Simulation of Water Resource Use and Allocation in Nyangores Sub-Catchment of the Upper Mara Basin, Bomet County
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Date
2016-11
Authors
Omonge, Paul Omondi
Journal Title
Journal ISSN
Volume Title
Publisher
Kenyatta University
Abstract
Allocation of available water resources to various competing uses is increasingly
necessary in basins that experience water scarcity. In the Nyangores sub-catchment, there
are currently a number of water abstractors, however, no water allocation plan exists for
either the River Nyangores or the entire sub-catchment hence creating room for conflict
between upstream and downstream users during periods of water stress. The subcatchment
is significant in that it forms a part of the Mara River basin that supports the
Mara and Serengeti ecosystems, a world heritage site. The main objective of this study
was to simulate the water resource use and allocation in the sub-catchment for the
purposes of planning and management. The study was guided by three specific objectives
(i) To identify existing major water sources of the sub-catchment ii) To determine the
current demand, supply and quality of water resources in the sub-catchment (iii) Simulate
the impact of planning and management options on the future of water use and allocation
in the sub-catchment. Water use data for the year 2014 and past hydro-meteorological
data for the period 1970 - 2014 was collected from field exercises, the Water Resource
Management Authority and the Meteorological department in Nairobi. Datasets on water
sources and sinks and their attributes were collected using Geographical Positioning
System and processed in ArcGIS 10.1 software to create a spatial database. Descriptive
statistics and STATA 11 software were used to analyze water quantity and quality data.
Water Evaluation and Planning tool was then applied to investigate the hydrology of the
Nyangores River to scenarios of increased water demand. Over 90% of the upstream
springs and wells were found to be active sources supporting the rural communities. In
the downstream arid and semi-arid area, 25% of the springs are completely dry and
another 25% are seasonal in nature thereby increasing the dependency on the river
Nyangores as a major water source. In overall, the spring flow rates during the
measurement campaign lay between 0.1 - 0.25 liters/second. The results also indicate
that the Total Dissolved Solids tend to increase in downstream sources, ranging from 40
to 1150 mg/L indicating deteriorating water quality generally. This can be attributed to
accumulation of pollutants and increase in sediment load, as the river winds its way
downstream. A positive correlation of{r = 0.47) was found between discharge rate and a
change in altitude. The current annual water, demand within the sub-catchment is 27.2
million m3 of which 24% is being met through improved and protected water sources
while 76% is met through informal and unprotected sources which are inefficient to cater
for future increases in demand. Under the Reference Scenario, by the year 2030, the
WEAP Model predicted an annual total inadequate supply of 8.1 Million m3 mostly in the
dry season. The current annual unmet water demand is 1.3 million m3 and is experienced
at the Irrigation demand site; also significant in the dry seasons of December through
February. While monthly unmet domestic demand under High Population Growth was
projected to be 1.06 million m3
, by year 2030. However, with Improved Water
Conservation Scenario, total water demand is projected to reduce by 24.2% in the same
period. The results indicate a definite inadequate water supply for the sub-catchment
within the next 15 years. Catchment water conservation measures, informed water works
and collective water planning and management must therefore be undertaken by the three
county governments that share the sub-catchment to ensure sustainable water supply and
demand allocation devoid of conflict among users.
Description
A Thesis Submitted in Partial Fulfillment of the Requirements for the
Award of the Degree of Master of Environmental Science in the School
of Environmental Studies of Kenyatta University