Browsing by Author "Raude, James M."

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Analysis of spatial and temporal drought variability in a tropical river basin using palmer drought severity index (PDSI)
(Academic Journals, 2017-08-31) Wambua, Raphael M.; Mutua, Benedict M.; Raude, James M.
Analysis of spatial and temporal drought variability in the upper Tana River basin using Palmer Drought Severity Index (PDSI) was conducted. The drought is critical for formulation of mitigation measures in the river basin. A monthly temporal and 90-m spatial resolution was applied. This was achieved within ArcGIS environment. Climatic data for 1970 to 2010 was used for computation of the PDSI while the missing data sets were filled using Artificial Neural Networks (ANNs). The results of PDSI for dry and wet seasons at meteorological stations indicate that the time series plots for the PDSI values for dry season are generally lower than those for the wet seasons. The PDSI values for meteorological stations located at the lower elevation of the basin are lower than those located at higher elevation. On the other hand, spatially distributed drought severity based on PDSI show that the ranges of maximum and minimum drought severity values in 1970 are -0.868 to -0.804 and -0.675 to -0.610 respectively. These values of drought severity occur respectively in the north-western and south-eastern areas of the basin. PDSI values increased from the range -0.675 to -0.610 in 1970 and from -1.087 to 0.957 in 2010 for the north-eastern areas of the upper basin. The south eastern areas of the basin are more prone to drought risks than north-western parts. Use of the PDSI reflects the spatial heterogeneity and temporal variability of drought across the basin. The drought assessment offer technical approach for comprehensive understanding of drought for effective drought-induced disaster mitigation and its management, with a view to reducing adverse effects on livelihoods.
Bathymetric survey of lake Naivasha and its satellite lake Oloiden in Kenya; using acoustic profiling system
(wileyonlinelibrary.com/journal/lre, 2018-10-23) Raude, James M.; Maina, Caroline W.; Sang, Joseph K.; Mutua, Benedict M.
Lakes and reservoirs play important roles as freshwater sources for domestic, indus-trial, agricultural, fisheries and recreational purposes. However, for the lakes to be sustainably exploited, there is need to understand their bathymetric characteristics by conducting bathymetric surveys. This aids in generating information that can guide lakes stakeholders and managers in establishing the volume of available water. It is recommended, therefore, that bathymetric surveys be conducted at ten-year intervals. Such continuous bathymetric information is lacking in many lakes, espe-cially in developing countries. One example is Lake Naivasha in Kenya, which is largely exploited for various socio-economic purposes. Despite its importance, its most recent published bathymetric data were collected in 1991. The goal of the pre-sent study, therefore, was to conduct a bathymetric survey of Lake Naivasha and its satellite Lake Oloiden, using an Acoustic Profiling System (APS) to generate Depth–Area–Volume relationships for the lakes. The survey results indicate the in the year 2016 mean depth, volume and surface area of the lake were 4.68 m, 722 × 106 m3and 154.17 × 106 m2, respectively. Because of limited information from the 1991 sur-vey, the 2016 survey results were comparable with those of 1983. The difference in the lakes mean, and maximum depth for the 1983 and 2016 survey was less by 0.23 and 2 m, respectively. This could be an indicator the lake is being affected by anthro-pogenic activities or environmental changes. The established Depth–Area–Volume relationships are crucial since they provide invaluable information to lake and water resources managers for making informed decisions regarding management of the lake’s water resources.
Characterization of greywater from urban and peri-urban areas of Nakuru municipality, Kenya
(Loughborough University, 2009) Raude, James M.; Mutua, Benedict M.; Chemelil, Mathew C.; Sleytr, Kirsten
Kenya faces serious challenges regarding water and sanitation services. Despite many years of government investment, existing facilities continue to deteriorate and have also failed to meet the demand of increasing population. These challenges are particularly severe in rapidly growing settlements of urban poor. One such settlement is Nakuru municipality which has an average annual population growth of about 8%. The municipality’s sewerage connection is inadequate (11% coverage) and only serves middle and high income areas. This study used a semi-structured questionnaire aiming at characterizing and determining the composition of greywater, besides identifying existing water supply and lifestyle characteristics. The total suspended solids range in greywater was 200-3500 mg/l and faecal coliform (FC) count 105 -106 100mL-1. High values of FC concentration in greywater can be associated with life style characteristics and the settlement patterns. These results were used to develop site specific greywater treatment systems ideal for peri-urban areas.
Detection of spatial, temporal and trend of meteorological drought using standardized precipitation index (spi) and effective drought index (edi) in the upper Tana river basin.
(Scientific Research Publishing, 2018-07-17) Raude, James M.; Wambua, Raphael M.; Mutua, Benedict M.
