Evaluating the performance of a deterministic daily rainfall–runoff model in a low-flow context     

V. Y. Smakhtin  K. Sami  D. A. Hughes 《水文研究》1998,12(5):797-812

The characterization of a stream's low-flow regime is required for ecological purposes, water quality studies and various other water projects. If observed stream flow records are insufficient, low-flow characteristics may need to be estimated from simulated daily stream flow time-series. The model employed should conceptualize low-flow generation mechanisms and surface–subsurface interactions adequately. The ability of the model to simulate low-flow regimes may be assessed by means of various low-flow analysis techniques. This paper illustrates the approach using the example of the physically based, semi-distributed VTI daily rainfall–runoff model. The model has been applied to five perennial headwater catchments in South Africa, which are located in different parts of the country, represent different physiographical environments and are characterized by different baseflow responses. The model simulations are evaluated in terms of both conventional goodness-of-fit criteria and several low-flow measures such as recession characteristics, baseflow volumes, flow duration curves and continuous low-flow events below specified threshold discharges. For all the catchments considered the model has been found to perform successfully in terms of conventional fit statistics and flow duration curves. However, its ability to reproduce recession characteristics and continuous low-flow spells appears to be less satisfactory. This suggests that daily model simulations should be evaluated by low-flow criteria, which are frequently ignored in water resource assessment practices. © 1998 John Wiley & Sons, Ltd.  相似文献   

Nitrogen Mass Fraction and Stable Isotope Ratios for Fourteen Geological Reference Materials: Evaluating the Applicability of Elemental Analyser Versus Sealed Tube Combustion Methods     

Toby J. Boocock  Sami Mikhail  Julie Prytulak  Tommaso Di Rocco  Eva E. Stüeken 《Geostandards and Geoanalytical Research》2020,44(3):537-551

Thirteen commercially available silicate reference materials (RM) and one in‐house reference material, eleven of which have no previously published values, were analysed for nitrogen mass fraction and isotopic ratios with an Elemental Analyser (EA), and a Sealed Tube Combustion line, coupled to a continuous flow isotope ratio mass spectrometer (IRMS). These materials ranged from < 10 μg g^?1 to 1% m/m nitrogen mass fractions and δ¹⁵N of ?0.5 to +19.8‰. Existing nitrogen RM BHVO‐2, MS#5 and SGR‐1b were used to assess the accuracy of the data from the sealed tube combustion line, which was found to be in good agreement with existing published values. In contrast, the EA‐IRMS failed to fully liberate nitrogen from all silicate rocks and minerals (achieving a mean of 44 ± 10% nitrogen yield) resulting in kinetic fractionation of isotope values by ?1.4‰ on average. Therefore, sealed tube combustion is better suited for analyses of silicate‐bound nitrogen. The EA worked reliably for organic samples, but care should be taken when using the EA for silicate nitrogen research. Moving forward, it is recommended that BHVO‐2, Biotite‐Fe, FK‐N and UB‐N be used as quality control materials as they appear to be most reproducible in terms of nitrogen mass fraction (relative error < 10%, 1s), and isotopic composition (< 0.6‰, 1s).  相似文献   

Aquifer modelling of the Ganga–Mahawa sub‐basin,a part of the Central Ganga Plain,Uttar Pradesh,India     

M. E. H. Ala Eldin  M. Sami Ahmed  V. V. S. Gurunadha Rao  R. L. Dhar 《水文研究》2000,14(2):297-315

The Ganga–Mahawa sub‐basin, which has an area of 1280 km² forms the western part of the Central Ganga Plain in the Moradabad and Badaun districts of western Uttar Pradesh, India. The Bundelkhand granite forms the basement complex, overlain unconformably by the upper Vindhyan sequence, which is further overlain by the Neogene (Middle and Upper) Siwaliks and finally by Quaternary alluvium. Four geomorphological units, the Varanasi older alluvial plain, Aligarh older alluvial plain, terrace zones and the Ganga recent floodplain, abandoned channels, channel scars and meander scars represent various landforms. The hydrogeological cross‐sections indicate the occurrence of a single aquifer down to 120 m. Some influent seepage from the River Ganga could be seen around Gangeswari, but the rest of the River Ganga is effluent. Groundwater‐flow modelling was carried out to assess the degree of Ganga river and aquifer interaction. The River Ganga marks the western boundary; boundaries to the northeast and southeast are set as fixed heads to simulate lateral inflow into and outflow from the sub‐basin respectively. The eastern boundary is simulated as a no‐flow condition. The Mahawa and Badmar rivers are considered to be effluent. The area modelled is covered by a grid of 34 rows×46 columns with three layers, viz., an unconfined aquifer, an aquitard which is underlain by a semi‐confined to confined aquifer. The permeability distribution was inferred from morphometric analysis and pumping tests. Natural recharge due to monsoon rainfall forms the main input. The River Ganga stage data at Ahar, Naora and Ramghat has been used for assigning surface water levels and river bed elevations in the model. Abstraction from all existing deep and shallow tube wells has been assigned as output at various cells. A steady state flow simulation was carried out and calibrated against the June 1986 water level; subsequent transient conditions were calibrated up to May 1995. The computed groundwater balance was comparable to that estimated from field investigations. The aquifer modelling study has attempted to integrate all available information and provided a tool that could be used for predictive simulation. Copyright © 2000 John Wiley & Sons, Ltd.  相似文献   

