Research Publications

2019 Publications

  1. Maina, C. W.,  Sang, J. K., Raude, J. M., Mutua, B. M., & Moriasi, D. N. (2019). Sediment distribution and accumulation in Lake Naivasha, Kenya over the past 50 years. https://doi.org/10.1111/lre.12272.
  2. Kilonzo, W.,  Home, W.,  Sang, J., & Kakoi, B. (2019). The Storage and Water Quality Characteristics of Rungiri Quarry Reservoir in Kiambu, Kenya, as a Potential Source of Urban Water. Hydrology 2019, 6(4), 93; https://doi.org/10.3390/hydrology6040093
  3. Ouedraogo, W. A. A., Gathenya, J. M., & Raude, J. M., (2019). Continuous Modeling of the Mkurumudzi River Catchment in Kenya Using the HEC-HMS Conceptual Model: Calibration, Validation, Model Performance Evaluation and Sensitivity Analysis. Hydrology 2018, 5(3), 44; https://doi.org/10.3390/hydrology5030044

  4. Ouedraogo, W. A. A., Gathenya, J. M., & Raude, J. M., (2019). Projecting Wet Season Rainfall Extremes Using Regional Climate Models Ensemble and the Advanced Delta Change Model: Impact on the Streamflow Peaks in Mkurumudzi Catchment, Kenya. Hydrology 2019, 6(3), 76; https://doi.org/10.3390/hydrology6030076

  5. Mireille, N. M., Mwangi, H. M., Mwangi, J. K., & Gathenya G. M., (2019). Analysis of Land Use Change and Its Impact on the Hydrology of Kakia and Esamburmbur Sub-Watersheds of Narok County, Kenya. Hydrology 2019, 6(4), 86; https://doi.org/10.3390/hydrology6040086
  6. Kimaru, A. N., Gathenya, J. M.  & Cheruiyot, C. K., (2019). The Temporal Variability of Rainfall and Streamflow into Lake Nakuru, Kenya, Assessed Using SWAT and Hydrometeorological Indices. Hydrology 2019, 6(4), 88; https://doi.org/10.3390/hydrology6040088

  7. Wendso A. Agathe Ouédraogo, John M. Gathenya, and James M. Raude (2019). Projecting Wet Season Rainfall Extremes Using Regional Climate Models Ensemble and the Advanced Delta Change Model: Impact on the Streamflow Peaks in Mkurumudzi Catchment, Kenya. Hydrology 2019, 6, 76; doi:10.3390/hydrology6030076.
  8. Celestine Kilongosi, James Raude, Raphael Wambua, Maimbo Malesu and Alex Oduor (2019) . Effectiveness of Moisture Conservation Techniques in Sorghum Production under Spate Irrigation: A Case Study of Ewaso Nyiro South Drainage Basin. JOURNAL OF SUSTAINABLE RESEARCH IN ENGINEERING, [S.l.], v. 5, n. 1, p. 12-24, july 2019. ISSN 2409-1243. Available at: <http://sri.jkuat.ac.ke/ojs/index.php
  9. Caroline W. Maina, Joseph K. Sang, James M. Raude and Benedict M. Mutua. Geochronological and spatial distribution of heavy metal contamination in sediment from Lake Naivasha, Kenya. Journal of Radiation Research and Applied Sciences; 2019, Pages 37-54.   https://doi.org/10.1080/16878507.2019.1593718
  10. Chepchumba, M. C., Raude, J., & Sang, J. (2019). Geospatial delineation and mapping of groundwater potential in Embu County, Kenya. Acque Sotterranee – Italian Journal of Groundwater. https://doi.org/10.7343/as-2019-369
  11. Lateiro S.  Sousa, Raphael M. Wambua, James M. Raude, Benedict M. Mutua. Assessment of Water Flow and Sedimentation Processes in Irrigation Schemes for Decision-Support Tool Development: A Case Review for the Chókwè Irrigation Scheme, Mozambique. AgriEngineering 2019, 1, 100–118; doi:10.3390/agriengineering1010008

2018 Publications

  1. Faith M. Muema, Patrick G. Home, James M. Raude. Application of Benchmarking and Principal Component Analysis in Measuring Performance of Public Irrigation Schemes in Kenya. Agriculture 2018, 8, 162; doi:10.3390/agriculture8100162.
  2. Caroline W. Maina, Joseph K. Sang, Benedict M. Mutua and James M. Raude. Bathymetric survey of Lake Naivasha and its satellite Lake Oloiden in Kenya; using acoustic profiling system. Lakes & Reservoirs: Science, Policy and Management for Sustainable Use,2018, https://doi.org/10.1111/lre.12247 .
  3. Isaac Larbi, Fabien C. C., Thompson A, Wilson A. Agyare, John M. Gathenya,  Amuzu J. Spatio-Temporal Trend Analysis of Rainfall and Temperatures Extremes in Vea Catchment, Ghana. Climate 2018, 6, 87; doi:10.3390/cli6040087.
  4. John Ng’ang’a Gathagu, Khaldoon A. Mourad and Joseph Sang (2018): Effectiveness of Contour Farming and Filter Strips on Ecosystem Services. Water.
  5. Kariuki, R. N., Njuguna, M., & Kaluli, J. W. (2018). Effect of Thermal Transmittance and Thermal Mass Walling Materials on Indoor Thermal Comfort in Nairobi. Africa Habitat Review Journal; 12 (1). http://journals.uonbi.ac.ke/index.php/afr/index.
  6. Wendso A. A. Ouédraogo, James M. Raude, John M. Gathenya.  Continuous Modeling of the Mkurumudzi River Catchment in Kenya Using the HEC-HMS Conceptual Model: Calibration, Validation, Model Performance Evaluation and Sensitivity Analysis. Hydrology 2018, 5, 44; doi:10.3390/hydrology5030044
  7. Caleb C. Amos, AtaurRahman, Fazlul Karim, John M. Gathenya.  A Scoping Review of Roof Harvested Rainwater Usage in Urban Agriculture: Australia and Kenya in Focus. Journal of Cleaner Production; 2018 https://doi.org/10.1016/j.jclepro.2018.08.108
  8. Halake G. Rendilicha, James M. Raude, Patrick G.  Home.  A review of groundwater vulnerability assessment in Kenya. Italian Journal of Groundwater. Acque Sotterranee – Italian Journal of Groundwater; Vol 7, No 2 (2018). DOI: https://doi.org/10.7343/as-2018-328
  9. John M. Gathenya: Increasing Financial Flows for Urban Sanitation; A Case Study of Nairobi City, Kenya. World Water Council Report; 2018http://www.worldwatercouncil.org/en/publications/increasing-financial-flows-urban-sanitation
  10. Caroline W Maina, Joseph K Sang, Benedict M Mutua, James M Raude (2018): A review of radiometric analysis on soil erosion and deposition studies in Africa. Geochronometria. Vol. 45, No. 1, 2018, pp 10-19.
  11. Patrick N. Namu, James M. Raude, Benedict M. Mutua, and Raphael M. Wambua (2018): Determination of Discrete Particles Optimum Design Parameters for Surface Irrigation System Settling Basin. Journal of Sustainable Research in Engineering. Vol. 4 (2), 33-44.
  12. Raphael M. Wambua, Benedict M. Mutua, James M. Raude (2018): Analysis of Drought and Wet-Events Using SWSI-Based Severity-Duration-Frequency (SDF) Curves for the Upper Tana River Basin, Kenya. Journal of Sustainable Research in Engineering 4 (2), 33-44.
  13. B.M Mutua, R.M Wambua,  J.M. Raude (2018): Drought forecasting under climate change scenarios using artificial neural networks for sustainable water resources management in upper Tana River basin, Kenya. https://papers.ssrn.com/sol3/papers.cfm?abstract_id=3210560, 1-6.
  14. R.M Wambua, B.M Mutua, and J.M Raude (2018): 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. Open Journal of Modern Hydrology 8 (1), 83-100
  15. J.M Raude, B.M Mutua, D.N. Kamau (2018): Simulation of the Hydraulics and Treatment Performance of Horizontal Subsurface Flow Constructed Wetland Treating Greywater. International Journal of Ecotoxicology and Ecobiology: http://www.ijeco.org
  16. A Otieno, G Karuku, J Raude, O Koech (2018): ACCUMULATION OF NITROGEN AND PHOSPHOROUS BY VETIVER GRASS (CHRYSOPOGON ZIZANIOIDES) IN A MODEL CONSTRUCTED WETLAND TREATMENT SYSTEM FOR POLISHING MUNICIPAL WASTEWATER. International Journal of Innovation and Applied Studies 22 (4), 291-298

