Big Bend Río Bravo - Lower Río Conchos Final 12 2015

The lower portion of the Rio Conchos basin - about 120 miles of river extending from the town of Julimes to the town of Ojinaga - is in the northern Mexican state of Chihuahua. As the largest Mexican tributary to the Rio Grande/Bravo, which forms the border between the United States and Mexico, interests in both countries rely on the waters of the Rio Conchos. The Rio Conchos rejuvenates flow to the almost dry Rio Grande/Bravo and; thus, supplies flow to Big Bend National Park of the United States and for a number of Natural Protected Areas of Mexico. The Rio Grande/Bravo forms the heart of the Chihuahuan Desert, a priority geography for both the World Wildlife Fund (WWF) and the Desert Landscape Conservation Cooperative (Desert LCC).
Geographic Boundary: The Rio Grande/Bravo’s most important tributary – the Rio Conchos of northern Chihuahua, Mexico – is born in the mountains of the Sierra Madres and travels to its confluence with the Rio Grande/Bravo. In the headwaters live the indigenous Tarahumara people. Further downstream Irrigation Districts (large-scale farmers) and Irrigation Units (smaller farms) dominate water use. In this area, the river is highly modified and is impacted by impoundments and channelization and is over-allocated with people using eight times more water than their water rights. After this agricultural zone, however, the river travels 120 miles of the amazing, arid environment of northern México to the confluence of the Rio Grande/Bravo.

Focal Species: Noted fauna include Mule Deer (Odocoileus hemionus), Grey Fox (Unocyon cineroargentinus), Jaguar (Panthera onca) and Javelina (Pecari tajacu). This area is also characterized by a wide variety of cacti species such as the abundant Ocotillo (Fouquieria splendens), Candelilla Wax (Euphorbia antisyphilitica) and the eagle claws cactus (Echinocactus horizonthalonius). Grasslands comprise about twenty percent of the desert vegetative cover and include Side-oats Grama (Bouteloua curtipendula), Black Grama (Chondrosum eriopodum), and Purple Three-awn Grass (Aristida purpurea). The Rio Conchos basin is also home to 48 species of fish of which 10 are considered endemic. Unfortunately, it has been estimated that one-half of the native fish of the Chihuahuan Desert portion of the river basin are already extinct or threatened with extinction. Extinction rates are likely to increase with the hotter and drier conditions climate change will bring.

Hydrologic Conditions: The Rio Conchos basin is one of the most important river basins in northern Mexico, draining area of 67,000 km2. It comprises 14 percent of and provides one-third of the water volume (2,553 million m3/year) to the Rio Grande/Rio Bravo basin. The Rio Conchos originates in the Sierra Madre Occidental, locally known as Sierra Tarahumara, at a mean altitude of 2,300 meters above sea level, and flows through Mexico to the Rio Grande/Bravo at the US–Mexican border. The river and its tributaries are regulated by seven main reservoirs with a total capacity of 3,654 cubic meters. Annual precipitation in the basin ranges from 700 millimeters in the upper portion of the basin to 250 millimeters in the lower portion. On average, 90 percent of the annual rainfall occurs during the wet season months, with the peak rainfall months of July and August - a consequence of the North American monsoons. In addition to the low precipitation values, the basin is prone to long periods of drought, such as the most recent, which extended from 1993 to 2005.

The Big Bend – Rio Bravo area is the heart of the Chihuahuan Desert and the core area for decades of bi-national conservation efforts. The nominated area covers 8.86 million acres (US = 4.88 & MX = 3.98) and contains eleven protected areas (see Appendix A for full list) all within the Rio Grande/Rio Bravo watershed. The proposed boundaries were chosen by selecting the HUC 8 & HUC 10 watersheds intersecting the six US protected areas and the boundaries of the five protected areas on the Mexico side. Watersheds were chosen because they represent natural, ecologically-significant boundaries relative for conservation efforts.  
There are numerous partnerships cooperating within the region including the Sister Park Partnership, the Big Bend – Rio Bravo Partnership, the Big Bend Conservation Cooperative, the Desert Fish Habitat Partnership, and the National Fish Habitat Partnership.

All three of the DLCC priority resources are located within the proposed pilot area at various levels of ecological integrity, from pristine to highly degraded, which provides opportunities for conservation of highly functional resources to restoration of highly degraded areas.