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1.
为解析大型水生植物大量生长情形的源头溪流营养盐滞留的水文、生物作用贡献,于2014年9月—2015年6月在南淝河流域某一芦苇占显著优势的农田源头溪流段,开展8次野外示踪实验,计算渠段雷诺数Re、弗劳德数Fr、曼宁糙率系数n等水动力学参数,估算NH4+、PO43-的总滞留率以及水文、生物过程的实际滞留贡献率和相对滞留贡献率。结果表明,整个研究期间溪流水体表现出显著的紊流特征,水流流态属于缓流类型,渠道曼宁糙率系数n变化范围为0.066~0.112,平均值为0.089;NH4+总滞留损失率变化范围为9.17%~28.27%,平均值为14.68%,水文作用和生物过程对NH4+实际滞留贡献率平均值分别为10.12%和4.57%,相对贡献率平均值分别为72.51%和27.49%,表明NH4+滞留损失主要来自水文过程的影响;PO43-总滞留损失率变化范围为5.75%~17.79%,平均值为12.53%,水文作用和生物过程对PO43-实际滞留贡献率平均值分别为10.12%和2.41%,相对贡献率平均值分别为81.42%和18.58%,表明PO43-滞留损失也主要来自水文因素的影响;n与Re、Fr和Q均呈显著的幂函数关系,而实际滞留率ηNH4、ηPO4与n、Re之间均没有表现出明显的相关关系。 相似文献
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源头溪流是流域污染负荷控制的关键节点。源头溪流接纳流域内输入的污染物后,通过促进污染物在河道内的滞留及消减,降低对流域下游的输出,为下游水域水环境治理减轻压力。本文从暂储理论出发,对源头溪流营养盐滞留的研究进行了综述。介绍了暂储的定义,探讨了影响暂储区的水文、地形地貌及生物因素,分析了暂储区对溪流中营养盐滞留的作用,辨析了目前研究中存在的不足,指出未来宜在国内诸多源头溪流尽快开展相关工作,研究暂储区变化对营养盐滞留的影响机理,从而为下游流域污染负荷削减、河流廊道生态恢复提供支撑。 相似文献
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多级拦水堰坝调控农田溪流营养盐滞留能力的仿真模拟 总被引：2，自引：1，他引：2
为揭示多级拦水堰坝对于低等级小河流营养盐滞留能力的影响,以巢湖流域某一典型的农田源头溪流为对象,在野外示踪实验和计算机模拟的基础上,针对构建的多级简易水坝,采用暂态存储和营养螺旋指标,仿真模拟多级拦水堰坝对于氮磷营养盐滞留能力的调控效果。结果表明:多级拦水堰坝Darcy-Weisbach阻力系数明显超过无堰坝情形,但其弗劳德数Fr和雷诺数Re则较无堰坝情景低些;多级拦水堰坝相应的交换长度Ls值较无堰坝情景低1~2个数量级,水力持留因子Rh则较无堰坝情景明显增大,表明多级拦水堰坝使溪流的暂态存储能力得到很大提升;在多级拦水堰坝情景下,NH4+和PO43-的吸收长度Sw均有大幅度的下降,其中NH4+削减幅度达70.27%~89.47%,PO43-为75.59%~81.92%;不仅如此,在多级堰坝情景下,NH4+和PO43-的物质传输系数Vf、吸收速率U均显著增大,表明多级拦水堰坝可以有效提高农田溪流氮磷营养盐的滞留潜力。 相似文献
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选择Na Cl作为保守性示踪剂、NH4Cl和KH2PO4为添加营养盐,在巢湖流域的二十埠河某一农田源头溪流段,采用恒定连续投加示踪剂的方式,开展野外示踪实验。通过对不同情景下暂态存储参数和营养螺旋指标模拟结果的比较,解析丁坝型挡板对于溪流暂态存储和氮磷滞留能力的调控效果。结果表明:丁坝型挡板使溪流交换系数α显著增大,其中间距为2.5 m的α值较无挡板情景高出132.36%,1.5 m和3.0 m间距则分别高出825.37%和641.29%;相对于无挡板情景,设置挡板的溪流交换长度Ls明显下降,水力持留因子Rh、行进时间中值F200med及过水断面面积和暂态存储区断面面积的比值As/A等出现不同程度的增大;设置挡板的氮磷吸收长度Sw较无挡板情景显著下降,吸收速度Vf则有不同程度的提高。丁坝型挡板对于农田溪流暂态存储和氮磷滞留能力具有很好的调控效果。 相似文献
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潘家口水库是华北地区的重要水源,对保障区域供水安全发挥着重要作用.本文以该水库为研究对象,分析了建库以来水库氮、磷营养盐的时空变化特征、滞留效应.结果表明:建库以来水库TP浓度呈上升趋势,最高达到0.37 mg/L;库区TN、硝酸盐的浓度较高,年际变化小,近15年平均浓度分别为4.4 mg/L、3.5 mg/L,氨氮浓... 相似文献
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农田暗管排水能力分析与提升方法探讨 总被引：2，自引：0，他引：2
在地下水位较高、地表易于形成积水的地区,探索经济可行的农田暗管排水措施,对于降低作物涝渍胁迫、提高作物产量具有重要意义。本文基于暗管排水流量理论公式分析了暗管排水能力影响因素及增强暗管排水能力的途径,提出在暗管出口处安装虹吸管,利用虹吸原理使其下端出流口降低到一定深度的虹吸增流方法。理论和试验表明,该方法可以大大提升浅埋暗管排水能力,且不增加暗管排水成本。浅暗管通过虹吸管出口降低到中埋和深埋时,即作用水头增加1.33倍和1.67倍时,排水流量增大33.3%和66.7%;由于浅埋管具有较小的渗流阻抗系数,其排水流量比相同出口的中埋管和深埋管大16%和27%。随积水层深度的减小,有虹吸的浅暗管排水流量虽然减小,但增流效果百分比在增大。该研究成果可为涝渍灾害易发地区建设高效除涝降渍减灾工程提供新途径。 相似文献
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农田控制排水与补充灌溉对作物产量和排水量影响的模拟分析 总被引：2，自引：0，他引：2
农田控制排水是减少硝态氮流失最直接有效的方法之一。本文利用典型涝渍区-淮北平原砂姜黑土地区实测土壤、气象、作物等资料,用DRAINMOD模型进行了长序列模拟分析,结果显示在当地气象条件下,干旱是影响冬小麦产量的主要因素,而涝渍则是影响棉花产量的主要因素。补充灌溉条件下,采用传统排水与控制排水两种措施的模拟结果显示,灌溉可使冬小麦产量得到大幅提高,但对棉花产量的影响不大。采取控制排水措施后,地下排水量大大减少,排水总量也显著降低,从而有利于区域水质的保护。 相似文献
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The geomorphic template of streams and rivers exerts strong controls on the structure and function of aquatic ecosystems. However, relationships between stream geomorphology and ecosystem structure and function are not always clear and have not been investigated equally across spatial scales. In montane regions, rivers often alternate between canyon‐confined segments and unconfined floodplain segments. Yet, few studies have evaluated how this pattern influences aquatic ecosystems. Here, we compared five confined river segments to five paired floodplain segments in terms of allochthonous inputs, aquatic primary producer and invertebrate production, stream retentive capacity, and aquatic invertebrate community composition. We found that floodplains had a higher (up to 4×) retentive capacity, a greater richness (58%) of aquatic invertebrates, and a distinctly different invertebrate community, relative to confined segments. Contrary to our expectations, allochthonous inputs were approximately 2× greater for confined segments, and aquatic primary and invertebrate production exhibited no consistent differences between segment types. However, results did indicate that floodplains had greater overall community respiration