Effect of flow forecasting quality on benefits of reservoir operation - a case study for the Geheyan reservoir (China)

This paper presents a methodology to determine the effect of flow forecasting quality on the benefits of reservoir operation. The benefits are calculated in terms of the electricity generated, and the quality of the flow forecasting is defined in terms of lead time and accuracy of the forecasts. In order to determine such an effect, an optimization model for reservoir operation was developed which consists of two sub-models: a long-term (monthly) and a short-term (daily) optimization sub-model. A methodology was developed to couple these two sub-models, so that both short-term benefits (time span in the order of the flow forecasting lead time) and long-term benefits (one year) were considered and balanced. Both sub-models use Discretized Dynamic Programming (DDP) as their optimization algorithms. The Geheyan reservoir on the Qingjiang River in China was taken as case study. Observed (from the 1997 hydrological year) and forecasted flow series were used to calculate the benefits. Forecasted flow series were created by adding noises to the observed series. Different magnitudes of noise reflected different levels of forecasting accuracies. The results reveal, first of all, a threshold lead time of 33 days, beyond which further extension of the forecasting lead time will not lead to a significant increase in benefits. Secondly, for lead times shorter than 33 days, a longer lead time will generally lead to a higher benefit. Thirdly, a perfect inflow forecasting with a lead time of 4 days will realize 87% of the theoretical maximum electricity generated in one year. Fourthly, for a certain lead time, more accurate forecasting leads to higher benefits. For inflow forecasting with a fixed lead time of 4 days and different forecasting accuracies, the benefits can increase by 5 to 9% compared to the actual operation results. It is concluded that the definition of the appropriate lead time will depend mainly on the physical conditions of the basin and on the characteristics of the reservoir. The derived threshold lead time (33 days) gives a theoretical upper limit for the extension of forecasting lead time. Criteria for the appropriate forecasting accuracy for a specific feasible lead-time should be defined from the benefit-accuracy relationship, starting from setting a preferred benefit level, in terms of percentage of the theoretical maximum. Inflow forecasting with a higher accuracy does not always increase the benefits, because these also depend on the operation strategies of the reservoir.\u

Plant traits associated with resistance to Thrips tabaci in cabbage (Brassica oleracea var capitata)

Thrips tabaci is a major problem in the cultivation of cabbage for storage, as this pest causes symptoms that necessitate the removal of affected leaves from the product. Between cabbage varieties large differences in susceptibility occur. This study aimed to identify plant traits associated with these differences, in field experiments with natural infestation in 2005 and 2006. One factor affecting the amount of thrips damage was the timing of the development of the head. In an experiment with different planting dates especially the early maturing, more susceptible varieties were shown to benefit from later planting. In comparisons of multiple varieties in both years, regression studies showed that more advanced plant development in August and early September increased thrips damage at the final harvest. However, no single plant trait explained more than 25% (2005, Brix) or 48% (2006, compactness) of the variation in thrips damage. Optimal regression models, explaining up to 75% of the variation in thrips damage included Brix and leaf surface wax late in the season, as well as an indicator of plant development earlier in the season, and in 2005 also leaf thickness. The possible role of these plant traits in relation to thrips is discusse

Earliness, leaf surface wax and sugar content predict varietal differences for thrips damage in cabbage

When cabbage is cultivated for storage in the Netherlands, it is usually harvested around mid-October. This type of cabbage crop may be severely damaged by thrips (Thrips tabaci). The thrips population on the plants and the more severe symptoms develop mostly during September and October. Also during cold storage symptoms continue to develop. The damage caused by thrips is due to the symptoms that develop after feeding, which are small callus-like growths that will turn brownish after some time and which may cover substantial amounts of leaf area. Large differences exist between cabbage varieties in their susceptibility to thrips damage. It is not clear whether these differences are due to resistance (affecting the thrips population in the plant) or to tolerance (affecting the development of symptoms upon thrips feeding). Further, not much is known about plant traits affecting the resistance or tolerance to thrips. In order to guide selection and breeding for resistance to thrips, this study aimed to identify plant traits causing these differences. In the years 2005, 2006 and 2007 we performed field experiments with collections of varieties differing in a number of plant traits, with earliness varying from moderately late to very late. In the field experiments we relied upon natural infestation by thrips. Several times during the period August-October plants were harvested and assessed for the amount of thrips damage and the number of thrips, as well as for several morphological and physiological traits, including head circumference, leaf thickness, developmental stage, head compactness, leaf surface wax, and Brix value as an indication of the content of soluble sugars. One factor affecting the amount of thrips damage was the timing of the development of the head. Regression studies showed that more advanced plant development at the end of August increased thrips damage at the final harvest. Other plant traits affecting thrips damage were Brix and the amount of leaf surface wax. However no single plant trait explained more than 45% of the variation in thrips damage at the final harvest. Optimal regression models, explaining up to 75% of the variation in thrips damage included Brix and leaf surface wax late in the season, as well as an indicator of plant development earlier in the season, and in 2005 also leaf thickness. The possible role of these plant traits in relation to thrips is discussed

On the modelling of biological effects on morphology in estuaries and seas

Morphological modelling aims to explain and predict the changes in rivers, seas and estuaries due to these interaction. In recent history, a lot of progress has been made, especially with stability analysis approaches. However, so far only the physical interactions have been taken into account. It is known however, that biological factors are important to the dynamics of the water systems. In this paper a first step is made in the inclusion of biology into the morphodynamic models. This inclusion is based on the effect that benthic organisms have on the erodibility of the bed. This can easily be included by a change of the critical bed shear stress. These changes in the critical bed shear stress then influence the morphology. This idea has been applied to two cases. The results of the first case indicate that this approach can reproduce the influence of benthic organisms on the mud content of the bed in estuaries. The second case shows that even low numbers of organisms can influence the characteristics of large bed forms

