Influences of land use/cover on water quality in the upper and middle reaches of River Njoro, Kenya

Data from 10 sampling sites along the River Njoro are used to examine the contribution of nutrients from upstream land uses draining each of the sampling sites. The data also are used to assess whether both the proportion of land uses and the size of the subwatersheds account for the variability in water quality in the River Njoro watershed. Geographical Information System analysis was used to determine the spatial distribution of land‐cover types and subwatersheds contributing run‐off to the sampling sites in the River Njoro. Standard Digital Elevation Model‐based routines were used to establish the watershed area contributing run‐off to each sampling site. Water and sediment samples were collected for chemical analysis, and the nutrient levels were related to the upstream land‐use types and the size of the subwatersheds. The mid‐stream portion of the River Njoro (near Egerton University) accounts for the highest nutrient contributions. The percentage contribution is magnified by additions from industrial, human settlements and agricultural land uses around the University. There is a significant decrease in nutrient levels downstream, however, indicating natural purification as the river flows through an area of large‐scale farming with intense, well‐preserved riparian and in‐stream vegetation. Steep slopes of the land upstream of Egerton University enhance erosion and nutrient losses from those subwatersheds. Mixed small‐scale agricultural and bare lands contribute over 55% of the phosphorus load to the upper and mid‐reaches of the River Njoro. The size of the subwatershed accounts for about 53% of the variability in the soluble phosphorus in the river. The land‐use subwatershed proportions are important for characterizing and modelling water quality in the River Njoro watershed. Upland land uses are as important as near‐stream land uses. We suggest that conservation of intact riparian corridor along the river and its tributaries contributes significantly to natural purification processes and recovery of the ecological integrity of the River Njoro ecosystem.     

Exotic introductions to the fishery of Lake Victoria: What are the management options?

Lake Victoria is Africa's most important source of inland fishery production, exhibiting annual catches of ≈ 400 000 mt. The predatory Nile perch, Lates niloticus, and the herbivorous tilapiines, Oreochromis niloticus, Oreochromis leucostictus, Tilapia zillii and Tilapia rendalii, were introduced in Lake Victoria in the 1950s and 1960s. Nile perch were introduced to convert the abundant, but bony, haplochromines to fish flesh, while the tilapiines were introduced to boost the declining fishery. Since that time, the fisheries of Lake Victoria have undergone dramatic social and ecological changes. The catches increased tremendously, changing the fishery from artisanal to commercial, in turn increasing fisher income and employment opportunities. However, there was a decline and, in some cases, the disappearance of many indigenous fish species, especially the haplochromine cichlids. This reduction was attributed to overexploitation, predation, and competition and hybridization with the introduced species. The decline of the native fish species has had impacts on the trophic and ecological status of the lake. Nile perch now dominate the formerly complex food web. The loss of phytoplanktivorous haplochromines has contributed to an increase in algal blooms, reduction in water quality and occasional fish kills. Water hyacinth, Eichhornia crassipes, invaded Lake Victoria in 1988, with high rates of infestation in shallow waters and bays, which are breeding and nursery grounds for most fish species. Catches of Nile perch decreased following the infestation, while those of Nile tilapia, lung fish (Protopterus aethiopicus) and mud fish (Clarias gariepinus) increased. Haplochromines species also showed some signs of recovery. In view of all these changes, the future of the Lake Victoria fishery is uncertain.     

