Manning’s ‘n’ co-efficient for flexible emergent vegetation in tandem configuration

A comprehensive laboratory study on the hydraulic resistance characteristics due to a group of slender cylindrical members representing flexible plantation has been carried out in a laboratory open channel. The model stem group comprised of individual members arranged in a tandem configuration. The tests with model vegetation were carried out by adopting different sizes for the individual stems and concentrations which were chosen in such a way that they would fall into practical ranges of vegetations in coastal forestry. The results indicate that the flow resistance varies with stem concentration, stem diameter and elastic properties of the individual members and the flow velocity. Based on the flume data, the Manning’s n, for various flow conditions as well as for vegetative parameters was determined. A new empirical equation is proposed for evaluating the Manning’s n friction coefficient for partially submerged flow when, the depth of flow is greater than 0.8 times the un-deflected plant height. It is expected that the Manning’s n thus determined will be useful in modelling shallow flows using shallow water equations.     

Two decades of Brazil’s participatory model for water resources management: from enthusiasm to frustration

In January 2017, the water community in Brazil celebrated the 20th anniversary of the promulgation of Brazil’s National Water Resources Policy (Federal Law 9.433). However, Brazil’s participatory model has not delivered the expected policy outcomes yet. Inclusiveness in decision making has become pointless since mechanisms of social control and accountability are almost nonexistent. Despite the widely celebrated opportunities for stakeholder engagement and decentralized water management, implementation of water policies remains largely dependent on state actors. These findings indicate the need for carefully planned and evidence-based water reforms in Brazil.     

Application of p-y Curve to Foundation Pit’s Ditch Enclosure Structure

目前p-y曲线法多数用于研究桩周土体未开挖情况下横向推力桩的变形性状,很少应用于计算基坑围护结构的变形。p-y曲线法考虑了土体的非线性位移,符合基坑内侧土体受围护结构挤压变形的实际状态。因此,以具体工程为例,用p-y曲线法计算基坑围护结构的位移,并与目前常用的弹性地基梁增量法计算值及实测值进行比较,以验证其合理性和优越性。研究表明:采用 p-y曲线法计算出的基坑围护结构侧向位移曲线与实测位移曲线相比,除了形态相似、符合基坑围护结构实际变形规律外,数值上也比弹性地基梁增量法的计算结果更加接近实测值。理论与实践均表明,采用p-y曲线法计算基坑围护结构位移是合理的。     

Budyko’s Based Method for Annual Runoff Characterization across Different Climatic Areas: an Application to United States

Runoff data knowledge is of fundamental importance for a wide range of hydrological, ecological, and socioeconomic applications. The reconstruction of annual runoff is a fundamental task for several activities related to water resources management, especially for ungauged basins. At catchment scales, the Budyko’s framework provides an extremely useful and, in some cases, accurate estimation of the long-term partitioning of precipitation into evapotranspiration and runoff as a function of the prevailing climatic conditions. Recently the same long-term partitioning rules have been successfully used to describe water partitioning also at the annual scale and calculate the annual runoff distribution within a simple analytic framework in arid and semi-arid basins. One of the main advantages of the latter method is that only annual precipitation and potential evapotranspiration statistics, and the Fu’s equation parameter ω are required to obtain the annual runoff probability distribution. The aim of this study is to test the limit and potentialities of the aforementioned method under different climatic conditions. To this aim, the model is applied to more than four hundred basins located in the United States. Catchments were grouped into five different samples, following the subdivision of the continental region in five homogeneous climatic zones according to Köppen-Geiger classification. The theoretical probability distribution of annual runoff at each basin has been compared with that derived from historical observations. The results confirm the capability of the tested technique to reproduce the empirical annual runoff distributions with similar and satisfactory performances across different areas, revealing a good option also in cases characterized by climate and hydrological conditions very different from those hypothesized during the original analytical model design, thus extending the geographical and conceptual limits of applicability of the framework.     

