Wastewater irrigation: the state of play

As demand for fresh water intensifies, wastewater is frequently being seen as a valuable resource. Furthermore, wise reuse of wastewater alleviates concerns attendant with its discharge to the environment. Globally, around 20 million ha of land are irrigated with wastewater, and this is likely to increase markedly during the next few decades as water stress intensifies. In 1995, around 2.3 billion people lived in water-stressed river basins and this could increase to 3.5 billion by 2025. We review the current status of wastewater irrigation by providing an overview of the extent of the practice throughout the world and through synthesizing the current understanding of factors influencing sustainable wastewater irrigation. A theme that emerges is that wastewater irrigation is not only more common in water-stressed regions such as the Near East, but the rationale for the practice also tends to differ between the developing and developed worlds. In developing nations, the prime drivers are livelihood dependence and food security, whereas environmental agendas appear to hold greater sway in the developed world. The following were identified as areas requiring greater understanding for the long-term sustainability of wastewater irrigation: (i) accumulation of bioavailable forms of heavy metals in soils, (ii) environmental fate of organics in wastewater-irrigated soils, (iii) influence of reuse schemes on catchment hydrology, including transport of salt loads, (iv) risk models for helminth infections (pertinent to developing nations), (v) microbiological contamination risks for aquifers and surface waters, (vi) transfer efficiencies of chemical contaminants from soil to plants, (vii) health effects of chronic exposure to chemical contaminants, and (viii) strategies for engaging the public.<br /

Niche partitioning of intertidal seagrasses: evidence of the influence of substrate temperature

• The influence of soil temperature on rhizome depths of four intertidal seagrass species was investigated in central Queensland, Australia. We postulated that certain intertidal seagrass species are soil temperature‐sensitive and vertically stratify rhizome depths. • Below‐ground vertical stratification of intertidal seagrass rhizome depths was analysed based upon microclimate (soil temperature) and microhabitat (soil type). • Soil temperature profiles exhibited heat transfer from surface layers to depth that varied by microhabitat, with vertical stratification of rhizome depths between species. Halodule uninervis rhizomes maintain a narrow median soil temperature envelope; compensating for high surface temperatures by occupying deeper, cooler soil substrates. Halophila decipiens, Halophila ovalis and Zostera muelleri rhizomes are shallow‐rooted and exposed to fluctuating temperatures, with broader median temperature envelopes. Halodule uninervis appears to be a niche specialist, with the two Halophila species considered as generalist niche usage species. • The implications of niche use based upon soil temperature profiles and rhizome rooting depths are discussed in the context of species’ thermal tolerances and below‐ground biomass O₂ demand associated with respiration and maintenance of oxic microshields. This preliminary evidence suggests that soil temperature interaction with rhizome rooting depths may be a factor that influences the distribution of intertidal seagrasses

Using a Bayesian network model to assess ecological responses to hydrological factor interactions

Interactions between environmental factors can dramatically influence the relationships between a species and its environment. However, multiple types of interaction are possible, and as such, some may be overlooked. We used a Bayesian network to model the response of a riparian tree species, Eucalyptus camaldulensis Dehnh., to the interactive influences of hydrological factors. We used a novel conceptual framework, which included not only synergistic and antagonistic interactions but also qualitative interactions (i.e. the effect of an environmental factor that switches from positive to negative or vice versa depending on the value of another factor). Synergistic, antagonistic and qualitative interactions were all detected in the response of E. camaldulensis to hydrological factor interactions. The predicted influence of environmental factors varied dramatically when interactions were considered. In some instances, the likelihood of a certain outcome differed by greater than 80% when interactions were considered. For example, the negative impact of grazing on E. camaldulensis was far greater in areas of deep groundwater relative to areas of shallow groundwater. Interactions also led to qualitatively different predictions (i.e. a qualitative interaction occurred). For example, frequent wetland inundation had a positive influence on tree vigour in wetlands minimally impacted by weirs, but a negative influence in wetlands close to weirs. Considering interactions may therefore substantially change understanding of ecohydrological relationships. Thinking of interactions between factors as potentially qualitative, and not only as synergistic and antagonistic, is likely to be important in situations where multiple management interventions are proposed

Towards an integrated maturity model of asset management capabilities

Asset service organisations often recognize asset management as a core competence to deliver benefits to their business. But how do organizations know whether their asset management processes are adequate? Asset management maturity models, which combine best practices and competencies, provide a useful approach to test the capacity of organisations to manage their assets. Asset management frameworks are required to meet the dynamic challenges of managing assets in contemporary society. Although existing models are subject to wide variations in their implementation and sophistication, they also display a distinct weakness in that they tend to focus primarily on the operational and technical level and neglect the levels of strategy, policy and governance as well as the social and human resources – the people elements. Moreover, asset management maturity models have to respond to the external environmental factors, including such as climate change and sustainability, stakeholders and community demand management. Drawing on five dimensions of effective asset management – spatial, temporal, organisational, statistical, and evaluation – as identified by Amadi Echendu et al. [1], this paper carries out a comprehensive comparative analysis of six existing maturity models to identify the gaps in key process areas. Results suggest incorporating these into an integrated approach to assess the maturity of asset-intensive organizations. It is contended that the adoption of an integrated asset management maturity model will enhance effective and efficient delivery of services