2017 Publications

  1. PG Home, PK Kinyari, JM Gathenya (2017): Domestic Roof Rainwater Harvesting Tank Sizing Calculator and Nomograph. JKUAT, Journal of Agriculture Science and Technology.
  2. Ismael Ouedraogo, Joseph K. Sang, Patrick G. Home (2017): HEC-HMS Model for Runoff Simulation in Ruiru Reservoir Watershed. American Journal of Engineering Research (AJER). Vol.6, No.4, 2017, pp 1-7.
  3. Joseph K Sang, James M Raude, Bancy M Mati, Urbanus N Mutwiwa, Franklin Ochieng (2017):  Dual Echo Sounder Bathymetric Survey for Enhanced Management of Ruiru Reservoir, Kenya. Journal  of  Sustainable  Research in Engineering. Vol.3, No.4, 2017, pp 113-118.
  4. John Ng’ang’ Gathagu, Joseph K Sang, Caroline W Maina (2017): Modelling the Impacts of Structural Conservation Measures on Sediment and Water Yield in Thika-Chania Catchment, Kenya. International Soil and Water Conservation Research. Elsevier publisher. 2017.

2016 Publications

  1. Maloi S. K., Sang J. K., Raude J. M. Mutwiwa U. N., Mati B. M., Maina C. W (2016): Assessment of Sedimentation Status of Ruiru Reservoir, Central Kenya. American Journal of Water Resources. Vol.4, No.2, 2016, pp 77-82.
  2. Kahiga PM, Gathenya JM, Home PG, Wamuongo JW, Namirembe S and Kosi NO: A Multi- stakeholder Decision Support Tool for Optimizing Sustainable Land Management Technologies: A case Study of the Upper Tana Catchment, Kenya: Handbook for Sustainable Land Management in Dry Lands of Kenya: Improving Land Productivity through Participatory Research and Technology Transfer, United Nations Development Programme – Kenya 2015, ISBN 978 9966 1805 5 1, Chapter 4. pg.52-80.
  3. Raphael M. Wambua, Benedict M. Mutua, James M. Raude. Prediction of Missing Hydro-Meteorological Data Series Using Artificial Neural Networks (ANN) for Upper Tana River Basin, Kenya. American Journal of Water Resources. Vol. 4, No. 2, 2016, pp 35-43. http://pubs.sciepub.com/ajwr/4

2015 Publications

1. Kituu Gareth, Chris Kanali, Douglas Shitanda, Charles Njoroge and Joseph Mailutha (2015):  Effect of Genetic Algorithm Optimised Dryer on Quality attributes of thin-layer dried fish. Journal of Aquatic Food Product Technology.

Abstract

Studies were undertaken to establish the performance of a genetic algorithm-optimized solar tunnel dryer in drying fish by comparing the quality attributes of the dried fish with that of fish dried in a non-optimized solar tunnel dryer in open sun. A two way Anova revealed a highly significant difference between moisture ratios for the fish dried under the optimized solar tunnel dryer and the other methods (F=53.59, Fcrit,1% =4.09). In addition, TBARS showed that fish dried in the optimized dryer did not develop rancidity (2.30µgMA/kg), that dried in non-optimized dryer approached rancid values (5.30µgMA/kg), while open sun dried fish was slightly rancid (795-8.0µgMA/kg) Further, based on TVB-N, fish under the three drying treatments did not develop significant putrefaction. Furthermore, it took 15, 22 and 28 hours to dry fish to equilibrium moisture content of 0.12 kg/kg (db), for the optimized solar tunnel dryers, and for the open sun drying, respectively. Thus, the optimized solar tunnel dryer is superior to both non-optimized solar tunnel dryer and open sun drying in the drying of fish.

2. Mwangi, H., Julich, S., Feger, K.-H., 2015. Introduction to Watershed Management. In: Köhl, M., Pancel, L. (Eds.), Tropical Forestry Handbook. Springer Berlin Heidelberg, pp. 1-23. DOI:10.1007/978-3-642-41554-8_153-1

Abstract

Scarcity and threats to freshwater resources from pollution, climate change, and overexploitation have made it increasingly important to have sound watershed management. The link between land, water, and people has further made it necessary to widen the scope of watershed management beyond the “water resources.” Overall ecosystem functions as well as the improvement of socioeconomic status of the local communities are of paramount importance for the success of watershed management. The chapter provides a general overview of watershed management and modern challenges originating from climate change and land-use pressures. It highlights some of the critical issues that should be addressed for successful watershed management with a regional emphasis on tropical Africa. In this context, sustainable forest management and also agroforestry is a key factor in water resources management in general and upland resources development in particular. Integrated water resources management (IWRM) including stakeholder participation, livelihood improvement, flood risk management, and financing of watershed management is presented. Furthermore, the scheme of watershed planning process which is fundamental for the development and implementation of watershed management plans is stressed. Watershed assessment, a key component of watershed planning, is outlined based on a case study in the Sasumua dam watershed, Kenya.

