Cladocera assemblages from reservoirs in Sri Lanka and their relationship to measured limnological variables

The potential of using surface‐sediment assemblages of Cladocera as bioindicators for reservoirs in Sri Lanka was assessed for their subfossil remains, along with contemporary physical and chemical measurements from each reservoir. The reservoirs span five climatic regions, from extremely arid environments to tropical montane forests, as well as three orders of magnitude changes in many physical and chemical variables. In total, although the remains of 39 Cladocera taxa from 21 genera were identified, only 31 taxa from 37 sites were present at sufficiently high abundances to assess their relation to measured environmental variables. Canonical correspondence analysis (CCA) identified surface area, maximum depth and chloride as the three most important measured environmental variables that could account for the variation in the cladoceran assemblages. Taxa such as Chydorus sphaericus, Alona aff. verrucosa and Leydigia acanthocercoides were more abundant in generally deeper, larger reservoirs, whereas Alonella excisa, Euryalona orientalis, Notoalona globulosa and Chydorus eurynotus were more abundant in shallow smaller reservoirs. Although there was a strong separation between climatic zones in terms of factors related to specific conductance, this factor only appears marginally important in separating cladoceran assemblages. Quantitative inference models developed to assess the strength of inferring environmental variables using partial least squares regression and calibration were all relatively weak, with jackknifed coefficient of determination values of 0.40, 0.28 and 0.27 for surface area, maximum depth and chloride, respectively. These results, in conjunction with large differences in eigenvalues between constrained and unconstrained ordinations, suggest that unmeasured environmental variables are also important in structuring cladoceran assemblages.     

Seasonal water level fluctuations: Implications for reservoir limnology and management

With the purpose of finding out whether seasonal water level fluctuations could affect water quality in a reservoir subjected to those changes, trends in environmental variables and in phytoplankton and zooplankton assemblages were analysed. The reservoir's hydrological cycle was characterized by three regimes. The maximum level phase lasted from January to the beginning of June, the emptying phase existed between mid‐June to the beginning of September and the minimum level phase lasted from mid‐September to the beginning of the first autumn/winter rain events. The highest values of total phosphorus, soluble reactive phosphorus, nitrate, water colour and chlorophyll a were found during the minimum level phase. The phytoplankton assemblage was dominated by taxa typical of meso‐eutrophic environments during the emptying and minimum level phases. However, during the maximum level phase, taxa generally found in more oligotrophic systems were observed here also. Similar to other disturbed systems, the zooplankton assemblage was dominated by Rotifera, except in summer and autumn when the cladoceran Ceriodaphnia quadrangula and/or the copepod Tropocyclops prasinus became dominant. Although those shifts seem to be related to water level variations, further research is needed to evaluate to what extent they might also be induced by other seasonal factors acting independently of water fluctuations. Based upon the obtained data, suggestions for reservoir management are proposed.     

Comparison of different trophic state indices applied to tropical reservoirs

Reservoirs represent impoundments of river flows for multiple human purposes, including hydropower generation and industrial, recreational and agricultural activities. In considering the current state of dammed rivers and future projects, there is a major concern in tropical areas regarding the water quality of these aquatic ecosystems, most being subjected to eutrophication process. To this end, the Carlson (1977), Toledo (1983), Lamparelli (2004) and Cunha (2013) trophic state indices were applied and compared in six interconnected reservoirs from the Paraíba do Sul Ecoregion in Brazil that differ in their morphometry, nutrient loadings, water retention times and altitudes. Limnological variables were measured in an extensive monitoring programme carried out from 2011 to 2014 during both the rainy and dry seasons. Application of the different numerical models resulted in different trophic state classifications. Toledo's trophic state index was considered the best for assessing the trophic state of the study reservoirs since it under‐evaluates water transparency, which can be related more to inorganic turbidity rather than to phytoplankton biomass in tropical water systems. The Carlson index, developed for temperate zone lakes, resulted in higher trophic classifications, thereby not being considered a reliable model for the study reservoirs. Both the Lamparelli and Cunha indices generally classified the study reservoirs as being in an oligotrophic state, thereby underestimating their trophic status. All the trophic state indices varied seasonally, with water transparency being the only variable significantly affected by rainfall variations. Based on the results of the present study, it was concluded that an arbitrary choice of existing trophic state indices to evaluate the water quality in tropical environments might lead to erroneous conclusions regarding the actual trophic conditions of tropical waterbodies. Further, the weak correlation observed between total phosphorus and chlorophyll‐a concentrations indicates total phosphorus might not be a key factor limiting algal growth in tropical water systems, thereby meriting more research focusing on tropical reservoirs, as well as development of new trophic state indices, including consideration of other potentially limiting factors.     

