Impact assessment (IA) has become one of the most prevalent environmental policy instruments today. Its introduction under the National Environmental Policy Act (US) in 1969 was revolutionary. Perhaps it is not surprising, then, that such a widely used tool has received its share of criticism, including that it fails to meet some of its fundamental goals. Over the last fifty years, IA has broadened in scope and application and embraced new techniques. It has followed evolved, but has not changed fundamentally.We believe that IA must continue to change to meet the societal and environmental challenges of the 21 st century. But will it be enough for IA to progress through incremental change (evolution), or is a complete overhaul of impact assessment (revolution) needed? We provide some ideas as to what 'evolution' and 'revolution' may look like, but rather then offering a definitive way forward now, we invite stakeholders to present their thoughts and suggestions at the IAIA19 Annual Conference in Brisbane, which carries the same theme as the title of this article.

The Western Corridor Recycled Water Scheme consists of three advanced water treatment plants (AWTPs), with the combined capacity to recycle 232 ML/d. Each AWTP process consists of pre-treatment, microfiltration (MF), reverse osmosis (RO), UV/peroxide advanced oxidation and chlorination. A key objective of the project is to improve the environmental health of regional waterways, particularly in relation to nutrient discharges. Reverse osmosis processes produce a concentrate stream (ROC), which is the main reject stream of the AWTPs. Options for management of ROC were assessed, and ultimate disposal to nearby waterways was the only feasible option identified. ROC flows for the scheme total 41 ML/d at full capacity, divided between the three AWTPs. The contaminants in this stream are generally 6 to 7 times more concentrated than in the feed water. Environmental risks were identified due to potential increased toxicity associated with these higher concentrations, which were exacerbated due to chlorine and ammonia dosed in the AWTP process. Target ROC contaminants have been identified as nitrogen, phosphorus, ammonia, metals and chlorine. The paper presents the selected toxicity management and nutrient reduction strategies for each AWTP, and the results of full-scale operation to date are also summarised.

Water quality monitoring is essential to understanding the complex dynamics of water ecosystems, the impact of human infrastructure on them and to ensure the safe use of water resources for drinking, recreation and transport. High frequency in-situ monitoring systems are being increasingly employed in water quality monitoring schemes due to their much finer temporal measurement scales possible and reduced cost associated with manual sampling, manpower and time needed to process results compared to traditional grab-sampling. Modelling water quality data at higher frequency reduces uncertainty and allows for the capture of transient events, although due to potential constraints of data storage, inducement of noise, and power conservation it is worthwhile not using an excessively high sampling frequency. In this study, high frequency data recorded in Bristol's Floating Harbour as part of the local UKRIC Urban Observatory activities is presented to analyse events not captured by the current manual sampling and laboratory analysis scheme. The frequency components of the time-series are analysed to work towards understanding the necessary sampling frequency of temperature, dissolved oxygen (DO), fluorescent dissolved organic matter (fDOM), turbidity and conductivity as indicators of water quality. This study is the first of its kind to explore a statistical approach for determining the optimum sampling frequency for different water quality parameters using a high frequency dataset. Furthermore, it provides practical tools to understand how different sampling frequencies are representative of the water quality changes.

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<p>Water quality monitoring is essential to understanding the complex dynamics of water ecosystems, the impact of human infrastructure on them and to ensure the safe use of water resources for drinking, recreation and transport. High frequency in-situ monitoring systems are being increasingly employed in water quality monitoring schemes due to their much finer temporal measurement scales possible and reduced cost associated with manual sampling, manpower and time needed to process results compared to traditional grab-sampling.</p><p>Modelling water quality data at higher frequency reduces uncertainty and allows for the capture of transient events, although due to potential constraints of data storage, inducement of noise, and power conservation it is worthwhile not using an excessively high sampling frequency.</p><p>This study explores the issue of frequency optimisation of water quality monitoring schemes by applying three different statistical approaches for determining the optimum sampling frequency.</p><p>The proposed approaches are tested utilising a high frequency dataset built from recording continuous physical and chemical water quality parameters (temperature, dissolved oxygen (DO), fluorescent dissolved organic matter (fDOM), turbidity and conductivity) with multiparameter sondes at 3 sites in Bristol’s Floating Harbour.</p><p>As a result, this analysis provides practical tools to understand how different sampling frequencies are representative of the water quality changes. Furthermore, it helps determine the minimum frequency required to communicate periodic fluctuations in water quality and investigate the additional benefit of recording data at a frequency higher than the minimum required.</p>