Quantifying Roof Catchment Yields for Improved Water Security in a Populated Built Dryland Ecosystem: The Case of Kitui Campus of Kenyatta University, Kenya

Document Type : Case Study

Authors

1 Department of Geography, Kenyatta University, Nairobi, Kenya.

2 Department of Agricultural Sciences and Technology Kenyatta University, Nairobi, Kenya.

3 Department of Geomatics Engineering and Geospatial Information Systems, Jomo Kenyatta University of Agriculture and Technology, Juja, Nairobi, Kenya.

Abstract

Water scarcity poses a significant challenge in semi-arid regions, with climate variability and growing demand exacerbating the strain on traditional water sources. As a contribution to sustainable water solution in a dryland region, this study reports the potential harvest from rooftop catchments in a populated built environment using Kenyatta University, Kitui Campus, in Kenya, as a case study. Roof catchment areas were computed using standard GIS procedures. Mean monthly rainfall was established using rainfall trends from 1981–2024. Estimated harvestable water was calculated standard formula for volume, but discounted for expected evaporation and seepage loses using applicable runoff coefficients. Results show that the entire campus can collect at least 11 million litres annually, with institutional buildings contributing 7.8 million litres and the staff quarters 3.4 million litres per year. With a population of about 1000 people coupled with water use efficiency, the campus can operate within a water secure scenario throughout the year. Seasonal analysis reveals that the October–December provides 361 mm of rainfall twice the volume of the March–May (MAM) which is 176 mm, necessitating strategic storage solutions to bridge dry periods. Based on the cost factor of above ground plastic tanks, this study proposes decentralized rainwater harvesting systems combining a series of large-capacity residential tanks available on the market (30,000-50,000 litres) for high-yield buildings and smaller tanks (5,000–20,000 litres) per individual residential houses. Lessons from this paper offer Kitui Campus, other learning environments, and households with ridged roof catchments, significantly opportunities through enhanced public health performance indicators and irrigation agriculture.

