Hydrobiological study of lake Mirik in Darjeeling Himalayas

Some hydrobiological features of lake Mirik, situated in the Darjeeling Himalayas were studied during May to October, 2000. Water temperature showed abrupt fluctuations. The pH was generally acidic. Dissolved oxygen increased steadily with increasing rainfall and recorded highest in late August (12.6 mgl(-1)). The gross primary productivity had a highest value of 87.50 mg C m(-3) hr(-1). Chlorophyceae and Cyanophyceae were identified among phytoplanktons. Zooplanktons were represented by Cladocerans and Copepods. The study revealed higher concentration of nutrients at certain pockets of the lake, which points to increasing human influences in the system, and, the water cannot serve as a scarcity alternative for drinking purpose.     

Hydrobiological notes on the high-salinity waters of the Sinai Peninsula

The Sinai Peninsula is surrounded by high-salinity seas and bordered by saline lagoons. The geologically long-lasting high-saline conditions have resulted in the formation of a metahaline marine fauna in the Red Sea. Metahaline marine elements also inhabit the saline lagoons with salinities up to 60 to 80 In open lagoons, beyond these values, a hyperhaline community of marine euryhaline organisms has established itself. Only beyond 100 S, or if the lagoon has no open connection with the sea, is this community replaced by hypersaline continental fresh-water elements. These observations are also discussed in the light of possible generalizations.     

Hydrobiological parameters during an annual cycle in the Arcachon Basin

Temperature, salinity, nutrients and phytoplankton biomass were monitored on a weekly to bimonthly frequency at six stations in the Bay of Arcachon from July 1984 to July 1985. This particular period appears to have differed from the last ten years in displaying higher amplitudes of both temperature and salinity (1.5° to 24.5°C and 20 to 34.5) at high tide. However, although in spring both temperature and salinity were normal (14°C, 28), an important phytoplankton spring bloom occurred, with maximum chlorophyll levels reaching 15 g l^-1 in April. Utilization of nutrients was high, particularly for nitrate and silicate, the concentrations of which decreased, respectively, from 10–15 to 0.1–2 M and 10–20 to 0.25–3 M from February to May. Exhaustion of nitrate was observed in May, except in areas subjected to river input. In contrast, silicate increased throughout the study area from May to July.     

Simulation study of the Lower Cretaceous geothermal reservoir for aquifer thermal energy storage

Environmental Geochemistry and Health - The aquifer thermal energy storage (ATES) has gained attention in several countries as an installation for increasing the energy efficiency of geothermal...     

水库流域生态补偿标准测算体系研究——以大伙房水库流域为例

生态补偿标准的测算是建立生态补偿机制的核心问题,也是难点所在。研究在对现有生态补偿标准计算方法进行总结分析的基础上,分别从供给方和需求方的角度探索建立了水库流域生态补偿标准测算体系。该体系对基于水库上游水源涵养区生态系统服务功能、生态保护建设总成本和基于下游用水城市意愿支付价格的补偿标准进行了比较分析,最终选择一个既能使水消费者承受得起,又能使生态保护者体会到有所回报的补偿金数额作为上下游协商确定补偿标准的依据。此体系较为全面地对补偿标准进行了测算,使得补偿标准更为公平、合理,进一步完善了水库流域生态补偿标准测算方法。并以大伙房水库流域为例,对其补偿标准进行测算,得出基于研究区生态系统服务功能的补偿标准为64661.3万元,基于研究区生态保护建设总成本的补偿标准为9221.4万元,基于下游用水城市意愿支付价格的补偿标准分别为8637.6万元、12956.4万元,最终认为10000万元是令补偿双方都比较容易接受的一个价格,可作为确定补偿标准的依据。     

降雨与植被耦合关系对土壤侵蚀的影响分析——以密云水库上游为例

基于TRMM降雨降雨资料时间序列数据和MODIS-NDVI16d合成产品的时间序列数据,分析密云水库上游降雨与植被的耦合关系对侵蚀的影响。结果表明：（1）侵蚀将发生在降雨强度大,同时植被覆盖差的时段,而密云水库上游地区植被的年内生长曲线形态与降雨的分布形态相似性较大,表明研究区的植被具有较好的保护水土能力;（2）研究区侵蚀主要发生在7—8月,而在1—3月以及11—12月几乎不会发生侵蚀;（3）研究区侵蚀的发生与植被覆盖有很紧密的联系,大部分的侵蚀发生在植被覆盖差的＂其他＂类内。研究方法可以清楚地了解研究区内降雨与植被的耦合关系及对侵蚀的影响,研究的结果将为在年内选择具有代表性的时段分析侵蚀状况提供很好的参考资料。     

