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961.
3个时期骆马湖大型水生植物的分布及变化 总被引：2，自引：0，他引：2
大型水生植物对湖泊的生物地球化学循环具有重要影响.一方面,大型水生植物在生长过程吸收营养;另一方面,其通过向水体释放氧气而影响磷元素以及其他相关因子,进而影响磷元素的生物地球化学循环.为了从宏观上了解骆马湖生态系统变化,以1990年9月20日、2000年5月2日和2008年10月15日Landsat TM/ETM+影像为主要数据源,以大型水生植物的归一化植被指数(NDVI)为测试变量,运用分类回归树(classifica-tion and regression tree,CART)方法确定分割阈值,通过构建知识决策树的方法识别骆马湖大型水生植物动态变化特征.3个时期的遥感分类的总体精度与kappa系数分别为92.28％和0.87、91.73％和0.86、93.38％和0.88,因此,该方法的分类精度完全满足骆马湖水生植物分布及变化的研究.研究结果表明,骆马湖大型水生植物分布面积由1990年的55.461 6 km2,减少到2000年的41.801 4 km2,2008年又增加到79.065 km2;大型水生植物主要分布在骆马湖北部河湖交汇区;人类活动干扰是造成骆马湖大型水生植物分布面积发生变化的主要原因. 相似文献
962.
963.
Timothy R. H. Davies Jeff Warburton Stuart A. Dunning Alodie A. P. Bubeck 《地球表面变化过程与地形》2013,38(11):1261-1268
Threlkeld Knotts (c. 500 m above sea level) in the English Lake District has hitherto been considered to be a glacially‐modified intrusion of microgranite. However, its surface features are incompatible with glacial modification; neither can these nor the subsurface structures revealed by ground‐penetrating radar (GPR) be explained by post‐glacial subaerial processes acting on a glacially‐modified microgranite intrusion. Here we re‐interpret Threlkeld Knotts as a very large post‐glacial landslide involving the microgranite, with an estimated volume of about 4 × 107 m3. This interpretation is tested against published and recent information on the geology of the site, the glacial geomorphic history of the area and newly‐acquired GPR data. More than 60 large post‐Last Glacial Maximum (LGM) rock–slope failures have significantly modified the glaciated landscape of the Lake District; this is one of the largest. Recognition of this major landslide deposit in such a well‐studied environment highlights the need to continuously re‐examine landscapes in the light of increasing knowledge of geomorphic processes and with available technology in currently active or de‐glaciating environments. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
964.
Abstract The Coupled Routing and Excess STorage model (CREST, jointly developed by the University of Oklahoma and NASA SERVIR) is a distributed hydrological model developed to simulate the spatial and temporal variation of land surface, and subsurface water fluxes and storages by cell-to-cell simulation. CREST's distinguishing characteristics include: (1) distributed rainfall–runoff generation and cell-to-cell routing; (2) coupled runoff generation and routing via three feedback mechanisms; and (3) representation of sub-grid cell variability of soil moisture storage capacity and sub-grid cell routing (via linear reservoirs). The coupling between the runoff generation and routing mechanisms allows detailed and realistic treatment of hydrological variables such as soil moisture. Furthermore, the representation of soil moisture variability and routing processes at the sub-grid scale enables the CREST model to be readily scalable to multi-scale modelling research. This paper presents the model development and demonstrates its applicability for a case study in the Nzoia basin located in Lake Victoria, Africa. Citation Wang, J., Yang, H., Li, L., Gourley, J. J., Sadiq, I. K., Yilmaz, K. K., Adler, R. F., Policelli, F. S., Habib, S., Irwn, D., Limaye, A. S., Korme, T. &; Okello, L. (2011) The coupled routing and excess storage (CREST) distributed hydrological model. Hydrol. Sci. J. 56(1), 84–98. 相似文献
965.
ABSTRACTWith global climate change and impacts of human activity, the water cycle, which has a close relationship with local water resources, has changed rapidly. Based on different greenhouse gas emission scenarios, five relatively independent global climate models are selected from 47 CMIP5 models to simulate future climatic conditions. Data are downscaled to the local projection, with bias neutralized before applying them to the hydrological models, by which availability of future water resources are calculated for the Dongting Lake basin. The results show that the water resources of the Dongting Lake basin are likely to increase in the future, but be distributed more unevenly. All scenarios indicate that water availability will increase during the flood season and decrease during the dry season, with a prominent increase in annual discharge. The scenarios also predict that the greater the greenhouse gas emissions, the more uneven the water distribution becomes. Overall, the water resources of the Dongting Lake catchment show the same increasing and unevenly distributed trend in the future, which could be further accelerated by human activities.
