Michael J. Stewardson

Taking the “Waste” Out of “Wastewater” for Human Water Security and Ecosystem Sustainability

Humans create vast quantities of wastewater through inefficiencies and poor management of water systems. The wasting of water poses sustainability challenges, depletes energy reserves, and undermines human water security and ecosystem health. Here we review emerging approaches for reusing wastewater and minimizing its generation. These complementary options make the most of scarce freshwater resources, serve the varying water needs of both developed and developing countries, and confer a variety of environmental benefits. Their widespread adoption will require changing how freshwater is sourced, used, managed, and priced.

Comparison of six rainfall-runoff modelling approaches

Abstract Six rainfall-runoff modelling approaches — simple polynomial equation, simple process equation (tanh equation), simple time-series equation (Tsykin equation), complex time-series model (IHACRES), simple conceptual model (SFB) and complex conceptual model (MODHYDROLOG) — are compared in this paper with the models used to simulate daily, monthly and annual flows in eight unregulated catchments. The complex conceptual model gives, by far, the best simulation of daily high and low flows, and can estimate adequately daily flows for the wetter catchments. It can provide satisfactory estimates of monthly and annual catchment yields in almost all catchments. However, the time-series approaches and the simple conceptual model can also provide adequate estimates of monthly and annual yields in the wetter catchments. As it is much easier to use these approaches than the complex conceptual model, the simpler methods may be used to estimate monthly and annual runoff in the wetter catchments.

USE OF WETTED PERIMETER IN DEFINING MINIMUM ENVIRONMENTAL FLOWS

In regulated rivers, the relationship between wetted perimeter and discharge is sometimes used as an expedient technique for determining the minimum flow allowable for environmental purposes. The critical minimum discharge is supposed to correspond to the point where there is a break in the shape of the curve (usually a logarithmic or power function). Below this discharge, wetted perimeter declines rapidly. This critical point on the curve is almost universally, but incorrectly, termed an ‘inflection’ point, and is usually determined subjectively by eye from a graph. The appearance of a break in the shape of the curve is strongly dependent on the relative scaling of the axes of the graph. This subjectivity can be overcome by defining the break in shape using mathematical techniques. The important break in the shape of the curve can be systematically defined by the point where the slope equals 1, or where the curvature is maximized. The technique can be applied to other habitat‐discharge relationships, provided the habitat variable increases with discharge. These techniques were applied to two regulated headwater streams located in the Melbourne catchment area. Channel survey data were used to model the relationship between discharge and wetted perimeter, flowing water perimeter and blackfish habitat area. A logarithmic function could be fitted to the wetted perimeter data for Starvation Creek, but the relationship for Armstrong Creek was linear. Both streams showed logarithmic relationships between discharge and flowing water perimeter. For these streams, the wetted perimeter relationships did not suggest an optimum environmental flow, nor did they suggest a flow level that would maintain the macroinvertebrate community in its unregulated state if it was applied for a long period of time. Fish habitat area does not necessarily increase with discharge, so the method of curve analysis suggested here for wetted perimeter may not be applicable to some fish habitat area data. Flowing water perimeter is preferable over wetted perimeter as a variable to define habitat suitable for macroinvertebrates.

Environmental flows for natural, hybrid, and novel riverine ecosystems in a changing world

The term “environmental flows” describes the quantities, quality, and patterns of water flows required to sustain freshwater and estuarine ecosystems and the ecosystem services they provide. Environmental flows may be achieved in a number of different ways, most of which are based on either (1) limiting alterations from the natural flow baseline to maintain biodiversity and ecological integrity or (2) designing flow regimes to achieve specific ecological and ecosystem service outcomes. We argue that the former practice is more applicable to natural and semi-natural rivers where the primary objective and opportunity is ecological conservation. The latter “designer” approach is better suited to modified and managed rivers where return to natural conditions is no longer feasible and the objective is to maximize natural capital as well as support economic growth, recreation, or cultural history. This permits elements of ecosystem design and adaptation to environmental change. In a future characterized by altered climates and intensive regulation, where hybrid and novel aquatic ecosystems predominate, the designer approach may be the only feasible option. This conclusion stems from a lack of natural ecosystems from which to draw analogs and the need to support broader socioeconomic benefits and valuable configurations of natural and social capital.

