Pantano Wash - Rillito River Watershed Arizona Rapid Watershed Assessment June 2007
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Pantano Wash - Rillito River Watershed Arizona Rapid Watershed Assessment June 2007 Prepared by: USDA Natural Resource Conservation Service – Arizona University of Arizona, Water Resources Research Center In cooperation with: Arizona Association of Conservation Districts Arizona Department of Agriculture Arizona Department of Environmental Quality Arizona Department of Water Resources Arizona Game & Fish Department Arizona State Land Department USDA Forest Service USDI Bureau of Land Management Released by: Sharon Megdal David McKay Director State Conservationist University of Arizona U.S. Department of Agriculture Water Resources Research Center Natural Resources Conservation Service Additional Principal Investigators: Dino DeSimone – Natural Resources Conservation Service, Phoenix, Arizona Keith Larson – Natural Resources Conservation Service, Phoenix, Arizona Kristine Uhlman – Water Resources Research Center, University of Arizona D. Phil Guertin – School of Natural Resources, University of Arizona Deborah Young – Associate Director, Cooperative Extension, University of Arizona The United States Department of Agriculture (USDA) prohibits discrimination in all its programs and activities on the basis of race, color, national origin, gender, religion, age, disability, political beliefs, sexual orientation, and marital or family status. (Not all prohibited bases apply to all programs.) Persons with disabilities who require alternative means for communication of program information (Braille, large print, audiotape, etc.) should contact USDA’s TARGET Center at 202-720-2600 (voice and TDD). To file a complaint of discrimination, write USDA, Director, Office of Civil Rights, Room 326W, Whitten Building, 14th and Independence Avenue, SW, Washington, D.C., 20250-9410 or call (202) 720-5964 (voice or TDD). USDA is an equal employment opportunity provider and employer. Pantano Wash - Rillito River An RWA can be used as a Watershed 15050302 communication tool between the Natural 8-Digit Hydrologic Unit Resources Conservation Service Rapid Watershed Assessment (NRCS) and partners for describing and prioritizing conservation work in selected watersheds. RWAs provide initial Section 1: Introduction estimates of conservation investments needed to address the identified Overview of Rapid Watershed resource concerns in the watershed. Assessments RWAs serve as a platform for conservation program delivery, provide A Rapid Watershed Assessment (RWA) useful information for development of is a concise report containing NRCS and Conservation District information on natural resource business plans, and lay a foundation for conditions and concerns within a future cooperative watershed planning. designated watershed. The "rapid" part refers to a relatively short time period to General Description of the Pantano develop the report as compared to a Wash – Rillito River Watershed more comprehensive watershed planning effort. The “assessment” part The Pantano Wash - Rillito River refers to a report containing maps, Watershed is located in the south- tables and other information sufficient to central portion of the state of Arizona, give an overview of the watershed and east of the city of Tucson. (Figure 1-1). for use as a building block for future The watershed can be defined as the planning. RWAs look at physical and area drained by the Pantano Wash to socioeconomic characteristics and the confluence with the Santa Cruz trends, as well as current and future River north of Tucson, near Oro Valley. conservation work. The watershed comprises 588,800 acres (920 square miles), and is located The assessments involve the collection approximately 90% in Pima County and of readily available quantitative and about 10% in Santa Cruz County. Thirty qualitative information to develop a two percent of the land is privately watershed profile, and sufficient analysis owned, 22% is State Land , 29% is of that information to generate an managed by the Forest Service, 9% is appraisal of the conservation needs of managed by the National Parks 7% is the watershed. These assessments are managed by the BLM, and 1% by the conducted by conservation planners, military . using Geographic Information System (GIS) technology, assessing current There are about 4,000 acres of irrigated levels of resource management, cropland in the watershed. Important identifying priority resource concerns, crops include alfalfa and cotton. The and making estimates of future remaining area is primarily rangeland, conservation work. Conservation with some forest land at the highest Districts and other local leaders, along elevations. Livestock use is dominated with public land management agencies, by ephemeral steer