Evan Davies

Climate mitigation policy implications for global irrigation water demand

Measures to limit greenhouse gas concentrations will result in dramatic changes to energy and land systems and in turn alter the character of human requirements for water. We employ the global change assessment model (GCAM), an integrated assessment model, to explore the interactions of energy, land, and water systems under combinations of three alternative radiative forcing stabilization levels and two carbon tax regimes. The paper analyzes two important research questions: i) how large may global irrigation water demands become over the next century, and ii) what are the potential impacts of emissions mitigation policies on global irrigation-water withdrawals. We find that increasing population and economic growth could more than double the demand for water for agricultural systems in the absence of climate policy, and policies to mitigate climate change further increase agricultural demands for water. The largest increases in agricultural irrigation water demand occur in scenarios where only fossil fuel emissions are priced (but not land use change emissions) and are primarily driven by rapid expansion in bio-energy production. Regions such as China, India, and other countries in South and East Asia are likely to experience the greatest increases in water demands. Finally, we test the sensitivity of water withdrawal demands to the share of bio-energy crops under irrigation and conclude that many regions have insufficient space for heavy bio-energy crop irrigation in the future—a result that calls into question the physical possibility of producing the associated biomass energy, especially under climate policy scenarios.

Scenarios of global municipal water-use demand projections over the 21st century

Abstract Three future projections of global municipal water use are established: business-as usual (BAU), low technological improvement (Low Tech), and high technological improvement (High Tech). A global municipal water demand model is constructed using global water-use statistics at the country scale, calibrated to the base year of 2005, and simulated to the end of the 21st century. Since the constructed water demand model hinges on socio-economic variables (population, income), water price, and end-use technology and efficiency improvement rates, projections of those input variables are adopted to characterize the uncertainty in future water demand estimates. The water demand model is linked to the Global Change Assessment Model (GCAM), a global change integrated assessment model. Under the reference (BAU) scenario, the global total water withdrawal increases from 466 km3 year−1 in 2005 to 1098 km3 year−1 in 2100, while withdrawals in the High and Low Tech scenarios are 437 and 2000 km3 year−1, respectively. Editor Z.W. Kundzewicz; Associate editor D. Gerten Citation Hejazi, M., Edmonds, J., Chaturvedi, V., Davies, E., and Eom, J.Y., 2013. Scenarios of global municipal water use demand projections over the 21st century. Hydrological Sciences Journal, 58 (3), 519–538

Balancing global water availability and use at basin scale in an integrated assessment model

Water is essential for the world’s food supply, for energy production, including bioenergy and hydroelectric power, and for power system cooling. Water is already scarce in many regions of the world and could present a critical constraint as society attempts simultaneously to mitigate climate forcing and adapt to climate change, and to provide for a larger and more prosperous human population. Numerous studies have pointed to growing pressures on the world’s scarce fresh water resources from population and economic growth, and climate change. This study goes further. We use the Global Change Assessment Model to analyze interactions between population, economic growth, energy, land, and water resources simultaneously in a dynamically evolving system where competing claims on water resources from all claimants—energy, land, and economy—are reconciled with water resource availability—from renewable water, non-renewable groundwater and desalinated water sources —across 14 geopolitical regions, 151 agriculture-ecological zones, and 235 major river basins. We find that previous estimates of global water withdrawal projections are overestimated. Model simulations show that it is more economical in some basins to alter agricultural and energy activities rather than utilize non-renewable groundwater or desalinated water. This study highlights the importance of accounting for water as a binding factor in agriculture, energy and land use decisions in integrated assessment models and implications for global responses to water scarcity, particularly in the trade of agricultural commodities and land-use decisions.

Global and Regional Evaluation of Energy for Water

Despite significant effort to quantify the interdependence of the water and energy sectors, global requirements of energy for water (E4W) are still poorly understood, which may result in biases in projections and consequently in water and energy management and policy. This study estimates water-related energy consumption by water source, sector, and process for 14 global regions from 1973 to 2012. Globally, E4W amounted to 10.2 EJ of primary energy consumption in 2010, accounting for 1.7%-2.7% of total global primary energy consumption, of which 58% pertains to fresh surface water, 30% to fresh groundwater, and 12% to nonfresh water, assuming median energy intensity levels. The sectoral E4W allocation includes municipal (45%), industrial (30%), and agricultural (25%), and main process-level contributions are from source/conveyance (39%), water purification (27%), water distribution (12%), and wastewater treatment (18%). While the United States was the largest E4W consumer from the 1970s until the 2000s, the largest consumers at present are the Middle East, India, and China, driven by rapid growth in desalination, groundwater-based irrigation, and industrial and municipal water use, respectively. The improved understanding of global E4W will enable enhanced consistency of both water and energy representations in integrated assessment models.

ANEMI: a new model for integrated assessment of global change

This paper describes a new model, ANEMI, for the integrated assessment of climate and global change. ANEMI reproduces the main characteristics of eight sectors of the society-biosphere-climate system – climate, carbon cycle, land use, population, surface water flow, water use, water quality, and the economy – and explores the manner in which interactions, or feedbacks, between these components determine the behaviour of the whole. The models reference behaviour forms the basis of comparison for the set of experiments undertaken to date with the model; these experiments and their goals are summarised. A sample Monte Carlo simulation illustrates typical model behaviour, and shows how change in one model variable affects the others. Conclusions reiterate the value of integrated assessment modelling and describe future additions to the model.

