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USE AND EFFECTIVENESS OF MUNICIPAL WATER RESTRICTIONS DURING DROUGHT IN COLORADO
<br />TABLE 4. Volumetric Range of Actual and Potential Water Saved Based on
<br />Net Use and Expected Use Methods (May through August, 2002).
<br />Actual Savings
<br />(acre feet)
<br />Over the Mandatory
<br />Municipal Entire Restrictions
<br />Water Study Period
<br />Provider Period (city - specific)
<br />Potential Savings (given the following hypothetical situations
<br />applied over the entire study period) (acre feet)
<br />Assuming Assuming Assuming Assuming
<br />Mandatory Savings Savings Savings
<br />Restrictions Typical of the Typical of the Typical of the
<br />Employed Every Third Twice Weekly Once a Week
<br />All Study Day Watering Watering Watering
<br />Period Schedule Schedule Schedule
<br />Aurora 2,842 to 5,522 3,617 to 5,614
<br />3,914 to 6,170 4,371 to 7,459 9,367 to 11,188 16,548 to18,986
<br />Boulder 2,805 to 3,287 2,956 to 3,268
<br />3,355 to 3,750 1,646 to 2,693. . 3,528 to 4,040 6,233 to 6,855
<br />Denver 9,528 to 18,768 10,066 to 15,938
<br />18,365 to 28,774 18,266 to 30,737 39,142 to 46,105 69,151 to 78,239
<br />Fort Collins 1,254 to 2,933 864 to 1,404
<br />2,409 to 3,959 2,028 to 3,556 4,345 to 5,334 7,677 to 9,051
<br />Lafayette 1,198 to 1,393 1,201 to 1,354
<br />1,372 to 1,557 361 to 610 774 to 916 1,368 to 1,554
<br />Louisville 1,031 to 1,141 1,069 to 1,138
<br />1,156 to 1,247 372 to 609 798 to 914 1,409 to 1,551
<br />Thornton -855 to 1,112 N/A
<br />N/A 1,426 to 2,673 3,055 to 4,010 5,397 to 6,804
<br />Westminster 460 to 1,844 500 to 946
<br />1,918 to 3,542 1,621 to 2,852 3,474 to 4,278 6,137 to 7,260
<br />TOTALS 18,263 to 36,000 20,272 to 29,662
<br />32,491 to 48,998 30,092 to 51,190 64,483 to 76,784 113,920 to 130,301
<br />lIn each cell, the lower number is the net use value, while the higher value uses the expected use calculation (see text for explanation).
<br />2 For these scenarios, the higher number is the product of the expected use in 2002 times the average savings percentage associated with the
<br />given scenario (from Table 3). For the scenario assuming "Mandatory Restrictions Employed All Study Period" the percentage values used
<br />are city- specific (e.g., 13 and 18 percent for Aurora). For the remaining three scenarios, the savings values are the multi -city averages: 14
<br />and 22 percent, respectively, for the every third day programs, 30 and 33 percent for the twice weekly programs, and 53 and 56 for the once
<br />weekly program.
<br />of outdoor watering restrictions declined as household
<br />size increased and for families with below average
<br />monthly use. Additionally, lumping all programs into
<br />"voluntary" or "mandatory" based primarily on the
<br />treatment of residential lawn watering restrictions is,
<br />as mentioned earlier, an inexact process, as enforce-
<br />ment of restrictions was inconsistent across the eight
<br />study regions and since other conservation elements
<br />were typically enacted simultaneously with the lawn
<br />watering restrictions. Cities can influence total deliv-
<br />eries in many ways other than restricting residential
<br />outdoor use, such as by curtailing their flushing and
<br />maintenance programs and by limiting water use in
<br />public landscapes. For these and related reasons, the
<br />primary use of Tables 3 and 4 should be to compare
<br />usage within cities under various water restriction
<br />conditions. By comparing cities to themselves, the
<br />unique character of each region is automatically con-
<br />trolled for, and the values calculated are therefore
<br />highly robust. Cross -city comparisons are useful for
<br />identifying more general trends.
<br />Discussion
<br />Percentage Water Savings. The primary results
<br />of the study are presented in Table 3. Regardless of
<br />whether the actual use calculations (i.e., net use and
<br />per capita use) or the predictive method (i.e., expected
<br />use per capita) is utilized, four major "findings"
<br />emerge from the data.
<br />(1) Mandatory Restrictions Were Effective in
<br />Reducing Water Use. In. every city or provider region,
<br />conservation programs featuring mandatory restric-
<br />tions were associated with significant savings in
<br />water use. Net use savings ranged widely from 13
<br />percent (in Aurora) to 53 percent (in Lafayette), equal
<br />to 15 to 55 percent when expressed in per capita
<br />terms. Expected use per capita for these same cities
<br />ranged from 18 to 56 percent, providing a clear and
<br />powerful confirmation of the effectiveness of mandato-
<br />ry water restrictions. The wide range of savings is
<br />likely related, in part, to the differences among the
<br />cities in terms of service populations and water sys-
<br />tems but is also undoubtedly linked to the differing
<br />stringencies of the restrictions programs (as shown in
<br />Finding 3).
<br />(2) Voluntary Restrictions Were of Limited Value.
<br />The performance of voluntary water restrictions was,
<br />with few exceptions, disappointing. In terms of net
<br />use, consumption in Thornton and Boulder actually
<br />went up during voluntary restrictions, a phenomenon
<br />that persisted in Boulder even after accounting for
<br />population growth. Note, however, that the Boulder
<br />JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION 83 JAWRA
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