RP-Department of Water and Environmental Engineering
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Item Analysis of Rainfall Trends and Periodicity in Ruiru Location, Kenya(The International Journal of Scientific and Research Publication (IJSRP), 2017) Nyakundi, R; Mwangi, J; Makokha, M; Obiero, C- Climate change is a serious issue in the world today with extreme weather conditions being experienced globally as characterised by devastating floods and prolonged droughts. This has often led to destruction of property and loss of life. These conditions are viewed as disasters requiring mitigation. Ruiru location being a peri-urban area has a lot of farming taking place and increased population due to settlement. This has increased the demand for water as stream flow is decreasing and boreholes are drying, with water scarcity prominent during droughts. Moreover during floods there is high surface runoff in the paved areas. The study sought to determine rainfall trends across the year for 31 years if any in Ruiru location. Monthly rainfall data for 31 years (1984-2014) obtained from four stations located within the location; Ting’ang’a, Ruiru mills, coffee research foundation and Doondu were used. Graphs were constructed to show trends within months and years and statistical significance of the observed trends tested using a linear regression model. Statistical analysis using Mann- Kendall, Spearman’s Rho, Linear Regression and Student’s t was employed to determine the significant difference among the four stations. High annual mean rainfall of 170mm and low annual mean rainfall of 37 mm were observed. Mann- Kendall, Spearman’s Rho, Linear Regression and Student’s t showed no significant difference of rainfall means between Ting’ang’a and Ruiru Mills stations, while the other stations were statistically insignificant. Linear regression models showed an upward trend which was statistically insignificant in all the four stations. There was no significant trend across the year for the past 31 years. The research findings will help in prediction of the occurrence of high and low rainfall amounts for proper planning and water resources management.Item Adsorption of Hexavalent Chromium from Aqueous Solution by Pumice: Equilibrium and Kinetic Study(SRI, 2022) Muriuki, Cecilia W.; Mutwiwa, Urbanus N.; Home, Patrick G.; Kilonzo, Fidelis N.—Chromium released into the environment primarily as a result of industrial activity such as leather and electroplating manufacturing process. This heavy metal has caused serious contaminations of water and soils with significant environmental and occupational concerns. Conventional methods of chromium removal are expensive especially for developing countries. This study investigates the use of pumice as a low cost and biosorbent material. Sorption of hexavalent Chromium (Cr (VI) onto pumice were carried out in batch at room temperatures, with parameters of initial chromium concentrations, and contact time being investigated. Removal of hexavalent chromium increased by increasing contact time, and reduced with increasing initial chromium concentration. Kinetic studies were conducted using the Pseudo-first-order and Pseudo-second- order models, while equilibrium data were fitted using Langmuir and Freundlich isotherm models. Fittings of obtained data onto kinetic models show that the pseudo-second –order kinetic model (R2=0.999) best describes the kinetic sorption of chromium ions onto pumice. Results also showed that Langmuir (R2=0.999) and Freundlich (R2=0.999) model agrees very well with experimental data. The RL and n values has proved the favorability of hexavalent chromium adsorption onto pumiceItem Performance of an Improved Fluidized System for Processing Green Tea(waset.org, 2016) Lang'at, Nickson Kipng'etich; Thoruwa, Thomas; Abraham, John; Wanyoko, JohnGreen tea is made from the top two leaves and buds of a shrub, Camellia sinensis, of the family Theaceae and the order Theales. The green tea leaves are picked and immediately sent to be dried or steamed to prevent fermentation. Fluid bed drying technique is a common drying method used in drying green tea because of its ease in design and construction and fluidization of fine tea particles. Major problems in this method are significant loss of chemical content of the leaf and green appearance of tea, retention of high moisture content in the leaves and bed channeling and defluidization. The energy associated with the drying technology has been shown to be a vital factor in determining the quality of green tea. As part of the implementation, prototype dryer was built that facilitated sequence of operations involving steaming, cooling, pre-drying and final drying. The major findings of the project were in terms of quality characteristics of tea leaves and energy consumption during processing. The optimal design achieved a moisture content of 4.2 ± 0.84%. With the optimum drying temperature of 100 ºC, the specific energy consumption was 1697.8 kj.Kg-1 and evaporation rate of 4.272 x 10-4 Kg.m-2.s-1. The energy consumption in a fluidized system can be further reduced by focusing on energy saving designs.Item Impact of Rainfall Variability on Groundwater Levels in Ruiru Municipality, Kenya(Taylor & Francis, 2015) Nyakundi, R.M.; Makokha, M.; Mwangi, J.K.; Obiero, C.Groundwater accounts for the largest fresh water resources in the world. However, there has been limited exploitation of this vital resource in many areas. Where