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Item Numerical Modeling ofSeawater Intrusion Management Measures(NII-Electronic Library Service, 200-06-30) Makokha, M.; Kobayashi, A.; Aoyama, S.Overexploitati oofn coastal aquifers has become a common issu ewith many coasta1 regions experiencing extensive seawater intmsio rnes,ulting i nsevere deteriorat ioofgnroundwater qualit yW.hen analyzing the freshwater qualit yextracted from the pumping wells in coastal aquifers, the movement of very iow concentrations of the solute is critical in analyzing the level of contamination in pumping wells, This researeh analyzes the effectiveness of four seawater control measures using a hypethetic aslteady-state salt distributi moondel in a representative cross-section perpendicul arto the coastline using a two-dimensional density-depende ntsolute transport model through homogeneous media, It is established that the shallow pumping wells are more preferabl ethan the deep pumping wells as they have relatively lower concentration value in the pumping well, Low permeable aquifers give high concentration values in thc pumping well and the extent ofseawater intrusi oins larg cthan the high perrneabl oenes. The leve lofcontamination in the pumping well is proportion atlo the extent of seawater intrusio wnedge. Pumping wells locate dfurth earway from the seashore are not affected by the presenc eof the seawater intrusio wnedge; however, this may not bc an effective method ofcontrolling seawater intrusio Dn.eep recharge wells closer to the pumping well seem to be the most effective method ofcontrolling the extent ofseawater intrusio annd the concentration value in tlie pumping well. Deep seawater pumping wells located relatively away from the pumping well could be used to cDntrol seawater intmsion if proper disposa lmethods fo rthe extracted saltwater are implemented .Low permeable barrier walls locate dcloser to the pumping well could be used, although the initi acolst of constmction may be high.Item Developments in solar drying using forced ventilation and solar regenerated desiccant materials(Elsevier, 1996) Thoruwa, T. F. N.; Smith, J. E.; Grant, A. D.; Johnstone, C. M.In many countries, grains are naturally sun dried in the field, resulting in large-scale spoilage. Purpose-built solar grain dryers are being introduced with some success, but to be effective, their performance must be carefully controlled to prevent cracking of grains, fungal growth and aflatoxin production during storage. This paper describes some of the performance aspects of an autonomous solar desiccant maize dryer developed for village use in Kenya. Since most commercial desiccants are expensive, a low cost solid desiccant was fabricated from bentonite clay and calcium chloride materials. This desiccant is capable of regeneration at 45°C, has high moisture sorption of 45% (dwb), significantly extends the drying process at night and reduces aflatoxin contamination of the grain. Laboratory and field testing took place to determine the drying performance and allow conclusions to be drawn. This showed the prototype dryer had the capability of drying 90kg of fresh maize from 38% (dwb) to 15% (dwb) within 24 hoursItem Regional Analysis of Conceptual Rainfall Runoff Models for Runoff Simulation In Ungauged Catchments: The Case Of Upper Ewaso Ngiro Drainage Basin in Kenya(Scientific & Academic Publishing, 2005) Olang, L. O.; Onyando, J. O.; Chemelil, M. C.Two rainfall - runoff models were calibrated and regionalized using data from upper Ewaso Ng'iro drainage basin in Kenya. The two models were Nash Cascade - Diskin Infiltration (NCDI) model and Nash Cascade - Green Ampt Infiltration (NCGAI) model. Both models ha ve physical and conceptual parameters. The former were derived from catchment characteristics by overlaying land cover and soil types within the framework of GIS. The latter were optimized using Schuffled Complex Evolution (SCE - UA) optimization algorithm. The conceptual parameters so determined were correlated with catchment physical parameters in a regionalisation process. This involved, in the case of suction at the wetting front and hydraulic conductivity, deriving the parameter values from soil texture. The remaining conceptual parameters were regionalised through stepwise optimization and adjustment of boundary conditions. The parameters realised were correlated with catchment characteristics through regression analysis in which values of R2 ranging fro m 0.92 to 0.99 were obtained. The regionalised models were then used to