Precipitation extremes during Indian summer monsoon: role of cyclonic disturbances     

J. V. Revadekar  Hamza Varikoden  B. Preethi  M. Mujumdar 《Natural Hazards》2016,81(3):1611-1625

  相似文献   

Implementing Digital Imaging for Improved Understanding of Microfine Cement Grout Permeation and Filtration     

El Mohtar  Chadi  Jaffal  Hamza  Miller  Anna Kate  Ward  Katie 《Geotechnical and Geological Engineering》2022,40(9):4473-4485

Geotechnical and Geological Engineering - Permeation grouting is a ground improvement method commonly used for strengthening and/or reducing permeability of soils with minimal disturbance to the...  相似文献   

Impact of the unpredictable changes in agricultural groundwater use on long-term sustainable exploitation: the case study of Bouhefna-Haffouz aquifer system,central Tunisia     

Jerbi  Hamza  Sebai  Amal  Massuel  Sylvain  Riaux  Jeanne  Leduc  Christian  Tarhouni  Jamila 《Hydrogeology Journal》2023,31(5):1181-1196

Long-term exploitation schemes in many regions are often based solely on hydrodynamic factors, while the agricultural use of groundwater undergoes significant changes over time. The Bouhefna-Haffouz aquifer system in central Tunisia is one of those cases where an aquifer exploitation scheme was well designed hydrodynamically to address the political needs at the time. Fifty years later, a numerical groundwater model has been conducted to assess the sustainability of the scheme. Results show that the scheme aimed to lower the groundwater level to reduce overflow to Merguellil Wadi and maintain it at a level that benefits agricultural profitability. This caused loss of the Merguellil baseflow, forcing farmers to switch from traditional irrigation canals to deep wells and motor pumps, thereby disrupting the hydrological budget even further. The numerical model indicates that the flow to the wadi reached zero in 1978, the average flow by vertical leakage decreased from 8 hm³ in 1970 to 2 hm³ in 2020, and the horizontal percolation between the regional aquifer units increased from 1 hm³ in 1970 to 6 hm³ in 2020. Although the groundwater exploitation scheme was not previously considered a factor in local hydrological changes, the results of this study demonstrate the significant impact of societal behavior following the scheme’s implementation on the hydrological budget of Merguellil Wadi.

  相似文献   

Numerical and functional representations of regional heat flow in South America   总被引：1，自引：0，他引：1  

Valiya M. Hamza  Fernando J.S. Silva Dias 《Physics of the Earth and Planetary Interiors》2005,152(4):223-256

A summary of heat flow data acquired over recent years in several areas in the eastern (Brazil and Paraguay) and western (Bolivia, Chile, Colombia and Ecuador) parts of South American continent are presented. The improvements in the database have allowed numerical representations of heat flow for southeastern and central segments of the Precambrian fold belts in Brazil, Central Andean cordilleras in Chile and Bolivia, Southern Volcanic arc in Peru, Neuquén Province in southwestern Argentina, Chaco basin in Paraguay, Oriente basin in Ecuador and the system of pericratonic basins in north central Colombia. The maps reveal considerable variability in heat flow, not only between the main tectonic units but also within them. The intra-regional variations seem to originate mainly from complexities in local geologic structures while the inter-regional ones seem to point to action of deep-seated tectonic processes. The cordilleran regions are, in general, characterized by relatively high heat flow (>70 mW/m²), compared with the coastal regions to the west and the Pre-cordilleran basins to the east. In the eastern part of the continent, heat flow is low to normal (<60 mW/m²), the exceptions being the Mesozoic rift basins, areas of Cenozoic alkaline intrusions and some isolated belts of overthrust tectonics in the central parts of Brazil. There are indications that heat flow is high in the Patagonian Platform relative to that found in the Brazilian Platform.In addition, polynomial methods were employed for examining large-scale variations of heat flow over the continent. Specifically, a general-purpose least square solution was used to determine the coefficients of up to fourth order in latitude and longitude. Some of the large-scale trends seen in low order polynomial representations seem to be indicative of the nature of deep-seated heat transfer processes. The systematic increase in regional heat flow in the north-south direction is an example. It is considered as the consequence of thermal blanketing effect of the continental segment of the South American lithosphere. Trends seen in higher order polynomials seem to be associated with regional tectonic patterns and subduction-related magmatism. Prominent among these are east-west trending belts of low heat flow in northern Peru and in central Chile, as well as the high heat flow belts in northern Chile, Altiplano of Bolivia and northwestern Argentina. Limitations arising from low data density and uneven geographic distribution warrant higher degree polynomial representations.  相似文献   

