St. David Watershed
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....,.7-/(. c ll9 ~ I FIELD EXAMINATION REPORT ST. DAVID WATERSHED Cochise County, Arizona UNITED STATES DEPARTMENT OF AGRICULTURE SOIL CONSERVATION SERVICE ST, DAVID WATERSHED PROJECT, /fl COCHISE COUNTYJ ARIZONA F I E L D E X A M I N A T I 0 N R E P O R T JULY 1976 Sponsoring Local Organizations San Pedro Natural Resource Conservation District St. David Irrigation District Cochise County Board of Supervisors St. David Flood Control District Prepared by: U. S. DEPARTMENT OF AGRICULTURE, Soil Conservation Service, under the authorities of the Watershed Protection and Flood Prevention Act (Public Law 566-83rd Congress). - OEPARTMENT OF - UBRA~A~!~,:i~o;{~~IVES SEP 23 1983 CONTENTS Summary General 1 Sponsoring Local Organizations 1 Project Status 1 Acknowledgment 2 Environmental Setting 3 Watershed Problems and Needs 5 Plan Development 7 Possible Changes in Watershed Boundary and Scope of Study 8 Possible Conflicts and Restraints Downstream Water Rights 9 Conclusions 9 FIGURES Following page Figure 1 Watershed terrain 6 Figure 2 - Watershed terrain Figure 3 - Cropland erosion damage Figure 4 - Flood damage Figure 5 - Flood damage Figure 6 - Flood damage Figure 7 - Flood damage Figure 8 - Sediment damage Figure 9 - Erosion damage Figure 10 - Erosion damage MAPS General Land Ownership Land Use ST. DAVID WATERSHED COCHISE COUNTY, ARIZONA FIELD EXAMINATION REPORT JULY 1976 SUMMARY General The watershed sponsors have submitted an application to the Secretary of Agriculture for assistance in planning and carrying out works· of improvement in the St. David Watershed under the Watershed Protection and Flood Prevention Act (Public Law 566-83, Congress). This report presents the results of reconnaissance level studies conducted to date in the watershed. The report will accompany a request to the Administrator, Soil Conservation Service, for planning authorization. Detailed studies and investigations will then be conducted. Sponsoring Local Organizations The watershed sponsors as stated in the application for assistance are the San Pedro Soil Conservation District, St. David Irrigation District, and Cochise County Board of Supervisors. There are two changes in sponsorship to be madeo One is the name change from San Pedro Soil Conservation District to the San Pedro Natural Resource Conservation District. The other is to add the St. David Flood Control District as an official sponsor. This district was formed in accordance with state statutes in September 1973 after the application for assistance was submitted. Project Status Reconnaissance level studies have been conducted by the U. S. Department of Agriculture as part of the U.S.D.A. Santa Cruz-San Pedro Cooperative River Basin Study. Public information meetings were held in the community of St. David on January 23, 1973; October 23, 1973; and March 16, 1976. An on-site inter-agency field examination of the watershed was conducted by the sponsors on March 16, 1976. All of these sources were most valuable in defining watershed conditions, problems and needs, possible solu• tions, local desires, and areas of possible conflict. This report summarizes information on the watershed as collected to date. 1 Acknowledgment The cooperation of the sponsors, individuals, organizations, and of federal, state, and local agencies who directly or indirectly aided in the preparation of this report is gratefully acknowledged. General highway maps prepared by the Arizona Department of Transportation were used in preparing the maps of the study area. Pictures in this report were supplied by several individuals. Appreciation is given to the University of Arizona Press, Tucson, Arizona for permission to quote Arizona Place Names in describing the history of the founding of the town of St. David. 2 ENVIRONMENTAL SETTING The St. David Watershed is located in western Cochise County, Arizona. The watershed drains westward fro'm Knob Hill on the western slopes of the Dragoon Mountains to the San Pedro River, a tributary to the Gila River. The watershed contains 8,320 acres (13 square miles), of which 4,490 acres are State Trust lands and 3,830 acres are in private ownership. (See General Land Ownership Map.) The unincorporated town of St. David, population 750, is within the watershed. The remainder of the watershed is uninhabited. Land use within the total watershed consists of 160 acres of urban and 1, 000 acres of irrigated cropland in the town of St. David and 7,160 acres of range• land east of the town. (See Land Use Map.) St. David is an agriculturally-oriented community founded by Mormon settlers in 1877. The following quote from Arizona Place Names describes the founding of the town. " .....