reservoir, Sennar reservoir, Roseires reservoir, Jabbel Awlia reservoir and Merowe reservoir. A reservoir is a man made water obstruction created in a river valley, which stores water during rainy season to be used or redistributed during summer time. During summer time the daily demand is greater than the daily inflow; therefore water has to be drawn from the reservoir to supplement the daily inflow to meet the daily demand. Releasing too much or too little may result in an economic loss, therefore water has to be released optionally to maximize the benefits from reservoirs on one hand and to meet the growing demands on the other. This growing demand is caused, in developing countries, by growing population, as well as continuous and rapid urbanization. In developing countries, the urbanization increases water demand in sectors like power generation and recreation. Although these sectors are not water consumptive, yet they may use water and may be in conflict with traditional largest water user in irrigation. To meet these growing demands, reservoir has to be operated optionally and water used efficiently by the rational water uses e.g. irrigation (Dafalla, 1999).
resources that can be developed and utilized for the wellbeing of the people. However, due to growing population density, deforestation and catchment land use changes are putting more and more pressure on lakes, reservoirs and rivers draini them (Becht and Harper, 2002 and Ayenew, 2004). As a result this resource is not yet exploited in proper and sustainable way to meet the increasing demand for food and clean water supply. Lake Hashenge is the only closed and high altitude lake in Tigray region lying at about 2440 m above sea level. As part of the surface water resource it can support the economic growth of the region through irrigated agriculture, fish industry and ecotourism farming.
Construction of dams and reservoirs in rivers fist mainly for flood control, hydropower generation, irrigation, navigation, water supply, fishing and recreation. Among multipurpose dams, hydropower and irrigation dams are predominant. Environmental impacts and long-term morphological changes of the natural water course due to human intervention are inevitable. Sedimentation is one of the major problems which endangers the performance and sustainability of reservoirs. It reduces the effective flood control volume. It also affects the operation of low-level outlets gates and valves, reduces stability, water quality and recreational benefits.
of view of physical property . A several studies are reported in this area of research. Jeene  discussed the role of clay sized minerals in trace element sorption by soils and sediments. Fu and Allen  studied the adsorption of cadmium by oxic sediments using multisided binding model. Veli and Alyuz  concluded that natural clay can be used as an effective adsorbent for removing Cu 2+ and Zn 2+ from aqueous solutions. In this context, in a previous research, the authors have used the sediment extracted from a water reservoir as amendment of agricultural soils irrigated by TWW since 1989 in order to: 1. Valorize the sediment which promote the sustainability of surface water resources and 2. Ameliorate the soil quality by avoid problems of alkalinity, salinity and heavy metals accumulation. The use of dredged sediment for irrigated area by TWW was practically carried out in the field from the point of view metal adsorption characteristics of the sediment . The plant uptake of metals was reduced due to the application of sediment. Significant differences were observed in heavy metals concentration in the plants seeded in the amended soil with sediment compared to control soil (without sediment). However, only the sediment sample extracted from Joumine reservoir with located in the north of Tunisia was tested. Also, the experiment was carried out at field conditions and with a constant rate of sediment (35 tons of sediment per hectare of soil) because of the difficulty of the management and the limited quantity of sediment. Supportive evidences for the adsorption effect of the sediment are required.
Depending on the annual sediment yield, quantities ranging from 10 to 20 million m3 of sediment were removed from the irrigation canals before the beginning of the coming season (Adam, A.M. 1997). In brief, the rate and magnitude of sedimentation in the new reservoirs and its impact on surface water management was received as a shock (Tan. Soon-Keat, Guoliang2005). This impact has manifested in progressive reduction in the irrigated areas of main crops The prevailing problems affecting Roseires Dam are several. They are mainly: Upstream downstream sediment transportation, diminishing downstream releases associated with decreasing and fluctuating cultivated areas.
There are numerours evidence that mangroves are one of the most productive and valuable ecosytem lying between land and sea especially in the tropical and sub-tropical region [1, 2]. Out of numerous functions, the most remarkable function of this ecosytem to coastal environment is to provide a suitable technique for trapping sediments, and due to afforementioned reason it is a recognized ecosytem that retains and accumulate suspended sediments [3- 6]. Sediment accretion means the accumulation of suspended sediments rich in organic and inorganic materials borne by tidal water during high tide [2, 7]. These suspended materials settle down in the forest floor during low tide, while the velocity of water- flow is very low [2, 6]. Besides, the unique and complex structure of mangrove trees having prop roots, knee roots and pneumatophore reduces the velocity of tidal flow and thus trap sediments which eventually plays key role in land building process [2, 8-11]. Pristine and undisturbed mangroves are able to trap and retain more than 80% of tidal sediments . In most of the studies, the annual rate of sedimentaion in mangrove areas were found within 1-8 mm .