Investigation of Groundwater Potential Zones in Hard Rock Terrain,Wadi Na'man,Saudi Arabia     

Bander A.M. Algaydi  Ali M. Subyani  Mohamed H.M.M. Hamza 《Ground water》2019,57(6):940-950

In arid and hyper-arid zones, groundwater exploration is one of the most significant ways to locate potential new water supplies. Geophysical prospecting is currently the most successfully used method for locating new supplies, but it is rather costly. Satellite remote sensing (RS) detection, however, with its integration of Geographic Information Systems (GIS) provides the best chance for identifying and initially evaluating water-bearing formations. In the western part of Saudi Arabia, Wadi Na'man has for centuries been one of the major water sources for the city of Makkah Al-Mukarramah. It is therefore very important to find appropriate groundwater potential (GP) zones in this wadi for water supply. This study utilizes RS and GIS techniques, and also studies the hydrogeological, geological, and geomorphological characteristics that have significant impact on groundwater occurrence in Wadi Na'man. Representative layers are generated for each component and each given a weight ratio that depends on the level of influence. The overlay and integration of these thematic layers was used to produce a map that shows the most promising potential groundwater areas and classifies local potentials as either low, medium, or high. The results also reveal that the areas overall-rated as “promising” (i.e., classified as medium or high) represent approximately 17-25% of the total basin area and consist mainly of Quaternary sediments and connected fractured rock areas.  相似文献   

Dynamics of westward propagation and intensification of Lakshadweep low in the southern Arabian Sea     

Zachariah  Johnson  Babu  Chethalan Anthony  Varikoden  Hamza 《Ocean Dynamics》2019,69(5):519-528

Ocean Dynamics - Westward propagation and the dynamics of intensification of Lakshadweep low (LL) have been investigated in detail. In this study, it is observed that LL is not propagated westwards...  相似文献   

Phytoplankton-pigment signatures and their relationship to spring–summer stratification in the Gulf of Gabes     

M. Bel Hassen  A. Hamza  Z. Drira  A. Zouari  F. Akrout  S. Messaoudi  L. Aleya  H. Ayadi 《Estuarine, Coastal and Shelf Science》2009

We investigated the phytoplankton dynamics (determined by CHEMTAX analysis of HPLC pigment data) and its relationships with nutrients and water column structure, during two oceanographic cruises in May–June and September 2006 in the Gulf of Gabes (south-eastern Mediterranean). The May–June cruise coincided with the beginning of the summer stratification, while a strong stratification occurred in September with a more than 30 m deepening of the thermocline, and a reduction of the euphotic depth. This strong stratification resulted in a shift in nitrogen sources from nitrates to ammonium as well as phosphate depletion (0.2 μM) and a decrease in silicate concentrations (<2 μM). With the exception of chlorophyll a, pigment concentrations were higher in September than in May–June samplings. The pico- and nanophytoplankton were the major contributors to phytoplankton total biomass, accounting for 90% and 87% of total chlorophyll a in May–June and September, respectively. Picoplankton persisted throughout the entire survey, occupying different depth layers. Chlorophytes were present at substantial amounts (average 23% of total chlorophyll a) during May–June; however, they declined in September (average 5%). Diatoms were overall poorly represented in this study (2% of total chlorophyll a), due probably to silicate shortage. Apparently, the nutrient availability, but also the water column stability seemed to be among the major factors determining phytoplankton dynamics. Indeed, cyanobacteria were prominent in surface samples during the period of strong stratification, whereas the relative contribution of chlorophytes decreased, probably due to low phosphate availability.  相似文献   