3. Odote, P. M. O., G. M. Kituu, D. Obiero, R. Ruwa, and N. H. Honell (2015). Performance evaluation of hybrid thin layer solar tunnel-windmill dryer in the drying of brined and non-brined Tafi (Siganussutor) Fish. AgricEngInt: CIGR Journal, 17(1): 273-283.

Abstract

Studies were carried out to evaluate the performance of hybrid solar tunnel-windmill dryer in thin layer drying of brined and non-brined Tafi (Siganus spp.) fish. The fish were, eviscerated, and split into pieces of approximately 6cm by 4cm by 5mm was soaked in brine at 0 and 5% concentrations. The samples were dried in the dryer for 44 hours. The moisture content of the drying fish was evaluated by the AOAC oven drying procedure. In addition, analysis was carried out to establish the best thin layer drying model that describes the drying of fish in the hybrid wind-solar tunnel dryer. The moisture content of the drying fish was found to reduce linearly from 4.2 and 3.9kg/kg (db), respectively for brined and non-brined fish to 0.8kg/kg (db). A two way Students t-test did not establish any significant difference in the drying of salted and unsalted fish (tstat=1.4032, tcrit, 5%=2.0687). Further, the page thin layer drying model was found to be the best model describing the thin layer drying of Tafi fish in the hybrd solar tunnel-windmill dryer (R2=0.9655 and 0.09434; RMSE=0.0539 and 0.0840 for unsalted; c2=0.0032 and 0.0077, for salted and unsalted fish, respectively). These results provide useful information in the modelling and design of solar drying systems for the drying of Tafi fish.

4. Mwangi, J. K., C. A. Shisanya, J. M. Gathenya, S. Namirembe, and D. N. Moriasi. 2015. A modeling approach to evaluate the impact of conservation practices on water and sediment yield in Sasumua Watershed, Kenya. Journal of Soil and Water Conservation 70(2):75-90.

Abstract

Degradation of agricultural watersheds often reduces their capacity to provide ecosystem services such as sediment retention, flow regulation, and water quality improvement. Soil and water conservation practices can be used to enhance the capacity of watersheds to produce these services. The objective of this study was to evaluate the impact of agricultural conservation practices on water and sediment yield using the Soil and Water Assessment Tool (SWAT) model. The study area was Sasumua Watershed (107 km2 [43 mi2]), where land degradation has affected watershed’s capacity to regulate flow and maintain water quality. The model was calibrated and validated for streamflow at the watershed outlet. Data on annual average erosion rates for the area was used to constrain soil erodibility factor (KUSLE) and practice erodibility factor (PUSLE) parameters during sediment calibration while measured three month sediment concentration data was used for validation. Model performance was assessed using the coefficient of determination (r2), Nash-Sutcliffe efficiency coefficient (ENS) and percent bias (PBIAS). Results gave monthly streamflow r2 values of 0.80 and 0.85, ENS values of 0.74 and 0.81, and PBIAS values of ±5% and ±6% during the calibration and validation. The model also satisfactorily simulated daily sediment concentrations with an r2 value of 0.54. However, ENS and PBIAS values were low, which was attributed to the short duration of measurement. The validated model was used to simulate sediment yield for the period 1970 to 2010. Mean annual watershed sediment yield was 40,934 t y−1 (90,243,096 lb yr−1). The impacts of filter strips, contour farming, parallel terraces, grassed waterways, and their combinations on water and sediment yield were simulated by adjusting relevant model parameters. The effectiveness of filter strips increased nonlinearly with width being optimum at 30 m (98.4 ft). A combination of 30 m (98.4 ft) wide filter strips and grassed waterways reduced sediment yield by 80%; parallel terraces, 10 m (32.8 ft) filter strips, and grassed waterways reduced sediment yield by 75%; 10 m (32.8 ft) filter strips and grassed waterways reduced yield by 73%; contour farming and grassed waterways reduced yield by 66%; and grassed waterways reduced yield by only 54%. Parallel terraces reduced surface runoff by 20% and increased base flow by 12%, while contour farming reduced surface runoff by 12% and increased base flow by 6.5%. Implementation of conservation practices can reduce sediment yield and increase water yield marginally. The results give an insight into the implications of the present land use management practices and can be used to devise ecologically sound watershed management and development plans.

5. Musau, J., Sang, J., Gathenya, J., Luedeling, E., Home, P., (2015) SWAT model parameter calibration and uncertainty analysis using the HydroPSO R package in Nzoia Basin, Kenya. Journal of Sustainable Research In Engineering, 1(3): 17-29.

Abstract

The parameter uncertainty in hydrological modelling has been accorded much attention in the recent past. Parameter uncertainty is a major source of overall model unreliability. In this study, the HydroPSO R package was used to assess parameter identification and uncertainty for the Soil and Water Assessment Tool (SWAT) model applied in the upper reaches of Nzoia River Basin. Fourteen parameters were selected based on previous studies and parameter sensitivity analysis using the Latin Hypercube Sampling method.

6. Sang, J., Allen, P., Dunbar, J., 2015. Determination of critical shear stress of non-cohesive soils using submerged jet test and Turbulent Kinetic Energy. Earth Surface Processes and Landforms

Abstract

Laboratory tests using Jet Erosion Testing (JET) apparatus, impinging normally on a horizontal boundary, were conducted to determine the critical shear stress (τc) of non-cohesive soil samples. A 3D SonTek/YSI 16 MHz Micro-Acoustic Doppler Velocimeter (MicroADV) was used to measure Turbulent Kinetic Energy (TKE) at a radial limit of entrainment in the wall jet zone and the measurements were used to calculate τc of the samples. The results showed that TKE increases exponentially with increasing particle size. The τc from this study were comparable (r2 = 0.8) to the theoretical τc from Shields diagram after bed roughness scale ratio (D/ks), due to the non-uniform bed conditions, was accounted for. This study demonstrated that JET and TKE can be used to determine τc of non-cohesive soils. The use of JET and TKE was found to be faster and easier when compared to the conventional approach of using flumes. A relationship of TKE at the onset of incipient motion (TKEc) and samples’ d50 developed in this study can be used to predict τc of non-cohesive soils under similar non-uniform conditions.

