Abstract—Preparation for global movement to urban regions

requires a holistic study of infrastructure interactions. The impact of water and energy on one another has been studied to show how they are dependent upon one another. Other infrastructure interactions also are vital to designing more sustainable cities. The primary infrastructures are: water, energy, land use, and transportation. Creating more sustainable cities may involve low-impact development techniques, opting for compact living, and studying alternatives for water, energy, and transportation provision. Every city is different, and infrastructure decisions should be tailored to fit each city. This group is primarily focused on the greater Atlanta region and the Phoenix area.

Index Terms—compact growth, low impact development, sustainability, sustainable urban infrastructure

I. INTRODUCTION

HE U.N. Environmental Program (UNEP) chief, Klaus

Toepfer, stated in 2005, “Cities pull in huge amounts of resources including water, food, timber, metals and people. They export large amounts of wastes including household and industrial wastes, wastewater and the gases linked with global

This work was supported by National Science Foundation under Grant

09-167. E. A. Minne, J. C. Crittenden, A. Pandit, H. Jeong, J. James, and Z. Lu

are with the Brook Byers Institute for Sustainable Systems and the Department of Civil & Environmental Engineering, Georgia Institute of Technology, Atlanta, GA 30332 USA (email: liz.minne@gatech.edu).

M. Xu is with the School of Natural Resources and Environment, University of Michigan, Ann Arbor, MI 48109 USA.

S. French and M. Subrahmanyam are with the Center for Geographic Information Systems and the School of City and Regional Planning, Georgia Institute of Technology, Atlanta, GA 30332 USA.

D. Noonan, M. Brown, and J. Wang and L. Hsieh are with the School of Public Policy, Georgia Institute of Technology, Atlanta, GA 30332 USA.

R. Desroches is with the Department of Civil & Environmental Engineering, Georgia Institute of Technology, Atlanta, GA 30332 USA.

B. Bras and J. Yen are with the George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA 30332 USA.

M. Begovic and I. Kim are with the School of Electrical and Computer Engineering, Georgia Institute of Technology, Atlanta, GA 30332 USA.

K. Li and P. Rao are with the Department of Biological and Agricultural Engineering, University of Georgia, Athens, GA 30602 USA.

warming. So the battle for sustainable development, for delivering a more environmentally stable, just, and healthier world, is going to be largely won and lost in our cities” [1]. The UNEP expects 68.7% of the world’s population to live in urban areas by 2050, a dramatic increase from 50.5% in 2010 [2]. In the United States, 82.3% of the population lived in urban areas in 2010, and that number is also expected to increase to 90.4% by 2050 [2].

A holistic view of infrastructure interactions is necessary to properly plan for sustainable cities. Studies of the way land use, water infrastructure, energy infrastructure, and transportation infrastructure interact are required. Other factors, such as socioeconomic, environment, and policy implementation, also will affect the decisions made in city planning. The goal of the Sustainable Infrastructure for Energy and Water Systems (SINEWS) is to develop a framework for sustainable and resilient infrastructure that incorporates the water-energy-transportation-socioeconomic-land use nexus. The framework will initially be developed for the test-bed cities of Atlanta and Phoenix, and then extended to other cities.

II. BACKGROUND

Every infrastructure decision not only affects its immediate material consumption, but also affects a myriad of other urban infrastructures. For example, the connection between water and energy has been well studied; the creation of energy consumes water, and energy is used to treat water. This becomes a serious consideration in times of dry, hot summers because more air conditioning usage places a huge strain on water and energy.

The water needed for different energy sources has been evaluated to show that some renewable energy sources (particularly some biofuels) actually use a significant amount of water. In terms of evaporative loss, hydro power loses 18.27 Gal/kWh, as compared to coal which loses 0.49 Gal/kWh [3]. Photovoltaic power may look like a viable option in comparison as it has a lower evaporative loss for the power created and a higher energy output as compared to energy invested than coal. However, if available land is a

Water, Energy, Land Use, Transportation and Socioeconomic Nexus: A Blue Print for More

Sustainable Urban Systems Elizabeth A. Minne, John C. Crittenden, Arka Pandit, Hyunju Jeong, Jean-Ann James, Zhongming Lu,

Ming Xu, Steve French, Muthukumar Subrahmanyam, Douglas Noonan, Lin-Han Chiang Hsieh, Marilyn Brown, Joy Wang, Reginald Desroches, Bert Bras, Jeff Yen, Miroslav Begovic, Insu Kim, Ke

Li, Preethi Rao

T

consideration, photovoltaic panels use much more land than coal-fired power plants, as shown in Table 1. Also, cost effectiveness must be considered. The costs provided in Table 1 are the overnight capital cost estimates of 2010 in US Dollars. The estimate for the coal plant does not include carbon capture and sequestration.