Drought events across the world are increasingly becoming a critical problem owing to its negative effects on water resources. There is need to understand on-site drought characteristics for the purpose of planning mitigation measures. In this paper, meteorological drought episodes on spatial, temporal and trend domains were detected using Standardized Precipitation Index (SPI) and Effective Drought Index (EDI) in the upper Tana River basin. 41 years (1980-2016) monthly precipitation data from eight meteorological stations were used in the study. The SPI and EDI were used for reconstruction of the drought events and used to characterize the spatial, temporal and trend distribution of drought occurrence. Drought frequency was estimated as the ratio of a defined severity to its total number of events. The change in drought events was detected using a non-parametric man-Kendall trend test. The main drought conditions detected by SPI and EDI are severe drought, moderate drought, near normal, moderate wet, very wet and extremely wet conditions. From the results the average drought frequency between 1970 and 2010 for the south-eastern and north-western areas ranged from 12.16 to 14.93 and 3.82 to 6.63 percent respectively. The Mann-Kendall trend test show that drought trend increased in the south-eastern parts of the basin at 90% and 95% significant levels. However, there was no significant trend that was detected in the North-western areas. This is an indication that the south-eastern parts are more drought-prone areas compared to the North-western areas of the upper Tana River basin. Both the SPI and the EDI were effective in detecting the on-set of drought, description of the temporal variability, severity and spatial extent across the basin. It is recommended that the findings be adopted for decision making for drought-early warning systems in the river basin.
Determination of discrete particles optimum design parameters for surface irrigation system settling basin
(2018-06-05) Namu, Patrick n.; Raude, James M.; Mutua, Benedict M.; Wambua, Raphael M.
Irrigated agriculture is faced with challenges that include sediment loading in the river basins and dams. The management of sediments in river basins and waterways has been an important issue for water managers throughout history. Water managers are faced with similar challenges caused by siltation of water reservoirs and irrigation water conveyance systems. As a copping strategy to counter the low irrigation application efficiency for surface irrigation systems, designs of settling tanks are typically oversized with an aim of having enough detention time for the sediment particles to settle. To settle discrete particles an optimum settling tank is important so as not to have problems over overdesigning and consequently costly projects. The optimum hydraulic design parameters for a settling basin were calibrated using a physical model prepared in the Civil Engineering laboratory at Jomo Kenyatta University of Agriculture and Technology. Using a dataset from a model a quartic equation 1.5844 42.341 385.56 1350.8 1188.8 4 3 2 T   x  x  x  x  was developed to calculate turbidity drop in a small-scale settling basin when the flow rate is known. Finally, a quadratic equation 0.0906 1.0975 5.7338 2 Y  X  X  was developed for calculating optimum surface area required for settling discrete particles for different flow rates. For this research the optimum design surface areas were Q1 = 2.42m2 , Q2 = 3.04 m2 , Q3 = 3.75 m2 , Q4 = 4.20 m2 and Q5 = 4.71 m2 corresponding to 5.7, 8.7l/min, 9.9 l/min, 10.5 l/min and 11.1 l/min respectively.
Drought forecasting under climate change scenarios using artificial neural networks for sustainable water resources management in upper Tana river basin, Kenya
(Elsevier, 2018-07-10) Mutua, Benedict M.; Wambua, Raphael M.; Raude, James M.
Climate change has continued to impact negatively on water resources globally. For instance, extreme weather conditions especially the drought phenomena have become frequent in Africa. This has prompted water engineers and hydrologists to formulate mitigation and adaptation measures to address these challenges. The frequency of drought event of a defined severity for a defined return period is fundamental in planning, designing, operating and managing water resources systems within a basin. This paper presents an analysis of the hydrological drought frequency for the upper Tana River basin in Kenya using the absolute Stream flow Drought Index (SDI) and modified Gumbel technique. The study used a 41-year (1970-2010) stream flow data and forecasted hydrological droughts for 2, 5, 10, 20, 50, 100, 200, 500 and 1000-year return periods in relation to the selected stream flows. The results provide an overview of drought trends within the river basin and therefore would be very useful in applying drought adaptation policies by water resource managers.
Drought forecasting using indices and artificial neural networks for upper Tana river basin, Kenya-a review concept
(OMICS Publishing Group, 2014-01-01) Wambua, Raphael M.; Mutua, Benedict M.; Raude, James M.
Due to increased impact of drought on water availability at different scales there is need to understand droughts especially in upper Tana River basin which is a critical and largest water system in Kenya. There is need to correlate trends of drought as influenced by the climate variability of the present times. Drought frequency, duration and intensity in the basin have been increasing. The influencing hydro-meteorological parameters and their interaction are necessary in developing measures for mitigating impacts of droughts. It is important to have a timely review of drought definitions and fundamental concepts of droughts, classification of droughts, types of drought indices, historical droughts and artificial neural networks with special focus of Kenyan a basin. Out of the review, this paper draws conclusions where gaps for more focused research especially for a typical river basin in Kenya exist. By developing effective.