Fate of turbid glacial inflows in a hydroelectric reservoir

Environmental Fluid Mechanics - Turbidity from glacial meltwater limits light penetration with potential ecological consequences. Using profiles of temperature, conductivity, and turbidity, we...     

A study on the accumulation of nine heavy metals in some important fish species from a natural reservoir in Riyadh,Saudi Arabia

Concentrations of nine heavy metals (Cr, Cd, Pb, Ni, Cu, Zn, Mn, As, and Fe) in the muscles of four fish species (O. niloticus, C. gariepinus, P. latipinna, and A. d. dispar) collected from the Riyadh River were detected using atomic absorption spectrophotometry in two different seasons in 2012. The concentrations of the studied heavy metals except Cd, Pb, Ni, and Cu in Aphanius d. dispar and Poecilia latipinna were found to be below the safe limits suggested by various authorities. This study also showed that Zn was predominant, while Cr was least accumulated metal in the studied fish muscles. Data demonstrated that there was a significant variation in the heavy-metal concentrations in different fish species in the Riyadh River. Significant positive correlations between heavy-metal concentrations in fish muscles were also found both in pre- and post-monsoon seasons. Metal pollution index was calculated to distinguish polluted from unpolluted ecosystems based upon current knowledge of metal bioavailability, bioconcentration, and bioaccumulation patterns. From the human health point of view, this study showed that there was a possible health risk to consumers due to the intake of Aphanius d. dispar and Poecilia latipinna under the current consumption rate in the country.     

Using artificial neural network for reservoir eutrophication prediction

Reservoirs provide approximately 70% of water supply for domestic and industrial use in Taiwan. The water quality of reservoirs is now one of the key factors in the operation and water quality management of reservoirs. Transient weather patterns result in highly variable magnitudes of precipitation and thereby sharp fluctuations in the surface elevation of the reservoirs. In addition, excessive watershed development in the past two decades has contributed to continuing increase in nutrient loads to the reservoirs. The difficulty in quantifying watershed nutrient loads and uncentainties in kinetic mechanism in the water column present a technical challenge to the mass balance based modeling of reservoir eutrophication. This study offers an alternative approach to quantifying the cause-and-effect relationship in reservoir eutrophication with a data-driven method, i.e., capturing non-linear relationships among the water quality variables in the reservoir. A commonly used back-propagation neural network was used to relate the key factors that influence a number of water quality indicators such as dissolved oxygen (DO), total phosphorus (TP), chlorophyll-a (Chl-a), and secchi disk depth (SD) in a reservoir in central Taiwan. Study results show that the neural network is able to predict these indicators with reasonable accuracy, suggesting that the neural network is a valuable tool for reservoir management in Taiwan.     

An optimization model for the economic control of reservoir eutrophication

An interdesciplinary attempt to formalize and numerically solve problems of the management of reservoir eutrophication is presented. A dynamic ecosystem model is treated by means of a generalized penalty optimization technique to calculate the combination of control actions that minimize cost under the condition that given water-quality indices are preserved.     