The heavy metal accumulation in the sediment and removal efficiency in stabilization ponds with Hydrocotyle ranunculoides filter were evaluated. Sediment and water were sampled in June, July and August 2018. The sedi- ment sampling for each lagoon was conducted at three sites forming a composite sample. The water samples were collected in the tributary and effluent pipelines to determine the heavy metal concentration and removal efficiency by Hydrocotyle ranunculoides. The determination of heavy metals was performed with the method of atomic flame absorption spectrophotometry. The mean concentration of heavy metals in the sediment, in a descending order, was: Fe > Zn > Pb > Cu > Cd. The concentrations of these metals ranged from 998.0 to 1365.02, from 488.01 to 600.30, from 88.23 to 95.01, from 1.47 to 1.53 and from 0.01 to 0.13 mg/Kg, respectively. In the four stabilization ponds, the pollution factor values for Cd, Cu and Fe qualified as low pollution factor. While for Zn and Pb, they qualified as moderate pollution factors. The heavy metal removal rates from the water varied by metal
The concentrations of heavy metals and arsenic in Lake Junín sediment were determined in order to evaluate their distribution and accumulation. Most of the mean values of the metal concentrations analyzed in the two sampling periods did not exceed the PEC, IAEA-SL-1 and ISQG reference material values. Cu and As exhibited mean values that exceeded the reference limit values at both sam- pling times. All heavy metals studied Fe, Cu, Cr, Cd, Pb Zn; as well as As in the sediments of the 10 Junin Lake sampling sites revealed a low contamination fac- tor ( CF < 1) for most metals, while the values of CF were qualified as moderate pollution factor and for Cd as considerable pollution factor. The PLI in sectors I, II and III of Lake Junin revealed that there is no appreciable contamination with these metals. The I geo obtained reveals that the sampling sites of Lake LJ1 and LJ3
Besides, there is another effect of investment, namely technological progress. R&D effort leads to firms moving technologically ahead. Thus, by investing in R&D and thereby accumulating knowledge in expectation firms also increase their tech- nology. We know that ∂Φ(∆) ∂∆ < 0 for ∆ > 0. Therefore, from (12) it is clear that investment grows faster the higher the technological lead. For the follower we know that ∂Φ(∆) ∂∆ > 0 for ∆ < 0. Hence, the firm that is behind invests more the closer it gets. This shows again the effects described for the benchmark case (cf. proposition 1). To see how these effects influence each other in the long run we would need to assess the overall dynamic properties of the model in terms of steady states. Unfortunately, as ∆ follows a stochastic process a steady state does not exist. However, we can for the moment assume ∆ to be constant to get an idea of the dynamics. Using equation (12) we are able to analyze ”temporary steady states”. This approach is closely related to literature on natural volatility. 22
The total concentration of metals in the Dams water is summarized in Table 2. The lead concentration in August increase downstream (247.77 -323.23µg/g d.w). Comparing these results with earlier work  on the dam’s sediment, there is an enrichment of about 10 -13 times the values reported (25µg/g d.w). Enrichment of 2 -10 times in recent sediment originated from mixed inputs of industrial, urban, domestic and agricultural sources . Since in this analysis, the values were above the stated value for enrichment, some extra (or more specific) sources of contamination have to be postulated. The vicinity of the Dam has long been used as the training ground for motorists. The exhaust from these cars deposit on both the soil and leaves of plants and later washed into the Dam. With recent increase of trainers on the site and the growth of settlement around the Dams area, it may be assume that the concentration of Pb and other metals will increase. There was also increase in Pb concentration in November (249.8 µ g/g d.w upstream and 268.43 µg/g d.w downstream) and in December (323.95 µg/g d.w). This may be due to the reduction in water volume during harmatan period that sets in earlier than usual that year (September). Lead adversely affects body system and inhibits enzymes required by all cells. Lead is said to modify the function and structure of kidney, bones, and central nervous system . It is therefore necessary to check the high concentration of the metal to avoid possible health risks on the consumers
The paper resumes the investigation of transformation of watershed ﬂ ow oﬀ caused by retention volumes of small water reservoirs (SWR) in landscape. Based on our work experience in the ﬁ eld of water reservoir design and research, we know that simple system of even small ﬁ shponds disposes of nonnegligible free retention volume. We decided to verify this assumption with aid of exact determination of discharge transformation within the basin containing realized system of small water reservoirs. The input water management data for design of water reservoirs are represented by water discharge in existing stream related to the point of designed SWR. In the Czech Republic, the data are provided by the Czech Hydrometeorological Institute (CHMI), however the data refer to an unaﬀ ected discharges, i.e. without consideration of transformation eﬀ ects of existing small water reservoirs within the basin. Although the total available volume for transformation purposes of investigated SWR system is relatively small, the results show the transformation eﬀ ect of such reservoirs is not insigniﬁ cant. Furthermore the transformation eﬀ ect is raised by proper design and functionality of the whole system of water reservoirs.