DNA metabarcoding of the phytoplankton of Great Salt Lake’s Gilbert Bay: Spatiotemporal assemblage changes and comparisons to microscopy

The Great Salt Lake (GSL) is a unique hypersaline system with an understudied phytoplankton assemblage supporting a productive open water ecosystem in the largest embayment of the lake, Gilbert Bay. Determination of phytoplankton by microscopy has practical limitations that can constrain the scope of a study, but DNA metabarcoding may improve upon this through higher taxonomic resolution and the capacity to generate a large volume of assemblage data in comparatively little time. To determine if metabarcoding could replicate microscopy and expand the assessment of GSL phytoplankton, a 23S SSU rRNA metabarcoding and microscopy survey of Gilbert Bay was conducted in 2017 and 2018. Assemblage composition and relative abundances from each method were compared, and spatial and temporal assemblage changes from metabarcoding data were investigated using non-metric multidimensional scaling. Metabarcoding differed from microscopy in multiple taxonomic assignments and relative abundances, with poor correlation for most categories. Diatoms were overrepresented by metabarcoding relative to microscopy, and chlorophytes underrepresented. However, metabarcoding revealed seasonal and spatial patterns in assemblage, detected seasonal patterns within phytoplankton sequences of very low abundance, and detected potential cryptic speciation within the lake’s dominant Dunaliella viridis. Phylogenetic analysis revealed greater phytoplankton diversity than observed before in GSL, but demonstrated the need to improve taxonomic assignment of the resulting sequences, particularly within the diatoms. The expansion of detectable diversity and isolation of DNA sequences that can be traced through time and analyzed against environmental variables make metabarcoding a potentially effective tool for parallel use with microscopy in future GSL research.     

A new formula for turbulent-flow velocity and an explanation of A. P. Zegzhda’s experiments

1. The basic influence exerted by hydraulic grade, and, as a consequence, Froude number, on the value of the coefficient of hydraulic resistance is disclosed; this is reflected by formulas (16) and (18), and has found confirmation in field investigations [3], and in Zegzhda's experiments.
2. In the design of canals, the coefficient of hydraulic resistance should be determined by calculation as a function of the grade and dimensions of the flow, and not assigned as a function of the frequency with which the surface of the channel is treated.

     

The use of NDVI and its Derivatives for Monitoring Lake Victoria’s Water Level and Drought Conditions

Normalized Difference Vegetation Index (NDVI), which is a measure of vegetation vigour, and lake water levels respond variably to precipitation and its deficiency. For a given lake catchment, NDVI may have the ability to depict localized natural variability in water levels in response to weather patterns. This information may be used to decipher natural from unnatural variations of a given lake’s surface. This study evaluates the potential of using NDVI and its associated derivatives (VCI (vegetation condition index), SVI (standardised vegetation index), AINDVI (annually integrated NDVI), green vegetation function (F _g ), and NDVIA (NDVI anomaly)) to depict Lake Victoria’s water levels. Thirty years of monthly mean water levels and a portion of the Global Inventory Modelling and Mapping Studies (GIMMS) AVHRR (Advanced Very High Resolution Radiometer) NDVI datasets were used. Their aggregate data structures and temporal co-variabilities were analysed using GIS/spatial analysis tools. Locally, NDVI was found to be more sensitive to drought (i.e., responded more strongly to reduced precipitation) than to water levels. It showed a good ability to depict water levels one-month in advance, especially in moderate to low precipitation years. SVI and SWL (standardized water levels) used in association with AINDVI and AMWLA (annual mean water levels anomaly) readily identified high precipitation years, which are also when NDVI has a low ability to depict water levels. NDVI also appears to be able to highlight unnatural variations in water levels. We propose an iterative approach for the better use of NDVI, which may be useful in developing an early warning mechanisms for the management of lake Victoria and other Lakes with similar characteristics.     

A numerical analysis of the influence of the cavitator’s deflection angle on flow features for a free moving supercavitated vehicle

When a high-speed cavitated weapon moves under water, the flow properties are important issues for the sake of the trajectory predication and control. In this paper, a single-fluid multiphase flow method coupled with a natural cavitation model is proposed to numerically simulate the flee moving phase of an underwater supercavitated vehicle under the action of the external thrust. The influence of the cavitator＇s deflection angle ranging from -3~ to 3~ on the cavity pattern, the hydrodynamics and the underwater trajectory is investigated. Based on computational results, several conclusions are qualitatively drawn by an analysis. The deflection angle has very little effect on the cavity pattern. When the deflection angle increases, the variation curves of the vertical linear velocity, the lift coefficient and the pitching moment coefficient become flatter. In the phase of the second natural cavitation, at a same time, the greater the deflection angle is, the lower the drag and the lift coefficients will be and the higher the pitching moment coefficient becomes. At the finishing time of the free moving phase, when the deflection angle lies in the small range of -1~ - 1~, the position of the center of mass and the pitching angle of the vehicle are more close to each other. However, when the deflection angle is less than -1° or greater than 1°, the position of the center of mass and the pitching angle change greatly. Ifa proper deflection angle of the cavitator is adopted, the underwater vehicle can navigate in a pseudo-fixed depth.     

