Policy 17 of this plan states that development in NE Santa Cruz County should be limited to a level that minimizes the potential for overdraft of the groundwater resource. This requires that water use be balanced with the average annual groundwater recharge. This appendix reviews and analyzes the studies that have attempted to quantify groundwater recharge in the Upper Cienega Creek Basin (UCCB), then proposes a reasonable-risk level of development based on that analysis and an estimate of current groundwater consumption.
There are three surface watersheds in NE Santa Cruz County, two of which are part of the larger Santa Cruz River Basin. See the map below for watershed boundaries. The Babocomari River flows east, through Elgin, toward the San Pedro River and the San Pedro National Riparian Conservation Area. Cienega Creek, which includes one of the few perennial stream reaches remaining in southeastern Arizona, flows north to Pantano Wash and the Santa Cruz River. Sonoita Creek flows southwest through Patagonia and The Nature Conservancy's preserve, toward the Santa Cruz River.
The groundwater picture is not so simple. The boundaries of the groundwater basins (groundwater divides) do not coincide with the boundaries of the watersheds. Available water level data indicate that groundwater which originates in the UCCB is discharged in the subsurface to the Sonoita Creek and, possibly, the Babocomari Rive groundwater basins. Note also that two different types of aquifers are used for water supplies. Some wells along O'Donnell Canyon and Sonoita and Turkey Creeks tap a shallow body of groundwater in the coarse alluvial material along the stream. Most wells in the area are completed in a deeper aquifer in variable, but generally finer-textured basin sediments.
Seven estimates of total recharge to the UCCB were identified. They are summarized in Table 1. The reader should note the term "estimates." None of the research cited here directly measured recharge. Each researcher calculated recharge based on a conceptual model of how groundwater enters and moves through the UCCB, and a set of assumptions about aquifer characteristics. The authors of these studies and other researchers generally share certain assumptions about the UCCB, including :
Most of the researchers also share a common database. All estimates of transmissivity (the rate at which groundwater flows through an aquifer) in the UCCB are based on well tests made by Geraghty & Miller in 1970 and Harshbarger and Associates in 1975. The researchers also use essentially the same precipitation, evapotranspiration, and stream flow data.
Researchers do not agree on some factors, including the direction and volume of groundwater flow from the UCCB to adjoining basins, the total amount of recharge, and the amount of recharge that can be attributed to each of the mountain ranges surrounding the UCCB.
Table 1 shows that the total recharge estimates obtained by different researchers vary considerably. The Geraghty & Miller and KafriB estimates apply only to the entire UCCB, most of which is in Pima County. The other five researchers made recharge estimates for each of the mountain ranges surrounding the UCCB, thus providing a basis for estimating recharge in NE Santa Cruz County.
The estimates of recharge contributed by different mountain ranges made by Boggs, Bota, KafriA, Knight, and Osterkamp were compared and adjusted, as necessary, to apply to NE Santa Cruz County. All recharge to the UCCB from the Canelo Hills and Mustang Mountains was attributed to NE Santa Cruz County. Recharge from the Santa Rita and Whetstone Mountains was attributed to NE Santa Cruz County based on the share of total channel length descending from the range into the UCCB that is in, or ends in, NE Santa Cruz County. The results of this attribution appear in Table 2.
The estimates of the five researchers were averaged, then compared against the averages to identify potentially anomalous results. Three figures were either double, or nearly so, or less than half the averages. Bota's estimate for the Canelo Hills is more than double the average. Bota notes this, but does not provide a plausible reason why his model produced a result that was so different. KafriA produced the highest overall estimate of recharge to the UCCB, primarily because of a high estimate of recharge from the Whetstones. Boggs suggests that KafriA overestimated infiltration into certain geological formations. After reviewing KafriA, this critique seems accurate. The infiltration rate KafriA used for the principal geological formation in the Whetstones is not consistent with the literature. Osterkamp's estimate of recharge from the Canelo Hills is less than half the average, but consistent with his estimates for other ranges and clearly explicable using his methodology.