Zooplankton as an indicator of trophic conditions in two large reservoirs in Brazil

The physical and chemical variables of the water, and the composition and structure of the zooplankton communities, in Três Marias and Furnas Reservoirs in Minas Gerais, Brazil, were compared to characterize these environments in relation to their trophic state. Higher values of electrical conductivity and chlorophyll‐a, total solids, suspended organic matter and total nitrogen concentrations were recorded in Três Marias Reservoir. Higher water transparency and nitrite and nitrate concentrations were observed in Furnas (P < 0.000). Higher zooplankton densities were always obtained in Três Marias Reservoir and, during the rainy period (P < 0.000), with mean values in the dry and rainy periods of 23 721 and 90 872 org m^?3, respectively, in Três Marias Reservoir and 9022 and 40 434 org m^?3, respectively, in Furnas Reservoir. Copepoda was the dominant group in both reservoirs, mainly the younger stages (nauplii and copepodids). Based on the absolute and relative values, the contribution of rotifers was higher in Três Marias Reservoir than in Furnas Reservoir. Although the Trophic State Index, based on water transparency and chlorophyll‐a and total phosphorus concentrations, indicated an oligotrophic state for both reservoirs, the higher densities of the zooplankton community in Três Marias Reservoir, as well as the predominance of cyclopoids and smaller‐sized species such as bosminids, characterized this environment as mesotrophic. Larger‐sized species such as calanoids, daphniids and sidids in Furnas Reservoir characterized the better water quality of this reservoir.     

Use of geographical information system and remote sensing techniques for planning culture‐based fisheries in non‐perennial reservoirs of Sri Lanka

The presence of a wide areal extent of small‐sized village reservoirs offers a considerable potential for the development of culture‐based fisheries (CBFs) in Sri Lanka. To this end, this study uses geographical information systems (GISs) and remote sensing (RS) techniques to determine the morphometric and biological characteristics most useful for classifying non‐perennial reservoirs for CBF development and for assessing the influence of catchment land‐use patterns on potential CBF yields. The reservoir shorelines at full water supply level were mapped with a Global Positioning System to determine shoreline length and reservoir areal extent. The ratio of shoreline length to reservoir extent, which was reported to be a powerful predictor variable of CBF yields, could be reliably quantified using RS techniques. The areal extent of reservoirs, quantified with RS techniques (RS extent), was used to estimate the ratio of forest cover plus scrubland cover to RS extent and was found to be significantly related to the CBF yield (R² = 0.400; P < 0.05). The results of this study indicated that morphometric characteristics and catchment land‐use patterns, which might be viewed as indices of biological productivity, can be quantified using RS and GIS techniques.     

溪洛渡-向家坝-三峡梯级水库水温分布特性

梯级水库蓄水运行后,改变了河流的天然水流情势和水体的年内热量分配,水库内的水温分布特性随之变化。为了解溪洛渡-向家坝-三峡梯级水库蓄水运行后河道水温分布特征,对梯级水库沿程19个断面水温进行了观测,并根据观测资料系统地分析了梯级水库进出库水温和沿程水温分布,以及垂向温度分布变化情况。研究结果表明:溪洛渡、向家坝、三峡梯级水库的下泄水温在降温季节略有增加,在升温季节略有下降,形成了"高温不高,低温不低"的平坦化现象;溪洛渡和向家坝水库坝前区域在垂向上均出现明显的温度分层,而三峡水库近坝区的温度分层现象在梯级水库运行后明显减弱,近几年表层和底层水温相差最大值仅为2.5℃。研究结果可为梯级水库联合调度、水生态研究、水库水温数学模型验证等提供参考。     

