Reconstruction of pristine morphology, flow, nutrient conditions and submerged vegetation of lowland river spree (Germany) from palaeomeanders
Reconstruction of pristine morphology, flow, nutrient conditions and submerged vegetation of lowland river spree (Germany) from palaeomeanders
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从古河滨重建低地河流施普雷（德国）的原始形态、流量、营养条件和水下植被
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发表时间：
2008
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通讯作者：
C. Engelhardt
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作者：
S. Hilt;Ilka Schönfelder;A. Rudnicka;Randi Carls;N. Nikolaevich;A. Sukhodolov;C. Engelhardt
《欧洲水框架指令》要求为每种类型的地表沃茨确定参考条件，以此作为建立分类系统的基础，在该系统中必须确定与这种高质量状态的偏差。为了重建斯普雷河下游的原始状态，我们使用古水文学和古湖沼学方法调查了古河道。这一地区的定居历史表明，在公元1700大卡之前的所有时期，人类活动的影响都很小。研究了三个代表亚北陆晚期/亚大西洋早期条件的古河道。利用河曲的横截面重建了平滩阶段的河流宽度和深度。在此基础上，建立了一个参数化模型，用于计算古滩流量。重建显示，与近期条件（分别为35 m和1.6 m）相比，未受干扰的施普雷河下游（平滩阶段平均宽度为20 m，平均深度为0.8 m）的河道更窄、更浅。在重建的亚化石河道中，平滩阶段的流速和流量较小（原始施普雷下游为0.5 m s−1和8 m3 s−1，而近期施普雷下游为0.9 m s−1和52 m3 s−1），流量变异性较高。平滩流量的增加，主要是由于砍伐森林和集水区排水，以及渠化、河岸保护和河流治理措施。沉积物芯底部的有机粉砂含有保存完好的硅藻化石组合。硅藻推断的总磷（DI-TP）浓度为59-73 µg L−1（中位数为62 µg L−1），表明富营养化至肥大状态，并表明自然营养水平略低于今天。这些过去的营养条件，形态和大量的大型化石遗迹表明沉水植物生长的最佳生长条件。结合古水文学和古湖沼学参数被证明是一个有用的方法来确定原始条件的低地河流。版权所有© 2008约翰威利父子有限公司。
The European Water Framework Directive requires the definition of reference conditions for each type of surface waters as a base to establish a classification system in which deviations from this high quality status must be determined. In order to reconstruct pristine conditions in the lower river Spree we investigated palaeomeanders using palaeohydrological and palaeolimnological methods. The settlement history of this region suggests low anthropogenic impact for all periods before ∼700 cal AD. Three palaeomeanders representing the conditions of the late Sub‐boreal/early Sub‐atlantic were investigated. River width and depth at bankfull stage were reconstructed using cross‐sections of the meanders. Based on these data and experiments on the recent river, a parametric model was developed to calculate the bankfull palaeodischarge. Reconstructions show narrower and shallower channels for the undisturbed lower Spree (∼20 m mean width and 0.8 m mean depth at bankfull stage) as compared to recent conditions (35 m and 1.6 m, respectively). Flow velocities and discharge at bankfull stage have been smaller in reconstructed sub‐fossil channels (0.5 m s−1 and 8 m3 s−1 in the pristine lower Spree as compared to 0.9 m s−1 and 52 m3 s−1 in the recent lower Spree) and flow variability was higher. The increase in bankfull discharge was mainly attributed to deforestation and drainage of the catchment as well as channelization, bank protection and river regulation measures. The organic silt at the base of the sediment cores contained well‐preserved fossil diatom assemblages. Diatom‐inferred total phosphorus (DI‐TP) concentrations of 59–73 µg L−1 (median 62 µg L−1) indicate eutrophic to hypertrophic conditions and suggest naturally slightly lower nutrient levels than today. These past nutrient conditions, morphology and large numbers of macrofossil remains indicate optimum growth conditions for submerged macrophytes growth. The combination of palaeohydrological and palaeolimnological parameters proved to be a useful approach for the determination of pristine conditions in a lowland river. Copyright © 2008 John Wiley & Sons, Ltd.