Abstract A case study, the Piano della Rocca dam (southern Italy) is discussed here in order to quantify the system performances under climate variability conditions. Different climate scenarios have been stochastically generated according to the tendencies in precipitation and air temperature observed during recent decades for the studied area. Climate variables have then been filtered through an ARMA model to generate, at the monthly scale, time series of reservoir inflow volumes. Controlled release has been computed considering the reservoir is operated following the standard linear operating policy (SLOP) and reservoir performances have been assessed through the calculation of reliability, resilience and vulnerability indices (Hashimoto et al. 1982), comparing current and future scenarios of climate variability. The proposed approach can be suggested as a valuable tool to mitigate the effects of moderate to severe and persistent droughts periods, through the allocation of new water resources or the planning of appropriate operational rules.
Constructing an accurate accumulation history is a vital but non-trivial component of most sediment- based palaeoenvironmental reconstructions (Telford et al., 2004; Blaauw and Heegaard, 2012). This is exemplified by the current generation of ‘high resolution’ relative sea-level (RSL) studies seeking to employ saltmarsh sediments as late Holocene ‘tide gauges’ (see Barlow et al., 2013). In this approach the age and altitude of palaeomarsh-surfaces (PMS) (Figure 1a) are combined with estimations of the height above sea level at which they formed (Figure 1b) in order to reconstruct the RSL change experienced at a study site (Figure 1c). Microfossils such as foraminifera are used to infer PMS height whilst age control is provided by AMS radiocarbon dating of saltmarsh plant remains. Whilst some microfossil samples are directly dated, the age of others must be inferred by interpolation between dated horizons. Although this situation is not unique to RSL reconstruction, establishing an accurate age-depth relationship is particularly important for saltmarsh-based studies since it directly impacts the magnitude of the reconstructed change as well as determining its timing (see Figure 1c and 1d). As core collection typically targets high marsh environments, the resulting RSL reconstruction is primarily controlled by the sedimentaccumulation history (Edwards, 2007).
predictions of changes in seawater conductivity for low sediment concentrations encountered in the open ocean, with different salinities, but also for the high concentrations encountered in estuaries, when the noise and the efficiency of pumping disturb the measurements. The errors in the measured conductivities (and practical salinities) caused by the sand in suspension are inferior to 0.001 mS cm -1 (on average), with concentrations usually seen in oceans fields, but they cannot be neglected in some coastal areas and near some seabed areas. Conductivity measurements to a few meters of light sediments deposits stirred by currents can be erroneous and can lead to underestimations of the density, which can disturb numerical models at the interface with the seabed. For density measurements the threshold for keeping errors inferior to 0.004 kg m -3 is much lower, 9 mg l -1 , and close to the concentrations encountered in the open ocean. With concentrations beyond this threshold, the differences between absolute salinity values determined from practical salinity measurements and from density measurements increase rapidly due to the opposite signs of the error slopes. Thereafter, complementary turbidity (or noise) measurements can be necessary to determine the need for correcting conductivity measurements, before the calculation of a practical salinity. When using a SBE 37 on mooring, the amplitude of the conductivity noise could be used to assess the SPM concentration, as a first approximation, thanks to a simple relation: N σ = 1.024x10 -5
While a case for diagenetic alteration of organic carbon can be made for the coarse fraction, it should be noted that the downcore changes in organic carbon could also be caused by a change in source. The 50% reduction in the mean organic carbon content in this fraction corresponds to the depth of the 1955- 1964 horizon (48-59 cm). This time period has also been correlated to peak timber production in the basin (Hackett, 1999). Because a large amount of the organic carbon from this fraction is derived from discrete woody pieces it is logical to conclude that intense logging and sawmill activity would generate more discrete woody debris. Therefore, the apparent downcore reduction in weight %OC can also be explained by a lower input of wood debris before 1955-1964.
The presence of glycoalkaloids in potato leaves, stems and tubers is associated with plant resistance to bacterial and fungal diseases as well as pests (Wierzbicka 2014). However, when total glycoalka- loid (TGA) concentration exceeds 100 mg/kg fresh matter, it contributes to a decline in flavour, and when the accumulation exceeds 200 mg/kg fresh matter, TGA are toxic to humans (Valkonen et al. 1996, Bejarano et al. 2000). According to many authors (Percival and Dixon 1996, Wierzbicka 2011, Hamouz et al. 2014, Zarzecka et al. 2015), glycoalkaloid content is cultivar-specific but can also be affected by weather conditions during the growing season as well as cultivation methods applied. Modern agriculture, in addition to pes- ticides, also makes use of a number of substances called biostimulants which stimulate life processes and enhance plant resistance to stress conditions (Maciejewski et al. 2007). The objective of the study reported here was to determine the impact of an application of biostimulants and herbicides on glycoalkaloid levels in the leaves and tubers of three table potato tubers as there seems to be little research on this subject.