simulate runoff from the five catchments upon which satisfactory results were realisedItem Assessment of the Biological Treatability of Black Tea Processing Effluent(2007) Omosa, I.B.; Oonge, Z.N. I.The anaerobic degradability of tea beverage processing effluent was assessed using a stationary upflow anaerobic filter. The filter, with an active column of 1.2m height, inner diameter of 100 mm and filled with rock as the attachment medium was operated at room temperature ranging between 20-250C throughout the study period in both batch and continuous modes. It was seeded with an anaerobic sewage sludge inoculum from an anaerobic pond of a Municipal Sewage Treatment Plant of the City of Nairobi at Ruai. The tea beverage processing effluent obtained from factory washing after processing operations at Kambaa Tea Factory was used as substrate The start-up took over three months for the anaerobic colonies to develop and to start digesting the factory effluent. The long period was for acclimation of the organisms to the new substrate. During this period the filter was operated in a batch mode at a hydraulic retention time (HRT) of 7 days. The operation lasted for 105 days. Immediately after introduction of the black tea effluent (substrate) from Kambaa Tea Factory, the system was in a shock for 28 days. However, it recovered from the shock from day 29 and by day 105 while maintaining the HRT of 7 days a chemical oxygen demand (COD) removal efficiency of 74% was achieved. From day 106 to day 162, the filter was operated on a continuous mode at a HRT of 36 hours with the substrate being fed at an organic loading rate (OLR) of 0.67 kg COD/m3-day. A COD removal efficiency of about 90% was achieved by the end of the period. Removal of suspended solids was 100% in this operation. Removal of colour was more than 85%Item Effect of Tidal Fluctuation on Velocity Distribution in Coastal Aquifers(National Institute of Informatics, 2008) Makokha, M. O.; Kobayashi, Akira; Shigeyasu, AoyamaThe fundamental effect of the change in saltwater level on velocity distribution is important in understanding the effect of tidal fluctuation in coastal aquifers. This study applied the laboratory experiments using the image analysis method and the numerical model to study the effect of varying the saltwater level on velocity distribution in coastal aquifers. It was established that the change in saltwater level affected the velocity distribution, such that; the velocity at the interface was more than twice the one in freshwater. In addition the tracer in the freshwater zone moved to the intersection between the saltwater level and the coastal slope while the tracer in the saltwater zone went along to the shape of the interface. The numerical model revealed that the drastic high velocities at the interface were due to the great buoyancy effects resulting from the varying fluid density between the saltwater and freshwater in the transition zone. The velocity in the freshwater zone was proportional to the global hydraulic gradient while in the saltwater zone, the velocity was inversely proportional to the global hydraulic gradient. Therefore the changes in saltwater level influence velocity distribution in coastal aquifers.Item Integrating MDGs in the Formulation of Strategies for Solid Waste Management – A Life Cycle Approach(UNESCO, 2008) Mwai, Marclus; Siebel, Maarten A.; Susanne, Rotter; Piet, LensThe state of solid wastes in most of the developing countries is a major threat to both human and environmental resources. One of the reasons why there is little progress being made is a lack of clear objectives, coupled with a lack of information and of a strong analytical base in which various policies and strategies can be formulated or aligned during the decision making processes. This study, a case study for Nairobi, Kenya aimed at bridging this gap by providing a methodological approach in which Millennium Development Goals (MDGs) can be aligned with SWM strategies. Performance indicators were used to relate SWM to MDGs and to compile impacts data of the ten identified SWM options. The Baseline showed a low contribution towards achievement of MDGs while Option 10 (17% recycling, 63% composting and 20% landfilling) showed the highest contribution. Option 5 (15% recycling, 15% composting and 70% landfilling) provided the most feasible approach for meeting the MDGs, given the present social-economic, legal, political and administrative conditions of the study area.Item Automated Extraction of Morphologic and Hydrologic Properties