This file was created by scanning the printed publication. Errors identified by the software have been corrected; however, some errors may remain. Rio Yaqui Watershed, Northwestern Mexico: Use and Management 1 Luis Bojorquez2, Raymundo Aguirre3 and Alfredo Ortega4 Abstract.-- This paper describes the uses and communi­ ty types of the Rio Yaqui Watershed in Sonora Mexico. The management problems are interrelated but there are no stud­ ies of sufficient regional scope to integrate the uses of the area. To cope with this, research activities associated with management have to be multidisciplinary. INTRODUCTION The use of an ecosystems often influ~ ences other natural systems (Ffolliott The State of Sonora, Mexico, is loca­ 1980). Riparian ecosystems utilization ted on the northwestern corner of The impact, and is impacted by, other uses of Mexican Republic. It is limited by the their basin. For this reason a study was Sierra Madre Occidental, on the east, by made to describe the vegetational community the State of Arizona on the north, by the types that occur in the Rio Yaqui Watershed state of Sinaloa, on the south, and by the and their sometimes conflicting usage. Gulf of California, on the east. Agriculture, ranching, mining, fores­ Sonora presents two main landforms: try, and recreation are the principal land uses at present (SAHOP 1980) and larger im­ Northwestern Coastal Plain.- It ex­ pacts and conflicts can be expected in the tenrls from the outlet of the Colorado future. Basic research is needed to recon­ River to the south along the coast. and cile apparently antagonistic requirements of individual components of some multipur­ Sierra Madre Occidental.- It is ad­ pose combinations (King 1980). jacent and parallel to the coastal plain. It is the longest and most continuous moun­ tain chain of Mexico ranging from the DESCRIPTION OF THE WATERSHED eastern border of Sonora and Arizona to central Mexico. The maximum altitudes in General Characteristics its Sonoran range arE: of more than 2, 800 m above sea level (a. s. l) (DETENAL 1982a). Rio Yaqui Watershed occupies an area of approximately 73,000 km2 (30/. of the The Sierra Madre Occidental has a state). It originates in the west aspect large influence on the hydrology of the of the Sierra M~dre Occidental and is area since is the zone of recharge of the adjacent to the Rio Sonora Watershed in Northwestern Coastal Plain (DETENAL 1981a) its west limit. The north limit lies in where the most important developments are Arizona, U.S. A., approximately 40 km north­ located. Rio Yaqui is the principal river east of Douglas. The direction of the of Sonora. It originates in the Sierra long axis is northeast from the outlet. Madre Occidental and discharges into the Though the area includes two states, 95/. Gulf of California. of the basin is in Sonora (SARH 1979). The complex drainage pattern in the lPaper presented at the Riparian Eco­ mountains is gradually reduced when the systems Management Conference. University Yaqui approaches to the coastal plain of Arizona, Tucson, Az. April 16-18, (DETENAL 198la), where several arroyos 198 5. join the main flow. The principal river 2Luis A. Bojorquez-Tapia is Graduate of the watershed is the Yaqui, which has Student of Watershed Management, Univer­ a mean annual runoff of about 2. 9 billion sity of Arizona, Tucson, Az. m3 (SARH 1979) The principal tributaries 3Raymundo Aguirre-deluna is Graduate are the Bavispe, the Moc.tezuma, and the Research Assistant Range Management Depar­ Sahuaripa. The Bavispe drains in to La tment, University of Arizona, Tucson Az. Angostura Reservoir and continues running 4Alfredo Ortega-Rubio is Researcher south, forming the Yaqui at the junction in Institute de Ecologia, A. C. Mexico, D. F. with the Sahuaripa river. The Moctezuma 475 flows southward on the western limit of most xeric aspects while P. ayacahuite the basin and is connected to the Yaqui prevails on more mesic slopes of canyons. by the Plutarco Elias Calles Dam, better known as El Novillo. From here, the Yaqui The similar ecological requirements of runs out southward to the Alvaro Obregon pines and oaks, their entangled successio­ Reservoir, which supplies water for the nal relationships, and the diversity of irrigation of 2, 250 km2 of agricultural microhabitats produce a mosaic of forest land. Fourteen drains deliver the water types hard to delineate (Rzedowski 1978). used by agriculture to Tobari Bay Oak forest components often can be found (Bojorquez 1983). above the lower limit of the pine forest specially in xeric aspects so it is possi­ Ciudad Obregon, Agua Prieta, and ble to recognize the following Nacozari are the most important cities in associations: the watershed. Bosgue de Pino-Encino.