It is pertinent to note that monitoring the concentration of heavy metals in water, sediment and even in aquatic fauna is important since knowledge of heavy metal levels in these matrices especially sediment gives vital information concerning their sources, distribution and degree of pollution (Adefemi et al, 2004; Oyakhilome et al, 2013). Contaminants in general discharged into aquatic systems, generally show a large propensity to bind to suspended matter, and thus, through sedimentation, accumulate in aquatic sediments (Wong et al., 2006; Kelderman and Osman, 2007; Saygi and Yiğit, 2012). Although this will lead to a provisional improvement of the overlying water quality, the potential release of sediment bound contaminants to the overlying water column may still pose a concealed threat to ecosystem health (Simpson et al., 2005; Kelderman and Osman, 2007). Consequently, sediments are extremely important in understanding geochemical cycling and bioavailability in aquatic ecosystems (Birch, 2003). In the aquatic environment, sediments have been widely used as environmental indicators for the assessment of metal pollution in the natural water (Islam et al.,2015a). The principal comportment of metals is a function of the suspended sediment composition and water chemistry in the natural water body (Mohiuddin et al.,2012).Contamination of heavy metals in the aquatic environment has attracted global attention owing to its abundance, persistence and environmental toxicity (Islam, et al.,2015, Ahmed et al.,2015b). The assessment of the potential risk of heavy metals contamination was proposed as a diagnostic tool for water pollution control purposes as a result of the increasing content of heavy metals in sediments and their subsequent release into the water, which could threaten ecological health.
mini-annular flume provides a suitable method for laboratory simulations, e.g. we managed to get low blanks and good experimental reproducibility, and are also able to see changes in P species within analytical precision. Re- sults showed that increase of shear stress (or SPM) caused release of inorganic P from sediment. This could be used as a fact to build a model to study P dy- namics during resuspension events in the river and estuaries environment.
We derive an equation (eq. 10) that relates rock volume changes estimated from deformation studies to the mass of extracted fluid from a flat reservoir, for a set of common simplifying assumptions. The equation shows that the change in reservoir volume, given the mass of extracted fluid, depends on fluid compressibility and elas- tic rock properties, as well as the rate of fluid recharge. We use examples from three different geothermal fields, where the ratio of deformation volume per mass of extracted fluid varies by one order of magnitude, to investigate how the obtained relation between de- formation, extraction and material properties can be applied. Using a stochastic approach we identify how varying parameter combi- nations affect the difference in the volume change per fluid mass extraction ratio, and find that the compressibilities of pore fluid and reservoir rock have a significant effect. For the Hellisheidi field in Iceland, for example, a combination of two-phase compressibil- ity and low reservoir bulk modulus, K 10 GPa, agree well with the observed deformation per fluid mass extracted, and with the deformation-based estimate of K of 1–6 GPa. For Reykjanes and The Geysers, results are less conclusive but indicate that deforma- tion per extracted fluid mass may be best explained by pure liquid compressibility at Reykjanes, and by pure steam compressibility at The Geysers. As a general result, our calculations indicate that large, order-of-magnitude differences in the ratio of reservoir vol- ume change per mass of extracted fluid (either between different geothermal systems, or for changes over the time in a single reser- voir) can be well explained by differences in fluid compressibility, which is determined by the reservoir fluid conditions (two-phase, liquid or steam). While the fluid compressibility may not be the only possible cause of such differences, we argue that it should be considered a plausible candidate that can be tested employing the equations and methods we used in this study.
Microplastics are a diverse array of synthetic polymer particles that vary in chemical composition, size (from low micrometre scale to an upper size range variously defined between 1 nm and 5 mm), density and shape (Andrady, 2011). They have been observed in most freshwater and marine environments (Eriksen et al., 2014; Corcoran, 2015; Eerkes-Medrano et al., 2015) to such an extent that they were included as sedimentary geochemical markers of the Anthropocene (Waters et al., 2016). Microplastics are often distinguished between those that are synthesized at the defined sizes for an intended application (primary microplastics) relative to particles derived from the breakdown of macroplastics (secondary microplastics). Microbeads are defined as primary microplastics that range in size between 0.1 µm to <5 mm (Environment Canada, 2015) and are used in a wide variety of industrial and consumer applications including personal care products (PCPs). Legislation banning the production of microbeads in PCPs comes into effect in 2017 as passed by the U.S. federal government and similar legislation is under review in Canada. While much of the legislative focus has been on microbeads used in PCPs, other common