groundwater resources have been utilised, they have been over-exploited, polluted, wasted and mismanaged. In Ruiru municipality, groundwater is a major component of the water supply, contributing about 70% of the water demand. Rising population numbers and industrial development have led to a high water demand, increased water scarcity and more reliance on ground water. Assessing the effect of rainfall variability on groundwater levels of boreholes in Ruiru municipality will help in assessing the sustainability of groundwater resources in the area. Groundwater levels were measured using a dipper and spatial locations of the boreholes were established and mapped using GIS. Rainfall data was collected from the Kenya Meteorological Department and the Water Resources Management Authority. The water table fluctuation method was used to estimate recharge. There was an impact of rainfall variability on groundwater levels. The results showed a decline in groundwater levels during low rainfall periods. The rainfall variability, caused by climate change, brought about prolonged droughts and low recharge in the area. Climate change should be mitigated to cap the decline in groundwater and abstraction controlled to ensure that groundwater resources are managed properly to avoid depletion.Item Assessing the Impacts of Environmental Changes on the Water Resources of the Upper Mara, Lake Victoria Basin: UNESCO-IHE PhD Thesis(CRC Press, 2014) Kilonzo, FidelisGrowing population and unregulated access to forest land have exerted high pressure on the land and water resources of the recharge areas of the transboundary Mara river, in the Lake Victoria region leading to changes in land and water use patterns in the basin. This thesis considers the interactions among climate change and variability, water quality, land surface cover, hydrology, and human systems, including societal adaptations to changing environmental conditions. The thesis explores the interaction between trends in climatic variables and the feedback response of vegetation variables. The effect of different land cover types on water quality is addressed, and alternative methods to treat data quality for hydrological model inputs and validation are discussed. The Soil and Water Assessment Tool (SWAT) hydrological model was adapted to the tropical watershed experiencing data scarcity, and used to assess the impacts of changes to the climate, land use and management practices. Different scenarios driven by the prevailing natural trends, strategic national development and economic policies were used to asses the potential impacts of changes.Item Land Degradation of the Mau Forest Complex in Eastern Africa: A Review for Management and Restoration Planning(2011) Olang, L. O.; Kundu, Peter MusulaThe Mau Forest Complex is the largest closed-canopy montane ecosystem in Eastern Africa. It encompasses seven forest blocks within the Mau Narok, Maasai Mau, Eastern Mau, Western Mau, Southern Mau, South West Mau and Transmara regions. The area is thus the largest water tower in the region, being the main catchment area for 12 rivers draining into Lake Baringo, Lake Nakuru, Lake Turkana, Lake Natron and the Trans-boundary Lake Victoria (Kundu et al., 2008; Olang & Fürst, 2011). However, in the past three decades or so, the Mau Forest Complex (MFC) has undergone significant land use changes due to increased human population demanding land for settlement and subsistence agriculture. The encroachment has led to drastic and considerable land fragmentation, deforestation of the headwater catchments and destruction of wetlands previously existing within the fertile upstream parts. Today, the effects of the anthropogenic activities are slowly taking toll as is evident from the diminishing river discharges during periods of low flows, and deterioration of river water qualities through pollution from point and non-point sources (Kenya Forests Working Group [KFWG], 2001; Baldyga et al., 2007). Augmented by the adverse effects of climate change and variability, the dwindling land and water resources has given rise to insecurity and conflicts associated with competition for the limited resources. It is hence becoming urgently important that renewed efforts are focused on this region to avail better information for appropriate planning and decision supportItem Assessing Spatio-Temporal Land Cover Changes Within the Nyando River Basin of Kenya Using Landsat Satellite Data Aided by Community Based Mapping – A Case Study(2014-07-28) Olang, L. O.; Kundu, Peter; Bauer, Thomas; Josef, FürstSpatio-temporal land cover changes witnessed within the Nyando River Basin of Kenya were assessed in this study. The land cover changes were mapped by classifying the predominant land cover classes on selected Landsat satellite images. The accuracy of the classifications were assessed using reference datasets developed and processed in a GIS with the help ground based information obtained through participatory community based mapping techniques. The results of the analysis indicated significant deforestation in the headwaters of the basin. Obviously apparent from the land cover conversion matrices was that the majority of the forest decline was a consequence of agricultural expansion. Despite the haphazard land use patterns and uncertainties related to poor data quality for environmental change assessment, the study successfully exposed the vast degradation and hence the dire need for both sustainable landuse