emission scenarios, RCP 4.5 (intermediate emission) and RCP 8.5 (high emission). Scenario results for flow and nutrient loads simulated by SWAT for the periods from 2021 to 2045 and from 2046 to 2070 are compared with baseline data from 1981 to 2005.Results for RCP 4.5 indicate that the catchment is likely to experience a decrease in mean annual runoff mainly during the spring season with further decrease for RCP 8.5. Projected mean seasonal nutrient loads follow the trends of flow with even greaterdecrease in terms of percentage. However, uncertainties reflected by varying results for monthly flows and nutrient loads from different GCM projections suggest that results from a single climate model must be interpreted with caution.