Jacelyn Rice, School of Sustainable Engineering and the Built Environment and DCDC Graduate Research Assistant, ASU
Amber Wutich, School of Human Evolution and Social Change, ASU
Paul Westerhoff, School of Sustainable Engineering and the Built Environment, ASU
De facto wastewater reuse is the incidental presence of treated wastewater in a water supply source. In 1980 the EPA identified drinking water treatment plants (DWTPs) impacted by upstream wastewater treatment plant (WWTP) discharges and found the top 25 most impacted DWTPs contained between 2% and 16% wastewater discharges from upstream locations (i.e., de facto reuse) under average streamflow conditions. This study is the first to provide an update to the 1980 EPA analysis. An ArcGIS model of DWTPs and WWTPs across the U.S. was created to quantify de facto reuse for the top 25 cities in the 1980 EPA study. From 1980 to 2008, de facto reuse increased for 17 of the 25 DWTPs, as municipal flows upstream of the sites increased by 68%. Under low streamflow conditions, de facto reuse in DWTP supplies ranged from 7% to 100%, illustrating the importance of wastewater in sustainable water supplies. Case studies were performed on four cities to analyze the reasons for changes in de facto reuse over time. Three of the four sites have greater than 20% treated wastewater effluent within their drinking water source for streamflow less than the 25th percentile historic flow.
The border region of southern Arizona and Sonora, Mexico faces the sustainability challenges of a semi-arid climate that experiences long periods of water scarcity. Economic, social and political cooperation will be required for the neighboring states to ensure the viability of their water resources in the future, says Arizona State University engineer Enrique Vivoni.
Vivoni is an associate professor in the School of Sustainable Engineering and the Built Environment, one of ASU’s Ira A. Fulton Schools of Engineering, and in the School of Earth and Space Exploration in ASU’s College of Liberal Arts and Sciences. Vivoni also is a researcher with Decision Center for a Desert City.
This summer, the program brought together 11 ASU students and 13 students from three Mexican universities (the Universidad de Sonora, the Instituto Tecnologico de Sonora and the Universidad Autonoma de Ciudad Juarez), along with 14 faculty members from ASU and other universities to gain a deeper understanding of the water scarcity problem in the Arizona-Sonora border region.
The group included professors and students in the fields of civil and environmental engineering, geology, ecology, agriculture, environmental science and global health.
Lessons in water conflicts
Their endeavor started with a week at ASU, where students spent time “organizing travel logistics, getting to know each other, preparing equipment and familiarizing themselves with the state of Sonora and the current water infrastructure,” explains Nolie Pierini, an ASU engineering doctoral student.
In the second week, students traveled to Mexico to learn about a major ongoing water dispute in Hermosillo, the largest city in Sonora and the state’s capitol, which has experienced significant population growth in the past decade. To meet the city’s increasing water demand, officials constructed a 162-kilometer-long aqueduct to transfer water from the Yaqui River Basin, a major supplier of water, to agricultural users in Ciudad Obregon.
“It’s a commonly seen water conflict between industrial water users and agricultural water users,” says Matthew Thompson, who is pursuing a master’s degree in civil engineering at ASU. “The problem is amplified in the case of Sonora because they are in an area with significant drought and not enough water to meet everyone’s needs.”
Hydrology field studies
Students visited both Hermosillo and Ciudad Obregon, and heard discussions and presentations from those on both sides of the water debate. They took field trips to an aqueduct, a dam and reservoir, a hydroelectric power plant and a water treatment plant – all parts of water infrastructure in the state of Sonora.
After a week of tours and presentations from water policymakers and stakeholders, the students traveled to the nearby rural city of Rayón for a week of hydrology field research.
One research project, led by David Gochis, a scientist with the National Center for Atmospheric Research in Boulder, Colo., involved attaching radiosonde sensors to large helium weather balloons to track various atmospheric conditions at altitudes as high as 20 kilometers (65,600 feet) at various times of the day. The radiosonde measures temperature, humidity and pressure in the atmosphere, data that is sent directly to a laptop computer and then used to create an atmospheric model that tracks monsoon-season weather dynamics and patterns.