Tidal and annual variability of the population structure of Eurytemora affinis in the middle part of the Seine Estuary during 2005     

David Devreker  Sami Souissi  Juan Carlos Molinero  Delphine Beyrend-Dur  Fernando Gomez  Joelle Forget-Leray 《Estuarine, Coastal and Shelf Science》2010

Annual variability in abundance and population structure of the copepod Eurytemora affinis was studied in the maximum turbidity zone of the Seine Estuary in 2005. An Eulerian sampling strategy was applied monthly from March to July and from September to December. Chlorophyll a and suspended particulate matter (SPM) concentration, copepod abundance and stage distribution, and phytoplankton abundance were measured in sub-surface and near-bottom water during the ebb phase. Total E. affinis abundance was at a maximum in March and April (>200 × 10³ ind. m⁻³), and decreased from May to September (<25 × 10³ ind. m⁻³). This decrease corresponds to annual increases in temperature, salinity, chlorophyll a concentration and phytoplankton abundance, which was dominated by large diatoms, and decreases in SPM and river discharge. The phenology observed in 2005 was almost two months earlier compared to previous studies in the 1990s, when E. affinis reached maximum abundance in May and June. The low proportion of nauplii (<50%) in the population and high abundance of ovigerous females suggests that low recruitment is probably related to anomalously low temperatures in late winter (<5 °C). Whatever the horizontal position of the population in the estuary, adult and late copepodid stages are distributed in higher salinity than naupliar stages. Overall E. affinis population abundance was driven by parameters that characterize water masses at the tidal scale and by river discharge and chlorophyll a at the annual scale. By integrating the tidal effect, the high-frequency sampling protocol used appears to be optimal for investigating annual variability of planktonic communities in megatidal estuaries.  相似文献   

Recharge processes during snowmelt: An isotopic and hydrometric investigation     

J. M. Buttle  K. Sami 《水文研究》1990,4(4):343-360

Results from hydrometric and isotopic investigations of unsaturated flow during snowmelt are presented for a hillslope underlain by well-sorted sands. Passage of melt and rainwater through the vadose zone was detected from temporal changes in soil water ²H concentrations obtained from sequential soil cores. Bypassing flow was indicated during the initial snowmelt phase, but was confined to the near-surface zone. Recharge below this zone was via translatory flow, as meltwater inputs displaced premelt soil water. Estimates of premelt water fluxes indicate that up to 19 per cent of the premelt soil water may have been immobile. Average water particle velocities during snowmelt ranged from 6.2 × 10^?7 to 1.1 × 10^?6 ms^?1, suggesting that direct groundwater recharge by meltwater during snowmelt was confined to areas where the premelt water table was within 1 m of the ground surface. Soil water ²H signatures showed a rapid response to isotopically-heavy rain-on-snow inputs late in the melt. In addition, spatial variations in soil moisture content at a given depth induced a pronounced lateral component to the predominantly vertical transport of water. Both factors may complicate isotopic profiles in the vadose zone, and should be considered when employing environmental isotopes to infer recharge processes during snowmelt.  相似文献   

Temperature and precipitation trend analysis of the Iraq Region under SRES scenarios during the twenty-first century     

Hashim  Bassim Mohammed  Al Maliki  Ali  Alraheem  Esam Abd  Al-Janabi  Ahmed Mohammed Sami  Halder  Bijay  Yaseen  Zaher Mundher 《Theoretical and Applied Climatology》2022,148(3-4):881-898

Theoretical and Applied Climatology - Iraq is classified as the fifth most vulnerable country in the world to decreased water and food availability, extreme temperatures, and associated health...  相似文献   