TABLE 1

ENERGY SOURCE COMPARISON

Energy Sources Photovoltaic Coal Energy Output

Energy Invested

[4] 9 5

Water Use [3] 0.001 Gal/kWhr 0.49 Gal/kWhr

Land Use 0.51 kWh/acre (RETScreen Simulation)

690 kWh/acre [5],[6],[7],[8],[9]

Overnight Cost[10] 4,755 $/kWh 2,844 $/kWh

The group has investigated the interactions of sectors of infrastructure. By looking at multiple systems at a time, each system can be made more efficient. For example, Vancouver decided to use green space to capture and treat stormwater, to protect their salmon-bearing streams. Treating the stormwater traditionally was expected to cost $4 billion dollars, but the low impact development method of green space treatment is projected to produce a $400 million dollar income from increased property values and taxes. This approach looked at land use and water treatment to optimize both systems. The interconnections among land use, energy, water, and transportation are shown in Fig. 1.

Fig.1. Urban infrastructure is interconnected. This figure shows the dependence of each system on one another, demonstrating that decisions should be made for infrastructure that considers the overall effect on the sustainability of a city.

As a demonstration of the interactions, the effects of all three sectors on transportation have been studied and are summarized in Table 2. Transportation depends on energy and water in the creation of fuel. Additionally, city planning for transportation networks affect the modes of transportation chosen. In the United States, urban sprawl has dominated many cities, and developing better land use, such as improved public transportation and more compact living, could significantly reduce reliance on energy, water and other resources.

TABLE 2 SYSTEM INERACTIONS WITH TRANSPORTATION

Effects Petroleum Effects Energy[11] 28% of total energy 71% of petroleum

Water (for fuel)[12] Biodiesel as high as 19 Gal/kWh

Petroleum as low as 0.03 Gal/kWh

Alternatives (Plug-in Hybrids)[13]

Energy could support 73% of

current US vehicle fleet

Reduce US dependence on oil by

52% (US imports 50% of oil)

III. RESULTS AND DISCUSSION After an extensive literature review and study of

infrastructure connections, the group began looking at alternative urban growth patterns. Using US Census data, land use and cover data from a local planning agency, and employment data from the counties and Department of Commerce, simulations were run in the program What If?™. Figure 2 displays urban growth projection for the year 2030. Two scenarios were used for comparison, Business as Usual and Compact Growth. Business as Usual continues the urban growth as it has been growing, and as Fig. 2 shows expanding sprawl (yellow). Compact Growth creates a denser population, and more land is undeveloped. Condensed living can lead to benefits in energy and water efficiency, while leaving more land for green space.

Land Use

Business as Usual Scenario Compact Growth Scenario

2030 2030

Fig. 2. The urban growth scenarios of the Atlanta area by 2030. Business as usual shows more sprawl and compact growth keeps a much larger portion of the land as undeveloped green space.

This group has studied energy-water nexus in the two test-bed cities for comparison. Those results are shown in Table3. These numbers demonstrate that the cities use vastly different resources. The water and energy use in Phoenix are more intensive owing to its desert climate and distance to water resource. With increasing global temperature, the water resources would be stressed further in hot summers. Hot summers increase the public-supply water demand, evaporation rate and energy demand for cooling purposes, all of which strain the water availability. This is a problem not only experienced in Phoenix, but also cities like Atlanta where a long drought and hot summer caused a “water war” between nearby states. Increasing temperatures will increase the number of cities which are affected by evaporating large amounts of water due to heat.

TABLE 3 WATER-ENERGY NEXUS

IV. FUTURE DIRECTIONS

In order to integrate the many elements of this research, the group is developing agent-based models. The idea is to create an agent based model that can predict social decision making and demand for urban infrastructure. The comprehensive model will integrate energy, water, transportation, and land use, as well as material use, policy decisions, and socio-economics.

To begin this complex undertaking, we have begun developing a toy model of the interactions of homebuyers, real estate agents, home developers, and the government. We hope to model how homebuyers chose their homes and what kind of economic and policy incentives may direct buyers to compact living space rather than traditional living space. Traditional living spaces refer to the traditional suburban lots today, with maximized house plots and small personal yards. Compact living spaces refers to smaller homes with public access to large green spaces. Encouragement of this behavior would be beneficial given the infrastructure efficiencies common to more compact spaces, such as lower energy and water demands, lower material intensity of infrastructure and a more efficient public transit.

Another aspect of this study is the material needs for development and redevelopment. We are working to determine the amount of material and energy needed to build and operate the urban systems for both the Compact Growth and Business as Usual scenarios shown in Figure 2. We predict that compact growth requires less materials and energy. The data from the What If?™ simulations can be given in square feet for (re)development for different sectors (industrial, residential, commercial) and then be converted into the materials needed for this growth. By comparing the results from both scenarios, the hypothesis is that the material and energy that is needed for Compact Growth would be significantly less, can be tested.

