Decoupling Urban Water Use and Growth in Response to Water Scarcity

Round 1

Reviewer 1 Report

The paper showed historical water consumption trend in twenty urban utilities in western US, and linked the observed decreases of water demands with different federal, state and local water conservation policies. The paper is interesting and it explored efficiencies of different policy measures taken to conserve water uses.

However, the way the article is written is not very adequate to justify the objectives of the study. Some of my specific comments are:

1. Very limited literature review is conducted. Mostly, the study refers different technical reports not the journals. Knowledge gaps are not explicitly explored. It seems that the study tried to investigate the reasons of decreasing water consumption in twenty urban utilities.
2. The methodology is poorly written. It shows what type of data were collected, but does not show their analysis. Was there any scientific test performed to link the reduction of water use and conservation policies? In Introduction section, it is mentioned that a survey was conducted, but nothing is written on how the survey was conducted.
3. Results section shows a summary table for historical reduction of water uses and increase of service population for twenty cities. What about the survey results?
4. Discussion section describes different conservation policies adopted in US, but how these were connected to the reduced water consumption in the selected twenty cities are not explored. This section is significantly long, compare to other sections.

Author Response

We very much appreciate the constructive comments from this reviewer. We respond here in numerical order:

1. We have redoubled our efforts in conducting a thorough review of the peer-reviewed journal literature, as well as 'grey literature' reports and websites. We have found very little published material specific to the concept of decoupling, with the exception of work from China, which we have now cited in our introductory section. While much has been published on the topic of urban reductions in per-capita use, these publications do not provide the opportunity to evaluate decoupling because service populations and water use are embedded in the per-capita metrics. We welcome any links to other relevant publications that we may have overlooked. It is not clear what is intended by this reviewer's statement that "Knowledge gaps are not explicitly explored." We believe that the water utility data largely speak for themselves, i.e., they document reductions in use while populations increased. We have also documented the reasons why these utilities were able to accomplish reductions in use. If other knowledge gaps can be articulated, we will be happy to address them.
2.  We have substantially elaborated on our methodology in the revised paper. Of importance to our methodology is our articulation of constraints in data access; we hope that our explanation of these constraints in our Methods section satisfies this reviewer's criticism of our Methods.
3.  The data table is, in fact, the summary of our results obtained by querying water utilities. Again, we hope that our revised methodology section adequately addresses the question posed here.
4.  In our revised methodology section, we have further clarified our rationale for our discussion of policies and incentives. We acknowledge that this discussion is somewhat lengthy, but we have provided it because we believe that some of our target audiences -- including both water utility managers and citizens advocating for stronger water conservation measures -- can learn how the surveyed utilities have accomplished their impressive reductions in water use. As described in our revised methodology section, we focused our discussion of policies and incentives on the strategies that the water utility staff emphasized as being most important or effective. If there is a concern for word count, we would be happy to shorten this section, perhaps by removing some of the strategies that were mentioned less frequently than others.

Reviewer 2 Report

This is a nice paper on a topic of interest.  It attempts to provide information on per capital water use across cities in the Western United States in a consistent format, something that can be difficult to do.  Due to the many authors, their roles, and the type of project, it may have been a class project.  If so, it is great that they are trying to get the results published. Regardless, I have some recommendations that improve the paper.The authors do not provide as supplementary materials the survey instrument they used and do not describe if they had to go through an institutional review board process, which is sometimes required if university study results are to be published. I am not sure if class projects are exempt. In any case, more information on how the survey was conducted would be helpful. Also, do they have permission to list the names of the contacts for each of the cities?  Their discussion of the drivers of the results does not include a table showing the prevalence of different programs across the communities.  Such an overview could be helpful because they bring out examples rather than indicating whether programs were common across communities.  Their citations seem a bit light in some instances, especially where they cite a working paper as their main citation regarding how water pricing affects water use.  At a minimum, a peer reviewed paper should be cited.  Also, there have been other studies, many in the grey literature, that have compared per capita water use across cities, but these are not cited.  Their first and only citation suggesting other looks at this topic is citation 1, which focuses on California.  The attachment includes a few more comments the authors should review.  Perhaps the most important one is that the authors refer to gallons and LPCD in the one place were they define LPCD.  The paper is well written, but they need to make sure they list references using a consistent format.

