Harrington Glenn A, Gardner W Payton, Munday Tim J
Commonwealth Scientific and Industrial Research Organisation, Water for a Healthy Country National Research Flagship, Adelaide, SA 5064, Australia.
Ground Water. 2014 Nov-Dec;52(6):837-52. doi: 10.1111/gwat.12124. Epub 2013 Oct 11.
Few studies have investigated large reaches of rivers in which multiple sources of groundwater are responsible for maintaining baseflow. This paper builds upon previous work undertaken along the Fitzroy River, one of the largest perennial river systems in north-western Australia. Synoptic regional-scale sampling of both river water and groundwater for a suite of environmental tracers ((4) He, (87) Sr/(86) Sr, (222) Rn and major ions), and subsequent modeling of tracer behavior in the river, has enabled definition and quantification of groundwater input from at least three different sources. We show unambiguous evidence of both shallow "local" groundwater, possibly recharged to alluvial aquifers beneath the adjacent floodplain during recent high-flow events, and old "regional" groundwater introduced via artesian flow from deep confined aquifers. We also invoke hyporheic exchange and either bank return flow or parafluvial flow to account for background (222) Rn activities and anomalous chloride trends along river reaches where there is no evidence of the local or regional groundwater inputs. Vertical conductivity sections acquired through an airborne electromagnetic (AEM) survey provide insights to the architecture of the aquifers associated with these sources and general groundwater quality characteristics. These data indicate fresh groundwater from about 300 m below ground preferentially discharging to the river, at locations consistent with those inferred from tracer data. The results demonstrate how sampling rivers for multiple environmental tracers of different types-including stable and radioactive isotopes, dissolved gases and major ions-can significantly improve conceptualization of groundwater-surface water interaction processes, particularly when coupled with geophysical techniques in complex hydrogeological settings.
很少有研究调查过由多种地下水来源维持基流的大河河段。本文基于此前在菲茨罗伊河开展的工作，该河是澳大利亚西北部最大的常年河系之一。对河水和地下水进行区域尺度的综合采样，分析一系列环境示踪剂（氦 - 4、锶 - 87/锶 - 86、氡 - 222和主要离子），并对示踪剂在河流中的行为进行后续建模，从而明确并量化了至少三种不同来源的地下水输入。我们明确证实了浅层“本地”地下水的存在，其可能是在近期高流量事件期间补给到邻近洪泛平原下方的冲积含水层中，同时也证实了通过承压自流从深部承压含水层引入的古老“区域”地下水的存在。我们还利用河溪交换以及河岸回流或准河漫滩水流来解释在没有本地或区域地下水输入证据的河段中氡 - 222的背景活度和异常的氯化物趋势。通过航空电磁（AEM）测量获得的垂直电导率剖面为与这些水源相关的含水层结构以及一般地下水质量特征提供了见解。这些数据表明，地下约300米深处的新鲜地下水优先排放到河流中，排放位置与示踪剂数据推断的位置一致。结果表明，对河流进行多种不同类型环境示踪剂（包括稳定和放射性同位素、溶解气体和主要离子）的采样，能够显著改善对地下水与地表水相互作用过程的概念理解，特别是在复杂水文地质环境中与地球物理技术结合使用时。
