3.3 – Sensitivity of wetlands

This dataset below shows the distribution and sensitivity of wetlands in the whole Albertine graben. ASTER, SPOT XS and a few Landsat 7 ETM+ satellite images of the period between 2006 and 2008 were used to map the wetlands. The images covered 70%, 21% and 9% of the land area of Uganda respectively. Of these 60% were for 2008. For all the images the spatial resolutions was restricted to between 15 and 20 m.

Wetlands in the Albertine graben fall into five of the eight major catchments. They are mainly in the Lake Albert but also in some parts of the Albert Nile, Lake Edward, Lake Victoria and Victoria Nile catchments. The wetlands are stratified into five land cover types namely papyrus, sedges, grassland, swamp forests and farmland. These are also categorized by water regime as seasonal (s) and permanent (p) wetlands. Seasonal wetlands are defined as those with water regime of between two to four months. While the permanent are those which retain water for at least four months.

The sensitivities of the wetlands were derived from the general sensitivities of the land cover classes (1 – 9). The calculations were based on the importance and difficulty of wetland restoration if affected by oil spills. The final sensitivity of each wetland was computed based on its hydrological function and ecological response. The specific variables used are ecological characteristics of a wetland; water regime and vegetation cover density. These resulted in sensitivity values ranging from 6 to 9. These were then standardized to the sensitivity range of 1-9 (See table 1).

Class   Name

Ecological

Water  Regime

 Density

Sensitivity     

Description

 

 

 

 

 land cover wetlands

 

Grassland (s)

3

2

1

6

1

Rangelands, pasture, open savannah may include scattered trees shrubs and thickets
Subsistence farmland (s)

3

2

1

6

1

Mixed farmland small holdings in use or recently used with or without trees
Palms and thickets (s)

3

2

2

7

4

Thick or sparse palm trees and or scattered trees and shrubs
Grassland (p)

3

4

1

8

6

Rangelands, pasture, open savannah may include scattered trees shrubs and thickets
Sedges (p)

3

4

1

8

6

Rangelands, pasture, open savannah may include scattered trees shrubs and thickets
Subsistence farmland (p)

3

4

1

8

6

Mixed farmland small holdings in use or recently used with or without trees
Papyrus (p)

3

4

2

9

9

Swamps with Papyrus   as dominant species
Swamp forest(p)

3

4

2

9

9

Thick closed canopy forests and woodlands

3_3_map_17