than confined segments. Together, these findings suggest that floodplain and confined segments do indeed differ in terms of aquatic ecosystem structure and function but not entirely as expected. Confined segments had greater allochthonous inputs but a lower capacity to retain those inputs, whereas floodplains had a high capacity to retain transported organic matter and also a more diverse community of invertebrates and higher overall community respiration to ‘digest’ retained organic matter. If these findings are generalizable, then they would indicate that confined segments are sources for organic matter within river networks, whereas floodplains act as filters, removing and processing organic matter transported from upstream confined segments. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
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Jamal Kabir;Giulio Biondi;Kieran J. Gething;Thomas Aspin;Tim Sykes;Rachel Stubbington; 《河流研究与利用》2024,40(5):863-874
Headwater springs and streams often occur in relatively remote areas, reducing their exposure to human influences and thus increasing their collective capacity to support high biodiversity. Their aquatic macroinvertebrate communities can include species of conservation interest, some of which are specialists associated with groundwater inputs, low water temperature or temporary flow. However, the inaccessibility of some spring and stream networks has left their communities poorly characterized, limiting our capacity to implement effective conservation strategies. We characterized the biodiversity and conservation value of macroinvertebrate communities in a network of 51 relatively inaccessible and unimpacted headwater spring and stream sites spanning multiple catchments in a single landscape type: the chalk downland of south England. At each site, we kick sampled macroinvertebrate communities and recorded environmental variables, including flow permanence. To represent each community, we calculated taxa richness, coverage-adjusted Hill-Shannon diversity, the local contribution to beta diversity, and an index of richness and species rarity. We used the latter three metrics to rank sites based on their biodiversity and conservation value and analyzed relationships between metrics and environmental variables. We found specialists of springs, cold waters, groundwaters and temporary flow regimes, including rare species of conservation value. Some metrics responded to environmental variables, but top-ranking sites had highly variable environmental characteristics. We highlight the value of individual headwater streams with contrasting characteristics as contributors to ecologically heterogeneous site networks. Our results can inform landscape-scale management strategies that protect headwaters as refuges that support biodiverse communities, including rare species, as they adapt to global change. 相似文献
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Leaf litter decomposition is an important process providing energy to freshwater biota. Flow regulation and dams can strongly alter freshwater ecosystems, but little is known about the effect of small impoundments on leaf litter decomposition rates in headwater streams. In this study, we examined the effect of small water storage impoundments (80 to 720 m3) on leaf litter decomposition by comparing sites located within 10‐m upstream and downstream of nine impoundments (Rhineland Palatinate, Germany) and sites located further upstream and downstream. The impoundments did not have a statistically significant effect on most physico‐chemical variables. However, the abundance of shredders and leaf litter decomposition rates decreased in study sites located within 10‐m upstream of the area flooded by impoundments. Small impoundments can locally reduce leaf litter decomposition rates in headwater streams. The effect of small impoundments on ecosystem functioning is minor and may require less attention by freshwater managers than other stressors, though this may differ for other ecological aspects such as connectivity. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
11.
