Flow resistance and hydraulic geometry in bedrock rivers with multiple roughness length scales

Many models of incision by bedrock rivers predict water depth and shear stress from discharge; conversely, palaeoflood discharge is sometimes reconstructed from flow depth markers in rock gorges. In both cases, assumptions are made about flow resistance. The depth–discharge relation in a bedrock river must depend on at least two roughness length scales (exposed rock and sediment cover) and possibly a third (sidewalls). A conceptually attractive way to model the depth–discharge relation in such situations is to partition the total shear stress and friction factor, but it is not obvious how to quantify the friction factor for rough walls in a way that can be used in incision process models. We show that a single flow resistance calculation using a spatially averaged roughness length scale closely approximates the partitioning of stress between sediment and rock, and between bed and walls, in idealized scenarios. Both approaches give closer fits to the measured depth–discharge relations in two small bedrock reaches than can be achieved using a fixed value of Manning's n or the Chézy friction factor. Sidewalls that are substantially rougher or smoother than the bed have a significant effect on the partitioning of shear stress between bed and sidewalls. More research is needed on how best to estimate roughness length scales from observable or measurable channel characteristics. © 2019 John Wiley & Sons, Ltd.     

底栖生物生产力现场测试系统(BCSPM)的建立及其初步实验结果

为对生态系统的健康评估及底栖生物资源的开发利用提供技术支撑,在胶州湾筏式养殖水域,建立了底栖生物生产力现场测试系统(BCSPM),并在光照和黑暗条件下测定了沉积物海水界面溶解氧随时间的变化、计算了氧通量、估算了底栖总初级生产力和群落呼吸。在光照较强的中午时刻测定的群落总生产力为20．76mgCm^-2h^-1;养殖水域沉积物中的群落呼吸要高于邻近水域。BCSPM整体运转良好,初步结果为系统的改进和进一步实验提供了依据。     

Local Groundwater Withdrawal Permitting Laws in the South‐Western U.S.: California in Comparative Context

The Sustainable Groundwater Management Act (SGMA) aims to control, for the first time in California's history, the state's significant use and depletion of groundwater. SGMA gives local agencies a high degree of discretion in relation to a new permitting power, but the discretion is a double‐edged sword: agencies gain maximum flexibility to tailor their regime to local conditions, yet the statute provides no direction on appropriate components of a groundwater permitting regime. We introduce SGMA and the broader legislative context to its permitting power, and we explain the continuing common law context in which the legislation operates. This information is used as the foundation for a comparative legal analysis of fundamental elements of permitting regimes. We compare a selection of six other south‐western permitting regimes established in legislation for areas recognized as requiring intensive management through permitting: “special permitting areas” (SPAs). We find that permitting regimes in south‐western SPAs share a structure containing several almost universal elements, although the policy settings that apply to those elements vary widely. The established permitting regimes in the other south‐western states' SPAs may inform Californian agencies seeking to use their new permitting power for the first time, as well as water agencies further afield, as to important components of a permitting regime, and the different policy settings that could apply to those components. Californian local agencies, and its Department of Water Resources, which is charged with providing local agencies technical advice, should have regard to these permitting possibilities.     

The degree of urbanization across the globe is not reflected in the δN of seagrass leaves

Many studies show that seagrass δ¹⁵N ratios increase with the amount of urbanization in coastal watersheds. However, there is little information on the relationship between urbanization and seagrass δ¹⁵N ratios on a global scale. We performed a meta-analysis on seagrass samples from 79 independent locations to test if seagrass δ¹⁵N ratios correlate with patterns of population density and fertilizer use within a radius of 10–200 km around the sample locations. Our results show that seagrass δ¹⁵N ratios are more influenced by intergeneric and latitudinal differences than the degree of urbanization or the amount of fertilizer used in nearby watersheds. The positive correlation between seagrass δ¹⁵N ratios and latitude hints at an underlying pattern in discrimination or a latitudinal gradient in the ¹⁵N isotopic signature of nitrogen assimilated by the plants. The actual mechanisms responsible for the correlation between δ¹⁵N and latitude remain unknown.     

