Streamflow and sediment yield responses of the Wooramel River to future global warming scenarios

[摘要] Shark Bay is a World Heritage Listed 'Property' containing the largest seagrass banks in the world, rare hypersaline environments and Stromatolites of Hamelin Pool. The Stromatolites were formed over millennia by blue-green algae (cyanobacteria) in the Shark Bay’s Hamelin Pool. The seagrasses collect sediments that build a barrier (Faure Sill) around the top of Hamelin Pool, limit in the ocean circulation. The trapped water in the pool evaporates at high rates and due to limited mixing with the wider ocean the water becomes exceptionally salty, creating an ideal environment for the Stromatolites to thrive.The impact of changes in the fluxes of water and sediments associated with changes in the Wooramel River flow regime can have impact on the unique Stromatolites and the Faure Sill.Within the “Caring for Our Country Research Project”, this study examines the Wooramel River flow regime under the present climate and the responses of streamflow and sediment yield to future global warming scenarios. The flow of the Wooramel River is intermittent and is mainly driven by rainfall events associated with occasional low pressure systems, which may include tropical cyclones. An increasing trend was detected in the number of days of tropical cyclone influence per year between 1911 and 2010. However, there are data quality issues that cloud the interpretation of this apparent trend. An increase in high flow (days where flow is above the 90th percentile of the flow distribution) event volumes and durations has been observed for the longer duration flow record of the Gascoyne River (adjacent to the Wooramel River).This trend is consistent with other changes observed in rivers to the north driven by monsoonal weather systems (though the results were not statistically significant).Projected changes (based on the realisation of SRES A2 emission scenario by two selected global climate models) suggest median increases in duration of flood-flows for the Wooramel River of 5-11%, 9-21% and 15-33% for years 2030, 2050 and 2070, respectively. The proportion of total flow occurring as flood flow volumes is predicted to increase with increase in global mean temperature by the output from the two GCMs analysed here.Conversely, the proportions for the low flow volumes exhibit a decreasing trend. Estimation of changes in future sediment yield from the Wooramel River catchment to Shark Bay cannot yet be reliably undertaken due to a lack of appropriate models.However, a shift to a more variable flow regime (even if total flow volumes do not change) the river has the potential to increase the sediment transport capacity of the Wooramel River and hence the fluvial sediment flux to Shark Bay.

[发布日期] 2012-06-12 [发布机构] CSIRO

[学科分类] 地球科学(综合)