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首页> 外文期刊>Journal of Geophysical Research. Biogeosciences >River-floodplain exchange and its effects on the fluvial oxygen regime in a large tropical river system (Kafue Flats, Zambia)
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River-floodplain exchange and its effects on the fluvial oxygen regime in a large tropical river system (Kafue Flats, Zambia)

机译：大型热带河流系统（赞比亚卡富特平原）中的河漫滩交换及其对河流氧气状况的影响

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摘要

Hydrological exchange between a river and its floodplain plays a critical role in maintaining key ecosystem services like habitat formation, nutrient transformation, and flood attenuation. We studied the spatial and temporal patterns of river-floodplain exchange in the Kafue Flats, a 6500-km 2, dam-impacted floodplain ecosystem in Zambia. In addition, we characterized the effects of floodplain runoff on river biogeochemistry and assessed dam-related changes in the hydrological regime. The basic flood pulse concept poorly describes conditions in the Kafue Flats. Instead, high resolution measurements of discharge and tracers (specific conductivity, δ ~(18)O-H _2O) along 410 km of river revealed substantial spatial variations in both the magnitude and direction of river-floodplain exchange. During peak discharge, a river channel constriction, 230 km into the floodplain, diverted as much as 80% of the river's ～700 m ~3 s ~(-1) discharge into the floodplain. As a net result, >80% of the water exiting the Kafue Flats via the river, either passed through the floodplain or originated from precipitation on the floodplain. This floodplain-derived water had a strong impact on river water quality, resulting in a seasonally recurring sharp decline in dissolved oxygen levels to <50 M that persisted for 150 km downstream. A comparison with historical flow data showed that concurrent bank overflow and floodplain inflows were a sustained pattern during the wet season. However, lateral exchange over an annual cycle has been reduced by as much as 50% due to dam operation.
机译：河流及其洪泛区之间的水文交换在维持重要的生态系统服务（例如栖息地形成，养分转化和洪水衰减）方面发挥着至关重要的作用。我们研究了Kafue Flats中河水漫滩交换的时空格局，Kafue Flats是赞比亚一个6500 km 2，受大坝影响的洪泛区生态系统。此外，我们表征了洪泛区径流对河流生物地球化学的影响，并评估了水文状况中与大坝相关的变化。基本的洪水脉冲概念很难描述Kafue Flats中的情况。取而代之的是，沿着410 km的河流进行了高分辨率的排泄物和示踪剂测量（比电导率，δ〜（18）O-H _2O），显示了河漫滩交换的幅度和方向都存在很大的空间变化。在洪峰排放期间，进入洪泛区230公里的一条河道收缩，将河流〜700 m〜3 s〜（-1）洪流中的80％转移到洪泛区。最终结果是，超过80％的水通过河流从Kafue Flats流出，要么流过洪泛区，要么源于洪泛区的降水。这种洪泛区衍生的水对河水水质有很大影响，导致季节性溶解氧水平急剧下降至<50 M，并持续下游150 km。与历史流量数据的比较表明，在雨季，同时发生的银行溢流和洪泛区流入是持续的模式。但是，由于大坝运行，一年周期的横向交换量减少了多达50％。

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