Land fragmentation due to rapid urbanization in the Phoenix Metropolitan Area: Analyzing the spatiotemporal patterns and drivers   总被引：4，自引：0，他引：4  

Milan K. Shrestha  Abigail M. YorkChristopher G. Boone  Sainan Zhang 《Applied geography (Sevenoaks, England)》2012,32(2):522-531

Rapid urbanization of the Phoenix Metropolitan Area exemplifies the dominant US Southwest urban growth pattern of the past six decades. Using a combination of multitemporal land cover data, gradient analysis, and landscape metrics, we quantify and characterize spatiotemporal patterns of land fragmentation observed in Phoenix. We analyze historical, qualitative data to identify five major socio-ecological drivers critical to understanding the urbanization processes and fragmentation patterns: population dynamics, water provisioning, technology and transportation, institutional factors, and topography. A second objective is to assess the applicability and accuracy of National Land cover Database (NLCD)-—a widely used land cover dataset—-to detect and measure urban growth and land fragmentation patterns in the relatively treeless desert biome of the US Southwest. In contrast to studies in the temperate eastern USA where NLCD has proved inaccurate for detection of exurban development, our study demonstrates that NLCD is a reliable data source for measuring land use in the southwest, even in low-density environments. By combining qualitative analyses of social-ecological drivers with fragmentation analyses, we move toward an improved understanding of urbanization and insights on the human modification framework used widely in land change science.  相似文献   

Shallow groundwater in a middle mountain catchment of Nepal: quantity and quality issues   总被引：1，自引：0，他引：1  

Bhawani S. Dongol  Juerg Merz  Monika Schaffner  Gopal Nakarmi  Pravakar B. Shah  Smita K. Shrestha  Pradeep M. Dangol  Madhav P. Dhakal 《Environmental Geology》2005,49(2):219-229

The use of shallow groundwater in middle mountain catchments of Nepal is a recent development. It was only in early 1998 that a number of dug wells had been constructed in the Jhikhu Khola catchment. But their numbers are rapidly increasing. While it seems to be a good way of accessing additional water resources both for domestic (current) and agricultural purposes (future), it is very important that the groundwater resources are not overexploited. Current dug wells are used to abstract groundwater, which is seasonally being recharged by the abundant monsoon rainfall. The water levels responded rapidly to the rainfall and differed according to the location of the well. The water quality parameters indicated that the water of most of the wells was not suitable for drinking purposes without prior treatment. Microbiological contamination is of particular concern, in addition to the high nitrate and phosphate levels. Some wells show elevated turbidity levels, indicating that there is an interaction between the muddy surface water and the water in the well.  相似文献   

Investigations on different positions of electrodes and their effects on the distribution of Cr at the water sediment interface     

R. Shrestha M. Phil. Ph.D.  R. Fischer Ph.D.  M. Sillanpää D.Sc. 《International Journal of Environmental Science and Technology》2007,4(4):413-420

In most mining areas, significant concentrations of metals such as Pb, Cu, Cr, Zn, Cd, Fe, Mn, Co, Ni, Hg, Ar, halogenated organic compounds and radionuclides are found. Of those, Cr is one of the well-known heavy metals that forms toxic species. It is necessary to study the mobilization and accumulation of Cr at the sediment water interface in an electric field at varying different positions and conditions of the electrode arrangement. The tests were carried out with a natural sediment containing heavy metals from the river Weisse Elster (Germany). The electrokinetic experiments have been performed in columns filled with sediment using electrodes made of conductive polymers (polyethylene with carbon black) at a maximum current density of 0.5 mA/cm². The experimental results suggest that the mobilization and accumulation of Cr highly depends on chemical factors for e.g., pH value, redox potential, respectively redox status and the content of Fe, A1 and organic matter in the soil or sediment. The sorption of Cr (III, VI) is very high in the pH range > 4.5. As expected, a high mobilization of Cr (III, VI) was seen in the case of the experiments with the anode at the sediment, because the pH value was lower than mentioned above. On the opposite, the best conditions for the Cr (III, VI) immobilization is high pH values (cathode at the sediment).  相似文献   

Contaminant Movement Under Pumpage-Recharge Condition in Steady Ground-Water Flow System     

A. Das Gupta  P. R. Onta Shrestha 《Ground water》1986,24(3):342-350

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Diurnal and seasonal variations of meteorology and aerosol concentrations in the foothills of the nepal himalayas (Nagarkot: 1,900 m asl)     

Rudra K. Shrestha  Martin W. Gallagher  Paul J. Connolly 《Asia-Pacific Journal of Atmospheric Sciences》2016,52(1):63-75

