HOW RELIABLE ARE OUR MUNICIPAL WATER SUPPLIES?

BY GEORGE WATLAND
Water Committee

Recently, the Los Angeles Dept. of Water and Power sent its annual water quality report to its customers. But the continuing drought conditions in California have led the City of Los Angeles to initiate another round of water restrictions. The large public investments corresponding to each remind us of the great value placed on safe and reliable drinking water needed to sustain growing municipalities.

Early in the last century many cities in the United States began building centralized municipal water systems as a public health measure. Water suppliers, both private and public, established the means to provide water of high enough quality to meet essential uses such as drinking, cooking, cleaning, healthcare, and fire safety as well as discretionary uses for lawn watering, washing cars, swimming, and many other public and commercial uses.

Visiting the LA Department of Water and Power (LADWP) Water Quality page at www.ladwp.com/ladwp/cms/ladwp000505.jsp, a reader is able to review detailed analysis of how safe its water supply has been. However, most municipalities including LADWP do not publish water reliability reports with similar detail for public review. Even water planning documents submitted to state water officials rarely present clear and concise information about the reliability of municipal water supplies.

If one tries to search for information about reliability in most urban water plans, most often one will find only general guiding statements about the importance of reliable water, but little quantifiable, concise information about what level of water reliability level is expected as urban population increase. Instead of detail cities provided general reassurances that someone is working to provide dependable water supplies as LADWP states on its Water Reliability page at www.ladwp.com/ladwp/cms/ladwp001620.jsp.

The story of the severe drought that hit the Atlanta, Georgia, area in late 2006 and 2007 provides an example of how quickly and severely drought-related hardship can surprise and affect all residents and businesses in a large, modern metropolitan area. At the time, Atlanta area policy makers moved quickly to mitigate the impact of drought using widely recognized best practices to implement the most severe water restrictions approved by the state in 2005. But the water restrictions were no match for the drought event that has been described variously as a 30-year or as much as a 100-year drought. More quickly than anyone had anticipated, the drought conditions nearly emptied Lake Lanier, the primary reservoir supplying all municipal water systems in the area.

For some perspective about the lessons learned from Atlanta's experience, a useful analysis was published by The Pacific Institute, the California non-profit organization recognized worldwide for its water expertise. In 2005, Institute experts met with Atlanta area officials and conducted an outside review of their long-term water plans. In general, the Institute gave them high marks for their efforts, but also included the following cautionary statement:

Our analysis, however, reveals that the [Atlanta Metropolitan Water] Plan may significantly overestimate future regional demand for water, and underestimate the potential for cost-effective demand management. Overestimating demand is not unusual; in fact, it is very common. Planners tend to rely on simplistic assumptions about future demand based on fairly constant water-intensity projections and population growth. In addition, risk aversion drives planners to emphasize supply, and adopt conservative estimates about the potential for demand management.

Thus, the Institute concluded that the Atlanta area was probably trying to acquire more water than needed for the 15-30 year forecasts presented in the plan. A water reliability analysis was not included in the plan as published, nor did the Institute cite that as a shortcoming. It is not common for water planners to present information of overall water reliability for public review, and in that way, Atlanta's plan was no different than those published for most large municipalities.

As the Atlanta drought continued without relief through 2007, the Pacific Institute added a subsequent post-script on their website describing the 2006 Atlanta report as follows:

The City of Atlanta is now facing something unprecedented for the world's wealthiest nation: the possibility of a major city running out of water in a matter of weeks. This analysis may now help offer some insight to leaders and planners who are asking 'how did this happen'.

The question of how might be a very tough question. But the question of what happened is not so tough -- the Atlanta area learned the hard way that their forecasted water supply was simply not reliable enough only 2 years after their water plan was updated.

The reliability of urban water systems is easy to describe, and just as easy to calculate. Forecasts of future urban water reliability use historical water supply and demand data to estimate how often water restrictions triggered by drought might occur in the future. Simply put, a higher reliability level means municipal water restrictions are expected to be less frequent and less severe during comparable drought events than for a lower reliability level.

A sample water reliability calculation starts by counting the number of days -- say 30 in a given year -- that water restrictions mandated by a drought management plan are in effect. Reliability can be expressed as a percent by dividing 360 days/year into the remaining 330 days that had no water restrictions to produce a value of 92% reliability -- 30 days/month and 360 days/year are frequently used for calculations in municipal water plans. For many cities, a reliability level between 95% and 97% might likely be a very reasonable goal.

But another more interesting advantage associated with municipal water reliability levels is that usual benefit-cost analyses conducted for all urban water plans are also able to use the water reliability goals to better determine how to invest taxpayer funds for the future. By comparing water conservation measures to potential acquisitions of greater water rights or proposed investments in new water development projects, water conservation programs can be better evaluated on a equal basis with other large capital investments to improve municipal water reliability.

Surprisingly, many large water projects compare poorly with currently available conservation programs because benefits due to water conservation tend to occur more quickly, last longer, and cost orders of magnitude less than other alternative. Furthermore, as the cost of enforcing water restrictions under drought management plans grows as restrictions become deeper, public support wanes over time if droughts occur more frequently and last longer. As choices for water conservation are encouraged in the near term, public support often grows as individual choices are directly associated with better municipal water reliability now and for the future.

For a list of references used in this article, and for some suggested readings, please send a request along with your feedback to gawatland@gmail.com.