Setting the System Boundaries of “Energy for Water” for Integrated Modeling

Modeling Page Kyle,*,† Nils Johnson,‡ Evan Davies, David L. Bijl, Ioanna Mouratiadou, Michela Bevione, Laurent Drouet, Shinichiro Fujimori, Yaling Liu,† and Mohamad Hejazi† †Joint Global Change Research Institute, Pacific Northwest National Laboratory, College Park, Maryland 20740, United States ‡International Institute for Applied Systems Analysis, Laxenburg, Austria University of Alberta, Edmonton, Alberta, Canada Copernicus Institute of Sustainable Development, Utrecht University, Utrecht, Netherlands Potsdam Institute for Climate Impact Research, Potsdam, Germany Fondazione Eni Enrico Mattei, Milan, Italy National Institute for Environmental Studies, Tsukuba, Japan

Climate policy implications for agricultural water demand

Energy, water and land are scarce resources, critical to humans. Developments in each affect the availability and cost of the others, and consequently human prosperity. Measures to limit greenhouse gas concentrations will inevitably exact dramatic changes on energy and land systems and in turn alter the character, magnitude and geographic distribution of human claims on water resources. We employ the Global Change Assessment Model (GCAM), an integrated assessment model to explore the interactions of energy, land and water systems in the context of alternative policies to limit climate change to three alternative levels: 2.5 Wm-2 (445 ppm CO2-e), 3.5 Wm-2 (535 ppm CO2-e) and 4.5 Wm-2 (645 ppm CO2-e). We explore the effects of two alternative land-use emissions mitigation policy options—one which taxes terrestrial carbon emissions equally with fossil fuel and industrial emissions, and an alternative which only taxes fossil fuel and industrial emissions but places no penalty on land-use change emissions. We find that increasing populations and economic growth could be anticipated to almost triple demand for water for agricultural systems across the century even in the absence of climate policy. In general policies to mitigate climate change increase agricultural demands for water still further, though the largest changes occur in the second half of the century, under both policy regimes. The two policies examined profoundly affected both the sources and magnitudes of the increase in irrigation water demands. The largest increases in agricultural irrigation water demand occurred in scenarios where only fossil fuel emissions were priced (but not land-use change emission) and were primarily driven by rapid expansion in bioenergy production. In these scenarios water demands were large relative to present-day total available water, calling into question whether it would be physically possible to produce the associated biomass energy. We explored the potential of improved water delivery and irrigation system efficiencies. These could potentially reduce demands substantially. However, overall demands remained high under our fossil-fuel-only tax policy. In contrast, when all carbon was priced, increases in agricultural water demands were smaller than under the fossil-fuel-only policy and were driven primarily by increased demands for water by non-biomass crops such as rice. Finally we estimate the geospatial pattern of water demands and find that regions such as China, India and other countries in south and east Asia might be expected to experience greatest increases in water demands.

Towards best water management policies: how current irrigation reservoir operation practices compare with theory in Alberta

ABSTRACT Improved reservoir operation policies based on river basin management simulations have typically not been implemented in the field. This article investigates this disconnect between reservoir operations theory and practice. Interviews with water managers in southern Alberta (Canada) reveal that reservoir operations are based on basin-wide cooperation, a focus on the current state of the system without hedging rules, and early-season announcements of water rationing. Model development should focus on multiple time-step optimization approaches that can produce optimal release decisions for various levels of risk, provide better insight into effects of alternative releases and potentially reduce supply shortfalls.

Monochloramine loss mechanisms and dissolved organic matter characterization in stormwater

Monochloramine (NH2Cl) is widely used for secondary disinfection by water utilities. However, Edmonton field stormwater sampling results have shown that NH2Cl, because of its long-lasting property, can cause stormwater contamination through outdoor potable water uses during the summer season. To protect water sources, it is important to understand NH2Cl dissipation mechanisms in stormwater. Natural organic matter (NOM) is the dominant species that contributes to NH2Cl decay in stormwater. In this research, it is proposed that NOM reacted with both NH2Cl and free chlorine through rapid and long-term reactions during NH2Cl dissipation. Based on this assumption, a kinetic model was developed and applied to estimate the NH2Cl decay in real stormwater samples, and the modeling results matched experimental data well under all the conditions. Further, the stormwater dissolved organic matter (SWDOM) collected from different neighborhoods was analyzed by Fourier transform infrared (FTIR) and fluorescence excitation-emission matrix (EEM) techniques. Humic substances were found to be dominant in SWDOM, and the samples from different neighborhoods had similar organic constituents. After reaction with excess NH2Cl, 25%-41% SWDOM fluorophores converted to inorganic components, while most of DOM remained in organic form. Humic substances as the major components in SWDON, are the dominant precursors of disinfection by-products in chloramination. Therefore, the potential reaction products of stormwater humic substances with NH2Cl should also be of concern. This research provided a useful method to estimate the NH2Cl dissipation in stormwater, and the methodology can also be applied for stormwater NH2Cl decay studies in other cities. Further, it is believed the SWDOM analysis in this research will contribute to future studies of NH2Cl NOM reaction mechanisms in both storm sewers and drinking water distribution systems.

Cities drive food and water security

Current global models omit the complex, unpredictable behaviours that socio-environmental systems exhibit. Now researchers have proposed a city- and trade-based integrated model that includes these behaviours and explained its use for food and water security research.