Hydrological drought frequency estimation using stream flow drought index and modified gumbel method in upper Tana river basin
(Radiance Research Academy, 2015-11-15) Wambua, Raphael M.; Mutua, Benedict M.; Raude, James M.
Objective: To estimate the hydrological drought frequency for upper Tana River basin in Kenya using absolute Stream flow Drought Index (SDI) and modified Gumbel technique. The frequency of drought event of a defined severity for a defined return period is fundamental in planning, designing and operation of water storage systems in the basin. Materials and Methods: Based on a 41-year (1970-2010) stream flow data, hydrological droughts of 2, 5, 10, 20, 50, 100, 200, 500 and 1000-year return periods are evaluated based on the stream flows, Stream flow Drought Index (SDI) and a simplified mathematical model for hydrological drought estimation which is formulated using Gumbel’s technique. Results: The absolute SDI increases while the magnitude of the stream flow decreases with return period. The minimum and maximum drought events were exhibited in gauge stations 4AC03 and 4CC03 with absolute SDI ranging from 0.667 to 1.265 and 1.213 to 2.42, and corresponding stream flows of 4.341 to 2.719 and 18.246 to 1.021m3 /s for a 2 and 1000-year return period respectively. Conclusion: A simplified mathematical model for estimating hydrological drought event that uses mean flows of the annual minimum and average of the first three minimum stream flows as input variables is formulated for different return periods for the river basin.
A review for hydraulic analysis of irrigation canals using HEC-RAS model: a case study of Mwea irrigation scheme, Kenya
(Science Publishing Group, 2014-12-19) Serede, Imbenzi J.; Mutua, Benedict M.; Raude, James M.
Hydraulic simulation models could be suitable tools for understanding the hydraulic characteristics of irrigation systems. In this study HEC-RAS model will be tested in terms of error estimation and used to determine canal capacity potential. Thiba main canal reach in Mwea Irrigation Scheme (MIS), approximately 100 Kilometers North East of Nairobi City was selected. MIS being a model scheme in the country, its contribution to food security and growth of the sector is inherent. Sluice gates and trapezoidal canals are amongst the structures in the Thiba main canal reach system. HEC-RAS model will be calibrated and validated using two sets of observed discharges, gate openings and water levels. Due to its minimal estimation errors, HEC-RAS model would be appropriate in evaluation of canal hydraulics steady state conditions to improve on scheme performance.
Simulation of the hydraulics and treatment performance of horizontal subsurface flow constructed wetland treating greywater
(Science Publishing Group, 2018-05-10) Raude, James M.; Mutua, Benedict M.; Kamau, David Ngugi
Constructed wetlands (CWs) have evolved as some of reliable wastewater treatment technologies. Various types of CWs differ in their main design characteristics and in processes responsible for pollutant removal. Classification of CWS is based on the type of vegetation used and hydrological parameters involved and can thus be classified as free water surface or subsurface flow systems. Further, subsurface flow systems can be classified according to flow direction as vertical or horizontal. This study considers horizontal subsurface flow constructed wetlands (HSFCWs) which introduces the mechanistic, dynamic compartmental model-Constructed Wetlands 2D (CW2D). The model has successfully been utilized to evaluate the performance of vertical flow constructed wetlands and is being tested on HFCWs. An outdoor pilot scale HSFCW system was established in Nakuru, Kenya. CW2D was calibrated, validated and used to simulate hydraulic performance of HSFCW system. The model was used in predicting effluent concentrations of the main greywater pollutants. In general, the results obtained showed a good match with the measured data. CW2D is an effective tool for evaluating the performance of CWs and can provide insights in treatment problems at an existing CW. The same methodology can be used to optimize existing systems.
Stochastic drought forecasting exploration for water resources management in the upper Tana river basin, Kenya
(IGI Global, 2016) Wambua, Raphael M.; Mutua, Benedict M.; Raude, James M.
This chapter presents the trend of drought as a stochastic natural disaster influenced by the climate variability for the upper Tana River basin in Kenya. Drought frequency, duration and intensity in the upper Tana River basin have been increasing over the years. To develop measures for mitigating impacts of drought, the influencing hydro-meteorological parameters and their interaction are necessary. Drought definitions, fundamental concepts of droughts, classification of droughts, types of drought indices, historical droughts and application of artificial neural networks in analyzing impacts of drought on water resources with special focus on a Kenyan river basin is presented. Gaps for more focused research are identified. Although drought forecasting is very vital in managing key sectors such as water, agriculture and hydro-power generation, drought forecasting techniques in Kenya are limited. There is need therefore to develop an effective drought forecasting tool for on-set detection, classification and drought forecasting. The forecasting is necessary for decision making on matters of drought preparedness and proper water resources planning and management.