Extending F‐Perceptory to model fuzzy objects with composite geometries for GIS          下载免费PDF全文

Besma Khalfi  Cyril de Runz  Sami Faiz  Herman Akdag 《Transactions in GIS》2017,21(6):1364-1378

When analyzing spatial issues, geographers are often confronted with many problems with regard to the imprecision of the available information. It is necessary to develop representation and design methods which are suited to imprecise spatiotemporal data. This led to the recent proposal of the F‐Perceptory approach. F‐Perceptory models fuzzy primitive geometries that are appropriate in representing homogeneous regions. However, the real world often contains cases that are much more complex, describing geographic features with composite structures such as a geometry aggregation or combination. From a conceptual point of view, these cases have not yet been managed with F‐Perceptory. This article proposes modeling fuzzy geographic objects with composite geometries, by extending the pictographic language of F‐Perceptory and its mapping to the Unified Modeling Language (UML) necessary to manage them in object/relational databases. Until now, the most commonly used object modeling tools have not considered imprecise data. The extended F‐Perceptory is implemented under a UML‐based modeling tool in order to support users in fuzzy conceptual data modeling. In addition, in order to properly define the related database design, an automatic derivation process is implemented to generate the fuzzy database model.  相似文献   

Environmetric techniques in water quality assessment and monitoring: a case study     

Aadil Hamid  Salim Aijaz Bhat  Sami Ullah Bhat  Arshid Jehangir 《Environmental Earth Sciences》2016,75(4):321

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Seismic tectono-stratigraphy of fluvio-deltaic to deep marine Miocene silicoclastic hydrocarbon reservoir systems in the Gulf of Hammamet,northeastern Tunisia     

Mourad Bédir  Afif Arbi  Sami Khomsi  Faten Houatmia  Mohamed Naceur Aissaoui 《Arabian Journal of Geosciences》2016,9(19):726

Most of hydrocarbon accumulations within the Gulf of Hammamet foreland basins in eastern Tunisia are reservoired within the Upper Miocene Birsa and Saouaf sandstones. It is the case of Birsa, Tazarka, Oudna, Baraka, Maamoura, Cosmos and Yasmine fields. These sandstones constitute oil and gas fields located on folded and faulted horst anticline highs and described as varying from shoreface to shallow marine and typically exhibit excellent reservoir quality of 30 to 35% porosity and good permeability from 500 to 1100 md. In addition, the fracturing of faults enhanced their reservoir quality potential. However, due to the lack of seismic stratigraphic studies to highlight depositional environment reservoir characterization and distribution, petroleum exploration faces structural and stratigraphic trap types and remains on targeting only high fold closures with limited reserve volumes of hydrocarbons. As an example of the Birsa concession case, syn-sedimentary tectonic structuring and geodynamic evolution during Middle to Upper Miocene Birsa reservoir sequences have guided the distribution of depositional environment of sandstone channel systems around horst and grabens by E-W, NE-SW and N-S strike slip flower faults controlling the subsidence distribution combined with the eustatic sea level variations. Seismic sequence stratigraphy study of Miocene Birsa reservoir horizons, based on the analysis and interpretations of E-W and N-S 3D selected regional lines that were compared and correlated to outcrops and calibrated by well data, permitted to highlight the basin configuration and sequence deposit nature and distribution. Sedimentary infilling of the basin from Langhian Ain Ghrab carbonate to Serravallian Tortonian Birsa and Saouaf sandstone and shale formations is organized in four third-order seismic sequences, limited by regional erosional toplap, onlap and downlap unconformity surfaces and by remarkable chronostratigraphic horizons of forced and normal erosive lowstand and highstand system tracts separated by transgressive and maximum flooding surfaces. Reconstructed sedimentary paleo-environment distribution vary from deltaic fluvial proximal deposits in the northern part of the high central Birsa horst to a delta front and prodelta coastal and shelf shore face and shore line channelized deposits in the surrounding borders of grabens. Distal deposits seem to be distributed from upper to lower slope fans and probably to the basin floor on the flanks of the subsiding grabens. Synthetic predictive paleogeographic depositional reservoir fairway map distribution of Lower, Middle and Upper Birsa sandstone reservoirs highlights four main domains of channelized superposed and shifted reservoirs to explore.  相似文献   

Reply to comment on `European provenance of the Numidian Flysch in northern Tunisia'     

Dorrik Stow  Christine Fildes  Sami Riahi  Mohamed Soussi  Urval Patel  J. Andy Milton  Stuart Marsh 《地学学报》2010,22(6):504-505

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