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961.
962.
Our study describes and evaluates environmental influences on assemblages of aquatic Coleoptera and Heteroptera in artificial ponds situated near Lake Steinhude in Lower Saxony (Germany). We determined temporal dynamics and colonization patterns for 14 ponds of different age. In total, we recorded 4941 individuals that represented 87 species of aquatic beetles and bugs. Between 30 and 40 species were found in most of the ponds. Heteropteran species of the families Corixidae and Notonectidae acted as pioneer species in new ponds, while aquatic coleopterans predominated in older ponds. The results of Canonical Correspondence Analyses (CCA) showed that among the key factors affecting community structure were land use, vegetation cover, water chemistry and the age of the ponds. We found that the distribution of adjacent ponds on areas with different land use has a positive influence on the diversity and abundance of the aquatic insect fauna. 相似文献
963.
Several pressure sensors were deployed in a small lake to determine its storage change. It could be shown that a deep enough deployment and an averaging over a time interval of 1 hour and 5 measuring points allowed for a measurement of 1 or 2 kg/m2 (i.e. 2 mm of water column) of changes in the storage on the scale of the lake size. This accuracy for the lake storage could not be achieved by other methods, especially if conditions were difficult, e.g. snowfall, or in cases when precipitation was small. Finally, the pressure measurement - originally intended to roughly determine the water level - turned out to be a direct measurement of water mass in the lake, which was the proper magnitude for exchanges between atmosphere and lake. Hence the measurement of lake storage could become an interesting approach even for meteorological measurements, such as precipitation and evaporation on a water surface. 相似文献
964.
Airborne light detection and ranging (LiDAR) bathymetry appears to be a useful technology for bed topography mapping of non‐navigable areas, offering high data density and a high acquisition rate. However, few studies have focused on continental waters, in particular, on very shallow waters (<2 m) where it is difficult to extract the surface and bottom positions that are typically mixed in the green LiDAR signal. This paper proposes two new processing methods for depth extraction based on the use of different LiDAR signals [green, near‐infrared (NIR), Raman] of the SHOALS‐1000T sensor. They have been tested on a very shallow coastal area (Golfe du Morbihan, France) as an analogy to very shallow rivers. The first method is based on a combination of mathematical and heuristic methods using the green and the NIR LiDAR signals to cross validate the information delivered by each signal. The second method extracts water depths from the Raman signal using statistical methods such as principal components analysis (PCA) and classification and regression tree (CART) analysis. The obtained results are then compared to the reference depths, and the performances of the different methods, as well as their advantages/disadvantages are evaluated. The green/NIR method supplies 42% more points compared to the operator process, with an equivalent mean error (?4·2 cm verusu ?4·5 cm) and a smaller standard deviation (25·3 cm verusu 33·5 cm). The Raman processing method provides very scattered results (standard deviation of 40·3 cm) with the lowest mean error (?3·1 cm) and 40% more points. The minimum detectable depth is also improved by the two presented methods, being around 1 m for the green/NIR approach and 0·5 m for the statistical approach, compared to 1·5 m for the data processed by the operator. Despite its ability to measure other parameters like water temperature, the Raman method needed a large amount of reference data to provide reliable depth measurements, as opposed to the green/NIR method. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
965.
966.
���������������¶�λ������� 总被引:3,自引:0,他引:3
????????λ???????????(111??120??E??35??42??N)1993??2004??6 771?ε???1.0??M??6.6???????λ???????λ???????????????????????????????????????????????;???o?????·???????????????????????????б???????????????????????????????????20 km????60 km???????25 km??34 km?????40 km;83%???????????λ??0??15 km??Χ?????????????λ???????????????(7??21 km)????????????????????????????????????????????????;???92%???????????λ??1??24 km??????24 km??????????????????????硣 相似文献
967.
胶东半岛地下水库水资源调蓄研究 总被引:1,自引:0,他引:1
胶东半岛是山东省的缺水地区,建设地下水库是提高该区水资源供应能力和改善生态环境的有效措施。该文系统分析了在胶东半岛建设地下水库的可行性及其水资源和生态环境意义,认为该区建设地下水库可大幅度提高水资源调蓄能力,解除海水入侵之患,生态环境得以逐步改善,其水资源效益、环境效益十分明显。 相似文献
968.
哈尔滨市松北区水库雍水浸没评价 总被引:2,自引:0,他引:2
浸没问题是平原型水库主要地质灾害之一。在分析了哈尔滨市松北区雍水浸没成控因素的基础上,采用地下水流数值模拟技术对研究区在不同开采方案下的雍水浸没进行评价,并综合考虑区内的地表覆盖情况、建筑物地基形式等因素,提出了适合研究区水文地质条件的浸没标准:农田区为粉质粘土2.50 m, 粉细砂1.50 m;建筑物区为粉质粘土3.50 m,粉细砂3.00 m。将研究区划分为可能浸没区、过渡浸没区和不发生浸没区,并确定了各浸没区的范围。 相似文献
969.
黄土震陷是地震发生时黄土地区发生的一种灾害。以典型马兰黄土(Q3)作为研究对象,对5组不同深度的原状黄土试样进行室内动三轴震陷试验,研究了该场地黄土震陷性随深度的变化特征。研究结果表明,(1)在天然含水率或是增湿、减湿情况下,黄土震陷深度曲线随动应力的增加均经历了一个从平稳、快速、再收敛至最大震陷深度的发展过程;(2)黄土震陷深度曲线的发展阶段动应力区间不尽相同,随着含水率的增加,黄土震陷快速发展期的动应力区间在变窄,最小动应力值变小,含水率20%条件下比5%最小动应力值可降低30%;(3)典型马兰黄土存在一个最大震陷深度,其最大震陷深度不受动应力、含水率影响,含水率仅能够降低达到最大震陷深度时最小动应力,加速黄土震陷深度的发展进程。在动应力不断增加的情况下,最终的黄土震陷深度曲线收敛于最大震陷深度,本次实验黄土场地的最大震陷深度约为15.5 m。 相似文献
970.