The total value of electricity potentially lost
due to the sedimentation of the lake is equivalent
to the sum of the monetary value of the energy
consumed for each category of consumer, i.e.
CFA francs 155.2 million (USD 279,274.73
1 )
per year. This amount represents the loss to Eneo
Cameroon due to sedimentation. Based on the
assumptions underlying this paper, the market
value of the preservation of the hydroelectric
potential of Lake Lagdo by agriculture is therefore also USD 279,274.73 per year. It is important to keep in mind that this value is still
underestimating the true value of foregone benefits arising from sedimentation. Only lost power
benefits were considered, though the dam and
reservoir serve other functions such as irrigation,
flood control, fisheries, and providing domestic
water supply. Measurement and valuation of the
impacts of watershed erosion on these other
services require much more information than is
currently available.
3.3 The Effects of Anti-Erosion
Measures on the Reduction
of the Sedimentation
of Lake Lagdo Dam
Considering 1984, the year of optimum filling of
the reservoir and the powering up of the Lagdo
power station, as a basis for calculating the rate
of alluvial flow, the reservoir fills at the rate of
40.80 million cubic meters per year. The calculation of sediment volumes accumulated in 2004
by the RCM is based on a relatively long time
span of 20 years and the accumulated deposits
for this period amount to 815.9 million cubic
meters. According to the MEADEN study, if the
current rate of dam filling remains constant and
taking into account the quantities of sediment
already accumulated in 2004, i.e. 815.9 million
cubic meters over 20 years, the useful reserve on
which electricity production basically depends
can be seriously affected by 2020. This means
that the accumulated sediments have reached the
minimum level (206 m) with a capacity of 1,450
million cubic meters.
The amount of sediment accumulated since
1984 reduced the storage capacity to 634 million
cubic meters. With this remaining capacity and a
siltation rate of 40.7 million cubic meters per
year, the lifetime of the structure is an additional
15 years, i.e. a lifetime of up to 2020.
In Table 5, if we assume scenarios for
reducing the siltation speed by the anti-erosive
installations of 15, 30 and 50%, we obtain results
in terms of the lifetime of the structure. Thus, a
reduction of 15, 30, and 50% increase the lifetime of the structure by three, seven, and
16 years, respectively, compared with the siltation rate of 2004. The monetary gain is equivalent to the number of additional years obtained as
a result of sediment reduction multiplied by the
total value of electricity potentially lost annually
as a result of lake sedimentation.
A necessary condition for the adoption of
these conservation practices in watershed farming is the allocation of secure claims over the
land. However, farmers in the Lagdo watershed
typically have no property rights to the land
(Ngondjeb et al. 2014). As a consequence, there
is no stake in ensuring its long-term productivity
and the potential gain from reducing the loss of
soil nutrients cannot be captured by the farmers.
Therefore, it is not surprising that farmers exploit
the land until its productivity declines and then
move on to a new plot (Ngondjeb et al. 2014).
With regard to the private incentives for conservation, it must be recognized that soil erosion
does not necessarily impose current costs on the
private land user as long as the topsoil layers are
not completely depleted. Only with the removal
of topsoil does the nutrient loss have a direct
impact on the current productivity of the land.
The substantial on-site benefits in terms of sustainable soil productivity will, in fact, result from
the adoption of conservation-oriented farming
and forestry practices. Watershed farmers, however, will adopt these practices (which are not
costless) only if they can capture the long-term
benefits that will accrue. This indicates that a
necessary condition for conservation is for
farmers to acquire a long-term stake in the land.
1
Exchange rate (2018): 1 USD = 555.75 CFA francs.
102
D. Y. Ngondjeb and E. Ayuk
due to the sedimentation of the lake is equivalent
to the sum of the monetary value of the energy
consumed for each category of consumer, i.e.
CFA francs 155.2 million (USD 279,274.73
1 )
per year. This amount represents the loss to Eneo
Cameroon due to sedimentation. Based on the
assumptions underlying this paper, the market
value of the preservation of the hydroelectric
potential of Lake Lagdo by agriculture is therefore also USD 279,274.73 per year. It is important to keep in mind that this value is still
underestimating the true value of foregone benefits arising from sedimentation. Only lost power
benefits were considered, though the dam and
reservoir serve other functions such as irrigation,
flood control, fisheries, and providing domestic
water supply. Measurement and valuation of the
impacts of watershed erosion on these other
services require much more information than is
currently available.
3.3 The Effects of Anti-Erosion
Measures on the Reduction
of the Sedimentation
of Lake Lagdo Dam
Considering 1984, the year of optimum filling of
the reservoir and the powering up of the Lagdo
power station, as a basis for calculating the rate
of alluvial flow, the reservoir fills at the rate of
40.80 million cubic meters per year. The calculation of sediment volumes accumulated in 2004
by the RCM is based on a relatively long time
span of 20 years and the accumulated deposits
for this period amount to 815.9 million cubic
meters. According to the MEADEN study, if the
current rate of dam filling remains constant and
taking into account the quantities of sediment
already accumulated in 2004, i.e. 815.9 million
cubic meters over 20 years, the useful reserve on
which electricity production basically depends
can be seriously affected by 2020. This means
that the accumulated sediments have reached the
minimum level (206 m) with a capacity of 1,450
million cubic meters.
The amount of sediment accumulated since
1984 reduced the storage capacity to 634 million
cubic meters. With this remaining capacity and a
siltation rate of 40.7 million cubic meters per
year, the lifetime of the structure is an additional
15 years, i.e. a lifetime of up to 2020.
In Table 5, if we assume scenarios for
reducing the siltation speed by the anti-erosive
installations of 15, 30 and 50%, we obtain results
in terms of the lifetime of the structure. Thus, a
reduction of 15, 30, and 50% increase the lifetime of the structure by three, seven, and
16 years, respectively, compared with the siltation rate of 2004. The monetary gain is equivalent to the number of additional years obtained as
a result of sediment reduction multiplied by the
total value of electricity potentially lost annually
as a result of lake sedimentation.
A necessary condition for the adoption of
these conservation practices in watershed farming is the allocation of secure claims over the
land. However, farmers in the Lagdo watershed
typically have no property rights to the land
(Ngondjeb et al. 2014). As a consequence, there
is no stake in ensuring its long-term productivity
and the potential gain from reducing the loss of
soil nutrients cannot be captured by the farmers.
Therefore, it is not surprising that farmers exploit
the land until its productivity declines and then
move on to a new plot (Ngondjeb et al. 2014).
With regard to the private incentives for conservation, it must be recognized that soil erosion
does not necessarily impose current costs on the
private land user as long as the topsoil layers are
not completely depleted. Only with the removal
of topsoil does the nutrient loss have a direct
impact on the current productivity of the land.
The substantial on-site benefits in terms of sustainable soil productivity will, in fact, result from
the adoption of conservation-oriented farming
and forestry practices. Watershed farmers, however, will adopt these practices (which are not
costless) only if they can capture the long-term
benefits that will accrue. This indicates that a
necessary condition for conservation is for
farmers to acquire a long-term stake in the land.
1
Exchange rate (2018): 1 USD = 555.75 CFA francs.
102
D. Y. Ngondjeb and E. Ayuk