6043 - Laserfiche WebLink

Home Browse Search

19 FISH HABITAT LOSS IN THE SAN PEDRO RIVER, ARIZONA. Randy M. McNatt, U.S. Fish and Wildlife Service, Riparian Habitat Analysis Group, Albuquerque, New Mexico. Abstract--The San Pedro River basin formerly consisted of a large perennial mainstream with associated springs and tributaries. Diversions, headeater impoundments, depletion of underground aquifiers, clearing of riparian habitats, and a possible regional tendency toward increasing aridity have reduced mainstream surface flow to that of an intermittent stream, with perennial flow in 3 sections which comprise only 50 km of the total river length of 250 km. Aravaipa Creek, the largest tributary, presently contains 7 of the 13 native species reported from the basin, and is the only portion of the entire drainage that supports a relatively secure native fish fauna. Of the 7 species in Aravaipa Creek, 4 have not been found elsewhere in the basin since at least 1963. Abstracto--E1 desaque de el Rio San Pedro, en tiempo, consisto en un gran corriente perenne con asociaciones de ojos y tributarios. Diversiones, lagunas en cabercera, depletion de aquifeeos subterraneo, sitio sin vegetation de ribereno, y posiblemente un tendencia regional para aumentar arideza, en reducido las corrientes principal de el superficie hasta que a creado una corrida intermitente. Corrientes perenne de los tres secciones solamente consiste en,cincuenta kilo- metros sobre dosciento cincuenta kilooetros de todo el rio. Arroyo Aravaipa, el mas grande de los tributarios, al presente tiene siete de los trece pescado nativos y solomente es el unico parte de todo el desaque que tiene pescados nativos que estan estable. De los siete pescados en el Arroyo Aravaipa, no han describrido cuatro pescados nativos en otras partes de la cuenca desde 1963. The San Pedro River, a major tributary to the Gila, enters the United States from Sonora, Mexico, approximately 100 km east of Nogales, Arizona. The river channel then runs NNW for approximately 200 km to its confluence with the Gila River near Winkelman, Arizona. Headwaters of the river are located 40 km south of the International Boundary near Cananea, Mexico. Total area of the San Pedro basin is 11,621 km2, of which 1,802 km2 occur in Sonora. El w'ation of the river channel is 1,303 m above mean sea level at the International Boundary, and drops to an elevation of 585 m at its confluence with the Gila River, an average gradient of 4 m/km (Roeske and Werrell, 1973)• The largest tributary to the San Pedro is Aravaipa Creek, which drains an area of 1,530 km and enters the San Pedro mainstream 19 km upstream from Winkelman'. Another tributary with small perennial flow sections is the Babacomari River, which joins the San Pedro 42 km north of the International Boundary. San Pedro Valley sediments, bounded by several desert mountain ranges composed of low-permeability, crystalline and consolidated