planning and catchment management strategies.Item Assessment of land cover changes in Lake Olbolossat region of the Central Kenyan highlands using Landsat satellite imagery(2013-04) Olang, L. O.; Muriithi, ZachariaThe region around Lake Olbolossat located in the central Kenyan highlands has witnessed significant land-use changes, which are today believed to be major cause of the dwindling Lake volumes. Very few studies have been carried out in the region due to limited observed in-situ data important for monitoring purposes. Itis thus urgent that contemporary cost effective techniques are explored to asses the space and time land cover changes with a view to provide information required for appropriate land and water resource management. In this preliminary study, the land cover changes around Lake Olbolossat region were investigated using remotely sensed data obtained from Landsat satellites. Two imageries for 1989 and 2010 when significant changes were witnessed in the area were selected for the study. The maximum-Likelihood function of the supervised classification technique was applied to classify and discern the changes. Five predominant land cover classes that included forestland, built-up area, water body, flood plain and farmland were selected for the study. From the results obtained, the area of the Lake (water body) was noted to have shrunk significantly by 68%. Farmlands in the region were noted to have increased by about 31% largely due to the favorable humid climatic conditions for commercial and subsistence agriculture. The study also revealed that built-up areas increased by about 33% consequent of the rise in the human population. The flood plain area was noted to have reduced by about 26% as most of the area were gradually been turned to farmland. The study also revealed intense deforestation in the upstream Aberdare forest, which was noted to have reduced in area by about 30% during the study period. In general, the study revealed significant land cover changes worth provoking the need for a better land-use planning system to avoid further decline and extinction of Lake Olbolossat.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 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 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 Land Degradation of the Mau Forest Complex in Eastern Africa: A Review for Management and Restoration Planning(InTech, 2011-11-04) Kundu, P. M.; Olang, L. O.The Mau Forest Complex is the largest closed-canopy montane ecosystem in Eastern Africa. It encompasses seven forest blocks within the Mau Narok, Maasai Mau, Eastern Mau, Western Mau, Southern Mau, South West Mau and Transmara regions. The area is thus the largest water tower in the region, being the main catchment area for 12 rivers draining into Lake Baringo, Lake Nakuru, Lake Turkana, Lake Natron and the Trans-boundary Lake Victoria (Kundu et al., 2008; Olang & Fürst, 2011). However, in the past three decades or so, the Mau Forest Complex (MFC) has undergone significant land use changes due to increased human population demanding land for settlement and subsistence agriculture. The encroachment has led to drastic and considerable land fragmentation, deforestation of the headwater catchments and destruction of wetlands previously existing within the fertile upstream parts. Today, the effects of the anthropogenic activities are slowly taking toll as is evident from the diminishing river discharges during periods of low flows, and deterioration of river water qualities through pollution from point and non-point sources (Kenya Forests Working Group [KFWG], 2001; Baldyga et al., 2007). Augmented by the adverse effects of climate change and variability, the dwindling land and water resources has given rise to insecurity and conflicts associated with competition for the limited resources. It is hence becoming urgently important that renewed efforts are focused on this region to avail better information for appropriate planning and decision support. Such a process will nonetheless, require an integrated characterization of the changing land and water flow regimes, and their concerned socio-economic effects on resource allocation and distribution (Krhoda, 1988; King, et al., 1999). Assessing the impacts of the environmental changes on water flow regimes generally require provision of time series meteorological, hydrological and land use datasets. However, like in a majority the developing countries, the MFC does not have good data infrastructure for monitoring purposes (Corey et al., 2007; Kundu et al., 2008). A majority of research studies in the area www.intechopen.com Environmental Monitoring 246 have relied on low resolution land cover datasets, including approximate physically-based procedures to understand the space and time surface alterations. Renewed efforts are thus underway in the MFC at present in order to avail high resolution information to be used for updating the existing databases with a view of improving future forecasts for restoration management as shown in Figure 1. Datasets from relevant research organization such as the World Agro-forestry Centre (ICRAF), Regional Centre for Mapping of Resources for Development (RCMRD), Regional Disaster Management Center of Excellence (RDMCOE) and IGAD – Climate Prediction and Application Centre (ICPAC) are hence being harmonized for use in evaluating the environmental effects of spatial changes, especially within hotspot regions of the complex. Cost effective computer-based techniques, which can efficiently analyze diverse physically-based variables are also under consideration to enhance the application of appropriate distributed-based management interventions (Kundu, 2007; Olang, 2009).