Another project, led by Agustin Robles-Morua, a professor at the Instituto Tecnologico de Sonora and a former postdoctoral researcher at ASU, surveyed people living in Rio San Miguel about water use practices, water quality and the impacts of new infrastructure.
Seth Morales, an ASU senior civil engineering major who is fluent in Spanish, was able to lead his group as they learned about different perspectives of water management and the water-use practices of specific users in the Rio San Miguel area near the town of Rayón.
ASU student Thompson, who worked with a team to install a weir (a barrier placed in a channel to enable measurement of water discharge) in a small stream, says he liked the hands-on aspect of the project. “It was gratifying to go to a remote, cool area and to use our hands to get a job done,” he says.
Seeing impact of research
Ara Ko, an ASU engineering doctoral student supervised by Vivoni, worked with water plant pressure chambers under the direction of Instituto Tecnologico de Sonora faculty member Enrico Yepez. Ko says she liked learning about semi-arid plant dynamics and exploring a climate and an ecosystem that is extremely different from her hometown in Korea.
Many of the students say learning about the region’s water issues during their first week in Mexico made the research experience more rewarding.
“Research like we did in Rayón can help us learn how to use water more efficiently and can ease future problems in water policy,” Pierini says.
“It was surprising to see how the research, or lack of research, can really have an impact on a whole community,” Morales says.
Along with gaining a renewed appreciation for thorough research, the ASU students say they enjoyed learning about a different culture.
“It was amazing to see people living in the same hot summer climate as in Arizona, but without abundant water resources,” Morales says. “Some homes only have access to water every three days for a two-hour window.”
Along with making him more appreciative of the quality of water infrastructure in the United States, Morales says the program was a “turning point” for him. The experience led him to decide that hydrosystems engineering is the career path he wants to pursue.
Thompson, a self-proclaimed lover of the hot Sonoran desert climate, says he is glad he had the opportunity to get to know some of his “neighbors to the south.” He enjoyed learning about the government, culture, universities and people in Mexico, and says he was surprised that he formed a bond with people in Mexico, despite the language barrier.
“It definitely forces you out of your comfort zone, which is something that is essential for anyone who wants to learn how to coexist with people from other cultures,” Thompson says.
Adds Morales, “Interaction with another culture opens your mind and impacts the way you view science in general.”
Moving Forward to Address Challenges Identified in the Study
In 2012, the Bureau of Reclamation, in partnership with the seven Colorado River Basin States, published the most comprehensive study of future supplies and demands on the Colorado River ever undertaken. The Colorado River Basin Water Supply and Demand Study confirmed what most experts knew: there are likely to be significant shortfalls between projected water supplies and demands in the Colorado River Basin in coming decades.
On May 28, 2013, Department of the Interior Assistant Secretary for Water and Science Anne Castle and Bureau of Reclamation Commissioner Michael L. Connor convened key stakeholders representing the Basin States, Native American Tribes, and the conservation community to discuss the future of the Colorado River Basin. The Moving Forward event in San Diego, California, identified next steps to address actions identified in the Study.
Those who rely on the Colorado River and its tributaries are committed to approaching these future challenges with the same steadfastness that they have approached and overcome past challenges. Following the call to action of the Study and as a first step in that commitment, all that rely on the Colorado are taking initial steps — working together — to identify positive solutions that can be implemented to meet the challenges ahead.
Next Steps – Phase 1
Phase 1 of the Next Steps activities includes the formation of a Coordination Team and three Workgroups with members who represent federal, state, tribal, agricultural, municipal, hydropower, environmental and recreational interests. The Coordination Team directs and reviews the efforts of the three workgroups, which are listed below. Each workgroup consists of members with subject-matter expertise from various entities in an effort to bring important and varying perspectives to build on collaborative findings to pursue the next steps identified in the Study.