7. Musau J., Sang J., Gathenya J. and Luedeling E (2015) Hydrological responses to climate change in Mt. Elgon watersheds, Journal of Hydrology: Regional Studies

Abstract

Study Region The Upper catchments of the Nzoia River basin in western Kenya. Study Focus The potential streamflow responses to climate change in the upper Nzoia River basin are studied. The Soil and Water Assessment Tool (SWAT) was forced with monthly temperature and precipitation change scenarios for the periods 2011–2040 (2020s), 2041–2070 (2050s) and 2071–2100 (2080s). Data from 10 climate models and three greenhouse gases emission scenarios was downscaled using the delta change method and used in the SWAT model. Streamflow data for the periods 1986–1998 and 1973–1985 was used for model calibration and validation respectively. New Hydrological Insights for the Region Comparison between the simulated baseline and future streamflow shows that in the Koitobos and Kimilili watersheds, August to December streamflow is likely to be highly altered. In the Kuywa watershed, March to June flows is likely to change considerably due to climate change. Major streamflow changes are likely in March to June and August to November in the Rongai watershed. Projected changes differed between the four watersheds despite their proximity, indicating different sensitivities to climate change and uncertainty about the potential hydrological impacts of climate change in the area.

8. Öborn, I., Kuyah, S., Jonsson, M., Sigrun Dahlin, A., Mwangi, H. and De Leeuw, J. (2015). Landscape-level constraints and opportunities for sustainable intensification in smallholder systems in the tropics. In Minang, P. A., Van Noordwijk, M., Freeman, O. E., Mbow, C., De Leeuw, J. and Catacutan, D. (Eds.) Climate-Smart Landscapes:Multifunctionality in Practice, 163-177. Nairobi, Kenya: World Agroforestry Centre (ICRAF).

2014 Publications

1. Korir M. K., Mutwiwa U., Kituu G. and Sila D. N. (2014). Simulation of saturation efficiency and cooling capacity of an unloaded near infrared reflecting charcoal cooler for on-farm storage of mango fruits. Journal of Sustainable Research in Engineering. Vol 1, No 2 (2014)

Abstract

Mango (Mangifera indica L.) fruit is a valuable fruit in Kenya due to its nutritive value and economic importance. However, at least 40 to 45% of mango fruit is lost during postharvest handling primarily due to inadequate storage facilities for mango fruits. In this study, saturation efficiency and cooling capacity of an unloaded improved evaporatively cooled store for onfarm storage of mango fruits were simulated. The cooler had a storage space of 0.75 m3 and its dimensions were 0.84 m x 0.84 m x 1.5 m. The external surfaces of the cooler were sprayed with a near infrared reflecting (NIR) paint. The cooler was constructed from locally available materials including hardwood and charcoal. The charcoal was kept moist by water dripping by gravity from horizontally laid pipes on the roof. The flow of water from an overhead tank approximately 2 m high to the cooler was monitored using a flow meter. The excess water which dripped was collected by gutters fixed at the lower ends of the charcoal walls and channeled to a water reservoir. A 12V pump was used to pump the water back to the overhead tank while a 12V fan located centrally on one of the sides directly opposite the door was used to draw air into the cooler. The pump and fan was powered by a 70Ah battery recharged by a 125 W solar panel. A computer model to simulate the saturation efficiency and cooling capacity of the cooler was developed on a java platform. The input parameters of the model were inlet air conditions, water conditions, air properties at selected ambient condition, and charcoal cooler characteristics. At varied inlet air velocities ranging from 3.0 m/s to 4.0 m/s at an interval of 0.2 m/s, the actual saturation efficiency of the cooler ranged from 68.9% to 66.9% while the predicted ranged from 69.0% to 66.9%. The actual cooling capacity of the cooler ranged from 1055667 kJ/h to 136477 kJ/h while the predicted ranged from 105726 kW/h to 136680 kW/h. The high coefficient of determination (R2=0.999) indicated a strong correlation between the actual and predicted results. A root mean square error (RMSE) corresponding to the actual and predicted saturated efficiency was 0.028% while that corresponding to the actual and predicted cooling capacity was 118 kJ/h. At 95% level of confidence, t test results showed no significant difference (tcalculated, 0.06; tcritical, 2.23) between the actual and predicted saturation efficiency. The t test results also indicated no significant difference (tcalculated, 0.01; tcritical, 2.23) between the actual and predicted cooling capacity.

2. Ronoh E. and Rath T. (2014) Investigations on the external thermal radiation exchanges between glass-covered greenhouse surfaces and the sky. DGG-Proceedings, Vol. 4, Dec. 2014, No. 6, p. 1-5. DOI: 10.5288/dgg-pr-04-06-er-2014

3. Sang J, Allen P, Dunbar J, Hanson G. 2014. Development of a semi-physically based model to predict the erosion rate of Kaolinite clay under different moisture content. Canadian Geotechnical Journal.10.1139/cgj-2012-0274

Abstract

Understanding the susceptibility of soils to concentrated flow erosion is imperative for predicting sustainability of various engineering structures and assessing environmental integrity. Currently, a widely used model is empirical in nature. In this study, we developed a semi-physically based model that predicts the rate of concentrated flow erosion of kaolinite clay based on tensile and erodibility characteristics. To develop this model, direct tensile tests and Jet Erosion Tests (JETs) were performed on kaolinite clay with different percent moisture content (MC). The direct tensile test results showed that the energy required to break interparticle bonds across a fracture plane and tensile strength decreases with an increase in MC, whereas the JET results showed that soil resistance to erosion decreases with an increase in MC. Results also showed that an efficiency index of the JET apparatus, which represents the fraction of jet power used in actual erosion processes, diminishes with a decrease in MC. This semi-physically based model predicted the rate of erosion of kaolinite clay for a range of MC and applied hydraulic shear stress. In model development and verification, 98% and 90% of the data, respectively, were within a discrepancy ratio of 0.50 and 2.0.

4. Nkonge L. K., Sang J. K., Gathenya J. M. and Home P. G. (2014) Comparison of two calibration-uncertainty methods for soil and water assessment tool in stream flow modeling. Journal of Sustainable Research In Engineering

Abstract

Hydrological models are increasingly being used as decision support tools in water resource management. It is therefore important that these models undergo calibration and uncertainty analysis before their application. This study addresses the application and comparison of two calibration-uncertainty methods for a distributed model in the Upper Tana Basin. The Generalized Likelihood Uncertainty Equation (GLUE) and Sequential Uncertainty Fitting Ver. 2 (SUFI-2) were used in this study to calibrate the Soil and Water Assessment Tool (SWAT). The performance of the GLUE and SUFI-2 was evaluated using three objective functions namely: coefficient of determination (R2), Nash–Sutcliffe Efficiency (NSE) and coefficient of determination divided by coefficient of regression (bR2). Uncertainty statistics used were the P-factor and R-factor. The study established the best method for calibration and uncertainty analysis is SUFI-2.

5. Kituu Gareth (2014, accepted) Effect of Genetic Algorithm Optimised Dryer on Quality attributes of thin-layer dried fish. Journal of Aquatic Food Product Technology.