Seaweeds as a reservoir of Candida yeasts in inshore waters

The yeast populations on 9 species of seaweeds and in seawater were estimated by cultural methods over a 16-month period in Narragansett Bay, Rhode Island (USA). Maximal numbers occurred on rhodophytes and a chlorophyte, while the lower numbers on phaeophytes were attributed to the release of inhibitory polyphenolic materials. All divisions of algae showed a similar seasonal variation in yeast populations, correlated with trends in solar radiation and water temperature which would affect both the host and its microflora. The exposure of intertidal algae to unseasonable air temperatures apparently has a detectable effect on their microflora. The population changes in the water surrounding the seaweeds paralleled those on the plants. Only colorless yeasts of the genus Candida were observed, except for brief occurrences of the pink yeast Rhodotorula in late spring, when it accounted for 3 to 35% of the yeast community. Ninety five percent of the 362 representative isolates were strains of Candida. The published properties of the 84 species accepted in the genus Candida were compared with those of the marine isolates using numerical analysis. There were 7 groups: 1 solely of named species, 3 small groups with both named species and marine isolates, and 3 large groups with only one or two named species that contained 75% of the seaweed and sea-water isolates. An apparent successional sequence for three groups may be due to differences in their biochemical activity. The same three groups were preferentially enriched by 5 of the algal species. The role of this persistent yeast population as a reservoir of inshore yeasts is discussed.     

Extraction timing and economic incentives for geothermal reservoir management

This article considers the best extraction program for a hot water geothermal reservoir with emphasis on the optimal time to begin extraction. Using a production function relating the rate of extraction to the quality of produced energy, an operational model is presented that gives the best time to begin production, the optimal pumping rate and the best planning horizon. Also investigated is the effect of economic parameters and incentives on these decision variables. This paper studies some means by which regulatory agencies can influence the timing and rate of exploitation of geothermal energy by manipulating economic incentives, and provides information for both public and private decision making in the management of this resource.     

白盆珠水库库区坡面径流侵蚀规律初步研究

在对白盆珠水库库区开展水土流失实地调查的基础上,选择库区典型的侵蚀地貌类型与植被类型进行降雨-径流-产沙规律的初步研究.通过6个径流小区试验对比,分析了在不同植被条件下产流、产沙的差异,结果表明缺乏地表草本植被的纯飞播造林的水土保持效益十分有限;库区降雨径流产沙是白盆珠水库淤积的重要来源.     

A simulation model of carbon and oxygen dynamics in a reservoir

The CORES model represents the long-term carbon and oxygen dynamics of the Conowingo Reservoir. The model, formulated using subsetted historical data, is readily validated using the remaining historical data for all state variables of importance. Sensitivity analyses make it clear that the flux of particulate organic carbon from upstream sources and its subsequent “trapping” and metabolism in the deeper regions of the reservoir are the major factors controlling the oxygen declines historically observed in the summer months. Increased natural vertical mixing (i.e., transport of oxygen from shallow to deep waters) can increase deep-water oxygen concentrations to some extent, but not to the degree necessary to meet water quality standards. Air-to-water diffusion adds substantial quantities of oxygen to surface waters in these mixing events. Simple solutions, such as requiring continuous flow, do not appear to adequately increase the dissolved oxygen levels in the deeper portion of the reservoir.     

Sediment-associated trace and major metals in the headwaters of a tropical reservoir

Bed sediment samples of the two headwaters of a tropical reservoir in Southwestern Nigeria were analysed for some metal concentrations using ICP-OES for a period of one year. Sediment samples were collected bi-monthly from both the lower and upper reaches of the streams from May 2013 to March 2014. Sediment samples were microwave-digested and analysed using ICP-OES. Concentrations of metals were higher in the lower reach than in the upper reach, and wet season concentrations were higher than in the dry season with the exception of Fe and Mn. The annual mean metal concentrations were as follows: Fe (121.72?±?6.82?µg/g); Mn (9.34?±?2.57?µg/g); Na (6.20?±?2.29?µg/g); K (0.65?±?0.57?µg/g); Mg (8.07?±?1.36?µg/g); Ca (13.92?±?2.85?µg/g); Ba (0.17?±?0.17?µg/g); Al (106.54?±?5.55?µg/g); and Se (0.6?±?0.19?µg/g). These values were lower in comparison with the baseline concentrations of elements on the earth’s crust. Contamination assessment of all the metals investigated in this study showed that metals in the bed sediments of the two headstreams had not reached pollution status with the exception of Se.     

Statistical accuracy for estimations of large wood blockage in a reservoir environment

Environmental Fluid Mechanics - The blockage of weirs or bridges by in-stream wood can reduce the flood discharge capacity, leading to hazardous situations. To assess the related risk, blocking...     