Comments for author File: Comments.pdf

Author Response

We very much appreciate the supportive and constructive review provided by this reviewer. 

The paper is the product of a team research project conducted by graduate students at the University of Virginia, guided by the lead author (Brian Richter), who teaches at the university. The university does not require institutional review of studies of this nature.

We have provided substantial elaboration of our results in our revised Methods section that includes an explanation of why we were unable to use a standardized survey instrument in our interactions with water utility staff (or their governmental records offices). The constraints encountered in our efforts forced us into a less formal interview process with individuals that were willing to speak with us, as explained in our revised methodology. We have received permission from each of the individuals mentioned in our acknowledgments. While the constraints discussed in our methodology precluded a uniform approach with each and every utility, we do believe that the results displayed in Table 1, along with our articulation of the policies, incentives, and other programs deployed by many of the surveyed utilities merits publication in this journal.

We redoubled our efforts to conduct a thorough literature search for published material -- both in peer-reviewed journals as well as 'grey' literature reports and websites -- on the concept of decoupling of water use from growth. The paucity of published material on this subject -- with the exception of work in China -- was a strong motivation for our research effort.  While there have been numerous reports documenting reductions in per-capita use, it is not possible to ascertain the degree to which water use has been decoupled from growth because of the fact that per-capita water use metrics combine population and water use into a single metric. However, we have bolstered our literature citations with additional peer-reviewed journal publications and grey literature reports.

While there are numerous reports and comparisons of per-capita water use across cities in the grey literature, we have cited only two in our paper because we have concluded that many such reports their findings are not sufficiently credible (the two cited are notable exceptions). Very few states within the US require standardized reporting of water data from utilities; our research revealed many disparities in reporting of per-capita water usage and therefore we believe that cross-state comparisons are suspect. 

On the subject of water pricing, we have also found a paucity of credible studies,  which is quite unfortunate given that many utilities expressed their belief that pricing was one of their most effective conservation strategies. In our paper we explain why it is quite difficult to conduct an evaluation of the specific effect of pricing. Even though our one cited study was not published in a peer-reviewed journal, our assessment of their work suggests that it is worthy of attention. If our reviewers or editor can suggest other studies we would be very happy to review them and possibly include them in our paper.

We appreciate this reviewer's identification of a typo in our paper where we mentioned both GPCD and LPCD; we have elaborated on our computations of LPCD in our revised Methods section.

We have also addressed this reviewer's comments provided in the attached markup document:

1. On line 33 of our revised manuscript, we are unsure of the journal's editorial preference when citing a paper with multiple authors, i.e., should we use "Abraham and others" or "Abraham et al."?
2.  We have clarified what is plotted in our Figure 1.
3.  We have heard others comment that the Bureau of Reclamation forecasts of future water demands in the Colorado River basin were influenced by the individual states' desire to inflate those estimates so that they could protect their access to additional future water supplies. However, without published documentation of this critique, we are hesitant to mention it here.
4.  We appreciate this reviewer's suggestion to change "twenty" to "20". 
5.  We appreciate this reviewer's mention of the study by Western Resource Advocates, which we have reviewed and cited in our revision. It is a very good example of a credible comparison of per-capita water use among different cities. However, as discussed above, comparisons of per-capita trends alone does not enable an evaluation of the decoupling of water use from population growth; for this reason, we have decided not to cite other studies based solely on per-capita water use trends.
6.  We appreciate this reviewer's question about whether the surveyed utilities are all public entities (i.e., agencies of the cities); this is in fact the case for the cities we included in our survey. We agree that it would be VERY interesting to compare these publicly-operated utilities with the performance of privately-operated utilities, and hope that someone will do this!
7.  As noted in our revised paper, we originally sought to conduct a more standardized survey that could have documented the frequency with which various conservation strategies have been implemented. Our revised Methods section explains why we were unable to do this.
8.  We have carefully modified many of our reference citations in our bibliography to comply with the journal's guidance.

Round 2

Reviewer 1 Report

The revised version of the paper is significantly improved, happy to accept as it is.

Reviewer 2 Report

Consider changing "was" to "were" on line 163.