| researcher | year | basis of estimate | total recharge estimate (acre-feet per year) |
|---|---|---|---|
| Boggs | 1980 | computer model | 10,700 |
| Bota | 1997 | computer model | 13,254 |
| Geraghty & Miller | 1970 | % of precipitation | 6,900 |
| KafriA | 1978 | soil infiltration | 19,560 |
| KafriB | 1978 | groundwater chemistry | 15,700 |
| Knight | 1996 | computer model | 11,947 |
| Osterkamp | 1973 | estimate of recharge per mile of mountain front | 5,300 |
| researcher | Canelo Hills | Mustang Mountains | Santa Rita Mountains | Whetstone Mountains | total |
|---|---|---|---|---|---|
| Boggs | 770 | 670 | 748 | 305 | 2,493 |
| Bota | 3,016 | 1,516 | 1,697 | 370 | 6,599 |
| KafriA | 770 | 1,820 | 740 | 803 | 4,132 |
| Knight | 1,516 | 1,508 | 1,697 | 370 | 5,091 |
| Osterkamp | 400 | 1,000 | 640 | with Mustangs | 2,040 |
| average | 1,293 | 1,304 | 1,104 | 462 | 4,163 |
| adjusted average | 893 | 1,304 | 1,104 | 348 | 3,650 |
To eliminate the influence of the clearly anomalous results, the averages were recalculated by substituting averages of the non-anomalous results for the anomalies. The result of this smoothing technique appears as the adjusted average in Table 2. These adjusted averages incorporate the interpretations of the various researchers into a result that can be used for planning until additional data are available.
How much development will 3,650 acre-feet of recharge support? That depends on how much water different types of development consume, and how much development there is. It also depends on other "uses" of groundwater.
Standard texts and the management plan for the Santa Cruz Active Management Area were used as a basis for estimating how much groundwater is presently consumed in NE Santa Cruz County. The results of these calculations appear in Table 3, which shows that human use of groundwater in the UCCB is far less than "natural" consumption.
| use | estimated consumption (acre-feet per year) | notes |
|---|---|---|
| residential | 245 | 160 gallons per capita per day |
| commercial | 15 | based on standard texts for existing uses at the Crossroads |
| agricultural | 330 | vineyards, livestock, fairgrounds |
| Cienega Creek | 865 | estimate based on stream flow measurements and use by vegetation, as reported by Boggs |
| Sonoita Creek | 1,150 | estimate based on share of basin perimeter and the underflow estimate of Ben-Asher |
| total | 2,605 |
Groundwater recharge is required to sustain the perennial reach of Cienega Creek and the endangered fish and other wildlife it supports. The allocation of 865 acre-feet per year is based on the assumptions that every part of the UCCB makes an equal contribution to the flow of Cienega Creek, and that sustaining the baseflow of the creek and the riparian vegetation along the creek requires at least 865 acre-feet.
There is general agreement that groundwater flows from the UCCB to the Sonoita Creek Basin. This requires an allocation of recharge to help sustain water table levels and the perennial stream flow in Sonoita Creek. Quantifying this allocation is difficult. Naeser and St. John measured the perimeter of the Sonoita Creek Basin and the joint boundary between the UCCB and the Sonoita Creek Basin, then applied the ratio between the two to the underflow estimate made by Ben-Asher, et al. That procedure seems as reasonable as any given the information available.
Subtracting the estimated groundwater consumption in NE Santa Cruz County from the average estimated recharge leaves a surplus of about 1,050 acre-feet. This is sufficient to support approximately 2,485 additional dwelling units, or the equivalent of that many additional dwellings in some combination of dwellings and new agricultural or commercial uses.
There is uncertainty about groundwater recharge to the UCCB. Estimates of total recharge and recharge from the contributing mountain ranges vary considerably. There is less uncertainty about groundwater consumption, but the single largest "use," the underflow from the UCCB to the Sonoita Creek Basin, is the least certain of all present use estimates.
This plan responds to the uncertainty about the groundwater supply in NE Santa Cruz County by relying on the best available information, as explained here, and setting a policy that minimizes the risk of excessive groundwater withdrawals, while calling for research that will provide more certainty. The costs of not addressing groundwater issues now could be high. The perennial reach of Cienega Creek is the featured attraction of the Empire-Cienega Ranch, a $41.7+ million public investment and habitat for three endangered fish species. Creating a local controversy like the ongoing debate over groundwater withdrawals that may affect the San Pedro National Riparian Conservation Area would be in no one's interest.
The groundwater study called for by Strategy 17.B (and by the previous comprehensive plan for Santa Cruz County) should be co-sponsored and funded by the Arizona Department of Water Resources, the Bureau of Land Management, Pima and Santa Cruz Counties, and other interested agencies and organizations. The study should be managed in a participatory, collaborative manner and produce the following information:
This study should be followed up with regular water level monitoring.
Arizona Department of Water Resources. Third Management Plan 2000-2010 Santa Cruz Active Management Area. Arizona Department of Water Resources. July 1999.
J. Ben-Asher, et al. Develop Water Management Methods for Watersheds Subject to Intensive Development (Partial Project Completion Report, OWRT Project No. A-069-ARIZ). Water Resources Research Center, University of Arizona. September 1980.
John Mark Boggs. Impact of Future Ground-Water Development in Cienega Creek Area, Pima, Santa Cruz, and Cochise Counties, Arizona. MS Thesis, Department of Hydrology and Water Resources, University of Arizona. 1980.