A 10-months long monitoring experiment to investigate the diurnal and seasonal variation of aerosol size distribution at Nagarkot (1,900 m asl) in the Kathmadu Valley was carried out as part of a study on katabatic and anabatic influence on pollution dispersion mechanisms. Seasonal means show total aerosol number concentration was highest during post-monsoon season (775 ± 417 cm^?3) followed by pre-monsoon (644 ± 429 cm^?3) and monsoon (293 ± 205 cm^?3) periods. Fine particle concentration (0.25 μm ≤ D_P ≤ 2.5 μm) dominated in all seasons, however, contribution by coarse particles (3.0 μm ≤ D_P ≤ 10.0 μm) is more significant in the monsoon season with contributions from particles larger than 10.0 μm being negligible. Our results show a regular diurnal pattern of aerosol concentration in the valley with a morning and an evening peak. The daily twin peaks are attributed to calm conditions followed by transitional growth and break down of the valley boundary layer below. The peaks are generally associated with enhancement of the coarse particle fraction. The evening peak is generally higher than the morning peak, and is caused by fresh evening pollution from the valley associated with increased local activities coupled with recirculation of these trapped pollutants. Relatively clean air masses from neighbouring valleys contribute to the smaller morning peak. Gap flows through the western passes of the Kathmandu Valley, which sweep away the valley pollutants towards the eastern passes modulated by the mountain - valley wind system, are mainly responsible for the dominant pollutant circulation patterns exhibited within the valley.  相似文献   

Ecopolitical battles at the Tarai frontier of Nepal: an emerging human and environmental crisis     

Shrestha NR  Conway D 《International journal of population geography : IJPG》1996,2(4):313-331

"In Nepal, the drama of human and environmental ills is increasingly being played out in the form of peasants' ecopolitical battles over common land access and control, such as in the Tarai frontier, a region bordering the Gangetic Plain of India. This is a complex battle, pitting peasants' day-to-day survival against environmental security on one front, and against the Nepalese State and its dominant class interests on the other. This article critically dissects this raging battle to gain a clear understanding of its complexities as well as its diverse roots."  相似文献   

Rain Erosion Hazard Evaluated from Microtopographic Erosion Features on Arable Fields and Forest: A Case Study in Nepal     

Lok Bahadur Kunwar  Eelko Bergsma  Drubha Pikha Shrestha 《Geografiska Annaler: Series A, Physical Geography》2003,85(3-4):313-321

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Utilizing Geo-information Tools for Mapping Spatio-temporal Changes in Population of <Emphasis Type="Italic">Prosopis cineraria</Emphasis> (khejri) in Agroforestry System of Arid Western Rajasthan     

P. C. Moharana  Ritu Nagdev  Uday Burman 《Journal of the Indian Society of Remote Sensing》2018,46(3):431-442

The present study is an attempt to assess the spatial variability and the changes in the population of Prosopis cineraia (khejri) trees in the agroforestry systems of arid part of western Rajasthan. This tree is regarded as an important natural resource for the rural livelihood of desert dwellers because of its multifarious uses. The tree populations were mapped in a geographical information system using available information from aerial photographs, google earth images and IRS-LISS-III satellite images to compare their populations between the past and the very recent period. Mapping carried out in a part of Nagaur district in western part of Rajasthan, indicated increase in khejri trees in the region in 2013–2014 compared to 1960s. The number and tree density were higher under irrigated croplands than under rainfed. Increase in rainfall, multiple uses of the tree, societal and scientific support are the key reasons for the observed changes in their population.  相似文献   

Assessment of a hydrologic model's reliability in simulating flow regime alterations in a changing climate   总被引：1，自引：0，他引：1       下载免费PDF全文

Rajesh R. Shrestha  Markus A. Schnorbus  Daniel L. Peters 《水文研究》2016,30(15):2628-2643

It is a common practice to employ hydrologic models for assessing present and future states of watersheds and assess the degree of alterations for a range of hydrologic indicators. Previous studies indicate that the hydrologic model may not be able to replicate some of the indicators of interest, which raises questions on the reliability of model simulated changes. Hence, we initiated a study to evaluate the replicability of the streamflow changes by employing the widely used variable infiltration capacity hydrologic model for sub‐basins and mainstem of the Fraser River Basin, Canada. Given that the hydrologic regime of the region is known to be influenced by teleconnections to the Pacific Decadal Oscillation (PDO) and El Niño–Southern Oscillation (ENSO), we used hydrologic responses to the PDO and ENSO states as analogues for evaluating the model's ability to simulate climate‐induced changes. The results revealed that the qualitative patterns of response, such as lower flows for the warm PDO state compared to the cool state, and progressively higher flows for the warm, neutral and cool ENSO states, were generally well reproduced for most hydrologic indicators. Additionally, while the directions of change between the different PDO and ENSO states were mostly well replicated, the magnitude of change for some of the indicators showed considerable differences. Hence, replicability of both magnitude and direction of change need to be carefully examined before using the simulated indicators for assessing future hydrologic changes, and a reliable replication increases the confidence of projected changes. Copyright © 2016 Her Majesty the Queen in Right of Canada. Hydrological Processes. © 2016 John Wiley & Sons, Ltd.  相似文献   

Fatigue reliability analysis in time domain for inspection strategy of fixed offshore structures   总被引：2，自引：0，他引：2  

T. M. Madhavan Pillai  A. Meher Prasad 《Ocean Engineering》2000,27(2):264

The paper describes a methodology for estimation of reliability of fixed offshore structures with respect to fatigue and extreme stress. The failure criteria for fatigue are formulated using fracture mechanics principle and that for extreme stress using API Code. Advanced Second Moment method is used to find the reliability index. The total life of the structure is divided into a set of stationary sea-states, occurring during storms and described by directional power spectrum. The method has been illustrated through application to a typical jacket platform. Usefulness of the methodology for planning in-service inspections has been highlighted.  相似文献