Spatial and seasonal variation in the phytoplankton community of Lake Victoria’s Mwanza Gulf,compared to northern parts of the lake

We investigated the phytoplankton species composition and abundance in two seasons in Mwanza Gulf, Lake Victoria (Tanzania). Phytoplankton was sampled and chlorophyll a content was measured in the dry and wet seasons of 2010–2011 at three stations, from the southern land-inward end of the Gulf towards the open lake. Cyanobacteria, mostly small colonial and filamentous species (e.g., Aphanocapsa spp., Planktolyngbya spp., Merismopedia spp.) dominated at each station (76–95 %), followed by Chlorophyta (5–21 %), whereas the contribution of Bacillariophyceae was small (0–6 %). Phytoplankton densities were generally higher in the rainy season and strongly increased going land-inward from the open lake. Low abundance of N-fixing phytoplankton species suggests that N-fixation was low. The chlorophyll a content in the mouth of the Gulf was low (mean values 4–6 µg/L) compared to values reported previously. Also, chlorophyll a values (means 11–14 µg/L) at land-inward stations of Mwanza Gulf were much lower than those in the northern gulfs (Napoleon Gulf, Murchison Bay and Nyanza Gulf). Between 2002 and 2009 the phytoplankton composition of Mwanza Gulf changed from a community mostly dominated by Bacillariophyceae into a community dominated by Cyanobacteria. In the open water of Lake Victoria, Bacillariophyceae and Cyanobacteria were both abundant. Cyanobacteria dominated both in the three northern gulfs and Mwanza Gulf, but all four showed substantial differences in species and genus compositions. Phytoplankton composition and abundance in Mwanza Gulf differs in many respects from the open water of Lake Victoria and its three northern gulfs.     

Managing Water Resources Under Conditions of Scarcity: On Consumers’ Willingness to Pay for Improving Water Supply Infrastructure

Conservation and efficient management of water resources is an essential ingredient for achieving sustainable development. River basins in Southern Europe are suffering from high water stress, while leakages in some areas far surpass recommended levels. This study uses the contingent valuation method in order to assess willingness to pay (WTP) by consumers in the Guadalquivir River basin in Spain for improving urban water supply infrastructure and reducing leakages. On average, individuals would be willing to pay an extra charge on their water bill ranging from €8.23 to €9.65. In addition to the expected positive effect of income on WTP, respondents with negative perceptions of their drinking water quality as well as those most affected by the economic crisis have a lower WTP. Conversely, WTP is higher for men and respondents showing greater commitment to the environment. These results provide policymakers with information that might help them to improve water-pricing policies in a context of severe water scarcity, especially considering the principle of cost recovery introduced by the EU Water Framework Directive in pricing water services.     

Can Sub-Saharan Africa feed itself? The role of irrigation development in the region’s drylands for food security

ABSTRACT

This paper assesses the potential role of investments in irrigation in Sub-Saharan Africa in improving food security and self-sufficiency in the region. Focusing on the region’s drylands, the study identifies a potential for expanded irrigated area of 6–14 million hectares (ha), depending on technology costs and other factors. Linkage of these results with a global agricultural trade model shows that accelerated irrigation investment can effectively reduce growing food import dependency from 54% under a business-as-usual scenario to a much smaller 17–40%; and can also reduce the population at risk of hunger and child under-nutrition.     

