Analysis of future hydropower development and operational scenarios on the zambezi river basin

The Zambezi River basin is the fourth largest in Africa. Covering an area of about 1 400 000 km2 that is shared among 8 countries, it is the home of over 30 million people. There are ample opportunities for development in the region, including on the hydropower sector, whose estimated potential still to be exploited amounts to over 8 000 MW. In the future, the Zambezi is thought to be particularly vulnerable to climatic changes, with sizable expected impacts on average runoff, and will play a key role in the challenges posed by regional water scarcity. How future and current hydropower schemes are laid out and operate will affect the valuable ecosystems still thriving in the riparian areas of the basin and impact economic, as well as societal aspects. The present contribution employs a daily flow routing model in order to evaluate the impacts of different future hydropower development scenarios on the Zambezi River basin. Resorting to it and a multi-objective optimization technique the trade-offs between environmental and hydropower production concerns were clearly identified

Waves generated by ship convoy: Comparison of physical and numerical modeling with in-situ measurements

A part of the domestic waste of the city of Geneva (Switzerland) is transported with ship convoys on the Rhone River to the waste incineration station. These convoys generate waves, which partially endangers the stability of the river banks and the riparian fauna. To reduce the dominant wave peaks, a flap was added at the stern of the barge. The efficiency of that flap was tested in physical and numerical model tests, and then compared to in-situ measurements. This case study focuses on a discussion of the appropriateness of the two models, by describing their accuracy for the present case. It indicates that the physical model reproduces the wave heights almost correctly, but does not re-produce adequately the dominant frequencies. In contrast, the numerical model damps the wave heights significantly, but gives correct dominant frequencies

Natural variation of potato allene oxide synthase 2 causes differential levels of jasmonates and pathogen resistance in Arabidopsis

Natural variation of plant pathogen resistance is often quantitative. This type of resistance can be genetically dissected in quantitative resistance loci (QRL). To unravel the molecular basis of QRL in potato (Solanum tuberosum), we employed the model plant Arabidopsis thaliana for functional analysis of natural variants of potato allene oxide synthase 2 (StAOS2). StAOS2 is a candidate gene for QRL on potato chromosome XI against the oömycete Phytophthora infestans causing late blight, and the bacterium Erwinia carotovora ssp. atroseptica causing stem black leg and tuber soft rot, both devastating diseases in potato cultivation. StAOS2 encodes a cytochrome P450 enzyme that is essential for biosynthesis of the defense signaling molecule jasmonic acid. Allele non-specific dsRNAi-mediated silencing of StAOS2 in potato drastically reduced jasmonic acid production and compromised quantitative late blight resistance. Five natural StAOS2 alleles were expressed in the null Arabidopsis aos mutant under control of the Arabidopsis AOS promoter and tested for differential complementation phenotypes. The aos mutant phenotypes evaluated were lack of jasmonates, male sterility and susceptibility to Erwinia carotovora ssp. carotovora. StAOS2 alleles that were associated with increased disease resistance in potato complemented all aos mutant phenotypes better than StAOS2 alleles associated with increased susceptibility. First structure models of ‘quantitative resistant’ versus ‘quantitative susceptible’ StAOS2 alleles suggested potential mechanisms for their differential activity. Our results demonstrate how a candidate gene approach in combination with using the homologous Arabidopsis mutant as functional reporter can help to dissect the molecular basis of complex traits in non model crop plants

Hysteresis effects in organic matter turnover in a tropical floodplain during a flood cycle

Tropical inland waters are increasingly recognized for their role in the global carbon cycle, but uncertainty about the effects of such systems on the transported organic matter remains. The seasonal interactions between river, floodplain, and vegetation result in highly dynamic systems, which can exhibit markedly different biogeochemical patterns throughout a flood cycle. In this study, we determined rates and governing processes of organic matter turnover. Multi-probes in the Barotse Plains, a pristine floodplain in the Upper Zambezi River (Zambia), provided a high-resolution data set over the course of a hydrological cycle. The concentrations of oxygen, carbon dioxide, dissolved organic carbon, and suspended particulate matter in the main channel showed clear hysteresis trends with expanding and receding water on the floodplain. Lower oxygen and suspended matter concentrations prevailed at longer travel times of water in the floodplain, while carbon dioxide and dissolved organic carbon concentrations were higher when the water spent more time on the floodplain. Maxima of particulate loads occurred before highest water levels, whereas the maximum in dissolved organic carbon load occurred during the transition of flooding and flood recession. Degradation of terrestrial organic matter occurred mainly on the floodplain at increased floodplain residence times. Our data suggest that floodplains become more intense hotspots at prolonged travel time of the flood pulse over the floodplain.ISSN:0168-2563ISSN:1573-515

