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1.
Growing up with rivers? Rivers in London children's worlds 总被引：1，自引：0，他引：1
Susan Tapsell Sylvia Tunstall Margaret House John Whomsley & Phillip Macnaghten 《Area》2001,33(2):177-189
This paper presents the results from exploratory research which set out to investigate London children's perceptions and uses of river environments. Mainly qualitative, multi-method research was carried out in four primary schools with children aged 9–11, focusing on two rivers near to the schools. Rivers were found to be marginal to the children's everyday lives and outdoor play, being perceived as polluted, neglected, and initially dangerous places. However, when experienced on visits observed as part of the research, some of these perceptions changed and rivers were also found to afford many special activities and experiences for the children. The visits were generally seen to have a positive effect on the children's perceptions of rivers, at least in the short term. This suggests that, if managed appropriately, rivers could be potentially rewarding play areas for children. Moreover, children could provide valuable input for river managers in suggesting ways of improving suitable local rivers for increased recreational uses. 相似文献
2.
朱圣钟 《云南地理环境研究》2006,18(5):8-13
历史时期四川凉山地区河流变迁研究在凉山地区研究中尚属薄弱环节，该文对历史时期凉山地区主要河流的水文状况进行了复原性探讨，并对各河流的水文状况的变化进行了研究．认为历史时期凉山地区河流河道变化小．各主要河流流域内的植被日趋萎缩，总体水量呈下降趋势，河流的泥沙含量呈上升趋势，这些变化主要是历史时期凉山地区经济开发力度加大破坏了局部地区的生态环境造成的。 相似文献
3.
吴忱 《地理与地理信息科学》2007,23(3):74-77
分布在华北北部山顶面上的“冰臼”,无论从地理环境、地貌演化,还是从海拔高度方面分析,都不是第四纪大冰盖的证据,而是古地貌面上流水侵蚀的遗迹。它分布在3个海拔高度不同的山地夷平面上和现代河流谷地内,与当时的地理环境和山地的地貌演化密切相关。未构成山地夷平面前准平原上的河流以河网密集的曲流河为主。随着准平原的抬升,河流也开始下切,下切的河流以溯源侵蚀为主。在源头地区的顺直型谷地中,一是河流流速较急,且挟有数量不多、颗粒较粗的砂砾石;二是源头地区大块石较多,容易形成涡流;三是河水不深,丰水期刚刚没过块石,枯水期块石露出水面。在质地不均的岩体(特别是花岗岩)中,挟带砂砾石的涡流在岩面上形成了壶穴。准平原及壶穴最后被抬升到山地的顶部,构成了山地夷平面。 相似文献
4.
滇池不同流域类型降雨径流对河流氮磷入湖总量的影响 总被引：25，自引：5，他引：20
通过对滇池三种不同流域类型的雨季初始期三场降雨径流的汇水河道的入湖口水质和流量监测 ,重点分析了典型城市纳污河流、城乡结合型河道和农业重污染区河道的营养盐携带状况与特征。研究结果表明 :不同流域类型河流的氮磷营养盐入湖总量受降雨过程及特征、流域类型特征、降雨径流流量、径流水营养盐浓度综合控制。城乡结合型河道 (大清河 )有最高的TP、KN (凯氏N)、NH3 N、NO3 N和NO2 N入湖总量 ,三场降雨累积量分别为11374 3、 12 7971 7、 85 36 5 4、 92 3 4和 84 1 2kg ;城市纳污河流 (乌龙河 )有最高的单位面积入湖总量负荷 ,TP、KN、NH3 N和NO2 N分别为 5 35 7、 5 86 0 5、 382 1 9和 2 4 6kg/km2 。 相似文献
5.
CheSalmahMR AbuHassanA AmeiliaZS 《湿地科学》2004,2(1):1-9
Odonata larvae were sampled from 16 tributaries of Kerian River in the Kerian River Basin (KRB) using a kick samphng technique from September 1998 to May 1999 encompassing both rainy and dry seasons. The distribution of odonate genera was significantly different ( F15.16 = 3.99) among rivers in both seasons ( F15.16 = 4.70) at P = 0.05. However, no seasonal influence was detected. Protoneuridae and Libellulidae were the most dominant families in this basin. Other families Gomphidae, Coenagrionidae, Macromiidae, Chlorocyphidae and Calopterygidae, were common but Aeshnidae and Eupheidae were rare. Several common species, Prodasineura autumnalis, Brachythemis contaminata, Macromia gerstaeckeri, Paragomphus, Orthetrum brunneum, Rhinocypha quadrimaculata and Copera marginipes were identified. The calculated values of biological indices ( H‘, D, E, R1 and R2) showed that the dragonfly fauna in this river basin was slightly poor. Varied physieo- chemical parameters of the river possibly as a result of human activities in surrounding areas were found to influence the distribution of the dragonfly larvae in the KRB. This study showed that the KRB provided favorable habitats for Protoneuridae and 1Libellulidae. Two most dominant species Prodasineura autumnalis and Brachythemis contaminata were obviously favoured slightly acidic water of the Kerian river tributaries. 相似文献
6.