This paper evaluates whether the property value capitalization effects measured with quasi-experimental methods offer reliable estimates of willingness to pay for changes in amenities. We propose the use of a market simulation as a robustness check. Two applications establish the method’s relevance. The first examines the conversion of land cover from desert to wet landscape. The second examines cleanup of hazardous waste sites. We find that even when quasi-experimental methods have access to ideal instruments, their performance in measuring general equilibrium willingness to pay cannot be assumed ideal. It needs to be evaluated considering the specific features of each application.
There is a fundamental distinction between estimating the effect of a policy that influences the value of a parcel on that land’s price and estimating what an individual would be willing to pay to obtain the policy. This issue is important to nearly all of the reduced form quasi-experimental (QE) and hedonic property value analyses conducted over the past decade. This distinction arises because the source of identifying information used to avoid biases in hedonic estimates that can arise from omitted variables and sorting behavior is not neutral to the economic interpretation of what is measured.1 Two approaches have been used to evaluate the empirical significance of this logical distinction in recovering estimates of economic trade-offs associated with a change in a nonmarket service. The first uses analytical models to describe the properties of these trade-off estimates, using the evaluation logic often associated with quasi experiments.2 The second approach uses simulation methods to evaluate the quantitative importance of distinguishing specific types of changes in site-specific amenities and [End Page 413] compares the evaluation logic to conventional cross-sectional hedonic methods.
The theoretical analysis by Kuminoff and Pope (2012) is an example of the first strategy. They adapt the Tinbergen-and-Jan-1959Tinbergen (1959)-Epple (1987) description of the features of a hedonic price function to describe a hedonic equilibrium. With this model they demonstrate that for an infinitesimal, exogenous change in a spatial attribute, conveyed with a house, the prechange and postchange marginal willingness to pay (MWTP) measures will be equal and correspond to the incremental price capitalization. However, in other situations the price differential associated with capitalization may not correspond to either the prechange or the postchange MWTP. In evaluating policies that are inherently nonmarginal, the close relationship between capitalization and willingness to pay (WTP) may not hold. In the current paper, we use simulation methods originating in the logic developed by Cropper, Deck, and McConnell (1988) and Kuminoff, Parameter, and Pope (2010) to provide a strategy for developing an understanding of this relationship as it arises in each specific type of application. An economic model, calibrated to a specific market, is used to simulate different hedonic equilibria and then to evaluate the performance of conventional cross-sectional hedonic models and methods based on the logic of program evaluation for estimating specific trade-offs people would make in response to changes in spatially varying amenities.
Our analysis complements the existing hedonic simulation papers and extends them to demonstrate how a market simulation can serve as a robustness check on the maintained assumptions of the evaluation logic when it is used to develop measures in property value applications of the trade-offs a person would make to secure more of a desirable amenity. For small changes, analysts have interpreted these measures as point estimates of the MWTP. For large, discrete changes associated with some applications of the evaluation framework, the appropriate interpretation of these measures is a topic of debate. Our analysis provides additional guidance on the interpretation of these measures. We focus on situations where the measure of interest is the general equilibrium willingness to pay (GE WTP) for changes in amenities, which is often the goal of policy analysis. We present two examples to illustrate the importance of a simulation check. Our findings in these examples imply that quasi experiments that are routinely a part of the evaluation logic can have large errors when their estimates of price capitalization are treated as estimates of WTP. We also find that the use of instruments with cross-sectional hedonic modeling can improve the quality of the estimates for the WTP for discrete changes in amenities. This is true even when the changes are large enough to induce re-sorting and result in a new hedonic price function. Finally, we find that the context for each application matters, so that general conclusions about robust strategies for estimating GE WTP do not follow; and therefore, it would be prudent to consider the use of similar simulations as a complement to empirical research on a case-by-case basis.
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