for River Njoro Catchment in Eastern Mau, Kenya(AGSE Publishing, 2008) Olang, L. O.; Kundu, P.M.During the past decade digital collection of geodata has become a common subject for the public. Due to the free availability of the GPS signal with selected availability off since May 2000, everybody on Earth is able to determine the actual geo-position within an accuracy radius of about ten meters. GPS is under revision and the new generation of satellites is currently installed in the orbit. This will provide a higher reliability and more precise position accuracy. In addition new and competitive global positioning systems have and will become available, e.g. the Chinese COMPASS, Russian GLONASS and finally the European GALILEO. The next decade will bring a series of new receivers and those will make advantage of all available GPS signal in combination. The public, professional geodetic services and especially the mapping community will truly benefit from these developments and open map services like Open Street Map (OSM) will provide increased geo-precision. Optical satellite remote sensing images are another important source for the acquisition of geoinformation. For the mapping of urban objects, a fine spatial resolution is necessary providing enough detail for reliable object recognition. A series of new spaceborne sensors have been launched recently, those collect image data with a spatial resolution up to 0.41 m in the panchromatic (pan) band. This spatial resolution can be compared with the detail-accuracy offered by classical aerial photos. However, some more advanced features are pushing the satellite images in the first position compared to aerials: spectral bands are not limited to three colors only, the radiometric capabilities exceed the image quality of aerial by far and finally the revisit period of these satellite sensors is in the range of about three days. [The price of the satellite images (per area unit) might be reduced compared to aerials but it will not be considered here.] Having all these criteria in mind we can state that a new generation of remote sensing information source has become available, a true substitute for the classical aerial photos. These two substantial new developments, combined GPS signals, 2nd generation, and super high resolution satellite remote sensing, will facilitate the precise mapping of urban areas substantially. On the one hand unplanned urban settlement regions with a highly diverse, inhomogeneous structure are difficult to survey, on the other hand especially these region need to be mapped first, because an infrastructure network has to be established. Infrastructure in these cases means: freshwater supply and wastewater drainage, electricity grid and a telecommunication network. The Kibera informal settlement in Nairobi, Kenia, is one of the rapidly changing suburban regions with a highly diverse, unmanaged -and in some areas unknown- structure. “Map Kibera” is the name of a mapping project especially for this slum, and Map Kibera may definitely benefit from the new developments of geodata acquisition..Item Hydrochemistry and source of high fluoride in groundwater of the Nairobi area, Kenya(Taylor & Francis, 2008) Marleen, Coetsiers; Kilonzo, Fidelis; Kristine, WalraevensThis study aims to identify the hydrogeochemical processes influencing the high fluoride concentrations in groundwater of the Nairobi area, Kenya. For this purpose 16 groundwater samples were collected and analysed. Fluoride concentrations above the WHO standard are found in the downstream areas. The high F- concentrations are correlated with high sodium and pH and low Ca2+ concentrations. Weathering of sodium-rich alkaline igneous rocks causes a pH increase resulting in an increase in HCO3- and CO32- by dissolution of CO2. Groundwater becomes oversaturated compared to calcite and calcite precipitation occurs, leading to a decrease in Ca2+. This causes a sub-saturation with respect to fluorite and dissolution of fluorite increases the F- concentration. These reactions were modelled using the PHREEQC model and the results showed a good agreement with the measured groundwater quality, indicating that the proposed reactions are plausible for explaining the observed concentrations in groundwater.Item Performance study of a consolidated manganese chloride-expanded graphite compound for sorption deep freezing processes(2009) Kiplagat, J.K.; Li, T.X.; Wang, R.Z.; Wang, L.W.A consolidated composite sorbent made from manganese chloride and expanded graphite was produced for