Influence of Hydropower Development on Flow Regime in the Zambezi River Basin for Different Scenarios of Environmental Flows

As the need for energy is increasing, the challenges in the future are to operate existing large hydraulic schemes in more sustainable ways and to develop future water resources projects that are able to achieve a better balance between environmental and socio-economic demands. In this context, scenarios combining different levels of environmental requirements as well as hydropower developments were simulated at a daily time step with a hydraulic-hydrological model (the Soil and Water Assessment Tool) over the Zambezi River Basin. For each scenario, the hydropower operation rules, the mean annual energy produced and the firm powers were considered. The impact on the flow regime was characterized by a hydrological alteration indicator and Pardé coefficients. In the present state, the total mean annual energy production is about 30,000GWh with a firm power of about 3,000MW. The impact of the dams on the flow regime is low in the Kafue flats and the Zambezi delta and high in the Mana Pools. The new run-of-river hydropower plants aim to increase the mean energy production by more than 90% and the firm power by about 40%. Releasing e-flows can reduce the impact in the Kafue flats and in the Zambezi delta, with a loss of less than 10% of mean annual energy production and about 15% of the firm power at Itezhi-Tezhi and Cahora Bassa. This reveals that a compromise between energy production and environmental sustainability can be reached

Pattern-oriented memory interpolation of sparse historical rainfall records

The pattern-oriented memory (POM) is a novel historical rainfall interpolation method that explicitly takes into account the time dimension in order to interpolate areal rainfall maps. The method is based on the idea that rainfall patterns exist and can be identified over a certain area by means of non-linear regressions. Having been previously benchmarked with a vast array of interpolation methods using proxy satellite data under different time and space availabilities, in the scope of the present contribution POM is applied to rain gauge data in order to produce areal rainfall maps. Tested over the Zambezi River Basin for the period from 1979 to 1997 (accurate satellite rainfall estimates based on spaceborne instruments are not available for dates prior to 1998), the novel pattern-oriented memory historical interpolation method has revealed itself as a better alternative than Kriging or Inverse Distance Weighing in the light of a Monte Carlo cross-validation procedure. Superior in most metrics to the other tested interpolation methods, in terms of the Pearson correlation coefficient and bias the accuracy of POM's historical interpolation results are even comparable with that of recent satellite rainfall products. The new method holds the possibility of calculating detailed and performing daily areal rainfall estimates, even in the case of sparse rain gauging grids. Besides their performance, the similarity to satellite rainfall estimates inherent to POM interpolations can contribute to substantially extend the length of the rainfall series used in hydrological models and water availability studies in remote areas. (C) 2014 Elsevier B.V. All rights reserved

Stress-induced in vivo recruitment of human cytotoxic natural killer cells favors subsets with distinct receptor profiles and associates with increased epinephrine levels

Acute stress drives a 'high-alert' response in the immune system. Psychoactive drugs induce distinct stress hormone profiles, offering a sought-after opportunity to dissect the in vivo immunological effects of acute stress in humans. 3,4-methylenedioxymethamphetamine (MDMA), methylphenidate (MPH), or both, were administered to healthy volunteers in a randomized, double-blind, placebo-controlled crossover-study. Lymphocyte subset frequencies, natural killer (NK) cell immune-phenotypes, and changes in effector function were assessed, and linked to stress hormone levels and expression of CD62L, CX3CR1, CD18, and stress hormone receptors on NK cells. MDMA/MPH > MDMA > MPH robustly induced an epinephrine-dominant stress response. Immunologically, rapid redistribution of peripheral blood lymphocyte-subsets towards phenotypically mature NK cells occurred. NK cytotoxicity was unaltered, but they expressed slightly reduced levels of the activating receptor NKG2D. Preferential circulation of mature NK cells was associated with high epinephrine receptor expression among this subset, as well as expression of integrin ligands previously linked to epinephrine-induced endothelial detachment. The acute epinephrine-induced stress response was characterized by rapid accumulation of mature and functional NK cells in the peripheral circulation. This is in line with studies using other acute stressors and supports the role of the acute stress response in rapidly mobilizing the innate immune system to counteract incoming threats