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 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 Land degradation and hydrological effects in the Mau Forest Complex of Kenya.(2012-03) Olang, L. O.; Kundu, P. M.The Mau Forest Complex is the largest riverine water tower in East Africa. The area is one of the main sources of the major rivers in Kenya. However, in the recent past, the ecological sustenance of the complex has been under severe threat due to massive deforestation and human induced socio-economic activities. There is thus the urgent need for comprehensive and consistent environmental change analysis to support management. In this study, the spatio-temporal land cover changes within the Mau Complex region was assessed through consistent classification of selected multispectral Landsat satellite images. A post-classification procedure employing the maximum-likelihood classifier was employed to discern the changes, and the accuracy of the classifications assessed from ground based information integrating indigenous knowledge obtained through participatory mapping techniques. Preliminary results of the study indicate significant land degradation, especially within the Eastern part of the Mau Forest Complex. Before 1986, the dominant pre-change land cover types were about 75% of forests, 12% of woodlands and 13% of farms. By 1989, the landscape had changed tremendously to about 60 % of forest and woodland and 40 % of agriculture and built-up area. Hydrologically, these changes have not only impaired the ability of the area to cleanse runoff based processes, but also amplified soil erosion and flooding processes leading to degradation of streams, lakes and other water bodies served by the complex. From the existing signatures, the Mau Forest Complex can be classified as highly vulnerable, considering the long term consequences of the degradation on the sustainability of the existing and important water resources.Item Assessment of Land Cover Changes in Lake Olbolosat Region of the Central Kenyan Highlands using Landsat Satellite Imagery Aided by Indigenous Knowledge(SciTechnol., 2013-04-18) Muriithi, Zacharia; Ako, E. O.; Kiplagat, Jeremiah; Maingi, S. M.; Olang, L. O.The region around Lake Olbolosat in the central Kenyan highlands has witnessed significant land-use changes, which are believed to be major cause of the dwindling Lake volumes. Very few studies have been carried out in the region due to limited observed insitu data necessary for monitoring the land surface conditions. It is hence important that feasible, straightforward and cost-effective techniques are explored to asses the space and time variations with a view of providing the essential information for improved land and water management. This study investigated the land cover changes around Lake Olbolosat region using data obtained from Landsat satellite remote sensing. Five predominant land cover classes including farmland, floodplain, build-up area, forests and water body were selected for study. Two imageries for 1989 and 2010 when significant changes were witnessed in the area were subsequently selected. The Maximum-Likelihood function of the supervised classification scheme was applied to discern the space and time changes with the support of the indigenous knowledge of the area. From the results obtained, the size of Lake Olbolosat was noted to have significantly shrunk by 68% between the periods of study. Farmlands were noted to have increased by about 31% owing to the rapid rise in commercial and subsistence agriculture favored by the humid tropical climatic conditions of the highlands. The study revealed intense deforestation of the upstream area, which reduced the forested area by about 30% during the study period. The floodplains were also noted to have reduced by about 26%, with a majority of the area being gradually turned to farmland. Built-up area generally increased by about 33% consequent of the rising human population. In summary, the study revealed significant negative land cover changes in the area and hence a critical need for improved land-use planning to curtail further decline of Lake Olbolosat.Item Evaluating the welfare effects of improved wastewater treatment using a discrete choice experiment(Journal of Environmental Management, 2013-07) Ndunda, E. N.; Mungatana, E. D.This paper employs the discrete choice experiment method to estimate the benefits of improved wastewater treatment programs to mitigate the impacts of water pollution in Nairobi, Kenya. Urban and peri-urban farmers who use wastewater for irrigation from Motoine to Ngong River in Nairobi were randomly selected for the study. A random parameter logit model was used to estimate the individual level willingness to pay for the wastewater treatment before reuse in irrigation. The results show that urban and peri-urban farmers are willing to pay significant monthly municipality taxes for treatment of wastewater. We find that the quality of treated wastewater, the quantity of treated wastewater and the riverine ecosystem restoration are significant factors of preference over alternative policy designs in reduction of water pollution.Item Towards a National Policy on Wastewater Reuse in Kenya(Journal of