sorption deep-freezing processes and used for cold production at a temperature as low as −35 °C. Experimental results showed that the addition of a porous graphite matrix can prevent the agglomeration and the attenuation of sorption capacity of reactive salt. The composite sorbent could incorporate 0.537 kg of ammonia per kg of reactive salt and the average specific cooling power (SCP) obtained varied between 200 W kg−1 and 700 W kg−1 when the evaporation temperature ranged from −35 °C to 0 °C. The analysis of the data suggested that the heat transfer characteristic in the composite sorbent was strongly influenced by chemical reaction and the conversion rate was very sensitive to the constraint temperatures. The SCP and coefficient of performance (COP) of a simple sorption deep-freezing system were 350 W kg−1 and 0.34, respectively, at the generation temperature of 180 °C, the heat sink temperature of 25 °C and the evaporation temperature of −30 °C.Item Security of Internet Transactions(Springer, 2009) Musau, F.; Ren, S.; Yu, ShouyiState-of-the-art IT facilities are ever more frequently applied in all areas of life. Nowadays, Internet connection, online resources and services are taken for granted. It is much quicker (almost immediate) and more convenient to access electronic information and use online services than to employ traditional methods. Therefore, more and more people take advantage of these options. Aware of the benefits, they often forget about network threats (that arise from inappropriate software protection and failure to follow necessary security rules) or simply underestimate them. This chapter deals with threats to Internet transactions with particular emphasis on new ways of obtaining information and data under false pretences and threats to services rendered in wireless networks.Item A combined doubleway chemisorption refrigeration cycle based on adsorption and resorption processes(2009) Kiplagat, J.K.; Li, T.X.; Wang, R.Z.; Wang, L.W.; Oliveira, R.G.An innovative combined double-way chemisorption refrigeration cycle based on adsorption and resorption processes is presented. Two different reactive salts were used as sorbents and ammonia was utilized as the refrigerant in the proposed cycle. The useful cold was obtained from the evaporation heat of the refrigerant during the adsorption process and from the reaction heat of the low-temperature salt during the resorption process. The proposed combined double-way cycle has a distinct advantage of higher coefficient of performance (COP) in comparison with conventional adsorption cycle or resorption cycle. Experimental verification indicated that the advanced combined double-way cycle is feasible for refrigeration application, and the ideal COP of the basic cycle was about 1.24. Theoretical results showed that the proposed combined double-way cycle could improve COP by 167% and 60% when compared with conventional adsorption cycle and resorption cycle, respectively.Item Thermodynamic study of a combined double-way solid–gas thermochemical sorption refrigeration cycle(2009) Kiplagat, J.K.; Li, T.X.; Wang, R.Z.; Wang, L.W.; Oliveira, R.G.A combined double-way thermochemical sorption refrigeration thermodynamic cycle was proposed and tested. Both adsorption refrigeration and resorption refrigeration processes were combined in order to improve the system performance. Two different consolidated composite materials were used as the reactive sorbents and ammonia was used as the refrigerant. Experimental results showed that a system operating with such proposed cycle can have two useful cold productions during one cycle at the expense of only one heat input at high temperature. The average specific cooling power (SCP) during the adsorption refrigeration phase was 301 W kg−1. Analysis of the experimental data showed that the driving equilibrium drop during the resorption process was much lower than that during the adsorption process, when the cold production temperature was similar. The proposed combined double-way sorption cycle has a larger cooling capacity per unit of heat input and the maximum theoretical coefficient of performance (COP) is 1.24 when MnCl2 and BaCl2 are used as the reactive sorbents.Item Performance of a 2-Element Plane Reflector Augmented Galvanized Pipe Flat Plate Collector for Solar Water Pasteurization(2009) Ako, E.O.; Thoruwa, T. F. N.; Maingi, S. M.; Njagi, E.N.M.About 80% of all infectious diseases including diarrhoea, typhoid, and cholera in developing countries are transmitted through consumption of