To create this complex model, a few options are being considered. We are debating which programs to use (e.g. What If?™, UrbanSim, or creating our own model). What If?™ [14] already has been set up for Atlanta, and uses suitability factors

to place infrastructure. We could add our own agent based simulations to What If?™. UrbanSim [15] is a much more complex model. It can be edited to create scenarios and add agent-based modeling, but takes years to set up for a city. This modeling has already been set up for the City of Phoenix, so we could use Phoenix as an example. Another alternative would be to create our own model. This gives us more flexibility with the modeling. Potential city designs might include creating a city that is compact, one that is polynuclear (has a few centers of dense activity), and one that shows urban sprawl. To see how different factors like policy and economics create these kinds of cities, we can start from a greenfield, which could be useful in influencing city planning for new cities. Additionally we can test those factors for the created general cities to see how population growth occurs and how to plan for it. This is useful, but not as specific for a city, like the UrbanSim model is, which gives UrbanSim the advantage for planning for a large, developed city like Atlanta. In order to decide on the best approach, an expansive literature review has been undertaken.

In developing the model, the next step would be to add the energy, water, and material footprints for the different land uses. As well as a life cycle impact analysis that could estimate the local, regional, and global impacts of the scenarios. Additionally, the model could test different infrastructure designs, such as decentralized and centralized water and energy provision, as well as options for stormwater management. Methods to conserve energy, water, and materials, and reduce the local, regional, and global impacts could be tested.

For example, the model could be used to test the difference in demand for compact and traditional growth, and for variation of the setup of the energy transmission grid. Both the water and energy systems will be tested to see if there is increased resilience when the systems are distributed or decentralized rather than centralized.

The transportation system will be input into the model. Based on the transportation, we can better understand how the transportation networks effect water, energy, and carbon footprints. Understanding how to optimally plan public transportation, along with highways, will be an essential part of growing cities.

With all of the data collected on optimal options for developing a city for growth, we hope to look to the policies, economics, and societal factors that influence these decision-making behaviors by the people of the city. We will be adding policies into the model to see how they can be made to best affect the outcome. To better understand how decisions are made by the people however, surveys will be initiated to better evaluate decision-making process. Additionally, work is being done in hedonics on the adoption of more sustainable technologies.

Creating a model this detailed with take time and a great number of people, but we hope to truly capture the complexity of sustainable urban growth.

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Press Release. http://na.unep.net/OnePlanetManyPeople/press_release.html, 2010.

[2] UNEP, Population Division of the Department of Economic and Social Affairs of the UN Secretariat, World Population Prospects: The 2009 Revision and World Urbanization Prospect.

[3] G. Klein, “The Water-Energy-Carbon Footprint Connection”, 2009. [4] L. Gagnon, “Life-cycle assessment of electricity generation options: The

status of research in 2001,” in Energy Policy, vol. 30(14), Elsevier, 2002, p.1267-1278.

[5] Georgia Power. (n.d.). Plant Bowen. Retrieved from Georgia Power: www.cscaweb.org/EMS/local_leadership/presentations/GA%20Power's%20Plant%20Bowen%20EMS.pdf

[6] Georgia Power. (n.d.). Plant Branch. Retrieved from Georgia Power: www.georgiapower.com/about/pdf/Plant%20branch%20Brochure.pdf

[7] Georgia Power. (n.d.). Plant Robert W. Scherer. Retrieved 2010, from Georgia Power: www.georgiapower.com/about/pdf/Plant%20sherer%20Brochure.pdf

[8] Georgia Power. (n.d.). Plant Wansley. Retrieved from Georgia Power: www.georgiapower.com/about/pdf/Plant%20Wansley%20Brochure.pdf

[9] Georgia Power. (n.d.). Plant Yates. Retrieved from Georgia Power: www.georgiapower.com/about/pdf/Plant%20Yates%20Brochure%20FINAL.pdf

[10] US Energy Information Administration, “Updated Capital Cost Estimates for Electricity Generation Plants,” 2010.

[11] US Energy Information Administration Database, 2008. [12] US Department of Energy, “Energy Demand on Water Resources,” US

DOE Report to congress on the interdependency of energy and water, 2006.

[13] M. Kintner-Meyer, “Impacts Assessment of Plug-in Hybrid Vehicles on Electric Utilities and Regional US Power Grids Part 1: Technical Analysis,” Pacific Northwest National Laboratory, 2007.

[14] What If?™ 2.0 Software. What If?™, Inc, 2010. <http://www.whatifinc.biz/>.

[15] UrbanSim. <http://www.urbansim.org/Main/UrbanSim>.