Browsing by Author "Otieno, Hesbon"

Now showing 1 - 4 of 4
  • Publication
    Publication
    Estimation of direct runoff and sediment yield in an AgNPS-GIS link: Case of river Njoro catchment in Kenya
    (LAP LAMBERT Academic Publishing, 2013-01-01) Otieno, Hesbon
    Most catchments in the developing world are ungauged due to the high cost of instrumentation involved and are therefore not monitored. However, lack of data from these catchments can not be an excuse for lack of proper management and hence data from these catchments is still needed for their management as well as design of structures in these areas. This book illustrates how direct runoff and sediment yield can be estimated in an AgNPS model-GIS link. A case study of the river Njoro catchment in Kenya is used and the results show a possibility of using the method in cases where in-situ measurements are lacking, so long as the model input parameters are accurately determined. Professionals in hydrology, environment and engineering fields or anyone else who may be involved in hydrological modelling will find this book useful.
  • Publication
    Publication
    Influence of Sub Basins with Dominant Land Covers on Spatial and Temporal Variations of Water Balance Components in the Sondu Miriu River Basin, Kenya
    (International Journal of Science and Research, 2022-09-09) Koech, Nancy C; Kitheka, Johnson U; Otieno, Hesbon
    Understanding the dynamics of the land cover changes and behaviour of hydrological processes in the river basin is important in the sustainable management of water resources. However, there is limitation of data and information on the extent to which dominant land use types particularly tea plantations, forests and mixed farming affects water balance components in tropical river basins and Kenya in particular. The main objective of this study was to determine the influence of sub basins with dominant land covers on spatial and temporal variations of water balance components. The study was undertaken in a 3,450 km2 Sondu Miriu river basin located in the western region of Kenya in the period between 1960 and 2020. Hydrological SWAT model was used to estimate the key hydrological components in the sub basins dominated by tea plantation, forest and mixed farming. These sub basins were Kipsonoi for mixed farming, Timbilil for tea plantations and Kiptiget for forest cover. Meteorological data was obtained from the Kenya Meteorological Services (KMS) and Water Resources Authority (WRA). Further, historical river discharges data was obtained from WRA and Ministry of Water, Sanitation and Irrigation. It was observed that land uses and land covers have insignificant influence on the rainfall variability in the three sub basins. Negative relation between area under forest cover and rainfall with correlation r of -0.37 was shown in the sub basin dominated by forest cover. But increase in rainfall in the sub basins led to expansion of tea plantations and mixed farming hence positive relations and reduction of forest cover. The positive relationship between evapotranspiration and mixed farming, evapotranspiration and forests cover was low ranging between correlation r of 0.05 and 0.14 while in tea plantations very low negative relation was shown. The sub basins dominated by tea plantations, forest and mixed farming shown an insignificant impact on soil moisture.
  • Publication
    Publication
    The effect of river flow and land use land cover dynamics on reservoir sedimentation in a small ASAL tropical basin in Kenya
    (IJISRT, 2023-05-23) Kasuki, M. M.; Kitheka, Johnson U.; Otieno, Hesbon
    Kalundu reservoir is one of the water reservoirs in arid and semi-arid lands in Kenya that has been experiencing periodic siltation since 1950s. Lack of data and information on the hydrological processes and land use practices has limited implementation of localized strategies to minimize sedimentation in the reservoir. The objective of this study was to determine the hydrological influences and land use practices that contributed to sedimentation of Kalundu reservoir in the period between (2000 – 2021). Hydrological datasets were acquired from three sampling stations established at different points along Kalundu River. Landsat imagery were used in the Land use and Land Cover analysis. Hydrological analysis showed that during the short rainy season, the mean river discharge ranged from 0.44- 1.00m3 /day and 0.11-0.50m3 /day during the long rains. Sediment load discharged into the reservoir was more during the short rains (134,028.84m3 )than during the long rains (28,448.87 m3 ) with a Trap Efficiency of 47.73%and 55.91%, respectively. The river discharge showed a significant relationship with TSSC (r=0.69, Pvalue=0.03), turbidity in the river (r=0.68, R2=0.45, pvalue=0.03) and sediment load (r=0.68, R2=0.46, pvalue=0.03). This results implied high sediment load is likely to be observed during high flows. From bathymetric analysis, Kalundu reservoir decreased its storage capacity by 70% from 500,000m3 in 2013 to 149,902m3 in 2021. This implied that 350,098m3 of sediments were deposited within that period at an estimated rate of 65,317 tons/yr or 2,722 tons/km2 /yr. The total surface area of the reservoir decreased by 11% from 48,500m2 in 2013 to 43,200m2 in 2021.In 2021, the mean water depth in the reservoir was 2.1m and the deepest part was 3.5m. The Useful Life Span of the dam was estimated to be about 3 years. LULC analysis showed that croplands and built-up areas increased significantly within a period 20 years (2000-2020). Bareland and abandoned croplands were attributed to soil erosion in the study area leading to sedimentation of Kalundu Dam particularly during short rainy seasons. Poor farming practices, urban land development activities, heavy infrastructural development and clearing of natural vegetation in the sub-basin were strongly attributed to the increased sedimentation of the dam in the period between (2010-2020).
  • Publication
    Publication
    The impacts of water abstraction in tropical rivers: a case of South West upper Tana basin, Kenya
    (IISTE, 2019-05-31) Mwendwa, Philip K.; Kitheka, Johnson U.; Mwangi, Moses; Otieno, Hesbon
    The study to determine the impacts of water abstraction in South West Upper Tana Basin which is part of thelarger Upper Tana basin was undertaken in four major rivers, Thika, Kimakia, Kiama and Chania. Data for thisstudy was obtained from the Kenya Meteorological department (KMD), Water Resources Management (WRA)and questionnaire surveys. The questionnaires were administered in the period between January 2018 andDecember 2018 to determine the impacts of water abstraction in both dry and wet seasons. Regression andcorrelation analysis was used to determine the nature and strength of relationships between different variables.The results of the study indicate that the main impacts of water abstraction are hydrological, environmental andsocio-economic. The hydrological impacts include reduced water levels, changes in stream morphology,decreased turbidity and reduced siltation. Socio-economic impacts include increased income from cropproduction and conflicts while environmental impacts were mainly changes in riparian vegetation. The studyestablished that the best combination of impacts of water abstraction in the South West Upper Tana Basin werechanges in water turbidity, decline in water levels, improved crop yields, changes in channel morphology andsiltation with a coefficient correlation r of 0.57 and coefficient of determination R2 of 0.52. To mitigate theseimpacts, there is a need for better enforcement of legislations on water abstraction and the monitoring of the riverbasins to curb water over-abstraction. Public awareness campaigns and involvement of stakeholders could alsominimize these impacts.