Recharge processes: piston flow vs preferential flow in semi-arid aquifers of India   总被引：3，自引：4，他引：3  

B. S. Sukhija  D. V. Reddy  P. Nagabhushanam  Syed Hussain 《Hydrogeology Journal》2003,11(3):387-395

Study of groundwater recharge processes is vital for quantification of total natural recharge to the aquifers. One of the recharge processes demonstrated earlier by tracer experiments in the unsaturated zone is that of piston flow movement of soil moisture. Based on this recharge process, environmental tritium, chloride and injected tritium studies have been carried out extensively in various geological environs of India. The purpose of this paper is to evaluate the validity of the piston flow concept in different geological environs viz. consolidated fractured and weathered granites, semi-consolidated sandstones and unconsolidated alluvial tracts, and quantify the contribution from this process as well as that from the preferential flow mechanism using different tracers. Analysis of tracer data demonstrates that the preferential flow recharge process contributes very significantly (an average of 75% of total recharge) in the case of fractured granites and is important (an average of 33% of total recharge) for semi-consolidated sandstones, whereas the preferential flow recharge component is minimal in unconsolidated alluvial tracts (piston flow model is applicable). These findings necessitate re-evaluation of the total natural recharge potential of the above mentioned geological environs in view of the significant preferential flow recharge that is evidenced and estimated. Electronic Publication  相似文献   

The design of visco‐acoustic weighted L1‐error frequency–space wavefield extrapolators          下载免费PDF全文

Syed Abdul Salam  Wail A. Mousa 《Geophysical Prospecting》2018,66(2):300-310

Seismic imaging is an important step for imaging the subsurface structures of the Earth. One of the attractive domains for seismic imaging is explicit frequency–space (f – x) prestack depth migration. So far, this domain focused on migrating seismic data in acoustic media, but very little work assumed visco‐acoustic media. In reality, seismic exploration data amplitudes suffer from attenuation. To tackle the problem of attenuation, new operators are required, which compensates for it. We propose the weighted L ₁ ‐error minimisation technique to design visco‐acoustic f – x wavefield extrapolators. The L ₁ ‐error wavenumber responses provide superior extrapolator designs as compared with the previously designed equiripple L ₄ ‐norm and L_∞‐norm extrapolation wavenumber responses. To verify the new compensating designs, prestack depth migration is performed on the challenging Marmousi model dataset. A reference migrated section is obtained using non‐compensating f – x extrapolators on an acoustic dataset. Then, both compensating and non‐compensating extrapolators are applied to a visco‐acoustic dataset, and both migrated sections are then compared. The final images show that the proposed weighted L ₁ ‐error method enhances the resolution and results in practically stable images.  相似文献   

Geo-Spatial Dynamics of Snow Cover and Hydro-Meteorological Parameters of Hunza Basin,HKH Region,Pakistan     

Ijaz Ahmad  Ahmad  Zulfiqar  Lisa  Mona  Mahmood  Syed Amer  Ali  Asad  Rehman  Obaid Ur 《Water Resources》2019,46(6):894-909

Water Resources - Snow cover dynamics play an important role in the hydrological characteristics of Upper Indus Basin (UIB) of Pakistan in terms of seasonal accumulation and depletions. The current...  相似文献   

Lithologic mapping of a forested montane terrain from Landsat 5 TM image     

Taufique H. Mahmood  Khaled Hasan  Syed Humayun Akhter 《国际地球制图》2019,34(7):750-768

Thick forest cover and poor infrastructures are the major hindrances for detailed lithologic mapping in an inaccessible montane landscape. To overcome these limitations, we utilize a Landsat 5 TM image to map lithology using vegetation and drainage pattern as an indicator of underlying rock types in a heavily forested region of the Chittagong Hill Tracts area located in southeastern Bangladesh. We use supervised and unsupervised classifiers for a vegetation-based approach while on-screen digitization is used for drainage patterns-based mapping. Field observations were used for mapping lithology and evaluating accuracy. Overall, our results agree well with the current geologic map and improve it by providing a more spatially detailed distribution of the sandstone and shale. The performances of all approaches are good at the inner and outer flanks of anticlines located in the study area while the drainage pattern mapping performs best at the mid-flank area.  相似文献   

Communicating human health risks associated with disinfection by-products in drinking water supplies: a fuzzy-based approach   总被引：1，自引：2，他引：1  

Rehan Sadiq  Manuel J. Rodriguez  Syed A. Imran  Homayoun Najjaran 《Stochastic Environmental Research and Risk Assessment (SERRA)》2007,21(4):341-353

Chlorine used for the disinfection of water supplies can react with naturally occurring organic compounds and form potentially harmful disinfection by-products (DBPs). A risk index for two regulated groups of chlorinated DBPs—trihalomethanes (THMs) and haloacetic acids (HAAs), using fuzzy C-means (FCM) clustering algorithm and fuzzy rule-based modeling is proposed for risk communication. The proposed index evaluates the cancer and non-cancer risks individually for THMs and HAAs using the FCM algorithm. Subsequently, two different fuzzy rule-bases were used to evaluate the overall risk-index based on cancer and non-cancer risks. The overall risk-index will provide drinking water utilities with an effective communication tool for communicating aggregated water quality compliance. Simulated DBP occurrence data obtained from the City of Quebec, Canada, is used to demonstrate the application of this methodology.  相似文献   

Stable isotope dynamics of groundwater interactions with Ganges river     

Prerona Das  Abhijit Mukherjee  Syed Aaquib Hussain  Md. Shahid Jamal  Kousik Das  Ashok Shaw  Mrinal K. Layek  Probal Sengupta 《水文研究》2021,35(1):e14002

