Investigating Parameters of Geomorphic Direct Runoff Hydrograph Models

Water Resources - Formulation of rainfall runoff models and identification of their parameters is difficult step especially for catchments having scanty or no data. Parameters of geomorphic...     

Bias correction method of high-resolution satellite-based precipitation product for Peninsular Malaysia

Theoretical and Applied Climatology - Satellite-based precipitation (SBP) is emerging as a reliable source for high-resolution rainfall estimates over the globe. However, uncertainty in SBP is...     

The planktonic food web of the Bizerte lagoon (south-western Mediterranean) during summer: I. Spatial distribution under different anthropogenic pressures

The structure and the trophic interactions of the planktonic food web were investigated during summer 2004 in a coastal lagoon of south-western Mediterranean Sea. Biomasses of planktonic components as well as bacterial and phytoplankton production and grazing by microzooplankton were quantified at four stations (MA, MB, MJ and R) inside the lagoon. Station MA was impacted by urban discharge, station MB was influenced by industrial activity, station MJ was located in a shellfish farming sector, while station R represented the lagoon central area. Biomasses and production rates of bacteria (7–33 mg C m⁻³; 17.5–35 mg C m⁻³ d⁻¹) and phytoplankton (80–299 mg C m⁻³; 34–210 mg C m⁻³ d⁻¹) showed high values at station MJ, where substantial concentrations of nutrients (NO₃⁻ and Si(OH)₄) were found. Microphytoplankton, which dominated the total algal biomass and production (>82%), were characterized by the proliferation of several chain-forming diatoms. Microzooplankton was mainly composed of dinoflagellates (Torodinium, Protoperidinium and Dinophysis) and aloricate (Lohmaniellea and Strombidium) and tintinnid (Tintinnopsis, Tintinnus, Favella and Eutintinnus) ciliates. Higher biomass of these protozoa (359 mg C m⁻³) was observed at station MB, where large tintinnids were encountered. Mesozooplankton mainly represented by Calanoida (Acartia, Temora, Calanus, Eucalanus, Paracalanus and Centropages) and Cyclopoida (Oithona) copepods, exhibited higher and lower biomasses at stations MA/MJ and MB, respectively. Bacterivory represented only 35% of bacterial production at stations MB and R, but higher fractions (65–70%) were observed at stations MA and MJ. Small heterotrophic flagellates and aloricate ciliates seemed to be the main controllers of bacteria. Pico- and nanophytoplankton represented a significant alternative carbon pool for micrograzers, which grazing represented 67–90% of pico- and nano-algal production in all stations. Microzooplankton has, however, a relatively low impact on microphytoplankton, as ≤45% of microalgal production was consumed in all stations. This implies that an important fraction of diatom production would be channelled by herbivorous meso-grazers to higher consumers at stations MA and MJ where copepods were numerous. Most of the microalgal production would, however, sink particularly at station MB where copepods were scare. These different trophic interactions suggest different food web structures between stations. A multivorous food web seemed to prevail in stations MJ and MA, whereas microbial web was dominant in the other stations.     

Provenance analyses of the heavy-mineral beach sands of the Annaba coast,northeast Algeria,and their consequences for the evaluation of fossil placer deposit

The paper presents the first study of heavy-mineral sand beaches from the Mediterranean coast of Annaba/Algeria. The studied beaches run along the basement outcrops of the Edough massif, which are mainly composed by micaschists, tourmaline-rich quartzo-feldspathic veins, gneisses, skarns and marbles. Sand samples were taken from three localities (Ain Achir, Plage-Militaire and El Nasr). The heavy-mineral fraction comprises between 74 and 91 vol%. The garnets of the beaches are almandine rich and tourmalines vary with respect to their location from schorl to dravite. Tourmaline at Ain Achir and the Plage-Militaire is schorlits, while at El Nasr beach dravite is ubiquitous. The World Shale Average normalised REE of the sands and the basement outcrops reveal: (i) Ain Achir beach: REE pattern of sand and the coastal rocks from the studied beaches reflects a multiple sources; (ii) Plage-Militaire: the sand and the coastal outcrops show similar LREE and a strong enrichment in HREE, suggesting the presence HREE-rich phases found as inclusions in staurolite; (iii) El Nasr: two types of sand patterns are found: one with flat REE pattern similar to the proximal rocks and other one enriched in HREE suggesting a mixed source.     

