Topological constraints in the reconnection of vortex braids

We study the relaxation of a topologically nontrivial vortex braid with zero net helicity in a barotropic fluid. The aim is to investigate the extent to which the topology of the vorticity field—characterized by braided vorticity field lines—determines the dynamics, particularly the asymptotic behavior under vortex reconnection in evolution at high Reynolds numbers (25 000). Analogous to the evolution of braided magnetic fields in plasma, we find that the relaxation of our vortex braid leads to a simplification of the topology into large-scale regions of opposite swirl, consistent with an inverse cascade of the helicity. The change of topology is facilitated by a cascade of vortex reconnection events. During this process, the existence of regions of positive and negative kinetic helicities imposes a lower bound for the kinetic energy. For the enstrophy, we derive analytically a lower bound given by the presence of unsigned kinetic helicity, which we confirm in our numerical experiments

A hydrologic and economic model for water trading and reallocation using linear programming techniques

Abstract: With the advent of water reform framework instigated by the Council of Australian Governments (COAG), water trading on a temporary and permanent basis has become a prominent feature in all major irrigation areas in Australia. Hydrologic network models, such as the Integrated Quantity and Quality Model (IQQM), although powerful in simulating entitlement-based water allocation at the catchment scale, are unable to deal with the water reallocation through trade driven by economic conditions such as crop and water price, variable production costs. To simulate water trading, linear programming techniques are used to maximize aggregate net return subject to land, water, and crop constraints. The volume of water traded is the difference between water allocated and water required for a given simulation period. The water trading model, known as WRAM, is coupled with IQQM for the Murrumbidgee basin. IQQM represents the irrigation area in the Murrumbidgee with 49 regulated irrigation nodes that grow a variety of summer, winter and perennial crops. The water trading model runs whenever a planting decision is required, taking into account water availability, crop growth stages, crop yield and price, variable production costs, fixed and variable water charges on the potential water movement through the distribution network. WRAM provides a dynamic link with IQQM in order to assess the impacts of water management policies at the whole-of-catchment scale. The result reported in this paper is part of a CRC Catchment Hydrology project on hydrologic and economic modelling for sustainable water allocation

Reconceptualizing ‘effectiveness’ in environmental management:can we measure values-related achievements?

AbstractThere have been recent calls for a shift to an evidence-based paradigm in environmental management, grounded in systematic monitoring and evaluation, but achieving this will be complex and difficult. Evaluating the educational components of environmental initiatives presents particular challenges, because these programs often have multiple concurrent goals and may value 'human outcomes', such as value change, which are intangible and difficult to quantify. This paper describes a fresh approach based on co-creating an entirely new values-based assessment framework with expert practitioners worldwide. We first discuss the development of a generic framework of 'Proto-Indicators' (reference criteria constituting prototypes for measurable indicators), and then demonstrate its application within a reforestation project in Mexico where indicators and assessment tools were localized to enhance context-relevance. Rigorously derived using unitary validity, with an emphasis on relevance, practicability and logical consistency from user perspectives, this framework represents a step-wise advance in the evaluation of non-formal EE/ESD programs. This article also highlights three important principles with broader implications for evaluation, valuation and assessment processes within environmental management: namely peer-elicitation, localizability, and an explicit focus on ethical values. We discuss these principles in relation to the development of sustainability indicators at local and global levels, especially in relation to post-2015 Sustainable Development Goals

Risk management frameworks:Supporting the next generation of Murray-Darling Basin water sharing plans

Water jurisdictions in Australia are required to prepare and implement water resource plans. In developing these plans the common goal is realising the best possible use of the water resources-maximising outcomes while minimising negative impacts. This requires managing the risks associated with assessing and balancing cultural, industrial, agricultural, social and environmental demands for water within a competitive and resource-limited environment. Recognising this, conformance to international risk management principles (ISO 31000:2009) have been embedded within the Murray-Darling Basin Plan. Yet, to date, there has been little strategic investment by water jurisdictions in bridging the gap between principle and practice. The ISO 31000 principles and the risk management framework that embodies them align well with an adaptive management paradigm within which to conduct water resource planning. They also provide an integrative framework for the development of workflows that link risk analysis with risk evaluation and mitigation (adaptation) scenarios, providing a transparent, repeatable and robust platform. This study, through a demonstration use case and a series of workflows, demonstrates to policy makers how these principles can be used to support the development of the next generation of water sharing plans in 2019. The workflows consider the uncertainty associated with climate and flow inputs, and model parameters on irrigation and hydropower production, meeting environmental flow objectives and recreational use of the water resource. The results provide insights to the risks associated with meeting a range of different objectives

Robust global sensitivity analysis of a river management model to assess nonlinear and interaction effects

The simulation of routing and distribution of water through a regulated river system with a river management model will quickly result in complex and nonlinear model behaviour. A robust sensitivity analysis increases the transparency of the model and provides both the modeller and the system manager with a better understanding and insight on how the model simulates reality and management operations. In this study, a robust, density-based sensitivity analysis, developed by Plischke et al. (2013), is applied to an eWater Source river management model. This sensitivity analysis methodology is extended to not only account for main effects but also for interaction effects. The combination of sensitivity indices and scatter plots enables the identification of major linear effects as well as subtle minor and nonlinear effects. The case study is an idealized river management model representing typical conditions of the southern Murray-Darling Basin in Australia for which the sensitivity of a variety of model outcomes to variations in the driving forces, inflow to the system, rainfall and potential evapotranspiration, is examined. The model outcomes are most sensitive to the inflow to the system, but the sensitivity analysis identified minor effects of potential evapotranspiration and nonlinear interaction effects between inflow and potential evapotranspiration

How Phytophthora cinnamomi became associated with the death of Eucalyptus marginata – the early investigations into jarrah dieback

The name jarrah dieback was used in the 1940s to describe a serious economic problem in the jarrah forest in the south west of Western Australia. This was the sudden death of groups of jarrah (Eucalyptus marginata) trees that occurred on previously logged sites that had a tendency to become waterlogged in winter. Although the cause was not determined at the time, from symptoms recorded in early investigations the most likely explanation is that the trees died as the result of waterlogging damage. In the 1960s it was shown that many of these sites were infested by the introduced oomycete Phytophthora cinnamomi and tree deaths, together with the deaths of many mid- and under-storey plants, were attributed to this pathogen. A chronology of the research, based on contemporary unpublished documents, shows that in 1968 the conclusion that P. cinnamomi caused jarrah deaths was not supported by the available evidence, because the work did not satisfy the first and fourth of Koch’s postulates. The evidence that P. cinnamomi killed many mid- and under-storey plants was much stronger. There are two problems that have been confused: the death of groups of jarrah trees (jarrah dieback) that is caused by waterlogging and the death of many mid- and under-storey plants (Phytophthora dieback) caused by P. cinnamomi infection

Life and living in advanced age: a cohort study in New Zealand - Te Puāwaitanga o Nga Tapuwae Kia Ora Tonu, LiLACS NZ: Study protocol

The number of people of advanced age (85 years and older) is increasing and health systems may be challenged by increasing health-related needs. Recent overseas evidence suggests relatively high levels of wellbeing in this group, however little is known about people of advanced age, particularly the indigenous Māori, in Aotearoa, New Zealand. This paper outlines the methods of the study Life and Living in Advanced Age: A Cohort Study in New Zealand. The study aimed to establish predictors of successful advanced ageing and understand the relative importance of health, frailty, cultural, social & economic factors to successful ageing for Māori and non-Māori in New Zealand