塔里木河流域水资源分析系统开发研究     

张云  左其亭  王小平  凌敏华 《干旱区地理》2006,29(6):823-828

根据水资源评价工作的基本任务和实际需求,充分利用计算机及地理信息系统技术,研究和探讨了塔里木河流域水资源分析系统(T-WRAS)的功能、结构、数据组织及其实现关键技术。同时介绍了降水量—高程量化模型(PEM)、自调节水量模拟模型(SRWQ)、基于“发展综合指标测度”的协调程度量化方法(DD)等一些模型和方法。该系统可对三源流汇流过程进行分析,对研究区进行数量、质量、开发利用及综合评价,评价结果以图、文、表等多种形式表达。系统的框架、建设思路及相关模型的研究有一定的理论和现实意义。  相似文献   

Spatiotemporal variations in vertical gravity gradients at the Campi Flegrei caldera (Italy): a case for source multiplicity during unrest?     

Joachim Gottsmann  Antonio G. Camacho  Kristy F. Tiampo  José Fernández 《Geophysical Journal International》2006,167(3):1089-1096

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Projecting land-use change processes in the Sierra Norte of Oaxaca, Mexico     

Leticia Gmez-Mendoza  Ernesto Vega-Pea  M. Isabel Ramírez  Jos Luis Palacio-Prieto  Leopoldo Galicia 《Applied geography (Sevenoaks, England)》2006,26(3-4):276-290

The objective of study was to explore short-term trends of processes that determine land-use change in Sierra Norte of Oaxaca (SNO), Mexico. Land use and land cover changes (LULCC) were estimated in a complex mosaic of vegetation in the SNO from 1980 to 2000, and projected them to 2020 through a Markovian model. SNO is highly vulnerable to climatic change according to a 2050 GCM scenario. However, 3% annual rate of tropical and temperate forest deforestation from agriculture and livestock encroachment, suggest the threat from land-use change is higher than that from climatic change for this study site. Productive land-use strategies are needed to reduce such high deforestation rates for tropical regions. Controlling deforestation would also reduce short-term effects of CO₂ emissions to the atmosphere. Because of the necessity to evaluate anthropogenic ecosystem changes, it is imperative to separate short-term influences such as deforestation, from long-term influences such as climatic change.  相似文献   

Identification of facies models in alluvial soil formation: The case of a Swiss alpine floodplain     

G. Bullinger-Weber  J.-M. Gobat 《Geomorphology》2006,74(1-4):181-195

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Modelling net erosion responses to enviroclimatic changes recorded upon multisecular timescales     

Nazzareno Diodato   《Geomorphology》2006,80(3-4):164-177

Land use change has been recognized throughout the Earth as one of the most important factors influencing the occurrence of rainfall-driven geomorphological processes. However, relating the occurrence of historical soil erosion rates is difficult because of the lack of long-term research projects in river basins. Also, complex models are not adequate to reconstruct erosion rate changes because they require significant input data not always available on long timescales. Given the problems with assessing sediment yield using complex erosion models, the objective of this study is to explore a parsimonious scale-adapted erosion model (ADT) from the original Thornes and Douglas algorithms, which aims at reconstruction of annual net erosion (ANE) upon multisecular timescales. As a test site, the Calore River basin (3015 km² in southern Italy) provides a peculiar and unique opportunity for modelling erosion responses to climate and land cover changes, where input-data generation and interpretation results were also supported by documented hydrogeomorphological events that occurred before and after land deforestation. In this way, ANE_ADT-values were reconstructed for the period 1675–2004 by using precipitation indexes, complemented by recent instrumental records, and by using land cover statistics from documented agrarian sources. Pulses of natural sedimentation in the predeforestation period have been related to Vesuvius volcanic activity and changes in rainstorm frequency. After deforestation, the basin system became unstable with sudden fluctuations in the hydrogeomorphological regime contributing significantly to increased erosion and, in turn, sediment transport sequences via river drainage towards the Tyrrhenian coast.  相似文献   

Structural and nutritional heterogeneity of riparian vegetation in Patagonia (Argentina) in relation to seasonal grazing by sheep     

V.R. Utrilla  M.A. Brizuela  A.F. Cibils 《Journal of Arid Environments》2006,67(4):661-670

Riparian meadows of southern Patagonia are temporally and spatially heterogeneous habitats. They are thought to play a key role in regulating the dynamics of arid grazed steppes of the region. We conducted a 2-year study with sheep to determine the influence of two grazing conditions (deferment and spring grazing) on structural and nutritional parameters of three vegetation types apparently associated with a soil moisture gradient in a riparian meadow in southern Santa Cruz (Argentina). Spring deferment allowed forage accumulation in very moist and intermediate vegetation types by the beginning of the summer and had no detrimental impact on forage quality. Deferment had no effect on biomass accumulation of the drier vegetation type at our study site. Structural attributes of the vegetation appeared to affect spatial grazing patterns of sheep. Soil-related patchiness, rather than sheep grazing, appeared to control vegetation structure and nutritional value. The proportion of more mesic plant communities in riparian habitats of Patagonia could determine the outcome of plant–animal interactions in these systems. Practical recommendations of grazing capacity in paddocks, or more theoretical considerations of ecosystem dynamics of the Patagonian steppes need to explicitly consider the internal patchiness of riparian habitats.  相似文献   