Effects of anthropogenic influences on the trophic status of two water supply reservoirs in Serbia

The results of hydrobiological investigations of Grošnica and Gruža Reservoirs near the city of Kragujevac in Serbia indicated differences in their trophic status. Although considerably younger than Grošnica Reservoir, Gruža Reservoir manifests all the signs of accelerated eutrophication. Primary and secondary plankton productivity is significantly greater in Gruža Reservoir, as is macrophyte production. Accelerated eutrophication also is indicated with the results of an ecological analysis. The manifested differences can be attributed mainly to the greater human influences, as well as the unfavourable morphometric characteristics of Gruža Reservoir, compared to Grošnica Reservoir.     

浙江5座水源水库浮游动物调查及水质评价

为研究浙江5座水源水库浮游动物群落结构特征及水质状况,分别于2014年8月(丰水期)和12月(枯水期)对浮游动物的群落组成、优势种、密度、生物量和多样性进行了调查分析。共鉴定出浮游动物53种,包括原生动物14种、轮虫18种、枝角类9种、桡足类12种,优势种为台湾温剑水蚤(Thermocyclopstaihokuensis)。水源水库物种年均密度和生物量分别为1088.85 ind./L和1.1 mg/L,丰水期(1869.49 ind./L和1.85 mg/L)明显高于枯水期(308.22 ind./L和0.35 mg/L)。运用香农威纳指数H'、Margalef物种丰富度指数d_M和Pielou均匀度指数J对5座中型水源水库综合评价,结果显示总体水质为清洁-轻污染水平,丰水期水质明显好于枯水期。     

浙江供水水库水质保护中存在的问题及对策

随着浙江省经济社会的快速发展，公众对饮用水水质的要求不断提高，安全、绿色饮水已成为公众的基本要求。由于降水时空分布不均，河道水质较差，水库已成为浙江省最重要的供水水源地。目前，浙江省水库水质安全面临许多隐患和深层次的矛盾。因此，建立完善的保护机制，开展具体工作保护水库水质，是实现“绿色饮水”．保障饮水安全的重中之重。     

大型灌区骨干水库分期旱限水位研究

水库作为常见的重要水利工程设施,在区域水资源承载力水量、水质、水生态和水流更新等要素调控中具有举足轻重的地位和作用,在降水径流减少的枯水季节显得尤其重要。旱限水位是水库在低水位调度运行的控制性特征水位,其合理设置与科学运用对区域水资源高效利用意义重大。为此以淠史杭灌区梅山水库的来水特性和用户需水特性为基础,首先采用Hausdorff维数分形方法划分了梅山水库入库径流干旱预警时段,进而通过不同水平年各预警期内来水、供水调节计算了初始旱限水位:旱警水位和旱枯水位,并以水库灌区水资源系统长系列模拟模型及优化模型为依托,优化确定了梅山水库不同预警期的旱限水位,最后分别从水库运行、灌区灌溉、生产生活供水、生态用水以及水力发电等多角度评估了旱限水位的合理性,为水利部门指导水库灌区抗旱运行,制订相应抗旱预案提供技术参考。     

浅析小型水库除险加固工程设计中水文水利计算

阐述小型水库除险加固工程设计中水文水利计算的基本方法,总结了在水文水利计算工作中应注意的问题和经验.     