- The pine-oak Climate association is formed by t~e same species of the pine and oak forests but with do­ The anticyclonic high pressure system minance of pines. It is found in the gives to Sonora its arid and semi-arid lower, more xeric areas of the pine forest. characteristics. The general trend is a gradient of aridity from the coast to high­ Bosgue de Encino-Pino.- This commu­ er elevations. Thus, for the watershed: nity establishes in disturbed zones in mean annual precipitation is about 559. 8 both the pine and the pine-oak forests. mm, from which 92. 07. is lost by evapotran­ Quercus and Pinus are the two main genera, spiration, 0. 47. infiltrates, and 7. 67. but oak is more abundant. The following leaves as runoff (DETENAL 1983b). Total species are common: P. cembroides, L annual precipitation ranges from 100-200 mm arizonica, P. emoryi, Cupressus arizonica, around the outlet to 1, 000-1, 200 mm in the and Juniperus deppeana. Sierra Madre (DETENAL 1981c). Mean annual temperature ranges from 24-26°C in areas Bosgue de Encino.- Deciduous oaks close to the ocean to 6-8°C in the highest dominate between 1000 and 2000 m a. s. l. elevations (DETENAL 1981d). in slopes and plateaus. The most abundant species is Q. chihuahuensis, although is However, the rugged topography in the displaced locally by Q. tuberculata and mountains causes combinations of climate Q. albocinta in more mesic habitats. types within this gradient (Rzedowski Other important species are: Q. fulva, 1978). According to the classification by Q. sipuraca, Q. santaclarensis, L Koeppen, the Northwestern Coastal Plain has hypoleuca, and Q. duranguensis. Bunchy subdivisions of climate types BS and Bw grasses are also important. while the Sierra Madre Occidental has sub­ divisions of climates BS and Cw (DETENAL Selva Baja Caducifolia 198la). This deciduous forest is typical of subhumid hot climates. The majority of the VEGETATIONAL COMMUNITIES individuals (757.-1007.) lose their leaves for long periods (6-8 months). The domi­ The variety of microenvironmental nant trees lack of spines and the highest conditions in the watershed causes a high are 15 m tall. It is widely distributed on overlapping of communities distributions. hillsides with good drainage between 300 to On the other hand, present knowledge of the 1200 m a. s. l. Common genera of this com­ vegetation in Mexico does not allow com­ munity are Ceiba, Bursera, Conzattia, parisons between community types in great Ipomea, Lysiloma, and Ficus. detail (Rzedowski 1978). In the present paper, the classification by DETENAL Bosque de Galeria (1981a) was followed. The watershed pre­ sents the following vegetational types: The riparian forest exists in areas where soil moisture is sufficiently high Forest to support a different community from the drier surroundings (Johnson and Carothers Bosque de Pino 1982). Populus, Platanus, and Taxodium are the most widely distributed along pere­ The pine forest includes the follo­ nnial streams upland. Prosopis and Acacia wing species distributed in the Sierra are present in arroyos (Rzedowski 1978). Madre Occidental between 1500 and 3000 m a. s. l.: Pinus reflexa, P. arizonica, P. Scrub lumholtzi, P. ayacahuite, and P. pondero­ ~- Microhabitats are important for the Matorral Desertico Microfilo predominance of a particular species, by example, P. reflexa is dominant on the This desert scrub vegetation type is composed of shrubs with small leaves or 476 folioles. Found on alluvial soils at USES OF THE COMMUNITY TYPES elevations from sea level to 800 m a. s. l., it can be divided in: Forestry Matorral Subinerme.- Thorny plants Pine communities were not exploited (30/.) and plants without spines (70/.) at the level programmed for 1984 (SFF form this vegetational type. Important· 1985). Pinus spp. were the most valuable species are: Fouguieria splendens, Yucca trees in Sonora. Total volume obtained in ~. C o n d a 1 i a s p. , Mi mo s a s p. , an d P r o s o p i s 1984 was about 43,300 m3. Sawlogs was the glandulosa. main product, but others were cellulose, posts, and c.rossties. Populus spp. saw­ Matorral Espinoso.- The proportion logs were also obtained but on a muc.h of thorny shrubs in this community is lower scale. higher than 707.. Prosopis spp., Acacia ~. C o n d a 1 i a s p p. , At r i p 1 e x s p p. , a n d On the contrary, scrub communities Fouguieria spp. are common. were overexploited. Th~ ~otal for the state was 113,300 m3 or 175/. the program­ Matorral Subtropical med volume (SFF 1985). Fuelwood and char­ coal were the principal products. Prosopis The subtropical scrub is typical in ~ and Olneya tesota were the most utili­ areas of ecological transition between zed for that purpose (SAHOP 1980). relatively humid conditions and more xeric scrubs. The majority of the plants lose Major problems of the forestry their leaves for long periods. This commu­ industry in Sonora are lack of product nity is denser with clearings occupied by classification systems and modern grasses in places of high human activity.