Sustainable organic plant breeding: Final report - a vision, choices, consequences and steps

In general, the characteristics of organic varieties - and by extension of organic plant breeding - differ from that of conventional breeding systems and conventional varieties. Realising an organic plant breeding system and subsequently steering it to meet changing demands is no less than a mammoth task. The many actions to be undertaken can be divided into short-term commercial and scientific activities, and longer or long-term commercial and scientific activities. Action must be taken in the short-term to ensure adequate quantities of organically propagated plants and seed. This is vital in consideration of Regulation 2092/91/EC which states that, as of 1 January 2000, all propagating material used in organic production must be of organic origin. Additional measures are needed to accelerate the development of organically propagated varieties. Within the breeding sector, variety groups should be established to streamline communication in the chain. Variety groups should have a large contingent of farmers, as well as representatives from the trade branch and breeders. Members should communicate intensively with each other, share experiences, and participate in trials and variety assessments. Questions, wishes and bottlenecks could be recorded by variety groups and passed on to other parties in the chain. The practical details of the plant health concept which is at the basis of organic breeding must be worked out (operationalised). This will require scientific research, for example on: root development and mineral absorption efficiency weed suppressive capacity in situ versus ex situ maintenance resistance breeding in combination with cultivation measures seed-transmitted diseases adaptive capacity alternatives for growth stimulants, silver nitrate and silver thiosulfate in the cultivation of cucumbers and pickles Such research should be carried out by academic institutions (such as Wageningen University and Research Centre) in collaboration with Louis Bolk Institute, Stichting Zaadgoed and private companies. A platform should be established to make an inventory of problems and priorities and to develop research proposals. Farmers could contribute their ideas to the platform through the variety groups. Conclusion A plant breeding system for organic production should be based on the organic concept of plant health and on the organic position on chain relationships. As the total land area under organic production is still relatively small, it is unlikely that commercial breeders will make large investments to develop organic breeding programmes without financial support from other parties, i.e. the government. In this early stage, it is vital that the government provides generous funding and plays an active enabling role. We hope that the action plan to stimulate organic plant breeding, as requested by Parliament, will dovetail with the activities described above

Experiences of carriers of multidrug-resistant organisms: a systematic review

Contains fulltext : 202240.pdf (publisher's version ) (Open Access)OBJECTIVES: A comprehensive overview of the ways control measures directed at carriers of multidrug-resistant organisms (MDRO) affect daily life of carriers is lacking. In this systematic literature review, we sought to explore how carriers experience being a carrier and how they experience being subjected to control measures by looking at the impact on basic capabilities. METHODS: We searched Medline, Embase and PsychINFO until 26 May 2016 for studies addressing experiences of MDRO carriers. Twenty-seven studies were included, addressing experiences with methicillin-resistant Staphylococcus aureus (n = 21), ESBL (n = 1), multiple MDRO (n = 4) and other (n = 1, not specified). We categorized reported experiences according to Nussbaum's capability approach. RESULTS: Carriage and control measures were found to interfere with quality of care, cause negative emotions, limit interactions with loved ones, cause stigmatization, limit recreational activities and create financial and professional insecurity. Further, carriers have difficulties with full comprehension of the problem of antimicrobial resistance, thus affecting six out of ten basic capabilities. CONCLUSIONS: Applying Nussbaum's capability approach visualizes an array of unintended consequences of control measures. Carriers experience stigmatization, especially in healthcare settings, and have limited understanding of their situation and the complexities of antimicrobial resistance

Participatory plant breeding: a way to arrive at better-adapted onion varieties

The search for varieties that are better adapted to organic farming is a current topic in the organic sector. Breeding programmes specific for organic agriculture should solve this problem. Collaborating with organic farmers in such programmes, particularly in the selection process, can potentially result in varieties better adapted to their needs. Here, we assume that organic farmers' perceptive of plant health is broader than that of conventional breeders. Two organic onion farmers and one conventional onion breeder were monitored in their selection activities in 2004 and 2005 in order to verify whether and in which way this broader view on plant health contributes to improvement of organic varieties. They made selections by positive mass selection in three segregating populations under organic conditions. The monitoring showed that the organic farmers selected in the field for earliness and downy mildew and after storage for bulb characteristics. The conventional breeder selected only after storage. Farmers and breeder applied identical selection directions for bulb traits as a round shape, better hardness and skin firmness. This resulted in smaller bulbs in the breeders’ populations, while the bulbs in the farmer populations were bigger than in the original population. In 2006 and 2007 the new onion populations will be compared with each other and the original populations to determine the selection response

A parameterization of flow separation over subaqueous dunes

Flow separation plays a key role in the development of dunes, and modeling the complicated flow behavior inside the flow separation zone requires much computational effort. To make a first step toward modeling dune development at reasonable temporal and spatial scales, a parameterization of the shape of the flow separation zone over two-dimensional dunes is proposed herein, in order to avoid modeling the complex flow inside the flow separation zone. Flow separation behind dunes, with an angle-of-repose slip face, is characterized by a large circulating leeside eddy, where a separation streamline forms the upper boundary of the recirculating eddy. Experimental data of turbulent flow over two-dimensional subaqueous bed forms are used to parameterize this separation streamline. The bed forms have various heights and height to length ratios, and a wide range of flow conditions is analyzed. This paper shows that the shape of the flow separation zone can be approximated by a third-order polynomial as a function of the distance away from the flow separation point. The coefficients of the polynomial can be estimated, independent of flow conditions, on the basis of bed form shape at the flow separation point and a constant angle of the separation streamline at the flow reattachment point. \ud \u