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541.
Pervaiz Sikandar Allah Bakhsh Muhammad Arshad Tariq Rana 《Environmental Earth Sciences》2010,60(5):1113-1129
A geoelectrical resistivity survey using vertical electrical sounding (VES) was conducted at Chaj Doab (land between rivers
Jhelum and Chenab, Pakistan) and Rachna Doab (land between rivers Chenab and Ravi, Pakistan), with the objective of investigating
groundwater conditions. A total of 90 sites were selected with 43 sites in Chaj and 47 sites in Rachna Doabs. The resistivity
meter (ABEM Terrameter SAS 4000, Sweden) was used to collect the VES data by employing a Schlumberger electrode configuration,
with half current electrode spacings (AB/2) ranging from 2 to 180 m and the potential electrode (MN) from 1 to 40 m. The field
data were interpreted using the Interpex IX1D computer software and the resistivity versus depth models for each location
was estimated. The outputs of subsurface layers with resistivities and thickness presented in contour maps and 3-D views by
using SURFER software were created. A total of 102 groundwater samples from nearby hydrowells at different depths were collected
to develop a correlation between the aquifer resistivity of VES and the electrical conductivity (EC) of the groundwater and
to confirm the resulted geophysical resistivity models. From the correlation developed, it was observed that the groundwater
salinity in the aquifer may be considered low and so safe for irrigation if resistivity >45 Ω m, and marginally fit for irrigation
having resistivity between 25 and 45 Ω m. The study area has resistivities from 3.9 to 2,222 Ω m at the top of the unsaturated
layer, between 1.21 and 171 Ω m, in the shallow aquifers, and 0.14–152 Ω m in the deep aquifers of the study area. The results
indicate that the quality of groundwater is better near the rivers and in the shallow layers compared to the deep layers. 相似文献
542.
Water Resources - Hydrological runoff prediction in a reliable and precise manner contributes significantly to the optimal management of hydropower resources. Considering the importance of runoff... 相似文献
543.
Stephan Schulz Rike Becker Juan Carlos Richard-Cerda Muhammad Usman Tim aus der Beek Ralf Merz Christoph Schüth 《水文研究》2021,35(3):e14077
Information on water balance components such as evapotranspiration and groundwater recharge are crucial for water management. Due to differences in physical conditions, but also due to limited budgets, there is not one universal best practice, but a wide range of different methods with specific advantages and disadvantages. In this study, we propose an approach to quantify actual evapotranspiration, groundwater recharge and water inflow, i.e. precipitation and irrigation, that considers the specific conditions of irrigated agriculture in warm, arid environments. This approach does not require direct measurements of precipitation or irrigation quantities and is therefore suitable for sites with an uncertain data basis. For this purpose, we combine soil moisture and energy balance monitoring, remote sensing data analysis and numerical modelling using Hydrus. Energy balance data and routine weather data serve to estimate ET0. Surface reflectance data from satellite images (Sentinel-2) are used to derive leaf area indices, which help to partition ET0 into energy limited evaporation and transpiration. Subsequently, first approximations of water inflow are derived based on observed soil moisture changes. These inflow estimates are used in a series of forward simulations that produce initial estimates of drainage and ETact, which in turn help improve the estimate of water inflow. Finally, the improved inflow estimates are incorporated into the model and then a parameter optimization is performed using the observed soil moisture as the reference figure. Forward simulations with calibrated soil parameters result in final estimates for ETact and groundwater recharge. The presented method is applied to an agricultural test site with a crop rotation of cotton and wheat in Punjab, Pakistan. The final model results, with an RMSE of 2.2% in volumetric water content, suggest a cumulative ETact and groundwater recharge of 769 and 297 mm over a period of 281 days, respectively. The total estimated water inflow accounts for 946 mm, of which 77% originates from irrigation. 相似文献
544.
Abstract Isotopic compositions of He, Ne and Ar were measured on Plio–Quaternary alkaline basalts of Marib–Sirwah and Shuqra volcanic fields in Yemen, south-western Arabian Peninsula. Very high 3 He/4 He isotope ratios were found in olivine phenocrysts of some Quaternary alkaline basalts in both volcanic fields, located on the margin of the dispersed Afar mantle plume, compared with the Afar–Ethiopian province in the center of the mantle plume. This suggests that the Afar mantle plume source may consist of common component (C or focal zone (FOZO)) with variable primordial 3 He/4 He ratio rather than high μ mantle (HIMU) component. The three component mixing C as the Afar mantle plume, depleted mantle (DM) as upper mantle and lithospheric mantle with a hybrid enriched mantle I–II (EM I–EM II) characteristics may be adequate to explain He–Sr–Nd–Pb isotope variation for the Afar–Arabian Cenozoic volcanics. The occurrence of high 3 He/4 He ratios in the Marib–Sirwah volcanic field appears to show that the primitive basaltic magma, derived from the margin of the dispersed trous-like Afar mantle plume during 15–0 Ma, was not by contamination of lithospheric and upper mantle materials in comparison with that from the center of the Afar mantle plume as a result of relatively low thermal anomaly. 相似文献
545.