A Dynamic Risk Assessment Methodology for Maintenance Decision Support

The failure mode and effect analysis (FMEA) is a widely applied technique for prioritizing equipment failures in the maintenance decision‐making domain. Recent improvements on the FMEA have largely focussed on addressing the shortcomings of the conventional FMEA of which the risk priority number is incorporated as a measure for prioritizing failure modes. In this regard, considerable research effort has been directed towards addressing uncertainties associated with the risk priority number metrics, that is occurrence, severity and detection. Despite these improvements, assigning these metrics remains largely subjective and mostly relies on expert elicitations, more so in instances where empirical data are sparse. Moreover, the FMEA results remain static and are seldom updated with the availability of new failure information. In this paper, a dynamic risk assessment methodology is proposed and based on the hierarchical Bayes theory. In the methodology, posterior distribution functions are derived for risk metrics associated with equipment failure of which the posterior function combines both prior functions elicited from experts and observed evidences based on empirical data. Thereafter, the posterior functions are incorporated as input to a Monte Carlo simulation model from which the expected cost of failure is generated and failure modes prioritized on this basis. A decision scheme for selecting appropriate maintenance strategy is proposed, and its applicability is demonstrated in the case study of thermal power plant equipment failures. Copyright © 2016 John Wiley & Sons, Ltd.     

企业标准化与环境管理的关系

本文从分析企业的环境现状，提出控制产品生命周期过程的现实和潜在环境影响因素的方法，导出企业标准化与环境管理的成功发展关系，为企业实施可持续发展奠定基础。     

Macroinvertebrate assemblages along a land-use gradient in the upper River Njoro watershed of Lake Nakuru drainage basin, Kenya

A study was conducted in the upper reaches of the River Njoro watershed to test the impacts of changing land‐use patterns, from predominantly forest to pasture and agriculture, on benthic macroinvertebrate communities. Stream sampling sites were chosen to correspond to the main offstream land uses, including forests, grazing, small‐scale agriculture, and intensive agriculture. Physicochemical variables were measured at each sampling site, and from collected water samples. Sampled macroinvertebrates were identified, and taxon diversity, richness, evenness and dominance were estimated for each site. Higher mean temperatures were recorded at the grazed and cultivated sites, compared to the forested sites. Higher ammonia concentrations were characteristic of the grazed parts of the watershed, while higher mean total phosphorus and total nitrogen concentrations were observed at the intensively cultivated sites. Baetis and Simulidae composed 65% by number of all the invertebrates collected. They dominated the benthos of the cultivated sections of the watershed, where they formed up to 75% of the observed invertebrate numbers. However, higher mean diversities, richness and evenness were recorded at forested sites, with a few taxa (notably Lepidostoma hirtum, Potamon sp., Leptophlebia sp. and Helodidae) being restricted to these unpolluted reaches, although many other taxa were common to all sites. Our findings suggest that a change from forestry to agriculture and grazing land uses have affected the physicochemical environment of the River Njoro, leading to a reduction in the diversity and evenness of benthic macroinvertebrates.     

"入世"要求与企业标准化

一、前言当前 ,我国加入世界贸易组织 (ＷＴＯ)的谈判和进展 ,已引起国内各界人士的广泛关注。从发展来看 ,“入世”将是我国市场开发的继续 ;从企业来看 ,“入世”意味着企业进入全方位的市场竞争 ;对消费者来说 ,“入世”使国人有更多的机会选择自己需要的或更满意的商品 ;对经营者或雇员来说 ,“入世”则对他们的经营或工作能力提出了更高的素质要求。所有这些 ,都说明“入世”将成为推动我国经济发展的机遇 ,但也是一种挑战。这种挑战 ,将决定我国标准化适应国际市场大循环的程度。因此 ,“入世”后 ,各级政府和企业经营者要重视企业标…     

Difficulties of fishing at Lake Naivasha,Kenya: is community participation in management the solution?

Unlike other lakes in tropical regions, Lake Naivasha exhibits low fish species diversity. The fishery is based on introduced fish species that are not native to the lake. The lake ecosystem is very fragile, as reflected in its fluctuating fish catches. The fishery almost completely collapsed in 2001, due partly to mismanagement and ignorance about needed conservation measures. The Kenyan government, like many governments around the world, recognized the need to involve fishers and other stakeholders, in order to ensure better management of the lake fisheries resources. Also referred to as collaborative management (co-management), this management approach provides the opportunity to share responsibility for managing the fishery resources between the government and the community. A total ban on fishing was imposed in February 2001, lasting for 1 year, to allow lake fish stocks to recover. This study analyses the co-management process for Lake Naivasha, and discusses the role played by the community during the fishing ban, as well as the successes and challenges encountered, and the tribulations and perceptions of the fishers regarding the new management strategy. It also comprises the first documentation of community participation in fisheries management begun for Lake Naivasha in the year 2001.     