Riparian Ecosystems in the 21st Century: Hotspots for Climate Change Adaptation?

Riparian ecosystems in the 21st century are likely to play a critical role in determining the vulnerability of natural and human systems to climate change, and in influencing the capacity of these systems to adapt. Some authors have suggested that riparian ecosystems are particularly vulnerable to climate change impacts due to their high levels of exposure and sensitivity to climatic stimuli, and their history of degradation. Others have highlighted the probable resilience of riparian ecosystems to climate change as a result of their evolution under high levels of climatic and environmental variability. We synthesize current knowledge of the vulnerability of riparian ecosystems to climate change by assessing the potential exposure, sensitivity, and adaptive capacity of their key components and processes, as well as ecosystem functions, goods and services, to projected global climatic changes. We review key pathways for ecological and human adaptation for the maintenance, restoration and enhancement of riparian ecosystem functions, goods and services and present emerging principles for planned adaptation. Our synthesis suggests that, in the absence of adaptation, riparian ecosystems are likely to be highly vulnerable to climate change impacts. However, given the critical role of riparian ecosystem functions in landscapes, as well as the strong links between riparian ecosystems and human well-being, considerable means, motives and opportunities for strategically planned adaptation to climate change also exist. The need for planned adaptation of and for riparian ecosystems is likely to be strengthened as the importance of many riparian ecosystem functions, goods and services will grow under a changing climate. Consequently, riparian ecosystems are likely to become adaptation ‘hotspots’ as the century unfolds.

Analyzing cause and effect in environmental assessments: using weighted evidence from the literature

Abstract.  Sound decision making in environmental research and management requires an understanding of causal relationships between stressors and ecological responses. However, demonstrating cause–effect relationships in natural systems is challenging because of difficulties with natural variability, performing experiments, lack of replication, and the presence of confounding influences. Thus, even the best-designed study may not establish causality. We describe a method that uses evidence available in the extensive published ecological literature to assess support for cause–effect hypotheses in environmental investigations. Our method, called Eco Evidence, is a form of causal criteria analysis—a technique developed by epidemiologists in the 1960s—who faced similar difficulties in attributing causation. The Eco Evidence method is an 8-step process in which the user conducts a systematic review of the evidence for one or more cause–effect hypotheses to assess the level of support for an overall question. In contrast to causal criteria analyses in epidemiology, users of Eco Evidence use a subset of criteria most relevant to environmental investigations and weight each piece of evidence according to its study design. Stronger studies contribute more to the assessment of causality, but weaker evidence is not discarded. This feature is important because environmental evidence is often scarce. The outputs of the analysis are a guide to the strength of evidence for or against the cause–effect hypotheses. They strengthen confidence in the conclusions drawn from that evidence, but cannot ever prove causality. They also indicate situations where knowledge gaps signify insufficient evidence to reach a conclusion. The method is supported by the freely available Eco Evidence software package, which produces a standard report, maximizing the transparency and repeatability of any assessment. Environmental science has lagged behind other disciplines in systematic assessment of evidence to improve research and management. Using the Eco Evidence method, environmental scientists can better use the extensive published literature to guide evidence-based decisions and undertake transparent assessments of ecological cause and effect.

Adapting Urban Water Systems to a Changing Climate: Lessons from the Millennium Drought in Southeast Australia