Determining hypocentral parameters for local earthquakes in 1-D using a genetic algorithm   总被引：1，自引：0，他引：1  

Woohan Kim  In-Kyeong Hahm  Sung Jin Ahn  Dong Hoon Lim 《Geophysical Journal International》2006,166(2):590-600

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Centennial to millennial geomagnetic secular variation     

M. Korte  C. G. Constable 《Geophysical Journal International》2006,167(1):43-52

A time-varying spherical harmonic model of the palaeomagnetic field for 0–7 ka is used to investigate large-scale global geomagnetic secular variation on centennial to millennial scales. We study dipole moment evolution over the past 7 kyr, and estimate its rate of change using the Gauss coefficients of degree 1 (dipole coefficients) from the CALS7K.2 field model and by two alternative methods that confirm the robustness of the predicted variations. All methods show substantial dipole moment variation on timescales ranging from centennial to millennial. The dipole moment from CALS7K.2 has the best resolution and is able to resolve the general decrease in dipole moment seen in historical observations since about 1830. The currently observed rate of dipole decay is underestimated by CALS7K.2, but is still not extraordinarily strong in comparison to the rates of change shown by the model over the whole 7 kyr interval. Truly continuous phases of dipole decrease or increase are decadal to centennial in length rather than longer-term features. The general large-scale secular variation shows substantial changes in power in higher spherical harmonic degrees on similar timescales to the dipole. Comparisons are made between statistical variations calculated directly from CALS7K.2 and longer-term palaeosecular variation models: CALS7K.2 has lower overall variance in the dipole and quadrupole terms, but exhibits an imbalance between dispersion in   g ¹₂  and   h ¹₂  , suggestive of long-term non-zonal structure in the secular variations.  相似文献   

Effects of fracture lineaments and in-situ rock stresses on groundwater flow in hard rocks: a case study from Sunnfjord, western Norway     

Helge Henriksen  Alvar Braathen 《Hydrogeology Journal》2006,14(4):444-461

Systematic field mapping of fracture lineaments observed on aerial photographs shows that almost all of these structures are positively correlated with zones of high macroscopic and mesoscopic fracture frequencies compared with the surroundings. The lineaments are subdivided into zones with different characteristics: (1) a central zone with fault rocks, high fracture frequency and connectivity but commonly with mineral sealed fractures, and (2) a damage zone divided into a proximal zone with a high fracture frequency of lineament parallel, non-mineralized and interconnected fractures, grading into a distal zone with lower fracture frequencies and which is transitional to the surrounding areas with general background fracturing. To examine the possible relations between lineament architecture and in-situ rock stress on groundwater flow, the geological fieldwork was followed up by in-situ stress measurements and test boreholes at selected sites. Geophysical well logging added valuable information about fracture distribution and fracture flow at depths. Based on the studies of in-situ stresses as well as the lineaments and associated fracture systems presented above, two working hypotheses for groundwater flow were formulated: (i) In areas with a general background fracturing and in the distal zone of lineaments, groundwater flow will mainly occur along fractures parallel with the largest in-situ rock stress, unless fractures are critically loaded or reactivated as shear fractures at angles around 30° to σ_H; (ii) In the influence area of lineaments, the largest potential for groundwater abstraction is in the proximal zone, where there is a high fracture frequency and connectivity with negligible fracture fillings. The testing of the two hypotheses does not give a clear and unequivocal answer in support of the two assumptions about groundwater flow in the study area. But most of the observed data are in agreement with the predictions from the models, and can be explained by the action of the present stress field on pre-existing fractures.  相似文献   

Natural and man-induced stress evolution of slopes: the Monte Mario hill in Rome     

F. Bozzano  S. Martino  M. Priori 《Environmental Geology》2006,50(4):505-524

The paper deals with stress-release effects induced by man-made cuts or excavations into natural stiff clay slopes that experienced erosion in response to valley deepening. The study was focused on the Monte Mario hill in Rome (Italy), which formed part of an area of recent urban expansion. The methodology of the study relied on a reference engineering-geology model, which was developed on the basis of site and laboratory data and stress–strain analyses. The latter analyses were carried out with the finite-difference code FLAC 4.0. Numerical modelling was based on a sequential approach, taking into account the main evolutionary stages of the Tiber river valley in Romeȁ9s urban area and then making cuts at the bottom of the slope located south of the Monte Mario Astronomical Observatory. The simulation revealed the stress-release effects that fluvial erosion and excavation fronts have caused on the investigated slopes and their consequent gravitational instabilities. These processes appear with metre-scale displacements, followed by stress-release cracks (actually observed on the slopes under review). In quantifying stress-release deformations, the simulation took into account the possible role of creep in the observed retardation of stress-release effects.Research activities were carried on with the co-operation of Dȁ9Arcangelo A. (Consorzio TREESSE, andrea.darcangelo@libero.it) and Moretti S. (IMG S.r.l. Servizi Tecnici per lȁ9Ingegneria e lȁ9Ambiente, moretti@img-srl.it)  相似文献