Evaluation of the Bankruptcy Approach for Water Resources Allocation Conflict Resolution at Basin Scale,Iran’s Lake Urmia Experience

Water conflicts appear when there are insufficient and less available water resources than water demands claimed by different agents. In this study, a new bankruptcy approach is investigated to resolve water conflicts in the Zarrinehroud River Basin, the largest and most important sub-basin of Lake Urmia’s Basin in the northwest of Iran. The new bankruptcy method is compared with the proportional rule (PRO) and another alternative based on the cessation of irrigated agriculture in the region proposed to supply and save environmentally in danger Lake Urmia. Four scenarios consisting of the current situation, optimistic, average and pessimistic scenarios regarding the future of water resources of the basin and agricultural developments were considered. According to the results, both bankruptcy rules helped Lake Urmia to receive more water, but neither could utterly overcome the water shortage of the Lake, so can be used as supplementary actions alongside other solutions. The cessation of irrigated agriculture throughout the basin overcame the average annual shortage of Lake Urmia in the first and second scenarios equal to 137 and 148 million cubic meters respectively. It showed disability to fully supply the lake in the third and fourth scenarios. These three methods must be combined with a social-economic policy like the purchase of decreased water allocations to farmers to be socially acceptable.     

Non-water factors in water governance and their implications for water sustainability: The case of Ontario’s water use reduction policy

Despite longstanding interest in reducing water use in Ontario, Canada’s most populous province, public policy responses have tended to be restricted to the water sector’s traditional remit, e.g., improving public access to water data. However, it is not clear that these type of measures will be enough to address concerns over water quantity and advance water sustainability, as they are tied to other socio-economic concerns, external to the water sector. The purpose of this study is to understand the range of external factors that influenced the development and implementation of the water use reduction (WUR) policy in Ontario, and to identify opportunities for harnessing these factors to advance WUR objectives. To do so, we propose a diagnostic framework that maps external factors in relation to a specific water governance situation. We carried out 13 semi-structured interviews and reviewed 56 documents. We combined deductive and inductive approaches to content analysis. We found many non-water factors influencing the governance of WUR in Ontario. Particularly, the economic development provincial objective strongly shaped Ontario’s WUR policy by influencing the adoption of a demand management approach centering on water efficiency, rather than conservation. Furthermore, the WUR policy primarily serves the economic development objective. An implication is that water policies can be used instrumentally, raising the question of what constitutes a “water policy”. In summary, this study argues that non-water factors can thus influence our path to water sustainability, in this case represented by the water conservation approach, by defining an enabling (or hindering), institutional framework.     

Locating Water Desalination Facilities for Municipal Drinking Water Based on Qualitative and Quantitative Characteristics of Groundwater in Iran’s Desert Regions

Groundwater resources have become the main resources for water supply due to the unavailability of surface water in arid zones. Arid zone’s damage to groundwater resources will have a high impact on human life in arid zones comparing to other regions. Due to the lack of surface water resources in these arid zones, groundwater is used as a resource for drinking and sanitation purposes due to the lack of surface water resources in these arid zones. Water desalination facilities are set up in locations where there is both sufficient amount of water (quantitative criteria) and the extracted water has adequate quality (qualitative criteria). Therefore, an optimization model should be used to locate optimal places for water desalination facilities. Multi-criteria decision-making models are mathematical techniques that, by using the geographic information system, are able to evaluate the options under complicated and indefinite geographic conditions. This research prepares information and factor maps to assign weights to qualitative water maps which were combined in the form of an inductive network. Therefore, by employing the concept of fuzzy fusion models, this article presents a method for solving multi-criteria geographically-indeterminate problems, and finally finds an appropriate location for the construction of a water desalination system in the desert region of Birjand in Iran.     

Operating experience with and problems of lightning protection for the first domestic 220-kV overhead lines from the lower Svir’ HPP to the Lenénergo

Results of analysis of operating experience with automatic disconnection of the first domestic 220-kV overhead lines from the Lower Svir’ HPP to a substation in the settlement of Kolpino in the Leningradskaya Oblast’ (two Svir’ 220-kV overheads lines with a length of 247 km) over a period of 21 years (1982–2002) in total volume of 10,400 km · year are presented. Operating indicators are established with respect to specific number of disconnects and stream of failures per 100 km of overhead lines. Indicators of lightning-surge protection on the 220-kV Svir’ overhead lines passing through the same corridor primarily along a swath cut through a forest in periods when the stranded cables were protected by different schemes — stranded cable only on approaches to substations, incomplete and nonuniform protection along the route — are compared. Recommendations are given for optimal cable protection of the 220-kV Svir’ overhead lines. __________ Translated from élektricheskie Stantsii, No. 4, April 2007, pp. 49–59