Editor Z.W. Kundzewicz; Associate editor Q. Zhang 相似文献
966.
《水文科学杂志》2013,58(1):98-99
Abstract Lake Poopó, within the large Altiplano basin of Bolivia, is connected upstream to Lake Titicaca and downstream to the salares, the big salt fields. Small changes in precipitation and river inflows strongly affect the extent of the lake surface area. For times when there are no satellite images, it is difficult to determine the extent of the lake from observations. Water balance computations were performed to create a water-level series for Lake Poopó extending back in time. The dominant water inflow to Lake Poopó is from the River Desaguadero, which constitutes the outflow of Lake Titicaca. The water-balance computations confirm the crude peasant knowledge about historical lake status. It is found that if the lake level is less than 1 m during the wet season, there is a risk that this shallow lake dries out in the dry season. 相似文献
967.
《水文科学杂志》2013,58(2):363-374
Abstract Lake ?uvintas, located in southern Lithuania in the Dovin? River basin, is one of the largest lakes and oldest nature reserves in the country. However, changes in the hydrology of the Dovin? River basin, caused by large-scale land reclamation and water management works carried out in the 20th century, have resulted in a significant decrease in the biodiversity of the lake and surrounding wetlands. In order to halt the ongoing deterioration of the lake and wetlands, solutions have to be found at the basin level. Using the SIMGRO model, various measures were therefore analysed to evaluate their impact on the water management in the Dovin? River basin. The results show that it is impossible to fully restore the water dynamics and flow pattern in the Dovin? River to their original state. However, a good measure for improving the hydrological conditions is to block drainage ditches and remove bushes and trees from the wetlands. 相似文献
968.
Roberto E. Galindo Domínguez William L. Bandy Carlos A. Mortera Gutiérrez José Ortega Ramírez 《Geofísica Internacional》2013,52(3):261-275
In August 2009, a marine geophysical survey was conducted in Lake Tequesquitengo (located in the state of Morelos, Mexico) to delineate the extent of the remains of a small town that has been submerged since the mid 19th century. The survey consists of the acquisition and mapping of magnetic, single beam bathymetric and side-scan sonar data. A dual receiver marine GPS navigation system was used to position the boat during the survey. Except for the larger structural remains that are visible on the side scan sonar images, the magnetic anomaly map proved to be most useful in delineating the extent of the town. These anomalies exhibit short wavelength components in the area surrounding a submerged church, with the shortest wavelength components being confined to the area immediately east of the church. These short wavelength components are only observed near the church; therefore, we propose that they delineate the buried remnants of the submerged town. 相似文献
969.
In this paper, the vertical variations of heavy metal elements (including Cd, Cr, Cu, Hg, Mn, Ni, Pb, and Zn) in the sediments of Songhua Lake are analyzed using sediment cores. A 70‐year evolutionary history of these heavy metal elements in Songhua Lake is described and the sources of the heavy metals in the sediments are investigated by evaluating the pollution characteristics of the metals in terms of their enrichment coefficients and geoaccumulation indexes. The results indicate that Cr, Cu, Mn, Ni, Pb, and Zn in the sediments originated mainly from basin erosion and were transported to the lake by rivers. Cd and Hg in the sediments also originated from basin erosion that occurred prior to the mid‐1990s, and these sediments have since been overlaid by artificial pollution. The distribution of heavy metals in the sediments of Songhua Lake is influenced by many factors, including sediment composition, the relative importance of fluvial input, and artificial pollution. 相似文献
970.
Human‐induced and natural interruptions with continuous streams of observational data necessitate the development of gap‐filling and prediction strategies towards better understanding, monitoring and management of aquatic systems. This study quantified the efficacy of multiple non‐linear regression (MNLR) versus artificial neural network (ANN) models as well as the temporal partitioning of diurnal versus nocturnal data for the predictions of chlorophyll‐a (chl‐a) and dissolved oxygen (DO) dynamics. The temporal partitioning increased the predictive performances of the best MNLR models of diurnal DO by 45% and nocturnal DO by 4%, relative to the best diel MNLR model of diel DO ($r_{{\rm adj}}^{2} = 68.8\%$ ). The ANN‐based predictions had a higher predictive power than the MNLR‐based predictions for both chl‐a and DO except for diurnal DO dynamics. The best ANNs based on independent validations were multilayer perceptron (MLP) for diel chl‐a, generalized feedforward (GFF) for diurnal and nocturnal chl‐a, MLP for diel DO, GFF for diurnal DO, and MLP for nocturnal DO. 相似文献