Applicability of Individual Transferable Quotas (ITQs) in Japanese fisheries: A comparison of rights-based fisheries management in Iceland, Japan, and United States

ITQs have not yet been introduced by the Government of Japan. In coastal areas, fishery cooperative associations have traditionally played an important role in managing fisheries through self-imposed rules and peer-monitoring systems. Recently, however, the economic competitiveness of Japanese fisheries in the international market is being questioned. In this paper, a detailed examination of the pros and cons of the current system in Japan is compared to the current fishery management measures of Iceland and the United States, where attaining economically or biologically efficient outcomes may be prioritized in making fisheries management decisions. For many coastal fisheries in Japan, maintaining a management scheme in which stakeholders play an active role in determining fisheries measures seems more relevant if their priority is to maintain the stability of coastal communities and equity of stakeholders. Intensive dialog among stakeholders would be necessary to identify shared objectives of their fishery operations and to make decisions to establish specific steps toward the goal of increasing economic efficiency, environmental sustainability, or stability of communities and equity of stakeholders.     

Playing Lotto with Rotto? Tourism,the environment and gambling with the ethos of a Western Australian island

Rottnest Island is a popular holiday destination offshore from Perth, the capital city of Western Australia. Rottnest (or Rotto) attracts approximately 500 000 visitors annually. The island is managed by a statutory government authority, the Rottnest Island Authority (RIA), for the purposes of providing recreation and holiday facilities and services, and protecting its natural and cultural values. While there are advantages in management by one body, there appears to be a conflict in managing both the tourism business and the environment, largely as a result of funding issues. While further tourism development would boost the RIA's self-funded operating budget, increased pressures may compromise the island environment and the Rottnest ethos, which revolves around a relaxed and casual social ambiance. The RIA aims to develop Rottnest as a model for sustainability, but are dilemmas surrounding economic sustainability potentially risking the island's environmental and social sustainability? This paper concludes that in the pursuit of economic returns from tourism, Rottnest Island's environmental and social values face an uncertain future.     

Environmental Radioxenon Levels in Europe: a Comprehensive Overview

Activity concentration data from ambient radioxenon measurements in ground level air, which were carried out in Europe in the framework of the International Noble Gas Experiment (INGE) in support of the development and build-up of a radioxenon monitoring network for the Comprehensive Nuclear-Test-Ban Treaty verification regime are presented and discussed. Six measurement stations provided data from 5 years of measurements performed between 2003 and 2008: Longyearbyen (Spitsbergen, Norway), Stockholm (Sweden), Dubna (Russian Federation), Schauinsland Mountain (Germany), Bruyères-le-Châtel and Marseille (both France). The noble gas systems used within the INGE are designed to continuously measure low concentrations of the four radioxenon isotopes which are most relevant for detection of nuclear explosions: ^131mXe, ^133mXe, ¹³³Xe and ¹³⁵Xe with a time resolution less than or equal to 24 h and a minimum detectable concentration of ¹³³Xe less than 1 mBq/m³. This European cluster of six stations is particularly interesting because it is highly influenced by a high density of nuclear power reactors and some radiopharmaceutical production facilities. The activity concentrations at the European INGE stations are studied to characterise the influence of civilian releases, to be able to distinguish them from possible nuclear explosions. It was found that the mean activity concentration of the most frequently detected isotope, ¹³³Xe, was 5–20 mBq/m³ within Central Europe where most nuclear installations are situated (Bruyères-le-Châtel and Schauinsland), 1.4–2.4 mBq/m³ just outside that region (Stockholm, Dubna and Marseille) and 0.2 mBq/m³ in the remote polar station of Spitsbergen. No seasonal trends could be observed from the data. Two interesting events have been examined and their source regions have been identified using atmospheric backtracking methods that deploy Lagrangian particle dispersion modelling and inversion techniques. The results are consistent with known releases of a radiopharmaceutical facility.     

EM and GPR investigations of contaminant spread around the Hoc Mon waste site,Vietnam

This paper is presenting the results from near-surface geophysical surveys near the waste site of Hoc Mon in southern Vietnam where leachate contamination has been recognized at the surface. Using EM and GPR surveys, we were able to determine the lateral extent of a contaminated area of high electrical conductivity and have identified channels that concentrate the contaminant flow. The simple relationship between the electrical resistivity and the leachate concentration is suggested and estimated the in situ leachate concentration from the inversion of the EM data; values are as high as 40%. Thanks to a permeability barrier leachate flow is confined to the shallow subsurface, making it easier to apply possible site remediation projects.