Temporal and bathymetric variation of epiphyte cover and leaf biomass in a southern Posidonia oceanica (L.) meadow: the case of Mahdia coast,Tunisia          下载免费PDF全文

Lotfi Mabrouk  Hamza Asma  Med N. Bradai 《Marine Ecology》2017,38(1)

The aim of this research was to study spatial and temporal variation in epiphyte cover and leaf biomass of Posidonia oceanica in Eastern Tunisia. Sampling was conducted at four stations on the Mahdia coast during October and December 2010, and April and August 2011, which correspond respectively to autumn, winter, spring and summer in this area. Posidonia oceanica shoots were collected at two depths (5 and 10 m). Cover of macroinvertebrates and macroalgae was estimated on adult leaves. The results showed that leaf and epiphyte biomasses vary significantly according to sampling date, with the highest values recorded in August. We found a high diversity of epiphytic assemblages on the leaves of P. oceanica with clear qualitative and quantitative dominance of Rhodophyceae compared to other groups, followed by Phaeophyceae. Most epiphyte species on the leaves of P. oceanica in Eastern Tunisia are the same as those in other parts of the Mediterranean Sea. No bathymetrical variation in the epiphytic community was found in our study area, which can be explained by the high levels of water clarity in Mahdia.  相似文献   

Variations in vapor pressure and standardized precipitation evapotranspiration index since AD 1861 over the western Himalaya in India: inference from tree ring-width records     

Somaru Ram  H. N. Singh  Ramesh Kumar Yadav  Hamza Varikoden  S. S. Nandargi  Manoj K. Srivastava 《Theoretical and Applied Climatology》2020,140(1):157-166

A regional tree ring-width index chronology prepared from various tree core samples of the western Himalaya has been analyzed in relation to climate fluctuations. The correlation analysis of tree ring chronology shows significant positive correlations with regional rainfall and standardized precipitation evapotranspiration index (SPEI) and negative correlations with temperature and vapor pressure (VP) during the spring season. The correlation coefficients (CCs) of tree ring-width index chronology with rainfall, temperature, SPEI, and VP during 1901–1990 are 0.50, −0.49, 0.65, and −0.51, respectively. All CCs are significant at 0.1% level. The highly significant CCs between tree ring-width index chronology and SPEI indicate that tree growth over the western Himalaya is more sensitive to soil moisture availability than rainfall, whereas the rising VP is found to have a significant moisture stress condition to tree growth by accelerating the evapotranspiration, which is not conducive for the development of tree growth in the region. So, based on the strong association between tree ring-width index chronology and SPEI; the reconstructions of SPEI and VP are developed back to AD 1861, that show the long period of dryness during 1936–1963.  相似文献   

Consideration of the use of direct recharge in analytical models of flood-wave response: a case study of the Merguellil alluvial aquifer,central Tunisia     

Hamza Jerbi 《Hydrogeology Journal》2018,26(7):2395-2409

In a stream–aquifer system, adequate knowledge of the aquifer hydraulic parameters is paramount for the analysis of groundwater/surface-water interaction. In such systems, analytical flood-wave response models are commonly used to assess these parameters. However, when an important means of direct recharge (precipitation) occurs simultaneously with the stream flood waves, the classical flood-wave response model (i.e. when only stream flood waves are considered as an input signal) leads to overestimated and variable values of the aquifer hydraulic parameters. In this study, an analytical flood-wave response model was implemented to determine hydraulic parameters of the Merguellil alluvial aquifer (central Tunisia) taking into account the recharge rate as a second input signal. An array of three piezometers and a river-stage gauge equipped with an automated Diver data logger were installed in the floodplain of the Merguellil Wadi. The results showed a good agreement between the observed and modelled hydrographs when the recharge rate was considered, which allows the model to provide the same value of diffusivity (50–70 m² h^?1) in the three piezometers and for all flood events being tested. However, when the recharge rate was not taken into account, the model gave an overestimated diffusivity with a very poor hydrograph match. Overall, the methodology described in this paper can be applicable to any area in the world because of its simplicity and its better estimation of aquifer hydraulic parameters.  相似文献