Over the past two decades there has been a growing interest in the geomorphological mosaic along large floodplain rivers where channel dynamics are seen to drive habitat-patch creation and turnover and to contribute to high biological diversity. This has required a new perspective on fluvial geomorphology that focuses on biological scales of space and time. This study examines the spatial pattern of surface fine sediment accumulations along a reach of a large gravel-bed river, the Tagliamento River in NE Italy; an area with a moist Mediterranean climate and seasonal flow regime. The study investigates changes in sediment characteristics during the summer low-flow period between April and September. Focussing on five areas representing a gradient from open, bar-braided to wooded island-braided morphologies, the paper demonstrates the importance of riparian vegetation and aeolian–fluvial interactions.Significant contrasts in particle size distributions and organic content of freshly deposited sand and finer sediments were found between sampling areas, geomorphological settings, and sampling dates. In particular, wooded floodplain and established islands supported consistently finer sediment deposits than both open bar surfaces and the lee of pioneer islands, and in September significantly finer sediments were also found in deposits located in the lee of pioneer islands than on open bar surfaces. Overall, the September samples had a greater variability in particle size characteristics than those obtained from the same sites in April, with a general coarsening of the D5 (φ) (i.e., the coarse tail of the particle size distribution). Also in September, crusts of fine sediment (30 μm < D50 < 64 μm) had formed on the surface of some of the open bar and pioneer island deposits within the more open sampling areas along the study reach. These crusts possessed similar particle size characteristics to aeolian crusts found in more arid environments. They were significantly finer than April samples and September subcrust samples obtained from the same sites and had similar particle size characteristics to some samples taken from wooded floodplain, established island surfaces and the lee of pioneer islands that were not crusted.Local climatological and river level data confirm significant wind and rainfall events during a period of consistently low river levels between the April and September sampling periods. These support deflation, deposition and rain wash of finer sediment during the summer, with windblown sediments being deposited on bar surfaces and in the lee of pioneer islands where wood and young trees provide foci for accelerated sedimentation and island growth as well as on marginal floodplains and established islands. We conclude that along braided rivers in moist settings but with a distinct dry season, aeolian reworking of sediment deposits may have a more important role in driving habitat dynamics than previously considered. 相似文献
7.
海南岛,台湾岛河流水化学比较研究 总被引：4，自引：0，他引：4
本文对我国两大岛屿——海南岛和台湾岛河流的主要离子化学及河流的物理和化学侵蚀率进行了比较研究,对两岛河流水化学的共同点和差异及其成因进行了探讨。研究表明,无论是河水离子总量,还是物理侵蚀率和化学侵蚀率,台湾岛均显著地高于海南岛。两岛河水中氯离子含量、物理侵蚀率和化学侵蚀率均为东部水系高于西部水系。 相似文献
8.
Alcemar Rodrigues Martello Carla Bender Kotzian Fernando Erthal 《Journal of Paleolimnology》2018,59(3):309-327
The degree to which a group of fossils reflects the original community from which it was derived can be estimated by comparing living communities with locally accumulated dead remains. Such live–dead approaches (LA/DA) can provide important baseline information on the ecological structure of ancient freshwater systems. This study explored variations in composition, richness, evenness and rank-abundance in live and dead mollusk assemblages recovered from the Ibicuí River Basin, southern Brazil. LA/DA was related to topography, river size, and sediment grain size, separated respectively into plain (altitude 0–100 m) versus slope (100–500 m), small versus medium-large stream orders, and gravel versus sand substrate. Positive correlation between LA and DA species composition was significant only in large rivers. Slope areas showed LA/DA species compositions that were significantly different, whereas the communities from sand and gravel substrates were quite similar. Important factors that affected live/dead similarity in the study area included (1) destruction of thin, fragile shells of dead animals by acidic waters that are common in the region, (2) downstream drift of small spherical shells from species common in slope areas, such as Potamolithus sp., and (3) high abundances of invasive species in the local death assemblage, especially in large rivers. High fidelity in large rivers is caused by the presence of favorable habitats for bivalve communities. Coarse sediments are an important driver of macro invertebrate diversity, acting as shell traps that slow the downstream drift of bivalve remains and improve the preservation of fluvial mollusks. The preservation potential of dead assemblages of the Ibicuí River showed that fossil assemblages are useful tools for recognizing ancient riverscapes, such as flat areas with sandy substrates. 相似文献
9.
本文依托国家自然科学基金青年项目“河水温度对干旱区宽浅型河床渗透系数影响的定量研究”,并梳理了其他相关研究,总结了中国西北干旱区间歇性河流与含水层水量交换研究所面临的基础科学问题及当前所取得的研究进展。主要结论为：以宽浅型沙质河床为基本特征的西北干旱区内陆河流域下游河流,其河床每年经历数次干湿交替与冻融过程。受河水温度与河流水动力条件的影响,河床作为河流与含水层相互作用的重要界面,其渗透性能具有高度时空变异性,已成为河水与地下水水量交换研究的难点与热点。分析指出,在环境变化和当前交叉学科迅猛发展的背景下,以河流与含水层相互作用为核心的潜流带水文学发展面临新的机遇与挑战。 相似文献
10.
利用中国境内红河流域23个气象站点1960-2007年的逐日降水数据,分析流域强降水事件频次和强度的变化特征及其相关影响。结果表明:①强降水频次和强度在空间上表现出由东南向西北逐渐递减的趋势,流域下游的河口-金平-绿春-江城一带为高值区,上游的巍山-南涧-弥渡一带则为低值区。②强降水频次和强度的变化趋势存在空间差异,趋势增加的站点大多分布在李仙江上游、元江中上游和藤条江流域,趋势减少的站点大多分布在李仙江下游、元江下游和盘龙河流域。③从流域整体来看,在α=0.05的显著性水平下,近48年来强降水频次和强度没有明显的上升趋势,频次和强度的趋势变化幅度分别为0.26 days/10a和0.18 mm·day-1/10a;研究时段内频次和强度在时间变化上没有显著突变点。④基于相关统计数据分析强降水变化的影响,表明近20年间强降水频次和强度的增加,增大了局部地区滑坡泥石流、洪涝灾害的风险,河流泥沙含量也随之增加。 相似文献