Abstract

Studies were undertaken to establish the performance of a genetic algorithm-optimized solar tunnel dryer in drying fish by comparing the quality attributes of the dried fish with that of fish dried in a non-optimized solar tunnel dryer in open sun. A two way Anova revealed a highly significant difference between moisture ratios for the fish dried under the optimized solar tunnel dryer and the other methods (F=53.59, Fcrit,1% =4.09). In addition, TBARS showed that fish dried in the optimized dryer did not develop rancidity (2.30µgMA/kg), that dried in non-optimized dryer approached rancid values (5.30µgMA/kg), while open sun dried fish was slightly rancid (795-8.0µgMA/kg) Further, based on TVB-N, fish under the three drying treatments did not develop significant putrefaction. Furthermore, it took 15, 22 and 28 hours to dry fish to equilibrium moisture content of 0.12 kg/kg (db), for the optimized solar tunnel dryers, and for the open sun drying, respectively. Thus, the optimized solar tunnel dryer is superior to both non-optimized solar tunnel dryer and open sun drying in the drying of fish.

6. Ruben, R., Hoebink, P., Ngutu, H., Mutwiwa, U.N., Njuguna, S., Elbers, W., Kempen, L., Rijsbergen, B., (2014). The Impact of Coffee Certification on Smallholder Farmers in Kenya. In The Impact of Coffee Certification on Smallholder Farmers in Kenya, Uganda and Ethiopia, Centre for International Development Issues Nijmegen (CIDIN), Radboud University Nijmegen, The Netherlands http://www.ru.nl/publish/pages/721725/final_report_solidaridad_impact_study_east_africa_290114.pdf3

6. Kadyampakeni, D.M., Kazombo-Phiri, S., Mati, B. and Fandika, I.R. (2014). Impacts of Small-Scale Water Management Interventions on Crop Yield, Water Use and Productivity in Two Agro-Ecologies of Malawi. Agricultural Sciences, 454-465. http://dx.doi.org/10.4236/as.2014.55046

Abstract

A study was conducted in Malawi to compare the performance of improved agricultural water ma- nagement interventions with traditional water management practices to assess the impact of the interventions on crop yield and water use productivity. The study used questionnaires and focused group discussions to collect data from farmers and key informants. The results showed significant gains in crop yield, farmer income, and water use productivity using the regulated surface irrigation compared with unregulated surface irrigation. Treadle pump irrigation increased crop production by 5% – 54% compared with water can irrigation. Treadle pumps also increased gross and net incomes by >12% suggesting that farmers using the treadle pump were able to realize higher incomes across all crop enterprises compared with farmers using water cans. However, there is a dire need to improve the efficiency of the surface irrigation systems for rice production because the water applied was about 2 to 3 times the gross irrigation requirement (~10,780 m3·ha-1) which could result in environmental degradation through increased salinity and water logging.

7. Nyang’au, W. O., Mati, B. M., Kalamwa, K., Wanjogu, R. K. and Kiplagat L. K. (2014). Estimating Rice Yield under Changing Weather Conditions in Kenya Using CERES Rice Model. International Journal of Agronomy, Volume 2014, Article ID 849496, 12 pages. http://dx.doi.org/10.1155/2014/849496

Abstract

Effects of change in weather conditions on the yields of Basmati 370 and IR 2793-80-1 cultivated under System of Rice Intensification (SRI) in Mwea and Western Kenya irrigation schemes were assessed through sensitivity analysis using the Ceres rice model v 4.5 of the DSSAT modeling system. Genetic coefficients were determined using 2010 experimental data. The model was validated using rice growth and development data during the 2011 cropping season. Two SRI farmers were selected randomly from each irrigation scheme and their farms were used as research fields. Daily maximum and minimum temperatures and precipitation were collected from the weather station in each of the irrigation schemes while daily solar radiation was generated using weatherman in the DSSAT shell. The study revealed that increase in both maximum and minimum temperatures affects Basmati 370 and IR 2793-80-1 grain yield under SRI. Increase in atmospheric CO2 concentration led to an increase in grain yield for both Basmati and IR 2793-80-1 under SRI and increase in solar radiation also had an increasing impact on both Basmati 370 and IR 2793-80-1 grain yield. The results of the study therefore show that weather conditions in Kenya affect rice yield under SRI and should be taken into consideration to improve food security.

8. Ngugi, H.N., Home, P.G. and Mutwiwa, U.N. 2014. Impacts of Water and Sanitation activities on the environment in the upper Mara basin, Civil and Environmental Research Vol. 6, No. 1, 9-16.

Abstract

The provision of reliable and safe water supplies is an essential element in improving the quality of life for mankind. However, over time the natural resource base has become severely stressed due to unsustainable use of the resources. This study was undertaken to evaluate the impacts of water, sanitation and hygiene (WASH) activities on the environment in the upper Mara River basin. Sampled water and sanitation projects were identified by observation and Geographic Information System (GIS) was used to map and report on these projects. Impacts of the projects on land and environmental quality were assessed using Land Quality Indicators (LQI); fresh water quality, solid and liquid waste generation and management and soil erosion. Water samples were analyzed for physical, chemical and bacteriological parameters and only 23.4% of sampled water sources were found suitable as domestic water sources. Most open water sources were contaminated with E. Coli caused by open defecation in the basin which on average was 38%. The study showed that, 21.3% of the sampled water supply projects had evidence of soil erosion around them which was mainly caused by livestock overcrowding at water points. Among the wastewater generating and management activities in upper Mara basin, Bomet municipal stabilization pond posed the greatest pollution threat to the environment since it lacked capacity to treat waste water to standards before it overflowed into the environment. This study recommended that WASH project implementers, users and managers should plan for and implement environmentally sustainable projects. In addition, WASH stakeholders in the basin should make comprehensive efforts to provide improved water sources and sanitation to all the residents.

9. Muriuki C.W., Mutwiwa U.N. and Home P.G., 2014; Adsorption of Hexavalent Chromium from Aqueous Solution by Pumice: Equilibrium and Kinetic Study, 2014 Annual International Sustainable Research and Innovation (SRI) Conference at AICAD, Juja, Kenya.

Abstract

Chromium released into the environment primarily as aresult 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 pumice.

2013
1. Ondimu Stephen N.(2013) Free and Open Source software for Development of Sustainable M-Health systems in Kenya. In IST-Africa 2013, 29-10th May 2013, Safari park Hotel, Nairobi, Kenya.