The grain sizes of 53 small lateral and mid‐channel deposits were evaluated on the 2.7 km long channel‐reach of a headwater piedmont stream that has been affected by check‐dams and bed sills constructions (ca. 14 constructions per km), riprap bank stabilisations and the removal of instream wood. Such interventions have led to the loss of natural vertically oscillating bedforms, and pool‐riffles have been replaced by plane beds. The evaluated sediment deposits were divided based on their positions relative to grade‐control structures on downstream, intermediate and upstream types. The individual types of deposits produced different downstream trends in the grain sizes that reflected their positions with respect to the grade‐control structures (GCSs). The downstream deposits generally produced slow downstream coarsening, which may point to the increased efficiency of the energy dissipation of the GCSs under a gradual downstream decrease in the channel slopes. However, they were generally not coarser than the other two types. The upstream deposits did not indicate any notable downstream grain‐size trend. Despite the significant downstream decrease in the channel slopes and related bankfull shear stresses at the positions of the intermediate deposits and the lack of a lateral sediment supply in the studied longitudinal profile, the sediment calibre of the deposits did not produce any systematic downstream fining. Thus, the observed grain sizes most likely pointed to the selective scouring of the fine sediments, which was caused by the presence of the GCSs and their effects on the decreasing sediment connectivity. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
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介绍了经典的湖泊生态修复理论在国内外的应用及发展现状,并总结了在该理论指导下实施城市湖泊生态修复过程中,内源及外源性营养盐、光照、浮游植物、底泥、生物扰动等因子对水生植物群落恢复的影响,及其应对策略。针对外源性点源、面源污染多的问题,通过修建污水管网以及人工湿地等水利设施进行控制;内源性污染如底泥,则可采用原位以及异位等处理技术进行控制;对水质产生较大影响的浮游植物可采用物理、化学、生物-生态学方法进行调控;人类干扰、鱼类牧食及其他水生动物、浮游植物等综合作用共同影响水生植物生长、分布。因此,在利用水生植物修复湖泊水体时,必须综合考虑多方面生态因子对其所造成的影响。 相似文献
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The Almbach, a headwater stream in the Upper Austrian foothills of the Alps bordered by mountain pastures was studied to gain insight into the benthic macroinvertebrate community and its habitat. Two springs, one of them fenced in to prevent livestock access, and two more sites of the headwater section were investigated. A discriminant analysis (DA) based on hydrochemistry and phytobenthos revealed three functions with 86% of all samples correctly classified to the four sites. The first function clearly separated the two springs with phosphorus and oxygen as the most important discriminating factors. Spring sites and headwater sites were split up by the second function mainly due to nitrate concentration, but no differences could be detected for the two stream sites. With the exception of the fenced spring, indicator taxa could be assigned to all sites by means of an Indicator Species Analysis (ISA). Polyvalent taxa groups such as Gastropoda and Ostracoda were indicators for the unfenced spring site. This is in accordance to observed low abundances of sensitive plecopteran taxa and suggests a negative impact of livestock trampling on the invertebrate community. Redundancy Analysis explained 99% of the macroinvertebrate‐environment relation. The first axis separated springs from stream sites and was correlated with nitrate, pH, water temperature and phytobenthos eveness. Phosphorus was responsible for splitting the unfenced spring and the downstream station from the fenced spring and the upstream location along the second axis. Ephemeropteran taxa like Habrophlebia sp. were related to elevated pH, increased water temperature and low nitrate concentrations. In accordance to the ISA, nitrate played an important role for tolerant Gastropoda and Ostracoda at the unfenced spring. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献