contaminated water. This study reports on the concept of heating water using low cost solar thermal energy systems to kill disease-causing microorganisms and gives the design philosophy, construction and measured thermal performances of a 2-element plane reflector augmented flat plate solar collector. A solar water pasteurization system was designed and constructed using locally available materials for direct water heating using solar energy in a flow-through system made of copper pipes. Standard car radiator thermostat valve was used to regulate pasteurization temperature at 82°C. The results demonstrated that solar heating of contaminated water could be achieved through a 2 m2 flat plate collector with mounted with a 2-element plane mirror reflector with an aperture area of 4 m2. The experimental collector was constructed with 20 mm diameter galvanized pipe fixed onto mild steel absorber plate. The collector without reflectors was used as control experiment. Under fair weather conditions, it was observed that the use of mirrors tremendously improved the performance of the collector by up to 94% producing 49-95 L of pasteurized water using the galvanized pipe collector. The microbiology water quality tests using presumptive test for total coliform and confirmed by Eijkman test showed no presence of E. coli in the solar pasteurized water samples. On the basis of the results, it was concluded that the solar water pasteurization system developed provides a cheaper alternative for water disinfection in Kenya and other sunny countries.Item Analysis of Land Cover Change Impact on Flood Events using Remote Sensing, GIS and Hydrological Models: A Case Study of the Nyando River Basin in Kenya(2009) Olang, L. O.In this study, land cover changes in the Nyando River basin (3500 km2) of Kenya were analyzed and their impact of floods quantified. Three Landsat satellite images for 1973, 1986 and 2000 were acquired, processed and classified based on seven major land cover classes prevalent in the basin using a hybrid of supervised and non supervised classification procedures. The detected land cover changes, together with a DEM and a soil map of the basin, were then used to estimate physically based parameters for the selected hydrological models. The models were then used to estimate local and flood peak discharges and volumes arising from selected storm events for each state of the classified land cover dataset. To further understand how changes in the land cover may impact on the flood hydrology, three scenarios that represent quite extreme alternatives were formulated to study the possible bandwidth during floods. Land cover classification results revealed immense land degradation over the span of study. Forests reduced by an area of 488 km2 representing a 20% decline, while agricultural fields expanded by 581 km2 representing a 16% increase over the same period of time (1973-2000). Hydrological modeling results indicated that the basin underwent significant increase in the peak discharge value. The flood peak discharges in the whole basin were noted to have increased by at least 16% over the period of 1973 -2000.Flood volumes were also noted to have increased by at least 10% over the same period of time. (author)Item Performance of a 2-Element Plane Reflector Augmented Galvanised Pipe Flat Plate Collector for Solar Water Pasteurisation(Medwell Online, 2009) Maingi, S. M.; Onyango, E.A.; Thoruwa, T.F.N.; Njagi, E.N.M.About 80% of all infectious diseases including diarrhoea, typhoid, cholera in developing countries are transmitted through consumption of contaminated water. This study reports on the concept of heating water using low cost solar thermal energy systems to kill disease-causing microorganisms and gives the design philosophy, construction and measured thermal performances of a 2-element plane reflector augmented flat plate solar collector. A solar water pasteurization system was designed and constructed using locally available materials for direct water heating using solar energy in a flow-through system made of copper pipes. Standard car radiator thermostat valve was used to regulate pasteurization temperature at 82°C. The results demonstrated that solar heating of contaminated water could be achieved through a 2 m2 flat plate collector with mounted with a 2-element plane mirror reflector with an aperture area of 4 m2. The experimental collector was constructed with 20 mm diameter galvanized pipe fixed onto mild steel absorber plate. The collector without reflectors was used as control