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61.
Ajman is a rapidly urbanizing emirate with land development succeeding at a fast pace. This study aims to monitor land use/land cover changes and assesses the impact of these changes on groundwater quality and quantity of the shallow aquifer using multitemporal remote sensing data and geographic information system (GIS). To monitor the land use/land cover changes, the Spectral Angle Mapper (SAM) and the Normalized Difference Vegetation Index (NDVI) algorithms were utilized. The obtained maps were correlated against a set of total dissolved solid (TDS); Mg, Cl, and NO3 groundwater quality index; and depth to the groundwater table maps constructed from groundwater data. The spatial analysis revealed a sharp depletion in groundwater quality and quantity related to the increase in the land use/land cover classes. The mean total TDS is from 21,971 to 26,450 mg/L and depth to groundwater level from ?12.33 to ?17.2 m over a period of 15 years. Maps of normalized difference and groundwater quality sustainability showed that the eastern side of the study area has a high value of groundwater quality sustainability and normalized difference, while the western side of the study area has a minimal value of groundwater quality sustainability and normalized difference. This study is of great assistance for decision makers and land developers to relate to municipal land allotment in rapidly developing regions such as Ajman. 相似文献
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Samy Ismail Elmahdy Mohamed Mostafa Mohamed 《Journal of the Indian Society of Remote Sensing》2016,44(1):1-10
Monitoring new changes in cities adjacent to dynamic sand dunes requires precise classifier technique. Unlike traditional techniques of supervised classification which use training sites, the integration of image transformation tasseled cap and automatic feature extraction module based on spectral signatures has provided to be sensitive and realistic techniques with time and cost effective. The proposed module was applied to Al Ain district, United Arab Emirates (UAE). The module consists of four steps in terms of segmentation, thresholding and clustering and computing attributes. The obtained greenness and classified maps were then enhanced by applying a 3?×?3 Sobel filter. The new changes were detected by combining the multi-temporal greenness and classification maps. Accuracy assessment and quantitative analysis were performed using confusion matrix and ground truthing. The results showed significant increasing in urban and agricultural areas from the year from 1990 to 2000 compared with the period of time from the year 2000 to 2006. The image difference showed that the vegetation and building classes had increased 7.58 and 20.28 km2 respectively. This study showed that image difference and fuzzy logic approach are the most sensitive techniques for detecting new changes in areas adjacent to dynamic sand dunes. 相似文献
64.
José Jorge Nader 《国际地质力学数值与分析法杂志》2013,37(12):1908-1910
In this note, we examine the flow towards a well in a confined aquifer in the presence of an interaction force defined by the sum of three terms, namely, a Darcy term (linear in the velocity), a Forchheimer term (quadratic in the velocity), and an added‐mass term (linear in the acceleration). We obtain the exact dynamic solution for the piezometric head distribution around the well and investigate the relative importance of the non‐Darcian terms. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
65.
Nahla S. El-Shenawy Richard Greenwood Ismail M. Abdel-Nabi Zohour I. Nabil 《Ocean Science Journal》2009,44(2):69-77
Passive sampling could provide the solution to problems associated with costly and time consuming sampling programmes and biomonitoring. Mussels (Mytilus edulis) and Chemcatcher passive sampler were simultaneously analyzed for sequestered pesticides and polychlorinated biphenyls (PCBs) by gas chromatography with mass spectrometry (GC/MSD). The Chemcatcher passive sampler based on a solid phase extraction disc with two types of diffusion-limiting membranes (polyethelene and polysulphone), were also compared. Diuron, atrazine, irgarol and lindane were accumulated in the polysulphone passive sampler in greater concentration than in the mussels or in the other passive samplers with polyethelene limiting-membrane. Mussels can accumulate in their tissue high concentration of non polar compounds such as PCB 52, dieldren and PCB 153; more than the passive sampler with polysulphone membrane. The device with polyethelene limiting membrane has high affinity capacity to concentrate high amount of phenenthrene, dieldrin, PCB 153 and PCB 52, so it acts as a sampler for non-polar compounds. The highest uptake rate of hydrophobic compounds by Chemcatcher was observed for analytes with log octanol-water partition coefficient (KOW) between 4.5 and 7.5. Laboratory-based studies using passive samplers to assess the potential for bioaccumulation could provide robust and reliable information at relatively low cost compared to biomonitoring data. Laboratory data obtained using passive samplers could be related to accumulation under field conditions where field assessments are required. 相似文献
66.
