1.1 Natural Lakes and Reservoirs
in Kenya
Kenya’s physiographic landscape, like the rest of
the world, is dotted with both natural lakes and
reservoirs. These lakes and reservoirs vary in
their biophysical characteristics and socioeconomic importance. Most natural lakes in
Kenya are in the Rift valley physiographic province. From North to South of the Rift valley the
lakes are outlined as: Turkana, Logipi, Baringo,
Bogoria, Nakuru, Elementeita, Naivasha and
Magadi (Becht et al. 2006). Lake Baringo and
Lake Naivasha are the only freshwater lakes in
the rift valley. Lake Victoria, Jipe, Chala Kamnarok, Solai, Chew Bahir are located outside the
Rift Valley. The location of the major lakes in
Kenya is shown in Fig. 1.
The lakes and reservoirs in Kenya vary in
their depths and storage capacity. As shown in
Table 1 the combined storage capacity of reservoirs in Kenya is about 4,100 M m
3 (FAO 2016;
World Bank 2011). The locations of these
reservoirs in Kenya are also shown in Fig. 1. The
purposes of these reservoirs are mainly hydropower and water supply. Currently, it is estimated that 82% of Kenya’s electricity supply is
from hydropower (Oludhe 2010) and the bulk of
this supply is from five reservoirs along the Tana
River. Concerning water supply, the capital city,
Nairobi, relies on Thika, Sasumua and Ruiru
reservoirs, (Fig. 1), albeit insufficiently, especially during the dry season. Other cities within
the country also rely on various reservoirs for
their water supply. Despite the socio-economic
importance of these reservoirs, the country has
not fully explored its reservoir storage potential.
In addition, a coherent management strategy,
including adequate monitoring, would be critical
(Hülsmann et al. 2020) for existing reservoirs but
has not been implemented.
Like the rest of the world, sedimentation
threatens the volume of natural lakes and reservoirs in Kenya. The scale of the sedimentation
problem in Kenya is illustrated by Wooldridge
(1984) who estimated a sediment inflow of 357
m
3 /km
2 /year to the Kamburu reservoir. In Kenya,
this information is available for four reservoirs
that have been surveyed. However, most of the
lakes and reservoirs in Kenya have not been
assessed to establish their current sedimentation
status. This is further exacerbated by the lack of
sediment load monitoring stations upstream of
these reservoirs. For the management of these
reservoirs and the watersheds upstream, it would
be vital to know sedimentation rates in these
reservoirs, identify the potential sources of the
sediment, propose mitigation measures, and
monitor the impacts of the proposed measures.
Hence, there is a need to monitor the sediment
load in upstream rivers or re-establish this from
the rate of sedimentation in reservoirs.
1.2 The Need for Reservoir
Sedimentation Assessment
Natural lakes and reservoirs support man’s socioeconomic activities and are hosts to a highly
diverse flora and fauna. Reservoirs are critical for
the spatial and temporal distribution of water for
domestic and industrial use, food production and
energy generation. In Kenya, without reservoirs,
most cities would be experiencing poor access to
water and sanitation. Reservoirs provide habitats
for various flora and fauna. Furthermore, this
flora and fauna support man’s socio-economic
activities like tourism, fishing, and sports. In
Kenya, loss of reservoir capacity could also
affect electricity generation and have a significant
impact on the economy. Hence, sedimentation
assessment plays a key role where regular monitoring of sediment load into the reservoir is not
undertaken.