experiment. Under fair weather conditions, it was observed that the use of mirrors tremendously improved the performance of the collector by up to 94% producing 49-95 L of pasteurized water using the galvanized pipe collector. The microbiology water quality tests using presumptive test for total coliform and confirmed by Eijkman test showed no presence of E. coli in the solar pasteurized water samples. On the basis of the results, it was concluded that the solar water pasteurization system developed provides a cheaper alternative for water disinfection in Kenya and other sunny countries.Item Novel Composite Sorbent for Resorption Systems and for Chemisorption Air Conditioners Driven by Low Generation Emperature(Elsevier, 2009-12-31) Kiplagat, J.K.; Oliveira, R.G.; Wang, R.Z.; Wang, C.Y.The utilization of a composite sorbent (NaBr and expanded graphite) in chemisorption air conditioning systems driven by low-grade heat source, and in resorption systems with simultaneous heating and cooling effects was experimentally investigated using bench-scale prototypes. The mass of ammonia desorbed and adsorbed was measured, and used to calculate the specific cooling capacity. The sorbent produced 219 kJ kg−1 of cooling at 5 °C and 510 kJ kg−1 at 15 °C, when the heat source temperature was 65 °C and the heat sink temperature was 30 °C. The air conditioning system mean specific cooling power (SCP), and mean coefficient of performance (COP) were calculated based on the desorbed and adsorbed masses, and on the variation of temperature in the reactors. For the same heat source and heat sink temperatures mentioned above, the air conditioning system had a SCP of 129 ± 7 W kg−1 and a COP of 0.46 ± 0.01, when cooling occurred at 15 °C. Regarding the utilization of the composite sorbent in resorption machines, the prototype was tested for production of cooling/heating at −5/50 °C, and at 10/70 °C. In the former condition, the COP was only 0.02, but in the latter condition, there was a tenfold increase in the COP, and the combined coefficient of performance and amplification reached 1.11, which indicates the energy saving potential of resorption systems using the studied sorbent.Item Assessment of environmental and public health hazards in wastewater used for urban agriculture in Nairobi, Kenya(Universidad Autonoma de Yucatan, 2010) Githuku, C.; Karanja, N.; Njenga, M.; Prain, G.; Kang’ethe, E.; Kironchi, G.; Kinyari, P.; Mutua, G.K.Thirty percent of residents in Nairobi practise urban agriculture (UA) with a majority of the farmers using untreated sewage to irrigate crop and fodder. Due to the environmental and health risks associated with wastewater irrigation, a study was carried out in partnership with farmers in Kibera and Maili Saba which are informal settlements along the Ngong River, a tributary of the Nairobi River Basin. Soil, water, crops and human faecal samples from the farming and non-farming households were analysed to elucidate sources, types and level of heavy metal pollutants in the wastewater and the pathogen loads in humans and vegetable crops. Heavy metal accumulation in soils collected from Kibera and Maili Saba were Cd (14.3 mg kg-1), Cr (9.7 mg kg-1) and Pb (1.7 mg kg-1) and Cd (98.7 mg kg-1), Cr (4.0 mg kg-1) and Pb (74.3 mg kg-1), respectively. This led to high phytoaccumulation of Cd, Cr and Pb in the crops that exceeded the maximum permissible limits. No parasitic eggs were detected in the vegetables but coliform count in the wastewater was 4.8 x108±2.2 x1011/100ml. Soils irrigated with this water had parasitic eggs and non-parasitic larvae counts of 54.62 and 27.5/kg respectively. Faecal coliform and parasitic eggs of common intestinal parasites increased in leafy vegetable sampled from the informal markets along the value chain.Item Lithium Chloride–Expanded Graphite Composite Sorbent for Solar Powered Ice Make(2010) Kiplagat, J.K.; Wang, R.Z.; Oliveira, R.G.; Li, T.X.Consolidated composite material made from expanded graphite (EG) powder impregnated with LiCl salt is proposed for use in solar powered adsorption ice makers. Laboratory experiments were done to test the adsorption and desorption performance of the sorbent under different temperature conditions suitable for solar energy utilization. More than 75% of the reaction between LiCl and ammonia was completed after 30 min of synthesis at evaporation temperatures of −10 and −5°C and adsorption temperature between 25 and 35°C. Under the same period, it was possible to obtain 80% conversion in the desorption phase, when the generation