The conditions under which the Saint Venant equations system for unsteady open channel flow, as an initial–boundary value problem, becomes self‐similar are investigated by utilizing one‐parameter Lie group of point scaling transformations. One of the advantages of this methodology is that the self‐similarity conditions due to the initial and boundary conditions can also be investigated thoroughly in addition to the conditions due to the governing equation. The obtained self‐similarity conditions are compared with the scaling relationships that are derived through the Froude similitude. It is shown that the initial–boundary value problem of a one‐dimensional unsteady open channel flow process in a prototype domain can be self‐similar with that of several different scaled domains. However, the values of all the flow variables (at specified time and space) under different scaled domains can be upscaled to the same values in the prototype domain (at the corresponding time and space), as shown in this study. Distortion in scales of different space dimensions has been implemented extensively in physical hydraulic modelling, mainly because of cost, space and time limitations. Unlike the traditional approach, the distinction is made between the longitudinal–horizontal and transverse–horizontal length scales in this study. The scaled domain obtained by the proposed approach, when scaling ratios of channel width and water depth are equal, is particularly important for the similarity of flow characteristics in a cross‐section because the width‐to‐depth ratio and the inclination angles of the banks are conserved in a cross‐section. It is also shown that the scaling ratio of the roughness coefficient under distorted channel conditions depends on that of hydraulic radius and longitudinal length. The proposed scaling relations obtained by the Lie group scaling approach may provide additional spatial, temporal and economical flexibility in setting up physical hydraulic models. Copyright © 2013 John Wiley & Sons, Ltd. 相似文献
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Groundwater exploration and modelling requires hydrological parameters and a large volume of hydrologic database. This study integrates remote sensing and geographic information system (GIS) to map and classify hydrological parameters indicates areas of groundwater recharge and discharge. Bivariate quadratic surfaces with moving window size of 5 × 5 were fitted to the digital elevation model and drainage basins, drainage network, topographic wetness index (TWI) and hydroforms were derived. The eight-direction algorithm (D8) that determines in which neighbouring pixel any water in a central pixel will flow naturally was used to delineate drainage basin and drainage network in the study area. The TWI was used to quantify the effect of local topography on hydrological processes and for modelling soil moisture. The results indicate the presence of intensive of stream network (1336 km2), wettest zones and accumulation zones (63.99 km2) within Wadi Bih, the UAE and Wadi Khasb, Oman, suggesting regional recharge. 相似文献
69.
This study employs two automated algorithms, the topographic fabric and the deterministic eight-node (D8), to reveal near surface geological fractures and their associated paleodrainages network from a 90?m DEM of the Shuttle Topographic Radar Mission sensor. The topographic fabric algorithm, which calculates the slope and aspect which define a vector normal to the earth’s surface and then compute direction cosines of normal vector at each point, was used to auto-detect fault zones. The deterministic eight-node (D8) algorithm, which determines in which neighbouring pixel any water in a central pixel will flow naturally, was used to delineate paleodrainages concealed beneath sand sheets. Seven sets of geological structures were recognized. Their major trends were found to be in the S46°W, S58°W, S81°W, N107°W, N–S, E–W and N152°W and share similar trends of the revealed paleodrainages. The results suggest a strong spatial relationship between the features extracted from DEM and groundwater potential. 相似文献
70.
Operational model for direct determination of evapotranspiration for well watered crops in Mediterranean region 总被引:1,自引:0,他引:1
Direct calculation of actual evapotranspiration ETc based on Penman-Monteith type models gives more accurate values than indirect models, which need the determination of reference evapotranspiration and crop coefficient. However, the direct models need the measurement of weather variables above the crop, which is limiting and not easily feasible in practice. An operational version of a known ETc direct model is described and tested. This new version is based on the determination of the weather variables collected in a standard agro-meteorological station. The original and the operational versions of the ETc model were validated on two crops with contrasting height: soybean (0.8 m) and sweet sorghum (3 m). For soybean, ETc calculated with the two versions gave results very similar at both hourly and daily scales. For sweet sorghum, ETc calculated with the operational version is good at daily scale and not as good, although acceptable, at the hourly scale. 相似文献