AffiliationTonto National Forest, Phoenix, Arizona
Southwestern Region, U.S.F.S., Albuquerque, New Mexico
KeywordsHydrology -- Arizona.
Water resources development -- Arizona.
Hydrology -- Southwestern states.
Water resources development -- Southwestern states.
Atterbury watershed (Tucson Ariz)
Universal soil loss equation
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RightsCopyright ©, where appropriate, is held by the author.
Collection InformationThis article is part of the Hydrology and Water Resources in Arizona and the Southwest collections. Digital access to this material is made possible by the Arizona-Nevada Academy of Science and the University of Arizona Libraries. For more information about items in this collection, contact email@example.com.
PublisherArizona-Nevada Academy of Science
AbstractA stochastic model is presented for the prediction of sediment yield in a semi-arid watershed based on rainfall data and watershed characteristics. Random variables which lead to uncertainty in the model are rainfall amount, storm duration, runoff, and peak flow. Soil conservation service formulas are used to compute the runoff and peak flow components of the universal soil loss equation, and a transformation of random variables is used to obtain the distribution function of sediment yield from the joint distribution of rainfall amount and storm duration. Applications of the model are in the planning of reservoirs and dams where the effective lifetime of the facility may be evaluated in terms of storage capacity as well as the effects of land management of the watershed. In order to calibrate the model and to evaluate the uncertainties involved, experimental data from the Atterbury watershed near Tucson, Arizona were used.
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Contaminants in water, sediment, and biota from the Bill Williams River National Wildlife Refuge, ArizonaRuiz, Leslie Diane, 1969- (The University of Arizona., 1994)One hundred sixty two composite samples were analyzed for organochlorine compound residues and 19 trace elements and heavy metals. There was no evidence that flushing of washes in times of flood increases contaminant levels in the Bill Williams River, or that historical mining operations currently contributed to the element load. There was evidence that Colorado River water increased selenium levels in biota in the delta; one hundred percent of fish collected from the confluence of the Bill Williams River and the Colorado River contained elevated selenium concentration (geometric mean = 9.98, range 2.80-17.56 μg/g dry weight). These levels exceed standards set for the protection of predatory species of fish and wildlife.
Paleomagnetism of Late Triassic and Jurassic sediments of the southwestern United States.Bazard, David Richard. (The University of Arizona., 1991)Paleomagnetic poles were obtained from the Chinle, Kayenta, Summerville, and Morrison Formations. Combined with paleomagnetic poles from the Moenave Formation, poles from the Chinle and Kayenta formations record ∼30 m.y. of North American apparent polar wander (APW) within a regional stratigraphic succession. During the Carnian and Norian stages of the Late Triassic, Chinle poles progress westward. During the Hettangian through Pliensbachian stages of the Early Jurassic, the pattern of APW changed to an eastward progression. Even after correction for 4° clockwise rotation of the Colorado Plateau, a sharp corner in the APW path (J1 cusp) is resolved near the pole from the Hettangian/Sinemurian (∼200 Ma) Moenave Formation (59.4°N; 59.2°E). The J1 cusp implies an abrupt change from counterclockwise rotation of Pangea prior to 200 Ma to clockwise rotation thereafter. Paleomagnetic poles obtained from the Summerville and Morrison formations are consistent with the Middle and Late Jurassic APW path described by the Corral Canyon and Glance Conglomerate paleomagnetic poles as well as a Late Jurassic Cusp (J2 cusp) in the APW path. The APW path described by the J2 cusp, a single Morrison Formation pole, and mid-Cretaceous paleomagnetic poles suggest from ∼150-126 Ma the North American plate experienced a minimum rate of motion of 0.93°/m.y. which is similar to rates calculated for the Late Triassic (0.73°/m.y.) and Jurassic (0.66°/m.y.). This rate is much lower than rates based on previous APW paths. Thermal demagnetization and data analysis indicate that within-site dispersion is an important criterion for selecting sites which retain a high unblocking-temperature, characteristic remanent magnetization (ChRM). This criterion was used to define at least three stratigraphically-distinct, antipodal polarity-zones within each member/formation, suggesting the ChRM was acquired soon after deposition. ChRMs from 15 to 22 sites in the Upper Shale Member of the Chinle Formation define an early Norian paleomagnetic pole position of 57.4°N, 87.8°E (K = 60, A₉₅ = 5.0°). ChRMs from 18 to 43 sites in the Owl Rock Member of the Chinle Formation define a middle Norian paleomagnetic pole position of 56.5°N, 66.4°E (K = 183, A₉₅ = 2.6°). ChRMs from 23 of 35 sites in the Kayenta Formation define a Pliensbachian pole position of 59.0°N, 66.6°E (K = 155, A₉₅ = 2.4°). ChRMs from 15 to 35 sites in the Summerville Formation define a late Callovian pole position of 53.8°N, 133.6°E (K = 25, A₉₅ = 7.5°). ChRMs from 15 sites in the Morrison Formation (9 from the study of Steiner and Helsley ) define a single, ∼147 Ma, paleomagnetic pole position of 64.1°N, 152.4°E (K = 113, A₉₅ = 3.6°).
Distribution of ground cover and its effects on runoff and sediment yield in the WEPP modelKidwell, Mary Rachel, 1962- (The University of Arizona., 1994)New methods were tested to evaluate the ground cover parameters used in the WEPP model. Rainfall simulator plot data, collected from fifteen rangeland ecosystems across the western United States, were used to evaluate modifications to the ground cover components for rill and interrill areas in the model. Observed and predicted values of average sediment yield were compared for six different configurations of the model. The modifications made to WEPP to incorporate measured ground cover distributions resulted in a lower r2 for predicted sediment yield than any of the configurations in which ground cover distribution was not modified. This result was due to a reduction in the calculated value of total interrill ground cover. The model equations used to adjust interrill erodibility for the effect of interrill ground cover were adversely affected. The result was that interrill erodibility values were increased for many of the plots tested.