Westland Resources, Inc. : Ecological Management Plan for Altar Valley

The Project
image of Altar Valley

In a project funded by the Arizona Water Protection Fund, Westland assisted the Altar Valley Conservation Alliance in executing a management plan for Altar Valley, an area in Southern Arizona approximately 52 miles long and 20 miles wide through which the Altar Wash flows northward from the Mexican border.

With a combined population of more than 20,000, the area includes a population concentration along the rural edge of the Greater Tucson metropolitan area. The southern third of the wash and it's tributaries makes up the Buenos Aires Wildlife Refuge. Nearly half the Valley is state trust land, with 20% of the remaining land privately owned. The rest of the area, roughly 20%, is shared by Indian reservations, Forest Service lands, BLM lands and county park lands.

A primary task executed by WestLand was collection of Geographic Information System (GIS) data and analysis of that data. The database produced for the Alliance was used to facilitate the analysis of resources in the Altar Valley and to assist in defining Conservation Action Sites.

The GIS database contained eight layers or coverages, which include cultural features, ecological sites, land ownership, soils, and vegetation. The cultural features database was divided into four GIS layers: fences, roads, stock tanks, and wells.

The ecological site is a basic mapping unit used in rangeland inventory. An ecological site is distinct in its ability to produce a characteristic natural plant community. The differentiation of sites is based upon physiographic features, soils, climatic factors, and native vegetation. This portion of the database included the type of ecosite, sub-groups within the ecosites, and number of acres within each group and sub-group.

The Land Ownership GIS layer contained polygons depicting general classes of land ownership, for example, private, state, or national wildlife refuge. WestLand obtained the Land Ownership coverage from Pima County and clipped it to the project boundaries. With input from NRCS and others the database was updated to reflect recent changes to the boundary of the Buenos Aires National Wildlife Refuge.

The soils layer contained polygons representing soil associations as defined by NRCS. The data was obtained from the Pima County Land Information System and clipped to the project boundary.

The vegetation layer contained polygons representing areas of similar vegetation. The data was digitized from USGS 1:24000 scale, 7.5-minute quadrangles.
All of the GIS layers were projected in State Plane, Arizona Central, North American Datum 1927. The data were stored in ArcView shapefile format. As with any good database all geographical data was field verified.

The information gathered for this project was also used by Pima County to assess the formation of cooperative groups with land holdings that contain special-status species, especially cactus ferruginous pygmy owls.