Liciniu Bota. Modeling of Groundwater Flow and Surface/Groundwater Interaction for Upper Cienega Creek Basin. MS Thesis, Department of Hydrology and Water Resources, University of Arizona. 1997.
Gayle Elizabeth Bradbeer. Hydrogeologic Evaluation of the Sonoita Creek Aquifer. MS Thesis, Department of Hydrology and Water Resources, University of Arizona. 1978.
Judith Camisa Davis. The Hydrology and Plant Community Relations of Canelo Hills-Cienega, An Emergent Wetland in Southeastern Arizona. MS Thesis, School of Renewable Natural Resources, University of Arizona. 1993.
Edward A. Du Bray. ed. Mineral Resource Potential and Geology of Coronado National Forest, Southeastern Arizona and Southwestern New Mexico. U. S. Department of Interior, U. S. Geological Survey Bulletin 2083-A-K. 1996.
Frank W. Eddy. A Sequence of Cultural and Alluvial Deposits in the Cienega Creek Basin, Southeastern Arizona. MA Thesis, Department of Anthropology, University of Arizona. 1958.
William Jess Ellett. Geologic Controls on the Occurrence and Movement of Water in the Lower Cienega Creek Basin. MS Thesis, Department of Hydrology and Water Resources, University of Arizona. 1994.
Geraghty & Miller, Inc. Ground-Water Supply Report, Empire Ranch Property, Pima and Santa Cruz Counties, Arizona. Geraghty & Miller, Inc. July 1970.
Harshbarger and Associates. Analysis of Groundwater Development Program in the Empire Ranch Area. Harshbarger and Associates. July 1975.
Hans Jarlath Huth. Hydrogeochemical Modeling of Western Mountain Front Recharge, Upper Cienega Creek Sub-Basin, Pima County, Arizona. MS Thesis, Department of Hydrology and Water Resources, University of Arizona. 1996.
U. Kafri and J. Ben Asher. Computer Estimates of Natural Recharge Through Soils in Southern Arizona, U.S.A. Journal of Hydrology. 38 (1978) 125-138.
Erik Lloyd Knight. A Water Budget and Land Management Recommendations for Upper Cienega Creek Basin. MS Thesis, Department of Hydrology and Water Resources, University of Arizona. 1996.
August Merz III. Mountain-Front Recharge from the Santa Rita Mountains to the Tucson Basin. MS Thesis, Department of Hydrology and Water Resources, University of Arizona. 1985.
B. A. Murphy and J. D. Hedley. Maps Showing Groundwater Conditions in the Upper Santa Cruz Basin Area, Pima, Santa Cruz, Pinal, and Cochise Counties, Arizona -- 1982. Arizona Department of Water Resources, Hydrologic Map Series Report Number 11. 1984.
Robert Naeser and Anne St. John. Water Use and the Future of the Sonoita Valley. Appleton-Whittell Research Ranch, National Audobon Society. 1996.
M. T. Nassereddin. Hydrogeological Analysis of Groundwater Flow in Sonoita Creek Basin, Santa Cruz County, Arizona. MS Thesis, Department of Geology, University of Arizona. 1967.
Carl Nuzman. Water Supply and Utilization, Empire-Sonoita Planning Area, Pima-Santa Cruz Counties, Arizona. Layne-Western Company, Inc. July 1970.
W. R. Osterkamp. Ground-Water Recharge in the Tucson Area, Arizona. U. S. Department of Interior, U. S. Geological Survey, Miscellaneous Investigations Series Map I-844-E. 1973.
Hugh Beresford Robotham. Evaluation of Alternative Water Resources Management Systems for the Sonoita Creek Watershed. MS Thesis, Department of Hydrology and Water Resources, University of Arizona. 1979.
Eric Mitchell Roudebush. The Influence of Bedrock on Perennial Streamflow in the Upper Cienega Creek Basin, Pima County, Arizona. MS Thesis, Department of Hydrology and Water Resources, University of Arizona. 1996.
Joseph A. Salvato. Environmental Engineering and Sanitation (Fourth Edition). John Wiley & Sons, Inc. 1992.
Peter N. Schwartzman. A Hydrogeologic Resource Assessment of the Lower Babocomari Watershed, Arizona. MS Thesis, Department of Hydrology and Water Resources, University of Arizona. 1990.
Mark David Williams. Evapotranspiration in Southeast Arizona Semi-Arid Watersheds: Walnut Gulch and Cienega Creek. MS Thesis, Department of Hydrology and Water Resources, University of Arizona. 1996.
Eldred D. Wilson, Richard T. Moore, and Robert T. O'Hare. Geologic Map of Pima and Santa Cruz Counties, Arizona. Arizona Bureau of Mines, University of Arizona. 1960.
Sonoita Crossroads Community Forum
P.O. Box 1274
Sonoita, AZ 85637
© 2000 Sonoita Crossroads Community Forum