A new Local Ocean Tide Model, has been produced for the Exclusive Economic Zone (EEZ) of Malaysia, which incorporates some of the latest TOPEX/POSEIDON data for the years 1992 to 1998. Local tide gauge data are used as a comparison, along with another leading Global Ocean Tide Model, Ori96. The leading diurnal and semidiurnal constituents M2, S2, N2, K1, O1, P1 and Q1 are reproduced using TOPEX/POSEIDON Sea Surface Heights (SSH) in a response analysis type least squares derivation following Munk and Cartwright (1966). 相似文献
546.
Population pressure, agricultural intensification and changes in rural systems in Bangladesh 总被引:1,自引:0,他引:1
Abu Muhammad Shajaat Ali 《Geoforum》2007,38(4):720-738
Sustainable agricultural growth is the key to rural system changes that include changes in rural bio-physical environment, economic infrastructure and social conditions. The present study has examined the temporal changes in 18 selected indicators of rural systems in Bangladesh during the period 1975-2000, and explored the influences of demographic, market forces, environmental, institutional and technological factors inducing and mediating such changes. An analysis of 64 district level published census data showed significant increase in agricultural intensity, cropping patterns, land productivity and farm income; decline in labor and technological productivities; and major improvement in rural housing, economic and social conditions during this period. Spatially, major agricultural growth and rural development were observed in districts with high population density, less constrained environments, and better access to markets, irrigation canals, and capital loans. 相似文献
547.
The problem of cosmological axially-symmetric viscous fluid interacting with the gravitational field has been investigated.
Exact solution have been obtained for the pressure and density of the fluid. Physical interpretation of the solutions regarding
the expansion factor, acceleration components and reality condition have been made.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
548.
Muhammad Khalifa Nadir Ahmed Elagib Bashir Mohammed Ahmed Lars Ribbe Karl Schneider 《水文科学杂志》2020,65(Z3):153-168
ABSTRACTUnderstanding the human–water–food–climate nexus is central to achieving sustainable intensification (SI) in agriculture. This research uses a socio-hydrological approach to understand the underpinning for implementing SI in the Gezira Irrigation Scheme, Sudan, by integrating vegetation indices derived from remote sensing, ancillary, gridded soil and precipitation data, supplemented by interviews with 393 farmers. The productivity gap was estimated as the difference between the potential and actual productivities. Based upon data on farmers’ socio-economic status and field practices, a regression tree model was built to determine the factors that control the sorghum yield. The model revealed that the financial status of farmers and access to water are the most influential factors on sorghum yield. A conceptual framework that elucidates SI and its bi-directional feedback to the environment, society and the economy is proposed. Implementing SI in the scheme has implications on water and food security in Sudan and beyond its borders. 相似文献
549.
During a severe earthquake, steel moment resisting frames are expected to experience significant inelastic deformation in their members and joints. This behaviour is dependent upon several design parameters such as member sizes, frame's overstrength, member deformation capacities and the detailing of components. In this study, the influence of such aspects on the inelastic response of frames is investigated. Inelastic static and dynamic analyses were performed on four frames of different designs for a typical six-storey building. The frames were designed and detailed in accordance with current North American code requirements. The computed response of each frame was compared with the behaviour expected by the codes. Recommendations for a design procedure are suggested for improving the structural performance of low-rise steel frames subjected to strong earthquake excitation. 相似文献
550.
Karez is an indigenous method of irrigation in which groundwater is tapped by a tunnel. After running for some distance the tunnel comes out in the open and the water is conducted to the command area. Karez irrigation is practised in 22 countries from China to Chile including Pakistan. In Pakistan it is confined to the province of Balochistan which has a tribal society.Karez is an old and stable irrigation system of Pakistan. It is a community enterprise managed by tribal tradition and run by social control. Spacing of the karez, their types, life, length, discharge, land development and allocation, water distribution and management are important aspects of karez irrigation which have been discussed in this paper. Differences in karez maintenance and management produced by differences in tradition and customs of various tribes inhabiting Balochistan are brought out. Furthermore recent changes in Karez irrigation caused by changes in the socio-economic conditions are also analysed. 相似文献