220
J. U. Kitheka et al.
Therefore, it is unlikely that efforts to reduce sediment load and control floods in the
basin can be successful without a deliberate effort to mitigate the root causes of land
degradation in the basin: rapid population growth and land-use changes.
Keywords Streamflow · Climate variability · Land use · Sediment loads · Floods ·
Nyando river basin · Kenya
1 Introduction
Climate change is affecting many river basins in Africa through increased occurrence of extreme hydrologic events, such as floods and droughts. In Kenya, like in
other countries in Africa, the manifestation of climate change is evident in increased
variability of streamflows. There is evidence that the frequency of occurrence of both
extremely low and extremely high streamflows has increased in the recent past. The
Nyando River Basin in Western Kenya is typical in experiencing increased streamflow variability with increased risk of floods and droughts due to climate change
(see also Opere and Ogallo 2006; Opere and Okello 2011a, b). Extreme hydrological
events in the basin have major socio-economic impacts because extreme variability
of streamflow is causing changes to ecosystems on which local communities depend
for survival. This has increased the vulnerability of communities to the impacts
of climate change, and is expected to increase more in the near future due to the
compounding impacts of climate change that can be attributed to land-use change
due to the rapidly increasing population and urbanization in the basin.
The status of the Nyando Basin is similar to other basins in Africa where occurrence of extreme hydrologic events has increased noticeably in the recent past,
affecting millions of people and significantly decelerating economic development.
As a result, considerable effort has been invested in the mitigation of drought- and
flood-induced damage over the last decade. In Kenya, floods are second to droughts
in terms of frequency and severity of impacts on land use, as droughts continue to
cause physical damage in major river basins, including the Nyando Basin. Within
the Nyando River Basin, interventions to address the impacts of extreme hydrologic
events have not yielded the desired results. This is partly because most mitigation
measures have not been based on hydrologic research and have also largely ignored
local perceptions and experiences. There has also been relatively limited research
to characterize the hydrologic response of tropical river basins in this era of climate
change. Similarly, there have been few hydrologic studies targeting degraded tropical river basins such as Nyando that are already experiencing the impacts of climate
change. The lack of such studies limits the effectiveness of drought and flood management intervention. There is therefore a need for studies to determine the extent to
which tropical river basins in Africa are being impacted by climate change in terms
of streamflow variability, soil erosion, and sediment yield. This need is amplified by
the fact that extreme hydrologic events have cumulative impacts that can in turn have
J. U. Kitheka et al.
Therefore, it is unlikely that efforts to reduce sediment load and control floods in the
basin can be successful without a deliberate effort to mitigate the root causes of land
degradation in the basin: rapid population growth and land-use changes.
Keywords Streamflow · Climate variability · Land use · Sediment loads · Floods ·
Nyando river basin · Kenya
1 Introduction
Climate change is affecting many river basins in Africa through increased occurrence of extreme hydrologic events, such as floods and droughts. In Kenya, like in
other countries in Africa, the manifestation of climate change is evident in increased
variability of streamflows. There is evidence that the frequency of occurrence of both
extremely low and extremely high streamflows has increased in the recent past. The
Nyando River Basin in Western Kenya is typical in experiencing increased streamflow variability with increased risk of floods and droughts due to climate change
(see also Opere and Ogallo 2006; Opere and Okello 2011a, b). Extreme hydrological
events in the basin have major socio-economic impacts because extreme variability
of streamflow is causing changes to ecosystems on which local communities depend
for survival. This has increased the vulnerability of communities to the impacts
of climate change, and is expected to increase more in the near future due to the
compounding impacts of climate change that can be attributed to land-use change
due to the rapidly increasing population and urbanization in the basin.
The status of the Nyando Basin is similar to other basins in Africa where occurrence of extreme hydrologic events has increased noticeably in the recent past,
affecting millions of people and significantly decelerating economic development.
As a result, considerable effort has been invested in the mitigation of drought- and
flood-induced damage over the last decade. In Kenya, floods are second to droughts
in terms of frequency and severity of impacts on land use, as droughts continue to
cause physical damage in major river basins, including the Nyando Basin. Within
the Nyando River Basin, interventions to address the impacts of extreme hydrologic
events have not yielded the desired results. This is partly because most mitigation
measures have not been based on hydrologic research and have also largely ignored
local perceptions and experiences. There has also been relatively limited research
to characterize the hydrologic response of tropical river basins in this era of climate
change. Similarly, there have been few hydrologic studies targeting degraded tropical river basins such as Nyando that are already experiencing the impacts of climate
change. The lack of such studies limits the effectiveness of drought and flood management intervention. There is therefore a need for studies to determine the extent to
which tropical river basins in Africa are being impacted by climate change in terms
of streamflow variability, soil erosion, and sediment yield. This need is amplified by
the fact that extreme hydrologic events have cumulative impacts that can in turn have