The following is an excerpt from a paper submitted by RECON Enviromental,
Inc. Titled "Land Cover Data Assessment in Pima County"

San Pedro GAP Update and Bingham Cienega Natural Preserve

The San Pedro watershed is a remote area of eastern Pima
County that The Nature Conservancy (TNC) manages for Pima
County Flood Control District. Bingham-Cienega Natural
Preserve is included in this area. Based on their collective
field experience, TNC managers Chris Fichtel, Dave Harris,
and Dave Gori revised the GAP vegetation mapping in this
area. They made changes only where they believed GAP data
was inaccurate based on their working knowledge of land cover
in that area (Fonseca, pers. com. 2000). These changes were
incorporated by DOT and further updated to include
agricultural lands delineated by the EROS coverage.  At the
series-level, San Pedro vegetation mapping revisions are an
improvement over GAP mapping, and represent the kind of
vegetation mapping updates that are needed for this phase of
the SDCP. Compared to WHIP and Cienega Creek mapping, San Pedro
revisions are fairly course-scale. Vegetation units that showed
a mosaic of agriculture, mixed riparian scrub, and riparian
forest in the GAP mapping are generalized in the San Pedro
coverage. The level of effort required to improve the detail
of this mapping would involve aerial photo interpretation plus
field reconnaissance, which would only be recommended if target
species mapping is needed for this area.  The San Pedro
vegetation coverage used in the composite map is shown in
Figure 5. The GIS coverage included GAP and EROS attribute data
for some polygons, and one unique attribute that contained
information about vegetation updates. Using this attribute and
a legend file, BLP codes were linked to each polygon, and were
added as a new attribute in the revised data layer. Some polygons
contain no BLP attribute data; these appear as "unclassified" in
Figure 5.