Spatial and seasonal variations in phytoplankton community structure in alkaline–saline Lake Nakuru,Kenya

Spatial and seasonal variations of phytoplankton, expressed in terms of species composition, cell density, biovolumes and biomass, collected at 10 sampling sites in alkaline–saline Lake Nakuru, Kenya, were investigated monthly from March 2004 to February 2005, in relation to selected physical and chemical water quality parameters. A total of eight species, belonging to five genera and three classes, were recorded. The Cyanophyceae comprised the bulk of the phytoplankton, followed by Euglenophyceae, while Bacillariophyceae were the least abundant. Arthrospira fusiformis was the most dominant species, in terms of density, among the Cyanophyceae, while Euglena spp. and Navicula elkabs dominated the Euglenophyceae and Bacillariophyceae density, respectively. Seasonal variations in phytoplankton species composition, density and biomass were significant (P < 0.05) with minimum cell density and biomass occurring during the dry season, and being maximum following the end of the two rainy seasons from May to November 2004, suggesting the possible influence of various environmental factors on the lake. Sampling sites located close to the inlets of inflowing rivers exhibited significantly (P < 0.05) higher phytoplankton cell density and biomass than those by the inshore sites. Soluble reactive phosphorus, ammonia‐nitrogen, conductivity and total alkalinity accounted for most of the variations in the cell densities of phytoplankton species.     

Performance measurement using overall equipment effectiveness (OEE): literature review and practical application discussion

The quest for improving productivity in the current global competitive environment has led to a need for rigorously defined performance-measurement systems for manufacturing processes. In this paper, overall equipment effectiveness (OEE) is described as one such performance-measurement tool that measures different types of production losses and indicates areas of process improvement. Analysis is done on how OEE has evolved leading to other tools like total equipment effectiveness performance, production equipment effectiveness, overall factory effectiveness, overall plant effectiveness, and overall asset effectiveness. Two industrial examples of OEE application are discussed, and the differences between theory and practice analysed. Finally, a framework for classifying and measuring production losses for overall production effectiveness is proposed. The framework harmonizes the differences between theory and practice and makes possible the presentation of overall production/asset effectiveness that can be customized with the manufacturers needs to improve productivity.     

Zooplankton partitioning in a tropical alkaline–saline endorheic Lake Nakuru,Kenya: Spatial and temporal trends in relation to the environment

Spatial and temporal zooplankton variations were studied for 1 year in tropical alkaline–saline Lake Nakuru to determine how they partition in the habitat, relative to environmental variables. Monthly samples were collected at 10 sampling sites, with subsurface tows, using 33.5‐μm mesh plankton nets. Physicochemical parameters displayed clear seasonal variations associated with precipitation patterns. Nine species, belonging to two main zooplankton taxonomic groups (ciliates; rotifers), were identified in the samples. Brachionus dimidiatus dominated the samples, accounting for 80% of the total zooplankton abundance. Kruskall–Wallis tests indicated significant (P < 0.05) temporal and spatial variations among all taxonomic groups. Different zooplankton species displayed a clear succession throughout the year. The total abundance of the rotifers and ciliates peaked at sampling sites near inlets during the long rainy seasons, while those in the inshore sites displayed variable succession patterns. Spatiotemporal structure of the zooplankton assemblages, and its correlation with environmental variables, indicated each species displayed distinct niche‐based partitioning. The ciliates niche was associated with increasing soluble reactive phosphorus, total phosphorus and nitrite–nitrogen (NO₂–N) concentrations. Niche partitioning in rotifers was associated with nitrate–nitrogen (NO₃–N), conductivity and pH. These results indicate physical niche separation, even in a small, relatively homogenous lake among species of rotifers and ciliates, providing information from which future changes in their abundance and spatial distributions can be predicted, given continuous water quality changes.