Impact of Land Cover, Land Use and Climate Change on the Hydrological Regimes of the Mara River Basin
Abstract
The Mara river basin is a serene sub-catchment of Lake Victoria basin and a part of the
upper catchments of the Nile Basin. Importantly, it is a lifeline to the internationally
renowned Mara - Serengeti ecosystem and a rich mix of physiography, indigenous
cultures and land use practices. The need for more land for the rapidly growing
population in the basin has resulted in the excision of large parts of the forests that were
formerly preserved, and encroachment to other fragile ecosystems, which has affected
the flow volumes of Mara River. Little information exists on how variation in the
human activities owing to climate change is affecting the hydrology of the basin. Lack
of such information hampers the ability of the various resources managers to formulate
a comprehensive ecosystems management strategy that would provide for sustainable
livelihoods. This study focuses on the nature, extent and rate of change in land cover,
land use and climatic scenarios and their impacts on hydrological regimes in Mara River
Basin. Land cover dynamics were analyzed from dry weather Landsat TM and ETM+
images for 1984, 1995, 2003, 2011 and 2016 under ENVI 5.0 and ArcGIS 10.4 software
environment. Thematic maps comprising eight land cover/use types were created from
the imageries using unsupervised land cover classification technique and FAO land use
classes. Time series analysis of the thematic maps was done using post classification
visual and area comparisons and overlay operations with significance of change tested
at α=0.05 using Chi-Square test statistic. Trends in the simulated long-term daily
records of maximum and minimum air temperature, rainfall and river discharge from
global weather geoportal were analyzed by use of Mann-Kendall test statistic and
Student t statistic, testing level of significance at α =0.05. The study analyzed the past
land cover, land use and climate scenarios and modelled future variations with respect
to the Mara hydrological regimes (flow volumes). SWAT hydrological model was to
simulate the land cover/use and climate scenarios and the river discharge. The simulated
data from global weather databases used in the simulation exercise because of lack of
complete and consistent hydro-climatic data in the basin. The simulated and observed
datasets were however, calibrated and validated for reliability and suitability of use and
gave a strong correlation, which meant that, the simulated datasets were good enough
for use in the study. The SWAT output data analyzed through the Multiple Regression
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and Correlation model. The analysis of land cover scenarios revealed significant
changes in which, forestland, shrub land and grassland are all decreasing in spatial
coverage while cropland and built-up areas are spatially increasing at accelerated rates
with wetlands, water bodies and bare land not having definite trends. Thus, between
1984 and 2016, forestland, shrub land and grassland reduced by 1.37%, 6.61% and
2.99% respectively while cropland and built-up area increased by 10.22% and 0.06%
respectively. The analyses of historical data revealed that the climate of the area has
progressively become warmer and drier from the 1980s with air temperature indicating
gradual upward trends while rainfall and river flow volumes indicate a decline in their
trends. When tested at α = 0.05, however, neither the mean monthly nor annual rainfall
values recorded significant change. The rains in the Mara are bimodal with the main
rainy season experienced between March and May while the second rains come from
September to November. The study detected a shifting trend in rainfall in the basin with
the usually wet months (MAM and SON) becoming relatively dry while the dry months
(DJF and JJA) are becoming relatively wet. On the other hand, the mean monthly
maximum and minimum air temperature recorded significant increments in some
months while the mean annual values had none at α = 0.05. The trends in land cover,
land use and climate expected to continue beyond 2030 with serious impact on the Mara
water resources and therefore livelihoods and environmental services. Conservation of
this former pristine basin is a critical matter that addressed by both governments of
Kenya and Tanzania respectively. This study provides useful methods and information
that can apply broadly to inform medium and long-term planning of water resources
management not only in the Mara River Basin but also in other basins in and outside
Kenya. The results should be incorporated in the mainstream economic strategies and
implementation of the National Water Master Plan, 2030.
Publisher
University of Nairobi
Subject
Land Use and Climate ChangeRights
Attribution-NonCommercial-NoDerivs 3.0 United StatesUsage Rights
http://creativecommons.org/licenses/by-nc-nd/3.0/us/Collections
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