Reservoir sediment assessment provides
multifunctional historical information about
sedimentation rates. This multifunctional information includes the current storage capacity of
the reservoirs, sediment thickness with its spatial
location as well as physical-chemistry characteristics of sediment and water within the reservoir. Some of this crucial information is currently
unknown, missing, or not up to date. When water
managers know the current volume, they can
adequately control the amount of water supply or
decide whether they require alternative sources
Multifunctional Historical Data for Improved Management of Reservoirs
83
in Kenya
Kenya’s physiographic landscape, like the rest of
the world, is dotted with both natural lakes and
reservoirs. These lakes and reservoirs vary in
their biophysical characteristics and socioeconomic importance. Most natural lakes in
Kenya are in the Rift valley physiographic province. From North to South of the Rift valley the
lakes are outlined as: Turkana, Logipi, Baringo,
Bogoria, Nakuru, Elementeita, Naivasha and
Magadi (Becht et al. 2006). Lake Baringo and
Lake Naivasha are the only freshwater lakes in
the rift valley. Lake Victoria, Jipe, Chala Kamnarok, Solai, Chew Bahir are located outside the
Rift Valley. The location of the major lakes in
Kenya is shown in Fig. 1.
The lakes and reservoirs in Kenya vary in
their depths and storage capacity. As shown in
Table 1 the combined storage capacity of reservoirs in Kenya is about 4,100 M m
3 (FAO 2016;
World Bank 2011). The locations of these
reservoirs in Kenya are also shown in Fig. 1. The
purposes of these reservoirs are mainly hydropower and water supply. Currently, it is estimated that 82% of Kenya’s electricity supply is
from hydropower (Oludhe 2010) and the bulk of
this supply is from five reservoirs along the Tana
River. Concerning water supply, the capital city,
Nairobi, relies on Thika, Sasumua and Ruiru
reservoirs, (Fig. 1), albeit insufficiently, especially during the dry season. Other cities within
the country also rely on various reservoirs for
their water supply. Despite the socio-economic
importance of these reservoirs, the country has
not fully explored its reservoir storage potential.
In addition, a coherent management strategy,
including adequate monitoring, would be critical
(Hülsmann et al. 2020) for existing reservoirs but
has not been implemented.
Like the rest of the world, sedimentation
threatens the volume of natural lakes and reservoirs in Kenya. The scale of the sedimentation
problem in Kenya is illustrated by Wooldridge
(1984) who estimated a sediment inflow of 357
m
3 /km
2 /year to the Kamburu reservoir. In Kenya,
this information is available for four reservoirs
that have been surveyed. However, most of the
lakes and reservoirs in Kenya have not been
assessed to establish their current sedimentation
status. This is further exacerbated by the lack of
sediment load monitoring stations upstream of
these reservoirs. For the management of these
reservoirs and the watersheds upstream, it would
be vital to know sedimentation rates in these
reservoirs, identify the potential sources of the
sediment, propose mitigation measures, and
monitor the impacts of the proposed measures.
Hence, there is a need to monitor the sediment
load in upstream rivers or re-establish this from
the rate of sedimentation in reservoirs.
1.2 The Need for Reservoir
Sedimentation Assessment
Natural lakes and reservoirs support man’s socioeconomic activities and are hosts to a highly
diverse flora and fauna. Reservoirs are critical for
the spatial and temporal distribution of water for
domestic and industrial use, food production and
energy generation. In Kenya, without reservoirs,
most cities would be experiencing poor access to
water and sanitation. Reservoirs provide habitats
for various flora and fauna. Furthermore, this
flora and fauna support man’s socio-economic
activities like tourism, fishing, and sports. In
Kenya, loss of reservoir capacity could also
affect electricity generation and have a significant
impact on the economy. Hence, sedimentation
assessment plays a key role where regular monitoring of sediment load into the reservoir is not
undertaken.
Reservoir sediment assessment provides
multifunctional historical information about
sedimentation rates. This multifunctional information includes the current storage capacity of
the reservoirs, sediment thickness with its spatial
location as well as physical-chemistry characteristics of sediment and water within the reservoir. Some of this crucial information is currently
unknown, missing, or not up to date. When water
managers know the current volume, they can
adequately control the amount of water supply or
decide whether they require alternative sources
Multifunctional Historical Data for Improved Management of Reservoirs
83