operations at the are involved in the assessment process. Pantano Wash – Rillito River Watershed Rapid Watershed Assessment Section 1 – Introduction page 1- 1 lower elevations, and cow calf operations at the higher elevations. Major towns and cities include Oro Valley, Tanque Verde, Mountain View, and Sonoita. Conservation assistance is provided through five Natural Resource Conservation Districts: Hereford, Pima, Redington, Santa Cruz and San Pedro. There is one U.S. Department of Agriculture (USDA) Service Center in the area, located in Tucson. Resource concerns in the watershed include soil erosion, rangeland site stability, rangeland hydrologic cycle, excessive runoff (causing flooding or ponding), aquifer overdraft, excessive suspended sediment and turbidity in surface water, effect of air quality on visibility and plant health, threatened or endangered plant and animal species, noxious and invasive plants, wildfire hazard, inadequate water for fish and wildlife, habitat fragmentation, and inadequate stock water for domestic animals (NRCS Factsheet) Pantano Wash – Rillito River Watershed Rapid Watershed Assessment Section 1 – Introduction page 1- 2 Section 2: Physical Description Summerhaven. The basin floor is generally level, and there are several Watershed Size primary and secondary drainage channels draining to the northwest. The Pantano Wash - Rillito River These channels convey surface runoff Watershed covers approximately 935 northward and westward through the square miles (598,235 acres), basin. The Santa Catalina, Rincon, representing about 1.0% of the state of Tucson and Tortillita ranges abut the Arizona. The watershed has a Pantano Wash area. The generally maximum width of about 25 miles east gentle slope of the basin floor tends to to west, and a maximum length of about increase rapidly as it nears the various 50 miles north to south. mountains ranges. The Pantano Wash - Rillito River The mountains surrounding the Tucson Watershed was delineated by the U.S. Basin are composed of metamorphic, Geological Survey and has been sedimentary, and intrusive igneous rock subdivided by the NRCS into smaller extending beneath the alluvial material watersheds or drainage areas. Each filling the basin (Pima County, 2006). drainage area has a unique hydrologic This impermeable material provides a unit code number (HUC) and a name physical boundary that forms the area’s based on the primary surface water ground water basins. Over time, erosion feature within the HUC. These drainage or weathering of the mountainous areas areas can be further subdivided into has resulted in the deposition of even smaller watersheds as needed. alluvium up to 7,000 feet thick in areas The Pantano Wash - Rillito River is an south and southeast of Tucson. A 8-digit HUC of 15070102 and contains stratigraphic section through the basin the following 10-digit HUCs: reveals, from the ground surface downward, superficial deposits • 1505030201 (Cienega Creek) (primarily stream channel and terrace deposits) of the Fort Lowell Formation, • 1505030202 (Agua Verde- the Tinaja beds, and the Pantano Pantano Wash) Formation. • 1505030203 (Tanque Verde The Pantano Formation is composed Creek -Rillito River) (Figure 1-2) primarily of Catalina granite and gneiss, ranging from loosely packed to weakly Geology cemented into place. The Tinaja beds are a series of beds composed of The Pantano Wash - Rillito River Catalina gneiss changing to volcanics Watershed is located in Eastern Pima with increasing depth, ranging from County within the Tucson Valley Basin. sandy gravel along the basin’s margins Elevations in this basin range from to gypsiferous clayey silt and mudstone 3,720 feet in the southeast to 2,030 feet in the center of the basin. The thickness in the northwest within the river of each unit varies throughout the basin, drainage, and approximately 9,440 feet with the deeper beds generally thicker at the watershed high-point near than those overlying them. Pantano Wash – Rillito River Watershed Rapid Watershed Assessment Section 2 – Physical Description page 2- 1 Terrestrial Ecosystem Surveys on The basin is interwoven with deep National Forest Lands within the geologic faults, which are considered to watershed. Lands outside of National be inactive. Figure 2-1 shows the Forests are included within the following geology of the Pantano Wash – Rillito NRCS Soil Surveys: “Soil Survey of River Watershed. Pima County, AZ, Eastern Part”; and “Soil Survey of Santa Cruz and Part of Soils Cochise and Pima Counties, AZ.” Soils data and maps from these Soil Surveys Soils in the Pantano Wash - Rillito River can be accessed through the NRCS Area are primarily the results of fluvial Web Soil Survey website: deposition of weathering products from http://websoilsurvey.nrcs.usda.gov. the surrounding mountains. Soil particle sizes