Feature pubs.acs.org/est Adapting Urban Water Systems to a Changing Climate: Lessons from the Millennium Drought in Southeast Australia Stanley B. Grant,* ,†,‡ Tim D. Fletcher, ⊥ David Feldman, § Jean-Daniel Saphores, †,§ Perran L. M. Cook, # Mike Stewardson, ‡ Kathleen Low, † Kristal Burry, ∇ and Andrew J. Hamilton ∥ Department of Civil and Environmental Engineering, E4130 Engineering Gateway, University of California, Irvine, Irvine, California 92697-2175, United States Department of Infrastructure Engineering, Melbourne School of Engineering, Engineering Block D, The University of Melbourne, Parkville 3010, Victoria, Australia Department of Planning, Policy, and Design, 300G Social Ecology I, University of California, Irvine, Irvine, California 92697-7075, United States Department of Agriculture and Food Systems, The University of Melbourne, 940 Dookie−Nalinga Road, Dookie College, Victoria 3647, Australia Melbourne School of Land and Environment, The University of Melbourne, Burnley Campus, 500 Yarra Boulevard, Richmond, Victoria 3121, Australia Water Studies Centre, School of Chemistry, Monash University, Victoria 3800, Australia Melbourne School of Land and Environment, The University of Melbourne, Parkville Campus, 207 Bouverie Street, Victoria 3052, Australia the way Melburnians source and use their water resources and discuss what these changes may portend for other large cities in water-scarce and climate-change-vulnerable regions of the world, in particular, the Southwest region of the United States. MELBOURNE’S WATER SUPPLY Melbourne sources most of its water from protected stream catchments located in uninhabited mountain ash (Eucalyptus regnans) forests to the north and northeast of the city (Figure 1). Runoff from these protected catchments flows by gravity into ten harvesting reservoirs and, from there, through a network of aqueducts and pipelines to storage reservoirs where it is distributed, after minimal treatment, to local service reservoirs. Since the first harvesting reservoir was built in the mid-1800s, Melbourne’s protected catchments have provided the city with a safe, low-energy, and mostly reliable source of high quality drinking water. However, they have also left the city vulnerable to water shortages during periods of very low precipitation. 5 To buffer against water shortages, Melbourne recently invested in various water supply augmentation schemes, including an interbasin transfer pipeline (the North−South or Sugarloaf Pipeline) and the largest desalination plant in the Southern Hemisphere (the Wonthaggi Desalination Plant) (Figure 1). These two projects were built at a capital cost of approximately AU

Australia's Drought: Lessons for California

700 million 6 and AU

Optimal dynamic water allocation: Irrigation extractions and environmental tradeoffs in the Murray River, Australia

6 billion, 7 respec- tively, and can deliver annually up to 75 and 150 GL of water to Melbourne; combined, that equates to about 40% of the city’s present day municipal water demand. However, since their completion in 2010 (Sugarloaf Pipeline) and 2012 (Wonthaggi Desalination Plant), neither A LONG HISTORY OF DROUGHT IN MELBOURNE Australia is the world’s driest inhabited continent, and its population is one of the most urban. As of 2010, 89% of Australia’s 21 million inhabitants lived in urban areas. 1 Finding adequate water resources to sustain Australia’s cities is an ongoing challenge. 2 Nowhere is that more apparent than in Melbourne, a coastal city of approximately 4 million people located on the country’s southeastern coast. Over its 166-year history, Melbourne has experienced eight major droughts. The most recent one, known as the Millennium Drought, started in 1997 and lasted more than a decade. By 2009, below-average precipitation and above-average temperatures drained the city’s drinking-water reservoirs and stoked bush fires, including the “Black Saturday” fire that damaged 30% of the city’s water supply catchment and claimed 173 lives. 3 The Millennium Drought also altered public perceptions about global climate change, water conservation, and water-use behaviors, and energized city managers and politicians to adopt a wide range of approaches for augmenting water supplies and conserving water resources, although the contribution of climate change to the Millennium drought, while plausible, remains unproven. 4 In this paper, we explore how the Millennium Drought changed

First-order contaminant removal in the hyporheic zone of streams: physical insights from a simple analytical model.

