Impact of Climate Change on Surface Runoff for Myponga Reservoir Catchment in South Australia, Australia

Aims: This paper is aimed to assess the future impact of climate change on some selected climatic variables and on surface runoff from Myponga catchment, South Australia.

Methodology: The six global climate models recommended for South Australia were compared among each other based on their performance to simulate observed climates in the study area. The monthly average statistically downscaled evapotranspiration and rainfall data for the period 2000-2005 were compared with respective observed climate data, graphically and statistically. On the other hand, four hydrological models in Australian rainfall-runoff library (RRL) were evaluated and compared among each other based on their performance in simulating surface runoff in the study area. Then, two GCMS, CanESM2 and MIROC5, and one hydrological model, AWBM, were selected for their better performance and used for climate projections and for runoff simulation for both base period (1990-2005) and future period (2026-2035) under two emission scenarios (RCP 4.5 and RCP 8.5), respectively. Finally, the impacts of climate change were estimated by comparing the long year’s average values of the climate projections and simulated runoff in the base and the future periods for different percentile values (10th, 50th, and 99th) under the two emission scenarios.

Results: The result showed that compared to the base period (1990-2005), by 2030s (2026-2035), for both climate models, two emission scenarios, and all the percentiles, the average annual evapotranspiration would generally increase, but the average annual rainfall would decrease. The average annual runoff showed different patterns across the climate model and emission scenarios. But, on average, percentage changes across climate models show a rise in average annual runoff in the range from 3.72 to 5.47 % across percentiles for the intermediate scenario and decline in the range from 17.13 to 20.15 % across percentiles for the high emission scenario.

Conclusion: It is expected that by 2030 there would be no significant problem with respect to water availability, drought, and flooding at an annual time scale under the intermediate emission scenario but there would be drier conditions in the catchment relative to the base period under the high emission scenario.

Recommendation: Therefore, adaptation and mitigation measures should be identified and applied at national and state levels to minimize possible negative impacts in the Myponga reservoir catchment.