•. During the first year at St. David the colonists built a small rock fort measuring sixty feet and forming a hollow square. The fort was three miles south of the present town. The old town was half mile south of the present town, but the site was moved because malaria was too prevalent at the first location. The first town MacDonald (cf. MacDonald) was named for Alexander F. MacDonald, a Mormon apostle, who was killed by the same mob which killed Joseph Smith in MissourL P.O. est. July 25, 1882. Joseph McRae, p.m •.... " ]) St. David residents have small gardens, orchards or farms in individual ownership of irrigated cropland ranging in size from one to sixty acres. Most households have supplemental income over that received from agricultural endeavors. Local employment consists of food and service establishments and state and county employment. Other nearby employment opportunities are at the explosives manu• facturing firm located just west of town across the San Pedro River and in the towns of Benson and Tombstoneo The 1970 census average unemploy• ment rate for Cochise County was 5.1 percent and per capita income was $2,563. This same rate would be applicable to St. David. The irrigated acreage in the watershed produces primarily forage crops for local livestock production" A small portion of the irrigated acreage is used for gardens and orchards. The St. David Irrigation District provides irrigation water by means of an unlined canal running north and west through the town. The canal begins 6 miles south of town where water is diverted from the San Pedro River. Surface supplies are supplemented during periods of low 1/ Reprinted by permission of Arizona Place Names, University of Arizona Press, Tucson, Arizona. Copyright, 1960. 3 river flow by two wells located at the upper end of the canal. There are no perennial streams in the watershed. Washes in the watershed are ephemeral; flowing only during and immediately after heavy thunderstorms. U.S. Highway 80 runs through St. David, and continues southeast through Tombstone, Bisbee and Douglas. U.S. Route 80 joins Interstate 10 at Benson, about 7 miles north of St. David. Tucson is about 52 miles northwest of St. David. The town of Sierra Vista and Fort Huachuca, a large military complex, are 30 miles south of St. David. Land values range from $500 per acre for rangeland to $4,000 per acre for urban and agricultural land. Home values range from $10,000 to $35,000. Two subdivisions and a mobile home park are new in the community to meet the needs of local people, as well as persons retiring to this area. Tourist attractions are as close as Tombstone, "The town too tough to die," which is located eighteen miles south of St. David. Recrea• tional facilities are available in the national forest lands in the nearby Whetstone, Rincon, Winchester and Dragoon Mountains. Deer, javelina, dove, quail and other small game attract hunters. The nearest public water-based recreation exists at Patagonia Lake (60 miles), Parker Canyon Lake (54 miles), and Pena Blanca Lake (84 miles). Climatic conditions are semi-arid with average annual precipitation of approximately 12 inches. Sixty percent of the precipitation occurs as rainfall during the summer months of July, August and September. Elevations in the watershed range from 3,580 to 4,680 feet (MSL). Temper• atures range from a low of 27° to a high of 107°. The.average monthly mean temperature is 52.3° with an average frost-free period of 226 days. Soils in the upper portion of the watershed are of the White House• Tubac-Forrest and Cruces associations. Soils of this association are typically deep, well drained, nearly level to hilly fine textured soils with lime accumulations at moderate depths. These soils have a high shrink-swell ration. Soils of the Cruces association are shallow, well drained, nearly level to strongly sloping fine textured soils with a lime cemented hardpan at shallow depths. Soils in the central portion of the watershed are of the Rough Broken Land-Gullied Land association. This association is composed of steep, and very steep deeply dissected land with many deep gullies and numerous moderately deep and shallow gullies (See Figure 1). Surface textures are gravelly loamy sand, and gravelly sand over thick beds of stratified silty clay loam to gravelly sandy loam alluvial deposits. The lower portions of the watershed have soils mainly of the Comoro• Anthony-Grabe association. These are deep, well drained, nearly level, medium and moderately coarse textured soils. Deep gullies are actively headcutting in these soils (See Figure 2). 4 The terraces are dissected and are presently eroding rapidly in a narrow band crossing the watershed just east of St. David. In the lower portion of the watershed the valley fill deposits are overlain by low alluvial fans and San Pedro River Alluvium. The erosion rates in the watershed vary from 0.2 to 2.0 acre-feet per square mile annually. The watershed is in the Southeastern Arizona Basin and Range Land Resource Areas. Rangeland vegetation consists predominantly of whitehorn, tarbush, creosote bush and mesquite. Other common species include black grama grass, bush muhly, tobosa, spike dropseed, alkali sacaton, sacaton, ocotillo ratany and catclaw.