Assessing livelihood for improvement: Samanalawewa reservoir environs,Sri Lanka

This paper explores household (HH)-level livelihood dynamics and determinants since construction of the Samanalawewa Hydroelectricity Reservoir (SHER) in the Samanalawewa watershed, Sri Lanka. The research is based on data from a structured questionnaire survey of 201 randomly selected households (HHs) in upstream and downstream areas. Livelihood dynamics at two separate points in time (1988 and 2008) were assessed based on a sustainable livelihood framework (SLF). Impact of livelihood determinants on livelihood was analysed using factor and regression analysis techniques, followed by an optimisation procedure to suggest requirements in selected significant determinants to improve the livelihood of various categories of farm HH. In both upstream and downstream areas, livelihood assets, viz. physical, social and human capital, increased significantly, while access to natural and financial capital decreased significantly and slightly, respectively, during last two decades. The factor analysis extracted six factors in the upstream area and seven in the downstream area. The derived regression models show that nine variables in the upstream area and ten in the downstream area are major determinants of HH livelihood. Based on optimisation results, policy implications are discussed in relation to needed improvements in livelihood determinants to improve overall livelihood of HHs.     

Laboratory study investigating the regeneration potential of iron particles by and the hydrodynamics of a dam-break generated flow from an infinite reservoir into a channel with an adverse slope

To determine the feasibility of using a dam-break generated flow from the sea into a storm-drain to aid in the regeneration of iron particles that control the production of H₂S in the storm-drain, a laboratory experimental investigation is carried out to measure the regeneration potential and the detailed hydrodynamics of the dam-break generated flow that causes the regeneration. The experiments are carried out using a reservoir of essentially infinite size, the sea, and a channel of limited width and adverse slope 1:20, the storm-drain. The regeneration experiments confirmed the ability of the dam-break generated flow to aid in the regeneration of the iron particles, however the regeneration potential varies from good to poor with distance away from the gate into the channel. The detailed measurements of the hydrodynamics highlighted that the dam-break generated flow from an infinite reservoir diverges little during the first uprush, has much smaller velocities during the first backwash and includes significant free surface waves. An initially wet channel bed reduces the flux into the channel. Close to the gate the flow depth increases more quickly but the velocity, and therefore the regeneration potential, is smaller.     

Denitrification and the nitrogen budget of a reservoir in an agricultural landscape.

Denitrification is an important process in aquatic sediments, but its role has not been assessed in the N mass balance of upper-Midwestern (USA) reservoirs that receive large agricultural riverine N inputs. We used a 4400-ha reservoir to determine the role of denitrification in the N mass balance and effectiveness in reducing downstream transport of NO(3-)N. Sediment denitrification was (1) measured monthly (March 2002-March 2003) at eight sites in the Lake Shelbyville reservoir in central Illinois using the acetylene inhibition, chloramphenicol technique, (2) scaled to the overall reservoir and compared to N not accounted for in a mass balance, and (3) estimated indirectly using long-term (1981-2003) mass balances of N in the reservoir. Denitrification rates in the reservoir were high during spring and early summer of 2002, when maximum NO(3-)N concentrations were measured (10-14 mg NO(3-)N/L). We estimated that denitrification for the year was between 2580 and 5150 Mg N. Missing N from the mass balance was 3004 Mg N, suggesting that sediment denitrification was the sink. Areal rates of sediment denitrification in the reservoir ranged from 62 to 225 g N x m(-2) x yr(-1), with rates a function of both denitrification intensity (microg N x g dry mass x h(-1)) and the overall mass of sediment present. From 1981 to 2003 the average NO(3-)N inlet flux was 8900 Mg N/yr. About 58% of the total NO(3-)N input was removed, and annual NO(3-)N removed as a percentage of inputs was significantly related to reservoir retention time (average = 0.36 yr for the 23 years, range = 0.21-0.84 yr). By scaling denitrification in Lake Shelbyville to other reservoirs in Illinois, we estimated a sink of 48900 Mg N/yr. When combined with estimated in-stream denitrification, 60900 Mg N/yr was estimated to be removed by sediment denitrification. This reduces riverine export from Illinois to the Gulf of Mexico, where the flux during the 1990s was about 244000 Mg N/yr, and illustrates the importance of reservoir denitrification as an N sink in Midwestern agricultural landscapes.