Department of Earth and Environmental Sciences, Macquarie University, North Ryde, 2109, NSW, Australia.
Department of Geography and Earth Sciences, Aberystwyth University, Aberystwyth, SY23 3DB, UK.
Sci Rep. 2020 Apr 20;10(1):6653. doi: 10.1038/s41598-020-63622-3.
Rivers provide crucial ecosystem services in water-stressed drylands. Australian dryland rivers are geomorphologically diverse, ranging from through-going, single channels to discontinuous, multi-channelled systems, yet we have limited understanding of their sensitivity to future hydroclimatic changes. Here, we characterise for the first time the geomorphology of 29 dryland rivers with catchments across a humid to arid gradient covering >1,800,000 km of continental eastern and central Australia. Statistical separation of five specific dominantly alluvial river types and quantification of their present-day catchment hydroclimates enables identification of potential thresholds of change. Projected aridity increases across eastern Australia by 2070 (RCP4.5) will result in ~80% of the dryland rivers crossing a threshold from one type to another, manifesting in major geomorphological changes. Dramatic cases will see currently through-going rivers (e.g. Murrumbidgee, Macintyre) experience step changes towards greater discontinuity, characterised by pronounced downstream declines in channel size and local termination. Expanding our approach to include other river styles (e.g. mixed bedrock-alluvial) would allow similar analyses of dryland rivers globally where hydroclimate is an important driver of change. Early identification of dryland river responses to future hydroclimatic change has far-reaching implications for the ~2 billion people that live in drylands and rely on riverine ecosystem services.
河流在水资源匮乏的干旱地区提供了至关重要的生态系统服务。澳大利亚干旱地区的河流地貌多样，从连续的单一河道到不连续的多河道系统都有，但我们对它们对未来水文气候变化的敏感性了解有限。在这里，我们首次对 29 条干旱河流的地貌进行了描述，这些河流的流域范围从湿润到干旱，横跨澳大利亚东部和中部大陆的超过 180 万平方千米。对五种主要冲积河流类型的统计分离和对其现今集水区水文气候的量化，使我们能够确定潜在的变化阈值。到 2070 年（RCP4.5），澳大利亚东部的干旱程度预计将增加，这将导致约 80%的干旱河流跨越从一种类型到另一种类型的阈值，表现为重大的地貌变化。在一些显著的情况下，目前连续的河流（如墨累河、麦金太尔河）将经历向更大不连续性的阶跃变化，其特征是下游河道尺寸和局部末端明显减小。将我们的方法扩展到包括其他河流类型（如混合基岩-冲积河流），将允许在水文气候是变化重要驱动因素的情况下，对全球干旱地区的河流进行类似的分析。早期识别干旱地区河流对未来水文气候变化的响应，对生活在干旱地区并依赖河流生态系统服务的约 20 亿人口具有深远的影响。
