Chapter 1 Minimum Flows and Levels - Southwest Florida Water ...

attributed to analytic precision differences. However, for presentation and
discussion purposes, we combined numerous land use types into fairly broad
categories, and thereby eliminated some of the error associated with use of the
two classification systems.
For our analyses, land use/cover types identified included: urban; uplands
(rangeland and upland forests); wetlands (wetland forests and non-forested
wetlands); mines; water; citrus; and other agriculture. We examined changes in
these use/cover types for the entire watershed and also for two major subbasins.
Before discussing individual sub-basin land use changes, it is informative to
discuss the entire watershed of the Braden River to get an appreciation of the
major land uses/covers and the changes that have occurred during the nearly 30
years for which land use maps are available. Land use/cover maps for 1972 and
1999 for the entire Braden River watershed are shown in Figures 2-3 and 2-4.
Based on these maps, the entire Braden River watershed is 83.6 square miles or
53,487 acres in size (Table 2-1).
Because we combine several agricultural land use types for our analysis,
temporal changes in land use from 1972 to 1999 (see Figure 2-5) may not reflect
the shift which has occurred from less intensive types of agricultural land use to
those requiring greater amounts of water. It should be noted, however, that of
the major land use categories, the amount of land converted to urban uses has
shown the single greatest increase. In many instances, within sub-basins, what
appears to be a substantial decrease in uplands and increase in wetlands is
actually an artifact of the disparity in resolution of features denoted in 1972 and
1999 mapping. While it appears that the amount of wetlands has increased in
most sub-basins, this is probably not the case. Because many wetlands are
small in size and interspersed within upland areas, they were not delineated
under the relatively coarser resolution employed in the 1972 mapping. Actual
increases in wetlands (resulting in a concomitant decrease in uplands) were the
consequence of increased resolution rather than the conversion of, for example,
uplands to wetlands. In many cases what appear to be substantial declines in
uplands should more appropriately be interpreted as an improvement in map
resolution. However, decreases in uplands have occurred in some sub-basins.
It is helpful when interpreting these data to view the sum of the wetlands and
uplands as natural area, and the decline in this total as a measure of conversion
to some other more intensive land use (e.g., agriculture, mining, urban).
2-4