Water level and atmospheric humidity history of Lake Ichkeul (northern Tunisia) during the last 3000 years

Changes in paleoecology and climate of northern Tunisia during the last 3000 years were reconstructed based on the flood history interpreted from a 172-cm sediment core of Lake Ichkeul (NW Tunisia). Seven wet/dry episodes were identified based on biological (ostracods, foraminifera and mollusks) and biotic indices (H and E index, species richness and abundance). These proxy-based environmental changes were supported by correspondence analyses (CAs) and ecophenotypic responses of the brackish taxon Cyprideis torosa in addition to a grain-size study. Two dry episodes were identified in the lower (EP1) and upper (EP7) parts of the core. These were marked by the dominance of the brackish ostracod C. torosa. High water salinity was indicated by the presence of the brackish ostracod Loxoconcha elliptica, the foraminifer Ammonia sp. and lagoonal mollusks. The occurrence of the freshwater ostracods Ilyocypris sp., Herpetocypris sp., Dawinula stevensoni and Limnocythere inopinata was associated with high species richness and ecophenotypic changes of C. torosa valves indicating lower salinity during three major wet episodes (EP2, EP4, and EP6). The ecological and environmental changes, occurring between 3050 and 50 cal. year BP, are most likely linked to an increase of fluvial inputs which are also recognized in several other Mediterranean lakes. The humid episodes were interrupted by two saline periods (EP3 and EP5) during which freshwater ostracod assemblages declined, diversity indices dropped to the lowest values, and fine-grained sediments became dominant. The top of the core is characterized by the remarkable dominance of L. elliptica coupled with C. torosa, the absence of freshwater ostracods, and the changes in grain-size sediment parameters which are most likely the result of anthropogenic activities. The changes in hydrochemistry and sedimentology were attributed to the deepening of the Bizerte navigation canal, main wadis damming, and Tinja sluice construction which mostly occurred in the XX^th century.     

Statistical detection and no-detection of rainfall change trends and breaks in semiarid Tunisia—50+ years over the Merguellil agro-hydro-climatic reference basin

Rainfall variability is an important feature of semiarid climates with major effects on hydrology, and beyond on key water-dependent societal aspects. Eventual changes in rainfall variability are a strong driver of change of hydrological processes, resources, and hazards, up to catchment signatures and spatial arrangements. We deal with observed precipitations and subsequent statistical coefficients available from a network of 15 rainfall gauges over and around the Merguellil catchment (1175 km²), with series ranging up to the 1961–2013 period. We look for eventual annual trends and breakpoints with a set of methods: Mann Kendall test, Pettitt test, Hubert segmentation procedure, Buishand U statistic, and Lee Heghinian Bayesian procedure. The results underline oscillation of dry and wet periods; several studied rain gauges (Tella, Oueslatia forêt, Majbar, Kesra forêt, Henchir Bhima, and Haffouz DGRE) denote significant trends in annual precipitation. Some breaks are detected but they are not synchronous. These methods reveal the variability of rainfall regimes in the semiarid region and provide a synoptic view of detection and no-detection of symptoms of change. This work gives opportunities to water stakeholders and climate experts in understanding the relationships between climate variability and water availability.     

Conservation planning as an adaptive strategy for climate change and groundwater depletion in Wadi El Natrun,Egypt

In drylands, groundwater is often the sole source of freshwater for industrial, domestic and agricultural uses, while concurrently supporting ecosystems. Many dryland aquifers are becoming depleted due to over-pumping and a lack of natural recharge, resulting in loss of storage and future water supplies, water-level declines that reduce access to freshwater, water quality problems, and, in extreme cases, geologic hazards. Conservation is often proposed as a strategy for managing groundwater to reduce or reverse the depletion, although there is a need to better understand its potential effectiveness and benefits at the local scale. This study assesses the impact of water-conservation planning strategies on groundwater resources in the Wadi El Natrun (WEN) area of northern Egypt. WEN has been subjected to groundwater depletion and quality degradation since the 1990s, attributed to agricultural and industrial groundwater usage. Initiatives have been proposed to increase the sustainability of the groundwater resource in the study area, but they have yet to be evaluated. Simultaneously, there are also proposals to increase the extent of arable land and thus demand for freshwater. In this study, three water management scenarios are developed and assessed to the 2060s for their impact on groundwater resources using a hydrogeologic model. Results demonstrate that demand management implemented through an optimized irrigation and crop rotation strategy has the greatest potential to significantly reduce risk of groundwater depletion compared to the other two scenarios—“business as usual” and “30% water-use reduction”—that were evaluated.