JAWRA Blog

August 2011 article (Early View): “Residential Demand for Water in the Chicago Metropolitan Area,” by Taro Mieno, and John B. Braden

The specification of the water price variable has been the most controversial issue in water demand estimation studies. This paper take a good look price effects based on eight Chicago-area municipalities which provided water tariff and residential consumption data for 1995-2007.

The quantity of water consumed by households is likely to be affected by many factors including price, demographic characteristics, existing economic policies, climate conditions, water-using technologies, and plumbing codes. Among these factors, the effect of water price, summarized in the price elasticity of water demand, is especially valuable because it is one of the few factors over which water managers have direct control. Price elasticity is defined as the ratio of the percentage change in quantity used to a percentage change in price:

where Q is quantity and P is price.

There are lots of details in the findings, too many to be covered here. Higher income municipalities in Northeastern Illinois appear to be less responsive to changes in water price, which implies that the use of pricing for water conservation can raise equity issues. Increasing prices in summer is a particularly effective way to constrain peak water use and, thus, needs for investments in additional infrastructure and water supply.

[Please note: I have quoted and paraphrased freely from the article, but the interpretation is my own!]

August 2011 article (Early View): “The Impacts of Water Conservation Strategies on Water Use: Four Case Studies,” by Yushiou Tsai, Sara Cohen, and Richard M. Vogel.

In coordination with with four communities in the Ipswich watershed, four water conservation projects were designed to simultaneously meet immediate municipal needs and demonstrate innovative water conservation strategies that could be evaluated with real-world data. The four projects are (1) installation of weather-sensitive irrigation controller switches (WSICS) at residences and at municipal athletic fields, (2) installation of rainwater harvesting systems at residences, (3) town-administered programs to provide home indoor water use audits and fixture retrofit kits and rebates for low-water-demand toilets and washing machines, and (4) soil amendments to improve moisture retention and reduce water demand at a municipal athletic field. Statistical hypothesis tests combined with con- trolled water conservation experiments were used to evaluate water savings.

So what worked best? (1) The WSICS appeared to reduce the variability of water use among residential participants, most notably by causing a reduction in water use of the highest historical water users. (2) Annual volumes of rainwater used were small compared with domestic water use, and reductions in domestic water use as a result of substitution with rainwater could not be dierned amidst the background fluctuations in domestic water use. (3) Nonstatistically significant savings of this group appeared to result from the small sample size and large variation in water savings among the participants. (4) The addition of a moisture and nutrient-retaining additive, zeolite, to the soil of a ball field resulted in healthy turf with less water applied than to an adjacent control field. For details and qualifications, read the paper!

[Please note: I have quoted and paraphrased freely from the article, but the interpretation is my own!]

December 2010 article: “Implementing Landscape Water Conservation in Public School Institutional Settings: A Case for Situational Problem Solving,” by Douglas C. Kilgren, Joanna Endter-Wada, Roger K. Kjelgren, and Paul G. Johnson

The authors studied irrigated landscape water conservation at public schools in Utah, controlling for type of irrigation and water conservation interventions. Their findings suggest ways for school districts to decide where, when, and how to intervene in promoting water conservation. To me, they seem a good combination of science and common sense.

Water conservation programs targeted at large institutional landscapes like public school grounds are likely to produce water savings mainly because of the size of irrigated acreage. However, water savings might best be realized by focusing resources and education primarily on locations that have historically over irrigated. Locations with high capacity to conserve water can be identified through analysis of water billing data and comparison to ETo-based thresholds that categorize landscape water use as conserving, acceptable, or wasteful. Absent the resources to conduct such analyses, conservation interventions would likely be most effective if they are targeted at schools that fit certain profiles (automated-irrigation systems, smaller grounds, high water pressure, and nine-month calendar) and at schools in certain circumstances (in transition from manual to automated-irrigation systems, experiencing custodian turn-over, exhibiting high water use variability between years). Monitoring water use and being strategic about when as well as where to undertake conservation efforts is important for achieving larger system efficiencies in water use and conservation program administration.

[Please note: I have quoted and paraphrased freely from the article, but the interpretation is my own!]