黄河上游调节性水库对河段水温的影响及其环境效应分析

大型水库对河道水温会产生一定的影响,特别是其累积影响是否会对生态环境产生衍生影响是很多专家关注的重点之一,因此,如何在水电规划环评或单项工程环评中选用合适的方法判断出准确的水温影响尤为重要。根据黄河上游龙羊峡一刘家峡河段多年的实测数据,分析黄河上游水电站运行产生的河段水温时空分布变化,研究大型调节性水库对河道水温的影响及其环境效应,同时将回顾成果与原环评结论进行对比,并针对刘家峡水电站这一具有特殊形态和运行方式的水库的水温结构分型方法进行探讨,提出了水温分析中所采用的模型及分析方法的合理性建议。     

大型水库功能演变对水库水质的影响——以河南省某大型水库为例

水库水质污染是水库利用过程中比较普遍发生的现象,与水库功能演变直接相关。河南省某大型水库目前集防洪、灌溉、城市供水、旅游、养殖、发电、航运等多种功能于一体,在区域社会发展中作用重大。以该水库为例,运用相关分析法,探讨了该水库自1997年以来的水质波动状况与其功能演变之间的关系,发现旅游经济、养殖业经济发展与水库总氮、总磷、石油类等水质指标之间存在比较显著的正相关关系,表明该水库发展旅游、养殖功能存在环境容量限制性,对大型水库功能调整必须注意其生态环境承载能力。     

塔里木灌区水库群水资源优化调度模型研究

塔里木灌区位于塔里木河上游,其引水量直接影响到塔河的综合治理。为缓和这一矛盾,本文采用大系统分解协调技术与动态规划相结合的方法对该灌区水库群系统水资源优化配置问题进行了分析和研究,构建了该灌区两层二级结构的水库优化调度系统的数学模型。应用该模型对该灌区水库群进行了实例计算分析,为灌区生产计划和水库调度提供了理论依据。     

Sensitivity of water quality indicators in a large tropical reservoir to selected climate and land‐use changes

This study compared the sensitivity of water quality in tropical Aguamilpa Reservoir, as represented by normalized algae mass and dissolved oxygen, to selected projected changes from global climate change and development. The sensitivity of reservoir stratification as an indicator of reservoir sensitivity also was analysed. Model simulations indicated the reservoir was more sensitive to changes during the warm‐dry season than at other times. Both indexes (normalized algal mass and dissolved oxygen mass) were more sensitive to changes in air temperature (climate change) and nitrogen loading (development) than to changes in flow. The sensitivity to air temperature was similar to, but generally less than, the sensitivity to nutrient inflow. At the bounding values for change (3 °C for temperature; 50% increase in nitrogen loading), the algae mass sensitivities were 0.15 mg L^?1 per 3 °C and 0.2 mg L^?1 per 50% nitrogen load increase, and the dissolved oxygen mass sensitivities were 0.7 mg L^?1 per 3 °C and 2.0 mg L^?1 per 50% load increase. Changes in air temperature and nitrogen loadings affect the reservoir in different ways, air temperature mostly changing the timing of the algal growth with little change in peak values, while nutrient loadings change the peak values with little change in the timing. While the sensitivities are similar, the total algal mass change is significantly larger for nitrogen loading, compared to air temperature changes. These results imply global climate change effects can be partially mitigated by implementing management measures in the surrounding watersheds to minimize nutrient inflows, especially nitrogen in the case of Aguamilpa Reservoir.     

观音阁--参窝水库补偿防洪调度汛限水位研究

参窝水库汛限水位与正常蓄水位相差10.4m,严重影响水库兴利效益的发挥。结合水库的实际情况,文章阐述运用库群补偿防洪调度的理论,使参窝水库的汛限水位得到补偿抬高,并分析由此产生的供水效益和发电效益。     

金沙江下游梯级水库汛期运行水位协同浮动调度研究

为验证梯级水库汛期运行水位协同浮动调度模型方法的合理性与普适性,在金沙江流域开展实例分析。首先考虑洪水预见期变化,应用动态多目标算法高效求解调度模型;然后评价汛期运行水位协同浮动调度的风险与效益;最后推求乌东德、白鹤滩、溪洛渡、向家坝水库的汛期运行水位协同浮动关系。研究结果表明：相比年汛限水位静态控制调度方案,梯级水库汛期运行水位协同浮动调度方案在不增加防洪风险前提下,各水库汛期运行水位均可适当抬升,汛期多年平均发电量和电站弃水减少量的最高值(改善率)可达1071亿kWh(11.1%)和649亿m³(14.3%),有效提高了洪水资源利用水平,综合效益巨大。