temperatures ranged between 75 and 80°C, and the condensation temperature varied from 25 to 35°C. The highest average specific cooling power during the synthesis phase was 117 W per kg of the block. The calculated theoretical coefficient of performance (COP) under different cycle conditions was nearly constant at 0.47. Moreover, the new composite sorbent showed higher Specific Cooling Capacity (SCC), compared to activated carbon (AC)/methanol pair. Experiments done with blocks with different proportion of EG, showed that the proportion of EG influence the cooling capacity per unit mass of salt and had almost no influence on the cooling capacity per unit mass of the block. Moreover, the reaction enthalpy (ΔH) and entropy (ΔS) were calculated from experimental data obtained experimentally, and confirmed previous reportedItem Query quality refinement in singular value decomposition to improve genetic algorithms for multimedia data retrieval(Multimedia Systems (, 2011) Mushi, Joseph Cosmas; Musau, Felix; Tan, Guan-Zheng; Cheruiyot, WilsonWith the development of internet and availability of multimedia data capturing devices, the size of Multimedia Digital Database (MDD) collection is increasing rapidly. The complex data presented by such systems do not have the total ordering property presented by the traditional data handled by Database Management Systems (DBMSs). The quality of the search experience in such systems is also normally a big challenge since users from various domains require efficient data searching, browsing and retrieval tools. This has triggered an important research topic in Multimedia information retrieval concerning efficient and effective image similarity search. Modern search algorithms are fast and effective on a wide range of problems, but on MDD with a large number of parameters and observations, manipulations of large matrices, storage and retrieval of large amounts of information may render an otherwise useful method slow or inoperable. The focus of this work is the application of image enhancement technique, using histogram equalization, to the images retrieved using singular value decomposition (SVD).SVD is a linear algebra technique used for discovering correlations within data. The approach, herein referred to as query quality refinement (QQR) technique, improves the image similarity search result, and when incorporated with genetic algorithms further optimizes the search. These beneficial applications can be extended to other different types of multimedia data in various areas such as the P2P and WiMAX networksItem Simulation of runoff process within the humid foot-slope catchments of Mt. Kenya: an assessment of two infiltration approaches for rainfall-runoff modelling(EGU General Assembly, 2011) Olang, L. O.The performance of the Diskin and Green-Ampt and the Nash cascade hydrologic models for runoff simulation were examined within the humid foot-slope sub-catchments of Mt Kenya. The major parameters of the models were treated as conceptual and derived with the help of the Schuffled Complex Evolution optimization algorithm due to their high degree of non-linearity and spatio-temporal variability. The relevant catchment based parameters were derived from spatial datasets with the help of GIS. A split-sampling procedure was used to apportion the selected observed rainfall-runoff events for calibration and validation purposes. For use in runoff generation and transformation, the models were combined into Nash-Cascade Green-Ampt and Nash-Cascade Diskin, and subsequently used to replicate the response of five upstream sub-catchments (6-26 km2) of the basin. Furthermore, a local regional analysis involving relating conceptual and physically based model parameters using transfer functions was also tested for the Nash-Cascade Diskin to enable extended use in the ungauged catchments of the same basin. From the results obtained, the Nash-Cascade Green-Ampt model generally produced better results for shorter runoff events predominant in the lower parts of the regions. The Nash-Cascade Diskin model provided better estimates for runoff events with longer durations. The model was also noted to be more dependable for higher intensity rainfall events. From the regional analysis, sufficiently reliable transfer functions were successfully developed. However, the regional efficiency was noted to diminish with the increasing number of conceptual parameters to be regionalized. Generally, both models demonstrated adequate dependability for use in extended hydrological predictions.