Land Form & Geology
As elevation changes, so do climate and vegetation, land use and economic development, all of which directly affect fire risk. The geologic features of the County which have evolved over time can be classified by distinct patterns of land forms, known as physiographic provinces. The northern edge of Catron County lies within the Colorado Plateau Province, characterized by scarped tablelands with broad valleys and local canyons.
The remainder of Catron County lies within the Datil-Mogollon province, a transitional area between the Colorado Plateau and the basin and range landscape to the south and east. It is characterized by widespread volcanic flows, high tablelands and scattered fault block ranges. Elevations range from a low of 4700 feet in the Glenwood area to nearly 10,900 feet in the Gila Wilderness area, which sits astride the Catron/Grant county line.
The major surface water basins, as designated by the U.S. Geological Survey, are the Lower Colorado River Basin and the Rio Grande Basin. Major sub-basins within the lower Colorado River Basin in Catron County include the Carrizo Wash, Little Colorado, San Francisco and Upper Gila. Sub-basins within the Rio Grande Basin include the North Plains, Rio Salado and Plains of San Agustin. The San Agustin Plains, in the Northeastern part of Catron County, lie within a closed basin which formed under large Pleistocene lakes.
Major mountain ranges include the Mogollon, San Francisco, Tularosa, Mangas, Gallos, Blue, Datil, Crosby, Sawtooth, Allegras, Horse, and Pellona Mountains.
Climate
Catron County is generally arid, and precipitation is seasonal. Wildfires will generally occur in late spring and into the summer. Within an area of this size, as might be expected, climate is nearly as varied as the terrain. The only unifying climatic variable is aridity; throughout the county evaporation potential exceeds the amount of precipitation typically received.
Due to the relatively limited number of weather stations which have continuous data available, only gross generalizations can be made.
The mean annual precipitation in the lower elevations is generally between 8 to 12 inches.
The mean annual precipitation in the mid range elevations between the flatlands and upper mountain areas ranges from about 12 to 16 inches and the mountain areas within the Gila and San Francisco River Basins ranges from about 16 to 30 inches with the average between 16 and 20 inches.
Information for rainfall from six weather stations in Catron County show that the distribution of the mean annual precipitation is generally the same for all stations; forty-four percent occurs in summer (June 1st to August 31st), twenty-six percent occurs in the fall (September 1st to November 30th), twenty percent occurs in the winter (December 1st to February 29th), and the remaining ten percent occurs in the spring (March 1st to May 31st). Summer and fall rainfall, very often from brief intensive thunderstorms, accounts for the largest percentage of annual rainfall.
Snow falls between October and into May in the mountain areas with most snowfall occurring between December and February, although March also has considerable snowfall. The mean annual snowfall ranges from about 0.3 inches in the lower elevations to 36.4 inches at higher elevations.
Soils And Vegetation
Soil types described in U.S.D.A. Soil Conservation Service (SCS) surveys are used in this Plan. They are grouped into major categories, and are subject to significant variation of depth and texture within a given category due to differences in underlying geologic materials from which the soils are formed, as well as localized weathering and biological factors.
Soil cover on mountain slopes is generally not more than a few inches deep where woodland cover is absent, while in forested areas it is usually thick with a much higher humus content.
Soils in closed drainage basins, where run-off from higher elevations collects, tend to be low in humus, high in soluble minerals, and are often alkaline.
Soils in the broader reaches of the Gila and the San Francisco River valleys are mostly sandy to silty, well drained, and suited to agriculture. Soils in drainages farther north tend to have a higher clay content, derived from shale parent material. They are usually much heavier than the soils of surrounding hills and mountains.
The soil resources are the basis of all habitat types in Catron County. Areas exist that are greatly susceptible to soil erosion after catastrophic fire and must be protected. For critical soils see The Soil Survey of Catron County NM available from the NRCS and USFS.
The two vegetation types below are the most common for Urban/Interface type development in Catron County.
Photo credit: Doug Boykin, NM State Forestry
Ponderosa Pine/Arizona Fescue Habitat Type Willow Creek Mesa 8,500 ft.
Photo credit: Doug Boykin, NM State Forestry
Pinyon/Juniper Woodlands intermixed with open meadows
Plant communities - subject to fire - play an important role in any soils discussion, being both dependent upon and, to a somewhat lesser degree, responsible for soil types in a given area. Vegetation is also very dependent upon geographic location. The area is influenced by two of the major biogeographic provinces of the southwest, the Great Basin in the North and the Chihuahuan Desert In the South.
Within the lower Colorado River Basin, the valley floor and adjacent slopes are mainly grassland and low brush, commonly dotted with piņon and oak on the intermediate slopes. Oak generally gives way to a greater prevalence of juniper in the more northerly latitudes. Ponderosa pine is common between 6,000 and 8,000 feet, with spruce, fir, and aspen found at altitudes above 8,000 feet. The initiation of fire suppression in the early 1900's has resulted in the piņon/juniper invasion of grasslands and increased ponderosa and mixed-conifer stand densities. In turn, this has reduced water delivery from the watershed. It has also contributed to increased erosion of soils and turbidity of surface flows.
Lower elevations in the closed basins are also dominated by grass and brushlands. Vertical progressions in these basins are similar to those of the lower Colorado Basin.
Riparian communities, represented by such species as cottonwood and invading salt cedar, are found along many of the lower perennial streams throughout the county. See Appendix Volume 2 Data (page 60-62)