Abstract

Health challenges present arguably the most significant barrier to sustainable global development. This is especially so in the undeveloped countries like Kenya where health care systems are faced with a myriad of constraints. Poor health care infrastructure and overwhelmingly small healthcare workforce are the most conspicuous of these challenges. It is in regard to this that the recent rapid rise in mobile phone penetration in Kenya has prompted a debate as to whether mobile phone technology can be leveraged to mitigate the numerous pressures facing health care in the country. The use of mobile devices for health care and public health services is called m-health. It is a form of e-health (i.e. use ICT for health care services). Kenya launched a pioneer m-health service dubbed ‘Daktari1525’ in the late 2011, aimed at reducing medical cost and to supplement other pioneer efforts being made by the government. A m-health system comprises of hardware, software/application, network, standards and services. Of these components, software/applications is the most critical. It influences network accessibility, standards and services. For any m-health program to be sustainable it must utilise up to date, versatile, less error prone and powerful software/applications. Unfortunately, such software/applications are very costly. Free and open source software (FOSS) presents a good way of mitigating this. FOSS is software that is both free software and open source. It grants users the right to use, copy, study, change, adapt and improve its design through the availability of its source code. The aim of this paper is to present different types of FOSS which can be utilised to provide sustainable and successful m-health services in Kenya and other developing countries. A systematic survey and review of literature on e-health, m-health and FOSS found that a rich resource of FOSS exists that can be utilised for the provision of m-health services (education and awareness, helpline, diagnostic and treatment support, communication and training for healthcare workers, disease and epidemic outbreak tracking, remote monitoring and data collection). The author recommends that this versatile, dynamic and up to date resource should be adapted to develop successful, sustainable and scalable m-health systems in Kenya. This will make a great positive contribution towards: increased access to healthcare and health-related information (particularly for hard-to-reach populations); improved ability to diagnose and track diseases; timelier, more actionable public health information and expanded access to ongoing medical education and training for health workers.

2. Home P G, J.T. Makanga, G. P. Wanjala, R.M. Ingolo (2013) Development and Performance Testing of Weeders Suitable for System of Rice Intensification (SRI) in Kenya. In Proceeding of Sustainable research and Innovation and innovation conference, JKUAT, Kenya.

Abstract

(Abstract) The availability of water for irrigation continues to decline worldwide due to competition from other uses and the changing climate. Traditional flood rice irrigation is especially unsustainable due to its wasteful use of water. It is therefore imperative to try novel irrigation methods such as System of Rice Intensification (SRI) in an attempt to save on irrigation water as well as an adaptation to climate change. SRI fundamentals are: transplanting of seedlings at a young age of 8-15 days, planting one seedling only, use of wider seedlings spacing, alternate wetting and drying of the fields, use of organic matter, and use of mechanical rotary weeder to control weeds. The use of mechanical weeder is especially important in controlling proliferation of weeds, enhancing aeration in the root zone and pruning of roots which enhances vigorous and deep root development. With the introduction of SRI in Kenya for the first time in 2010, there were no suitable weeders in the market. Through financial support from JICA/AICAD, a project to develop rotary weeders suitable for soils in East Africa, particularly for Mwea Irrigation Scheme wasinitiated. Eight different weeders from Tanzania, India, Japan and one locally made were selected, tested and evaluated under SRI conditions in Mwea. Among the eight weeders, four of them were found to perform reasonably well and were selected for modification. The modified weeders underwent various field evaluations and further modifications, until their performance in terms of weeding efficiency and energy requirements were satisfactory. The final prototypes were then fabricated, multiplied and a final evaluation done. The evaluation indicated that the performance of the weeders was acceptable. These weeders are now available for bulk production.

3. Mutwiwa, U. N., Mwangi, H. M., and D. Mbalo (2013). Technical Challenges Hindering Accessibility of Clean Water Among the Residents of Mathare and Mukuru Informal Settlements in Nairobi, Kenya. Proceedings of the Mechanical Engineering Annual Conference on Sustainable Research and Innovation, held in African Institute for Capacity Development 24th to 26th APRIL 2013, pp 340-343

Abstract

Abstract: As an economic hub for the Eastern African region, Nairobi employs 25% of Kenyans and 43% of the country’s urban workers with over 60% of the population living in slums of which only 22% of the households have water connections [1]. Water kiosks are the most common technical solution adopted to provide water supply in the two areas under study. This option was followed by communal yard taps where the individual household served by a yard tap paid a “minimum tariff” based on an assumed water consumption of 10m³/household/month. The water vendors obtain water from the existing water sources to sell to consumers who lack water connection and those who do not use unprotected springs as water sources due to public health concerns. Challenges observed included perceived high cost of water tied to low incomes due to limited opportunities for employment; low water pressure at stand pipes and water kiosk due to the presence of illegal and spaghetti connections as well as frequent pipe bursts; due to the high population density, there was lack of space making connection of individual households to the main water line difficult; and poor pipeline connections hence the visible presence of exposed pipelines crossing contaminated drains. Opportunities include the presence of water distribution mainlines, high demand for water services, willingness of the development partners to fund water services, and local knowledge on household water treatment technology. Based on these findings, the authors recommend regular maintenance of water systems, development of standards for water infrastructure (quality of pipes, design and installation) the installation of plastic meters instead of metallic (brass) meters which has become target of vandalism for scrap metal, regular monitoring of water quality within the pipeline system as well as intensification and expansion of water reticulation networks to ensure that water connection reaches as nearer as possible to the people to avoid spaghetti connections.

4. Omari J N, U.N., Mutwiwa JT and Mailutha J T (2013). Environmental and health effects of e-waste. In Proceedings of the Mechanical Engineering Annual Conference on Sustainable Research and Innovation, held in African Institute for Capacity Development 24th to 26th APRIL 2013, pp 372-378.

Abstract

Electronic waste or e-waste is one of the rapidly growing problems of the world. E-waste is growing exponentially in recent years because the markets in which these products are produced are also growing rapidly. The United States Environmental protection Agency (US-EPA) has estimated a 5 to 10% increase in the generation of e-waste each year globally. Directive 5/442/EEC, Article 1(a) defines “waste” as “any substance or object, which the holder disposes of or is required to dispose of pursuant to the provisions of national law in force. “This is global. e-Waste comprises of a multitude of components, some containing toxic substances that can have an adverse impact on the environment and health-Waste problem is of global concern because of the nature of production and disposal of waste in a globalized world. However, it is the rapid growth of computing that is driving the e-waste production. In the next five years, one billion computers will be retired worldwide. In Developing countries, e-waste management assumes greater significance not only due to the generation of its own e-waste but also because of the dumping of e-waste from developed countries. This is coupled with lack of appropriate infrastructure and procedures for its disposal and recycling. The effect to health and environment is enormous. Unlike many traditional wastes, the main environmental impacts of e-waste mainly arise due to inappropriate processing. Some of the e-waste management systems such as; storage, recycling, landfill, incineration and export are not adequate for its effect on environment and health and may require other remedial treatments. This review article intends to give data on components and hazardous substances of e-waste that are creating environmental pollution and human exposure to these chemicals, resulting adverse effects due to recycling, incineration and landfill disposal of e-waste. It also gives some of the initiatives of e-waste management. Bioremediation is a general concept that includes all those processes and actions that take place in order to biotransform an environment, already altered by contaminants, to its original status. An attempt to rejuvenate the affected land by the use of bioremediation is inevitable to ungraded land.

