Pat Call's playing with water numbers

A. County supervisor Pat Call has been saying for years that the average rural water use in Cochise County is 312 gallons/person/day.

1.  The source of the "312" figure was hard to find.  Call wouldn't tell me, and sometimes got pretty dramatic; for instance, on March 19, 2007, I asked him for the source of the number; first he said he didn't like me, then said he would answer, leaned over as if to answer, but cunningly backed away without answering.

2.  On March 19, 2007, I knew where to find the "312" figure, but I didn't know how it was actually calculated.  It took two government employees (thank you both!) to find the calculation.  I got it on March 21.  It's in a document not readily available.  Its relevant part is now online at

3.  Call's misuse of the "312" figure shows his ignorance of the calculation (it was either ignorant or intentional misuse; let's be charitable.)

4.  The "312" number was calculated in a study of the Sierra Vista and Benson sub-areas of the Watershed, based on properties including irrigated pastures and gardens of up to 2 acres, watered by domestic wells.  Other parts of the county, such as the Sulphur Springs Valley, have very different conditions, and the "312" figure could not be used for them.  And the "312" figure doesn't apply to any property that doesn't include substantial areas of irrigation of crops or livestock.

B.  The document that the above link leads to has several estimates of domestic well use.  This article discusses all of them.

1.  For water use inside homes, the document adopted figures from an area near Tucson.  In 1987, the area was like much of rural Cochise County:  "landscaping was primarily low water use although fruit trees and livestock were observed.  Irrigated pasture was not observed and exterior water use characteristics are not believed to have changed significantly since the survey."  The average lot size is 1.3 acres, and the population in 2000 was 7086.  The average residential water use during 1992-2002 was about 107 gallons/person/day, including watering a small amount of fruit trees and livestock.
    The document uses this as the basic residential use by rural areas on domestic wells in Cochise County.

2.  Of course, many households also use water outside for more than a few fruit trees and livestock.  This intensive use was calculated, not measured, for parcels containing pastures or gardens of up to 2 acres, irrigated from domestic wells, around Sierra Vista and Benson.  This process led to the "312" figure that Call has been using.
    Such pastures and gardens comprised 572 acres around Sierra Vista, and 307 acres around Benson.  Their total water use (according to a complicated and imprecise calculation) was 1490 acre-feet/year around Sierra Vista, and 906 acre-feet/year around Benson.  Dividing by the number of people using domestic wells in 1990, the average was 205 gallons/person/day around Sierra Vista, and 393 gallons/person/day around Benson.

3.  To obtain total water use, the pasture or garden figures were added to the 107 gallons/person/day for inside use.
    Around Sierra Vista, the total was 312 gallons/person/day -- the "312" that Call has been using.  Around Benson, the total is even higher, 500 gallons/person/day.
    However, properties using a private well for a residence and a few fruit trees and livestock would use an average of 107 gallons/person/day.  This is the situation in much of rural Cochise County.
    The erroneous "312" figure that Pat Call likes to use ignores this data.

C. The document's other estimates of rural domestic well use

1.  One estimate for "a typical household of three persons and irrigation and the watering of pets and farmyard animals on an adjoining 0.2 ac of land" is a total of 298 gallons/person/day, consisting of 50 to 69 gallons/person/day indoors, and 229 to 248 gallons/person/day on the .2 acres outdoors.

2.  A New Mexico study estimated 114 gallons/person/day.

3.  A Phoenix study estimated that a "four family household" (probably meaning 4 persons) used about 45 gallons/person/day inside, plus 1094 gallons/person/day per acre outside.

4.  Another study from Phoenix estimated domestic well use at 152 gallons/person/day.  However, this urban figure is not a good indicator of rural well use.

D. Estimates of water usage from outside the document

1.  A 2005 Department Of Water Resources report states that, for Cochise County's largest water companies, the average use is from 124 to 196 gallons/person/day.  However, the largest companies serve Sierra Vista, Ft. Huachuca, and Benson.  Rural areas tend to be served by smaller water companies, often serving only private households.  Data from small rural Cochise County water companies show an average use of 90 gallons/person/day.

2.  The International Arid Lands Consortium says that nationally, "a typical household that gets its water from a private well or cistern uses about 200 gallons for a family of four," or 50 gallons/person/day, a surprisingly small figure.

E. Summary and evaluation

1.  For basic in-home use from domestic wells in rural areas, the Cochise County figure is 107 gallons/person/day.  Other estimates range from 45 to 152 gallons/person/day, with an average of 84.  107 gallons/person/day appears to be a reasonably accurate figure.

2.  For pastures or gardens up to 2 acres, using domestic wells, 205 gallons/person/day is accurate around Sierra Vista, and 393 gallons/person/day is accurate around Benson.  The "312" figure that Call uses, obtained by adding the basic 107 gallons/person/day to the 205 gallons/person/day around Sierra Vista, is inappropriate for other areas of Cochise County, and for any property that does not include a substantial area of intensive irrigation of pastures or crops.

3.  With all the water data assembled above, does the county really need another study that will take years?
    During the length of the study, builders continue to get credit for "conserving water," while their plans for water use actually exceed what rural people use.  We have enough facts to act, if we wanted to; studies that last for years can only add another decimal point to data that are already good enough for all practical purposes.

4.  Now that Call knows the derivation of the "312" figure, shouldn't he "clarify the waters" by informing his past and future audiences that he has been making inaccurate representations while speaking for the county?
    The county has the right to ask Call to correct his misstatements, if he will not do it on his own.