| dc.description.abstract | Anthropogenic activities reduce availability of water resources by nature of,use, which alter flow
regimes within surface water systems. In Sosiani catchment, information. on impact of the
abstraction on river flow, security of supply and reserve flow enforcement at a hydrologically
. daily timescale is scanty. However, water allocation hence abstraction continues to be carried out
albeit without adequate knowledge of the spatio-temporal availability status of the resource in
the catchment. This study evaluated the potential effects of surface water abstraction on flow
regimes by comparing abstraction to streamflow on a daily basis in Sosiani catchment. The study
aimed to simulate abstractions for water allocation planning in Sosiani catchment. Specific
objectives of the study were to determine the water balance for Sosiani catchment in Nzoia River
basin; simulate water abstraction in Sosiani catchment based on current water uses and to
examine various water abstraction scenarios for effective water allocation and planning. A mix
of empirical cross-sectional descriptive, experimental and evaluation research designs were
adopted in the study. Purposive survey sampling technique was employed targeting all 124
surface water abstractors. A structured questionnaire was administered to abstractors to gather
qualitative and quantitative primary data on water abstraction in the catchment. Hydrological and
meteorological data was obtained from WRA and KMD respectively. HEC HMS SMA model
was used to analyze water balance in Ellegirini, Endoroto and Sosiani Kapsaos sub-catchments
in Sosiani catchment. Modified surface water balance method was used to simulate water
abstraction while Water Evaluation and Planning System (WEAP) model was used to evaluate
various scenarios indicating future water demands based on current water allocation practice.
Falkenmark, IWMI and UN water scarcity indicators were used to assess the water stress levels.
Nash-Sutcliffe coefficient and coefficient of determination were used to assess performance of
HEC HMS model. The HEC HMS model well simulated total flow volumes as estimated residue
in percentage of total observed flow was 0.2%, 14.05% and 27% for Endoroto, Ellegirini and·
Sosiani Kapsaos sub-catchments respectively. Model validation results yielded 6% - 17% of the
simulated flows as given by residual in percentage of total observed discharge and Nash
Sachliffe that ranged from 58% to 74%. This depicted a satisfactory representation of
hydrological characteristics of Sosiani. The current water withdrawal relative to available water
is low «10%) as "depicted by 8.35%, 2.29% and 4.53% in Sosiani Kapsaos, Ellegirini and
Endoroto sub-catchments in that order. This suggests thatthe catchment is not vulnerable to water
scarcity. A projected 3.3% population growth by 2030 will increase water abstraction by 6.6%-
29.1%. By 2030, moderate water scarcity is expected in Endoroto and Sosiani Kapsaos subcatchments
while little or no scarcity of water is expected in Ellegirini sub-catchment based on
water withdrawal with respect to available water. A projected 10% increment in water
withdrawal by 2030 indicates that Sosiani Kapsaos sub-catchment will have a deficit of 6%-
103% by volume in December, January, February and March; 6%-61% deficit in November and
December in Endoroto sub-catchment while Ellegirini sub-catchment will experience no water
deficits. The available flows in Sosiani catchment can adequately meet current net water
demand/abstraction. However, enforcement of the reserve flow reduces the available flow
especially during dry seasons to cause water deficits. These results are useful for assessing
sustainability of the supply source to meet current and future water demands and for planning
and sustainable management of the resource. | en_US |