5. Urbanus N M, H. J. Tantau, Uwe Schmidt Johannes Max (2013) Evaluation of Gas Exchange System for Online Monitoring of Plant Response. In Proceeding of The 7th JKUAT Scientific Conference held in the African Institute for Capacity Development Nairobi November 2012.

Abstract

The development of intelligent systems for judging plant response to greenhouse microclimate is important since it avoids intensive and expensive technical measurements and may help to alleviate stress situations. The direct monitoring of a crop is preferable since it does not require a full knowledge of all biotic and abiotic factors in the crop environment, but offers physiologically valuable interpretation of plant measured data. Since many problems in plants are initiated by stress conditions caused by biotic or abiotic factors, data from continuous measurements of the plant reaction to the greenhouse microclimate will be useful in early detection of stress causes so that corrective actions could be taken. The incorporation of the data into greenhouse control programs may contribute greatly in the optimisation of the greenhouse climate to overcome such stresses. This paper presents findings from online measurement of plant response to greenhouse microclimate. The experiments were conducted in four greenhouses, each measuring 20 m long by 10 m wide. All greenhouses were covered with a UV-blocking polyethylene film on the roof. One greenhouse was equipped with an evaporative cooling system. A second greenhouse was covered with a 50-mesh insect-proof net on the sidewalls and roof ventilation openings. The remaining two greenhouses were covered with a 78-mesh insect-proof net on the sidewalls and ventilation openings. A shading paint with NIR-reflecting pigment was applied on the roof of one of the greenhouses with 78-mesh insect-proof nets while the other was left as control. Tomato Solanum lycopersicum cv FMTT260 plants were grown inside the greenhouses at a density of 1.5 plants m-2 and maintained following commercial practices. Plant response to different treatments was done by pair-wise measurements using a gas exchange system. The results indicate that cooling method used influenced the microclimate around the crop hence plant response. Although decoupling of other environmental factors was not possible, the results suggest that the greenhouse microclimate significantly influences both net photosynthesis and leaf transpiration. Moreover, results show that there is a time delay between when changes occur in the greenhouse microclimate and when the plants respond.

6. Kahiga.M.P, Gathenya J.M, Home.P.G and Wamuongo J.W (2013) Climate Change Shocks, Impacts and Adaptation Strategies for Land and Water Management in the Upper Tana Catchment, Kenya. In the Proceedings of 2013 Mechanical Engineering Annual Conference on Sustainable Research and Innovation, 24-26th April, 2013, African Institute for Capacity and Development (AICAD), Juja, Kenya. Vol.5. ISSN 2079-6226 PP 150-155.

Abstract

Climate change is expected to have negative significant impacts on agriculture, which is one of the most important sectors in Kenya. These negative effects may necessitate substantial change in land and water management practices at catchment level. In this regard, adaptation mechanisms to climate change will play a paramount role in reducing the impact on agricultural production and food security. Small scale farmers are the most vulnerable to climate change leaving them with no alternative but to adapt to the changing climatic changes. The purpose of this study was to determine the capacity of the small scale farmers to monitor the local climate trends, their effects and the adaptation strategies. This paper highlights the types of climate shocks perceived by the farmers, the effects caused in the upper Tana catchment and the adaptation mechanisms embraced in their land and water management. The study was done in nine Agro-Ecological Zones (AEZs) cutting across the catchment. The methodology involved administering of six questionnaires to randomly selected farmers among those practicing sustainable land management in the AEZs. The results showed that farmers are aware of the changing climatic trends and have adopted various land and water management practices in response to the climatic trends.

7. Kahiga.M.P, Gathenya J.M, Home.P.G and Wamuongo J.W. Namirembe. S and Odhiambo. N.K, (2013) Development of a Decision Support (DST-MATSIM) Tool for Selecting Sustainable Land Management Technologies in the Upper Tana Catchment. In Proceedings of the WOCAT Share Fair and the 16th WOCAT Workshop and Steering Meeting (WWSM), 27 May to 1st June 2013, Pretoria, Republic of South Africa.

Abstract

In this work, a computer based Decision Support Tool (DST-MATSIM TOOL) for Sustainable Land Management (SLM) technologies in the Upper Tana catchment is developed using Microsoft Access VBA software. The tool was designed to assist the farmers and other watershed managers in decision making on SLM technologies suitable for enhancing eco-system services and climate change adaptation. It contains a set of SLM technologies that has been evaluated and analyzed at field level using World Overview of Conservation Approaches and Technologies (WOCAT) methodology. Every SLM Technology in the set has been documented and presented using a standardized WOCAT global template. The decision of the appropriate SLM technologies to be used depends on a number of factors which the user must know in order to arrive at appropriate decision. In this model, the type of SLM technology chosen follows a specified hierarchy. The Upper Tana catchment provides a typical example of other basins in Kenya characterized by diverse conflicting land uses which do not promote sustainable land management. Therefore, this paper presents a conceptual framework which can be adopted in order to arrive at an appropriate decision for sustainable land management at catchment level. The tool creates a knowledge sharing platform for farmers to share knowledge on SLM technologies within the same Agro-ecological Zones (AEZs). The paper highlights how decision support systems can be used for sustainable land use management.

8. Ngugi H.N., Home P. G. and Mutwiwa U. N. (2013): Impacts of WASH (Activities on the Environment in the Upper Mara Basin, presented at 8th JKUAT scientific, Technological and Industrialization conference, Juja Kenya
9. Ngugi H.N., Home P. G.
and Mutwiwa U. N. (2013): Evaluation of the Impacts of WASH (Water, Sanitation and Hygiene) Activities on the Environment in the Upper Mara using the WEAP model presented at the 1st Pan African Conference of science, computing and Technology (PACT 2013) Lusaka, Zambia

2012

  • Mati, B. M. 2012. Promoting the Adoption of the System of Rice Intensification (SRI) through Participatory Research and Outreach in Kenya. Paper Presented at NIB/MIAD and Collaborators Research Workshop, Kenya School of Monetary Studies, Nairobi, 30-31st May 2012.
  • Mati, B.M. 2012. Gender and Economic Water Uses. Proceedings of the Session on Concrete Actions: Advancing the Integration of Gender, Water and Food Security. World Water Week, 27 August 2012. Stockholm, Sweden, pg 6.
  • Ndiiri, J.A., Mati, B.M., Home, P.G., Odongo, B. and Uphoff, N. 2012. Comparison of water savings of paddy rice under system of rice intensification (SRI) growing rice in Mwea, Kenya. Vol 04 / Issue 6. International Journal of Current Research and Review (IJCRR); 63-73.
  • Nyamai, M., Mati, B.M., Home P.G., Odongo, B., Wanjogu, R. and Thuranira E.G. 2012. Improving land and water productivity in basin rice cultivation in Kenya through System of Rice Intensification (SRI). Agric Eng Int: CIGR Journal, 2012, 14, 2, 1-9.

