Kreibich Jan, Bino Gilad, Zheng Hongxing, Chiew Francis, Glamore William, Woods Jamie, Kingsford Richard T
Centre for Ecosystem Science, School of Biological, Earth and Environmental Sciences, UNSW Sydney, NSW, 2052, Australia; Water Research Laboratory, School of Civil and Environmental Engineering, UNSW Sydney, NSW, 2093, Australia.
Centre for Ecosystem Science, School of Biological, Earth and Environmental Sciences, UNSW Sydney, NSW, 2052, Australia.
J Environ Manage. 2024 Nov;370:122962. doi: 10.1016/j.jenvman.2024.122962. Epub 2024 Oct 22.
Freshwater ecosystems, including rivers and floodplain wetlands, face severe stress from unsustainable water resources development, with climate change exerting further pressure. This study compares the relative effects of river regulation and projected climate change on river flows to the semi-arid Lowbidgee Floodplain (3250 km), the largest wetland ecosystem on the heavily regulated Murrumbidgee River, Australia's second longest river, within the Murray-Darling Basin. We modelled annual natural streamflow in the lower Murrumbidgee River before major dam constructions and water diversions (1890-1927), linking river flows to runoff from the upper Murrumbidgee catchment. Extending this analysis to the full rainfall-runoff dataset (1890-2018), we compared modelled natural flows to observed river flows affected by dams and water withdrawals. Additionally, we modelled climate change impacts on river discharge and overbank flows, which reduced inundation of riparian habitats. Current river regulation has reduced median annual streamflow by 43% from 2565 × 10 m³ to 1490 × 10 m³ during 1958-2018, relative to modelled natural flows, with a more pronounced 55% reduction in the last three decades (1988-2018). The return period of major overbank flows, essential for river-floodplain habitat connectivity, more than doubled from once every 2.0 years to once every 4.4 years (1916-2018). Mean climate change projections indicated an additional 7-10% decrease in median annual streamflow by 2047-2075, relative to 1977-2005. The annual duration of major floods declined from an average of 11.3 days under natural flow conditions to 4.5 days under the current regulated river flow regime, with a further reduction to 1.6-1.8 days (83-85% decrease) projected by 2047-2075, due to climate change. We recommend prioritising mitigation of river regulation effects, as these pose the most immediate threats to riverine ecosystems, including their native biodiversity, in the Murrumbidgee River catchment. Our 'natural flow' model offers critical insights for shaping environmental policy and managing environmental flows to mimic natural flow regimes, supporting the conservation and restoration of freshwater ecosystems, like the Lowbidgee Floodplain wetlands. Our approach is transferable to other large river systems globally, using available or modelled streamflow data.
包括河流和洪泛平原湿地在内的淡水生态系统，正面临着不可持续水资源开发带来的严重压力，气候变化更是雪上加霜。本研究比较了河流调控和预计气候变化对澳大利亚第二长河墨累-达令盆地内受严格调控的墨累河上最大湿地生态系统——半干旱的洛比奇洪泛平原（3250平方公里）河流水量的相对影响。我们模拟了在大型水坝建设和调水工程之前（1890 - 1927年）墨累河下游的年自然径流量，将河流水量与墨累河上游集水区的径流量联系起来。将此分析扩展到完整的降雨 - 径流数据集（1890 - 2018年），我们将模拟的自然流量与受水坝和取水影响的实测河流水量进行了比较。此外，我们还模拟了气候变化对河流流量和漫滩流量的影响，这减少了河岸栖息地的淹没。相对于模拟的自然流量，当前的河流调控已使1958 - 2018年期间的年平均径流量中位数从2565×10立方米降至1,490×10立方米，减少了43%，在过去三十年（1988 - 2018年）减少更为显著，达55%。对于河流 - 洪泛平原栖息地连通性至关重要的主要漫滩流量的重现期，从每2.0年一次增加到每4.4年一次（1916 - 2018年），增加了一倍多。平均气候变化预测表明，到2047 - 2075年，年平均径流量中位数相对于1977 - 2005年将再减少7 - 10%。由于气候变化，主要洪水的年持续时间从自然流量条件下的平均11.3天降至当前调控河流水流状态下的4.5天，预计到2047 - 2075年将进一步降至1.6 - 1.8天（减少83 - 85%）。我们建议优先减轻河流调控的影响，因为这些影响对墨累河流域的河流生态系统，包括其原生生物多样性，构成了最直接的威胁。我们的“自然流量”模型为制定环境政策和管理环境流量以模拟自然水流状态提供了关键见解，有助于保护和恢复像洛比奇洪泛平原湿地这样的淡水生态系统。我们的方法可通过使用现有的或模拟的水流数据应用于全球其他大型河流系统。