Agriculture science and Technology, 2011) Mwangi, B. M.; Kaluli, J. W.; Githuku, C.; Home, P.Kenya is a water-scarce country with the capital city, Nairobi, receiving less than 100 l/capita/day. Potable water for irrigation and industrial use is generally unavailable, and this calls for alternative water sources. Despite use of wastewater being illegal in Kenya, it is used to irrigate over 720 ha in Nairobi. In order to justify the formulation of a national policy to support wastewater reuse, secondary data which included the authors’ previous work was reviewed. In a study done between 2006 and 2007, the levels of nitrates (100 mg/l) and TDS (630 mg/l) in the wastewater were found to be within the acceptable NEMA standards. The concentration of lead was 0.1 mg/lwhile cadmium and chromium were non-detectable. However, levels of BOD and Coliform bacteria were higher than NEMA limits. This implied that Nairobi sewage needed to be treated for the removal of BOD, turbidity and microbial contamination. In order to allow for safe use of wastewater in Kenya, there is need to formulate a national wastewater reuse policy which provides guidelines for maximum allowable levels of pesticides, herbicides, and heavy metals in wastewater reuse. Such a policy should also indicate the required water quality monitoring frequency for faecal indicators (Escherichia coli, faecal coliforms, enterococci), and suggest the maximum allowable concentration of nutrients (nitrogen and phosphorus) which may are usually abundant in wastewater. Key words: National policy, policy, wastewater, reuseItem Toward a Hydro-Economic Approach for Risk Assessment and Mitigation Planning of Water Disasters in Semi-Arid Kenya(Risk Management in Environment, Production and Economy, 2011-09) Cush, Ngonzo Luwesi; Shisanya, C.A.; Obando, Joy ApiyoThe study objectives were to: (i) assess socio-economic and environmental externalities affecting efficient use of water and land resources in farming activities at Muooni dam site; (ii) determine the extent to which land use activities affect the active water storage capacity of Muooni dam; (iii) simulate the variations of farmers‟ water demand and related operational costs resulting from rainfall fluctuation in Muooni catchment; (iv) and estimate the farmers‟ water economic order quantity and limit average cost related to their production efficiency under fluctuating rainfall regimes. To achieve these goals, the following empirical tools were used: an on-farm field survey (involving 66 farmers) and off-farm in-depth interviews (of 60 key informants). Numerical tools of data analysis comprised descriptive, non-parametric and time series statistical analyses along with operational research simulations, utilizing SPSS and MS EXCEL spreadsheets and DOVIEW logic models. The study reveals that land-use activities assessed at Muooni dam site do not have a significant impact on its soil erosion and water over-abstraction (as attested by Mann-Witney U-test and Spearman‟s rank correlation with 99.8% confidence degree). However, the siltation of the dam reservoir may explain 61% of the total variation of the dam‟s active water storage capacity decrease (as certified by Spearman‟s Rho test with 99.5% confidence degree). This is mainly explained by off-site soil erosion impacts (due to external agents like El Niño floods and droughts, heavy winds pressure, footpaths and roadside erosion, sand harvesting and deforestation) and alien trees planting adverse effects on water. Rainfall fluctuation is the main controlling factor of land-use at Muooni dam site. Also, land management is highly correlated with farmers‟ education and poverty levels. Along with farmlands sub-division, it accelerates the risk of soil erosion and water excess loss in the catchment. These in turn increase water cost (through significant shortage costs) and affect farming yields and incomes. Farmers have therefore adopted multiple cropping of about 9 perennial crops and 6 seasonal species on small farmlands as a strategy for facing poor incomes, especially during unpredictable droughts. Yet, farmers cannot meet their actual crops water requirements. The operational research simulations reveal that LSF, MSF and SSF farmers are ordering respectively 29%, 12% and 4% of their respective actual crops water requirement. An increase of about 175%, 518% and 11,437% of their actual total costs is observed respectively under ANOR, NOR and BNOR scenarios. For efficiency, LSF, MSF and SSF farmers are urged to increase their respective actual water demand by an average of 148%, 142% and 152% to meet their water EOQ. By so doing, they could expect a fall of their operational costs up to 40%, 70% and 98% under the three respective scenarios. The study recommends that they limit their current average costs increase below 100 %, if the viability of their economic activities is to improve. They have also to limit their production under a MES ranging from 68% to 98% of their average costs, especially under NOR and BNOR scenarios, while their water demand variation is limited to 129% and 972% (instead of 518% and 11,437%). The differential rate has to be compensated either by rainfall input or better by hydropolitical strategies, efficient on-farm management techniques and technological innovation. The Government of Kenya was urged to put in place policy intervention measures that back farmers‟ initiatives within a CMS of the Athi Catchment and a SCMP of Muooni Sub-Catchment.