Table 15.2
Yield reductions under current, and potential future invasions, estimated by a range of modelling studies which assumed that invasions would be
allowed to expand to occupy the available land
Study
Catchment(s)
Reservoirs
Upland/
Riparian
Definition of
Yield
Assumptions about
future Invasions
% Yield
Reduction
Current
% Yield
Reduction
Future
Larsen et al.
(2001)
George water supply
catchments
Garden Route and
Malgas Dams
Upland and
riparian
Firm yield
a
40 Years
4
18
Gillham and
Haynes (2001)
Mgeni upstream of
Inanda Dam
Inanda Dam
Riparian
only
99%
Assurance
All invadable areas
5
8
Le Maitre and
Görgens
(2003)
Mgeni upstream of
Midmar Dam
Hypothetical
1-MAR dam
Upland and
riparian
Firm yield
10 Years
2
3
Riviersonderend
System
”
”
”
”
13
17
Upper Wilge System
”
”
”
”
1
2
Sabie-Sand System
”
”
”
”
45
64
Dzvukamanja
et al. (2005)
Mhlatuze River
System
Hypothetical
1-MAR dam
Upland tall
trees
Firm yield
All invadable areas
Not modelled
21
Mhlatuze River
System
Hypothetical
1-MAR dam
Riparian
tall trees
Firm yield
All invadable areas
Not modelled
16
Cullis et al. (2007) All QuaternariesMAP
>800 mm/a
All existing large
dams
Upland and
riparian
98%
Assurance
87.5% All invadable
areas
1
4
”
Run-of-river
”
Run-of-river
”
1
9
Thukela River Basin Integrated system
Upland
98%
Assurance
”
1
1 2
Usuthu to Mhlatuze
Rivers
Five Integrated
systems
Upland
”
”
1
1 4
Le Maitre et al.
(2018, 2019)
Western Cape Water
Supply System
Integrated system of
six large dams
Upland and
riparian
98%
Assurance
45 Years
7
23
442
D. C. Le Maitre et al.