COMMENTARY Refl ective scientifi c treatises Strengthening citizen science LETTERS I BOOKS I POLICY FORUM I EDUCATION FORUM I PERSPECTIVES LETTERS edited by Jennifer Sills 28 MARCH 2014 sumptive activities—such as daytime lawn watering and car washing—to rules promot- ing efficient water use—such as require- ments for shutoff valves on hoses. Out of those temporary restrictions, permanent restrictions grew. Some areas in Australia still restrict daytime sprinkler use. Perhaps most relevant for worried Californians is how the Australian public received these changes. Studies cite an overall spirit of goodwill and cooperation fostered by the stress of drought (6). The Millennium Drought brought about profound changes in Australians’ concep- tion of the environment, climate change, and water. The sticking power of those les- sons and the success of the resulting policies and strategies will be tested by the next big drought. One lesson California can glean from the Australian experience is empower- ment. Individuals making frugal water deci- sions can make a big difference in urban areas. Water markets and other measures that increase the fl exibility of irrigation farmers in their response to drought can have big payoffs. Sustaining critical environmental water requirements will provide the basis for postdrought environmental recovery. A spirit of cooperation rather than contention can prevail even when tough decisions are made to address the needs of farmers and city residents. AMIR AGHAKOUCHAK, 1 * DAVID FELDMAN, 1 MICHAEL J. STEWARDSON, 2 JEAN-DANIEL SAPHORES, 1 STANLEY GRANT, 1,2 BRETT SANDERS 1 The Henry Samueli School of Engineering, University of California, Irvine, Irvine, CA 92697, USA. 2 Melbourne School of Engineering, The University of Melbourne, Parkville, VIC 3010, Australia. *Corresponding author. E-mail: amir.a@uci.edu References 1. A. I. Dijk et al., Water Resources Res. 49, 1040 (2013). 2. Z. Hao et al., Sci. Data 1, 1 (2014). 3. S. Dolnicar, A. I. Schafer, J. Environ. Manage. 90, 888 VOL 343 SCIENCE www.sciencemag.org Published by AAAS Downloaded from www.sciencemag.org on March 27, 2014 MOST OF CALIFORNIA IS SUFFERING FROM AN extreme drought, and storage levels in the major reservoirs are well below historic lev- els. For the past several months, an unusually stubborn ridge of high pressure off the West Coast of the United States has been blocking normal winter storms and the rain they carry. California’s history of drought has led to state- wide strategies to save water, but Californian residents and policy-makers can do even more: They can look to the story of Australia’s experi- ence with a drought so intense and long-lasting that it was dramatically dubbed the Millennium Drought (1). The Millennium Drought lasted from 1997 until late 2009 (2). Australia’s economy and environment were hit hard. The drought accel- erated the same trends facing farmers in devel- oping countries worldwide: Small farms were squeezed out. Midsized farms were most vul- nerable because they could neither achieve the economies of scale available to larger produc- ers nor buffer losses with off-farm employ- ment like the smallest farms could. Amazingly, despite blows to crop yields and Dried out. As of February 2014, most of California is in Extreme to Exceptional Drought (see red and livestock numbers, Australia’s rate of growth in dark red areas on map). agricultural production has quickly returned to predrought trends. The impacts of this major drought on irrigation communities were buffered by some critical water reforms. These included: (i) well-developed water markets that allowed water trade to farmers in the greatest need; (ii) modernization of irrigation infrastructure that increased the effi ciency of water delivery; and (iii) establishment of clear water entitlements for the environment that protected critical refuge habitats and populations as water availability declined. The use of water markets was particularly critical. More than 40% of annual water alloca- tions were traded at the height of the drought in 2007. For example, increased water prices allowed dairy farmers to sell their allocation and purchase fodder with the proceeds rather than irrigate pasture. Fruit growers and other producers who needed to maintain irrigation through- out the drought could purchase the dairy farmers’ water to keep their operations viable. In urban areas, strategies to increase supply and decrease demand were brought to bear. Expensive desalination and water recycling plants were built. Australians were more comfort- able with the desalinated water (3, 4), despite the recycled water’s safety and the desalination plants’ greater cost and large carbon and environmental footprints (4). Between 2002 and 2009, per capita municipal water use in southeast Australia decreased by nearly 50% (5). Water use restrictions ranged from outright bans of conspicuously con- CREDIT: DATA FROM THE GLOBAL INTEGRATED DROUGHT MONITORING AND PREDICTION SYSTEM (GIDMAPS) (2) Australia’s Drought: Lessons for California