School of Earth, Atmosphere and Environment, Monash University, Clayton, VIC 3800, Australia.
School of Earth, Atmosphere and Environment, Monash University, Clayton, VIC 3800, Australia.
Sci Total Environ. 2021 Dec 20;801:149725. doi: 10.1016/j.scitotenv.2021.149725. Epub 2021 Aug 18.
Documenting the distribution, sources and fluxes of baseflow discharge into rivers is important for their management and for maintaining ecosystem health. This study uses major ion geochemistry, Rn, and H to differentiate between the input of low-salinity near-river waters (bank storage and return waters and/or interflow) and regional groundwater in an intermittent river from southeast Australia that is undergoing long-term changes in flow resulting from climate change. Baseflow discharge calculated by Rn mass balance was up to 1.3 m/m/day in the high flow period in July 2019 and up to 0.1 m/m/day at low flow conditions in November 2019. The distribution of Rn activities implies higher baseflow fluxes in the upper and middle reaches that have relatively steep topography and higher hydraulic gradients. The lower reaches received less baseflow due to subdued topography and fine-grained sediments. The observation that Cl concentrations did not increase uniformly downstream, however, implies that much of the baseflow may comprise bank return flow or interflow. This conclusion is also consistent with water mass balance calculations and the observation that H activities (1.85-3.00 TU) in the river were higher than in the groundwater (<0.45 TU). Intermittent streams are likely to be less well connected to regional groundwater, and thus near-river water stores will be more important in sustaining streamflow during dry periods than regional groundwater. These rivers and their ecosystems may be less susceptible to the impacts of groundwater extraction and the near-river waters will provide a buffer zone from potentially contaminated regional groundwater. However, these near river stores are vulnerable to short-term climate variability, and changes to flow regimes resulting from climate change may significantly impact water supplies and ecosystem health.
记录基流排放到河流中的分布、来源和通量对于河流的管理和维持生态系统健康非常重要。本研究使用主要离子地球化学、Rn 和 H 来区分低含盐度近河水源（河岸储存水和回流水以及/或壤中流）和澳大利亚东南部间歇性河流中区域地下水，该河流由于气候变化导致长期流量变化。2019 年 7 月高流量期间，通过 Rn 质量平衡计算的基流排放量高达 1.3 m/m/天，2019 年 11 月低流量条件下高达 0.1 m/m/天。Rn 活度的分布意味着在上游和中游具有相对陡峭地形和较高水力梯度的地方，基流通量较高。由于地形平缓和细粒沉积物，下游接收的基流量较少。然而，Cl 浓度并没有沿下游均匀增加的观察结果表明，大部分基流可能由河岸回流或壤中流组成。这一结论也与水质量平衡计算和 H 活度（1.85-3.00 TU）在河流中高于地下水（<0.45 TU）的观察结果一致。间歇性溪流与区域地下水的连通性可能较差，因此在干旱时期，近河水源对于维持溪流流量比区域地下水更为重要。这些河流及其生态系统可能不容易受到地下水开采的影响，近河水源将为可能受到污染的区域地下水提供缓冲区。然而，这些近河水源易受短期气候变化的影响，气候变化导致的流量变化可能会对供水和生态系统健康产生重大影响。