2011

  1. Mwangi H., M. Gathenya, B. Mati, J. Kimani 2011. Simulating the impact of land use change on watershed services in Sasumua watershed using SWAT. Applied Geoinformatics for Society and Environment Conference (AGSE, held on 15th-19th August 2011 at Jomo Kenyatta University of Agriculture and Technology.
  2. Gathenya M., H. Mwangi, R. Coe and J. Sang 2011. Climate and Land use induced risks to watershed services in the Nyando River basin, Kenya. Experimental Agriculture, volume 47 (2), pp. 339–356.

    Abstract

    Climate change and land use change are two forces influencing the hydrology of watersheds and their ability to provide ecosystem services, such as clean and well-regulated streamflow and control of soil erosion and sediment yield. The Soil Water Assessment Tool, SWAT, a distributed, watershed-scale hydrological model was used with 18 scenarios of rainfall, temperature and infiltration capacity of land surface to investigate the spatial distribution of watershed services over the 3587 km2 Nyando basin in Western Kenya and how it is affected by these two forces. The total annual water yield varied over the 50 sub-basins from 35 to 600 mm while the annual sediment yield ranged from 0 to 104 tons ha−1. Temperature change had a relatively minor effect on streamflow and sediment yield compared to change in rainfall and land surface condition. Improvements in land surface condition that result in higher infiltration are an effective adaptation strategy to moderate the effects of climate change on supply of watershed services. Spatial heterogeneity in response to climate and land use change is large, and hence it is necessary to understand it if interventions to modify hydrology or adapt to climate change are to be effective.

2010

  • Gathenya, J. M., Ngeera, C. 2010. Dynamics and Environmental Impacts Land Use Cover Changes in River Buathonaro Catchment in Meru County, Kenya. International Journal of Sustainable Water and Environmental Systems. (paper accepted 24 November, 2010.
  • Gathenya, J.M., Kinyari, P.K. and Home, P.G. (2010) Domestic Rainwater Harvesting Tank Sizing Calculator and Nomograph. Journal of Agriculture Science and Technology. Accepted for Publication April 2010.
  • Ronoh, E.K., Kanali, C.L., Mailutha, J.T. and Shitanda, D. (2010). Thin layer drying kinetics of amaranth (Amaranthus cruentus) grains in a natural convection solar tent dryer. African Journal of Food, Agriculture, Nutrition and Development (AJFAND), 10(3): 2218–2234.

2009

  • Max, J. F. J.; Horst, W. J.; Mutwiwa, U. N.; Tantau, H.-J. (2009): Effects of Greenhouse Cooling Method on Growth, Fruit Yield and Quality of Tomato (Solanum lycopersicum L.) in a Tropical Climate. Available online 13 June 2009, Scientia Horticulturae 122 (2), pp. 179-186
  • Mutwiwa, U. N. and Tantau, H.J. (2009). Insect Screens for Integrated Plant Protection In Greenhouses. Acta Horticulturae (ISHS) 807:85-90.

2009

  • Ronoh, E.K., Kanali, C.L., Mailutha, J.T. and Shitanda, D. (2009). Modeling thin layer drying of amaranth seeds under open sun and natural convection solar tent dryer. Agricultural Engineering International: the CIGR EJournal. Manuscript 1420. Vol. XI. November, 2009.

2008

  • Ajwang O. P and H‐J. Tantau 2008. A simulation model for functional design of insect‐proof greenhouses for the humid tropics. Research paper submitted to European Journal of Horticultural Sciences.

2007

  • Mutwiwa, U.N. (2007): Effects of Different Cooling Methods on Microclimate nd Plant Growth in Greenhouses in the Tropics. ISSN 0930-8180, ISBN 978-3-926203-39-7. Publication No 66,2007, University of Hannover, Germany

    Abstract

    Cooling greenhouses in the humid tropics is especially challenging due to the high intensity of solar radiation and humidity prevalent in these regions. The effect of natural ventilation and evaporative cooling on the greenhouse microclimate, growth and production of tomato Solanum lycopersicum cv FMTT260 were evaluated. The research was carried out in two greenhouses (measuring 20 m long by 10 m wide) at the experimental site of the “Protected Cultivation Project” on the campus of the “Asian Institute of Technology” (AIT), situated 44 km north of Bangkok in Khlong Luang, Pathum Thani, central Thailand, (14° 04’ N, 100° 37’ E, altitude 2.3 m). The naturally ventilated greenhouse was covered with a UVabsorbing plastic film on the roof and a 50-mesh insect proof net on the sidewalls and roof ventilation opening. The evaporative cooled greenhouse was completely covered with the UV-absorbing plastic film and was equipped with a fan and pad cooling system. In each greenhouse, 300 tomato plants were grown at a density of 1.5 plants m-2 and maintained for 15 to 20 weeks. Results from two seasons show that the cooling method influenced the greenhouse microclimate, plant growth and yield. Although evaporative cooling lowered greenhouse temperature, the unwanted increase in humidity resulted in fungi infections and reduced transpiration. Plants grown in evaporatively cooled greenhouse were 30 cm to 45 cm shorter than those grown in naturally ventilated one. Differences were also noted in flowering, leaf area, dry matter partitioning and harvested yield. The significance of cooling method and greenhouse covering material on plant growth and production in protected cultivation systems in the tropics is discussed.

2006

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2005

  • Ajwang O. P. 2005. Prediction of the effects of insect‐proof screens on the climate in naturally ventilated greenhouses in the humid tropics. PhD. dissertation, Institute of Biosystems and Horticultural Engineering, University of Hannover, Germany.

    Abstract

    The impact of different types of insect-proof screens on greenhouse climate in humid tropics needs to be quantified in order to develop technically and economically optimal greenhouse constructions. Thus, physical properties of various insect-proof screens were determined in the laboratory at the Institute of Horticultural and Agricultural Engineering, University of Hannover, Germany. Specially adapted experimental greenhouses were built at AIT campus in Bangkok, Thailand. A dynamic energy and mass balance model of the greenhouse system was developed to predict the greenhouse climate from external weather data and properties of insect screens. Scenario simulations were carried out to predict the effect of screen properties on greenhouse climate. External and greenhouse climate measurements were made in Bangkok. The internal climate measurements were carried out concurrently in two similar, naturally-ventilated greenhouses covered with different insect-proof screens on ventilation openings. Tomato (Lycopersicon esculentum ‘King Kong II’) plants were grown in the greenhouse during the experimental period. Model predictions of greenhouse air temperature were compared to measurements from the two greenhouses and good agreement was achieved. The results form a good basis for decisions on screened greenhouse design improvements and climate control interventions in screened greenhouses in the humid tropical climates.