Groundwater depletion has been an emerging crisis in recent years, especially in highly urbanized areas as a result of unregulated exploitation, thus leaving behind an insufficient volume of usable freshwater. Presently Ganges river basin, the sixth largest prolific fluvial system and sustaining a huge population in South Asia, is witnessed to face (i) aquifer vulnerability through surface waterborne pollutant and (ii) groundwater stress due to summer drying of river as a result of indiscriminate groundwater abstraction. The present study focuses on a detailed sub-hourly to seasonally varying interaction study and flux quantification between river Ganges and groundwater in the Indian subcontinent which is one of the first documentations done on a drying perennial river system that feeds an enormous population. Contributing parameters to the total discharge of a river at its middle course on both temporal and spatial scale is estimated through three-component hydrograph separation and end-member mixing analysis using high-resolution water isotope (δ¹⁸O and δ²H) and electrical conductivity data. Results from this model report groundwater discharge in river to be the highest in pre-monsoon, that is, 30%, whereas, during post-monsoon the contribution lowers to 25%; on the contrary, during peak monsoon, the flow direction reverses thus recharging the groundwater which is also justified using annual piezometric hydrographs of both river water and groundwater. River water-groundwater interaction also shows quantitative variability depending on river morphometry. The current study also provides insight on aquifer vulnerability as a result of pollutant mixing through interaction and plausible attempts towards groundwater management. The present study is one of the first in South Asian countries that provides temporally and spatially variable detailed quantification of baseflow and estimates contributing parameters to the river for a drying mega fluvial system.  相似文献   

Hydro-climatic aspects of Indus River flow propagation     

Syed Ahmad Hassan  M. Rashid Kamal Ansari 《Arabian Journal of Geosciences》2015,8(12):10977-10982

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Tectonic process analysis in Zagros Mountain with the aid of drainage networks and topography maps dated 1950–2001 in GIS     

Saied Pirasteh  Biswajeet Pradhan  Syed M. Rizvi 《Arabian Journal of Geosciences》2011,4(1-2):171-180

In this study, a digital elevation model was used for hydrological study/watershed management, topography, geology, tectonic geomorphology, and morphometric analysis. Geographical information system provides a specialized set of tools for the analysis of topography, watersheds, and drainage networks that enables to interpret the tectonic activities of an area. The drainage system maps of Zagros Mountains in southwest Iran have been produced using multi-temporal datasets between 1950 and 2001 to establish the changes between geomorphic signatures and geomorphic aspect during time and to correlate them with recent neo-tectonics. This paper discusses the role of drainage for interpreting the scenario of the tectonic processes as one of important signatures. The study shows variation in drainage network derived from topography maps. Thus, changes in drainage pattern, stream length, stream gradient, and the number of segment drainage order from 1950 to 2001 indicate that Zagros Mountain has been subjected to recent neo-tectonic processes and emphasized to be a newly active zone.  相似文献   

Fractal measures of drainage network to investigate surface deformation from remote sensing data: A paradigm from Hindukush (NE-Afghanistan)   总被引：1，自引：0，他引：1  

Syed Amer MAHMOOD  Richard GLOAGUEN 《山地科学学报》2011,8(5):641-654

This approach represents the relative susceptibility of the topography of the earth to active deformation by means of geometrical distinctiveness of the river networks. This investigation employs the fractal analysis of drainage system extracted from ASTER Global Digital Elevation Model (GDEM-30m resolution). The objective is to mark active structures and to pinpoint the areas robustly influenced by neotectonics. This approach was examined in the Hindukush, NE-Afghanistan. This region is frequently affected by deadly earthquakes and the modern fault activities and deformation are driven by the collision between the northward-moving Indian subcontinent and Eurasia. This attempt is based on the fact that drainage system is strained to linearize due to neotectonic deformation. Hence, the low fractal dimensions of the Kabul, Panjsher, Laghman, Andarab, Alingar and Kocha Rivers are credited to active tectonics. A comprehensive textural examination is conducted to probe the linearization, heterogeneity and connectivity of the drainage patterns. The aspects for these natural textures are computed by using the fractal dimension (FD), lacunarity (LA) and succolarity (SA) approach. All these methods are naturally interrelated, i.e. objects with similar FD can be further differentiated with LA and/or SA analysis. The maps of FD, LA and SA values are generated by using a sliding window of 50 arc seconds by 50 arc seconds (50" × 50"). Afterwards, the maps are interpreted in terms of regional susceptibility to neotectonics. This method is useful to pinpoint numerous zones where the drainage system is highly controlled by Hindukush active structures. In the North-Northeast of the Kabul block, we recognized active tectonic blocks. The region comprising, Kabul, Panjsher, Andrab, Alingar and Badakhshan is more susceptible to damaging events. This investigation concludes that the fractal analysis of the river networks is a bonus tool to localize areas vulnerable to deadly incidents influencing the Earth’s topography and consequently intimidate human lives.  相似文献   

An interacting scenario for dark energy in a Bianchi type-I universe     

Hassan Amirhashchi  Syed Nasrullah Ali Qazi  Hishamuddin Zainuddin 《中国天文和天体物理学报》2014,(11)

We study the interaction between dark energy(DE) and dark matter in the scope of anisotropic Bianchi type-I space-time. First we derive the general form of the DE equation of state(EoS) parameter in both non-interacting and interacting cases and then we examine its future by applying a hyperbolic scale factor. It is shown that in the non-interacting case, depending on the value of the anisotropy parameter K,the DE EoS parameter varies from phantom to quintessence whereas in the interacting case the EoS parameter varies in the quintessence region. However, in both cases, the DE EoS parameter ωdeultimately(i.e. at z =-1) tends to the cosmological constant(ωde=-1). Moreover, we fix the cosmological bound on the anisotropy parameter K by using recent observational data about the Hubble parameter.  相似文献