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Main Subjects

References

Behera, S. K., Luo, J. J., Masson, S., Delecluse, P., Gualdi, S., Navarra, A., & Yamagata, T. (2005). Paramount impact of the Indian Ocean Dipole on the East African short rains: A CGCM study. Journal of Climate, 18(21), 4514–4530. https://doi.org/10.1175/JCLI3541.1
Black, E., Slingo, J., & Sperber, K. R. (2003). An observational study of the relationship between excessively strong short rains in coastal East Africa and Indian Ocean SST. Monthly Weather Review, 131(1), 74–94. https://doi.org/10.1175/1520-0493 
Bluman, A. G. (2009). Elementary Statistics: A step by step approach 9e. McGraw Hill.
CGK. (2023). Kitui County integrated development plan 2023-2027. County Government of Kitui.
Chepyegon, C. and Kamiya, D. (2018) Challenges Faced by the Kenya Water Sector Management in Improving Water Supply Coverage. Journal of Water Resource and Protection, 10, 85-105. https://doi.org/10.4236/jwarp.2018.101006 
FAO. (2022). Drought response and recovery in the Horn of Africa. Food and Agriculture Organization. https://doi.org/10.4060/cc0638en
Fewkes, A. (2000). Modelling the performance of rainwater collection systems: Towards a generalised approach. Urban Water, 1(4), 323–333. https://doi.org/10.1016/S1462-0758(00)00026-1
Gaikwad, S., Gaikwad, S., Meshram, D., Wagh, V., Kandekar, A. and Kadam, A. (2019) Geochemical Mobility of Ions in Groundwater from the Tropical Western Coast of Maharashtra, India: Implication to Groundwater Quality. Environment, Development and Sustainability, 22, 2591-2624. https://doi.org/10.1007/s10668-019-00312-9
Ngigi S.N. (2003). Rainwater Harvesting for Improved Food Security: Promising technologies in the Greater Horn of Africa. Kenya Rainwater Association, Nairobi, Kenya. ISBN: 9966-9767-1-X
Gould, J., & Nissen-Petersen, E. (1999). Rainwater catchment systems for domestic supply: Design, construction, and implementation. Intermediate Technology Publications. https://doi.org/10.3362/9781780445694
Kahinda, J. M., Taigbenu, A. E., & Boroto, J. R. (2007). Domestic rainwater harvesting to improve water supply in rural South Africa. Physics and Chemistry of the Earth, 32(15–18), 1050–1057.  https://doi.org/10.1016/j.pce.2007.07.007
Kathula, J., & Abdinoor, A. (2024). Innovative and cost-effective water harvesting and value addition in agriculture for sustainability: Case study of Kitui and Wajir Counties, Kenya. International Journal of Applied Agricultural Sciences, 10(6), 310–327. https://doi.org/10.11648/j.ijaas.20241006.15
Kumar, M. D. (2004).  Roof Water Harvesting for Domestic Water Security: Who Gains and Who Loses? Water International 29(1):43-53, https://doi.org/10.1080/02508060408691747
van Vuuren, D., van Dam, D., Dekker, M., Oates, L., Tagomori, I., van der Veen, R., & Würschinger, C. (2024). WHAT ARE JUST AND FEASIBLE CLIMATE TARGETS FOR THE NETHERLANDS?. PBL Netherlands Environmental Assessment Agency.
Malesu, M. M., Oduor, A. R., & Odhiambo, O. J. (2007). Rainwater harvesting innovations in response to water scarcity. World Agroforestry Centre.
Mendez, C. B., Klenzendorf, J. B., Afshar, B. R., Simmons, M. T., Barrett, M. E., Kinney, K. A., & Kirisits, M. J. (2011). The effect of roofing material on the quality of harvested rainwater. Water Research, 45(5), 2049–2059. https://doi.org/10.1016/j.watres.2010.12.015
Mugume, S. N., Melville-Shreeve, P., Gomez, D., & Butler, D. (2017, June). Multifunctional urban flood resilience enhancement strategies. In Proceedings of the Institution of Civil Engineers-water management (Vol. 170, No. 3, pp. 115-127). Thomas Telford Ltd. https://doi.org/10.1680/jwama.15.00078 
Mulwa, F., Li, Z., & Fangninou, F. F. (2021). Water scarcity in Kenya: Current status and mitigation strategies. Sustainability, 13(4), 1234. https://doi.org/10.4236/oalib.11070996   
Mutschinski, K., & Coles, N. A. (2023). Adoption of rainwater harvesting as a sustainable approach to improving the climate resilience of small landholders in Kenya. World Water Policy, 9(4), 913-928. https://doi.org/10.1002/wwp2.12134
Mutsotso, R. B., Sichangi, A. W., & Makokha, G. O. (2018). Spatio-temporal drought characterization in Kenya from 1987 to 2016. Advances in Remote Sensing. 07. 125-143. https://doi.org/10.4236/ars.2018.72009
Mwangi, K. K., Musili, A. M., Otieno, V. A., Endris, H. S., Sabiiti, G., Hassan, M. A., ... & Kanyanya, E. (2020). Vulnerability of Kenya’s water towers to future climate change: an assessment to inform decision making in watershed management. American Journal of Climate Change, 9(3), 317-353.  https://doi.org/10.4236/ajcc.2020.93020   
Mwenge, M. J., Taigbenu, A. E., & Boroto, J. R. (2009). Rainwater harvesting in South Africa: Challenges and opportunities. Physics and Chemistry of the Earth, 34(13–16), 893–900.  https://doi.org/10.1016/J.PCE.2011.08.011
National Water Harvesting and Storage Strategy (2020–2025), Ministry of Water, Sanitation and Irrigation.
Ngaina, J. N., & Mutai, B. (2013). Observational evidence of climate change on extreme events over East Africa. Global Meteorology, 2, 2. https://doi.org/10.4081/gm.2013.e2
Nicholson, S. E. (2017). Climate and Climatic Variability of Rainfall over Eastern Africa. Reviews of Geophysics, 55, 590-635. https://doi.org/10.1002/2016RG000544
Okinyo, J. (2025). Types of Roofs Used in Kenya’s Building. Structrum Limited. https://structrumlimited.co.ke/types-of-roof-used-in-kenyas-building/
Ongoma, V., Chen, H., & Gao, C. (2018). Projected changes in mean rainfall and temperature over East Africa based on CMIP5 models. International journal of Climatology, 38(3), 1375-1392. https://doi.org/10.1002/joc.5252  
Opiyo, F., Wasonga, O., Nyangito, M., Schilling, J., & Munang, R. (2015). Drought adaptation and coping strategies among the Turkana pastoralists of northern Kenya. International Journal of Disaster Risk Science, 6(3), 295-309. https://doi.org/10.1007/s13753-015-0063-4
Oxfarm Wash. (2026). Rainwater Harvesting Guidelines. Technical Brief. https://www.oxfamwash.org/rain-water-harvesting-guidelines/  (Accessed 8th May, 2026).
Van Rooy, M. P. (1965). A rainfall anomally index independent of time and space, Weather Bur s Afr, 14, 43-48
Engineering Tool Box. (2023). Storm-Water Runoff Coefficients vs. Surface. https://www.engineeringtoolbox.com/storm-water-surface-runoff-coefficients-d_2216.html
Thomas, T., & Durham, B. (2003). Integrated water resource management: Looking at the whole picture. Desalination, 156(1–3), 21–28. https://doi.org/10.1016/S0011-9164(03)00320-5
Umukiza, E., Ntole, R., Chikavumbwa, S. R., Bwambale, E., Sibale, D., Jeremaih, Z., ... & Petroselli, A. (2023). Rainwater harvesting in arid and semi-arid lands of Africa: challenges and opportunities. Acta Scientiarum Polonorum. Formatio Circumiectus, 22(2), 41-52. https://doi.org/10.15576/ASP.FC/2023.22.2
UNEP. (2018). Kenya water atlas. United Nations Environment Programme.
UN-Habitat. (2011). Rainwater harvesting: A lifeline for human well-being. United Nations Human Settlements Programme. https://unhabitat.org/rainwater-harvesting-a-lifeline-for-human-well-being
UN-Water. (2018). Integrated water resources management: A global perspective. United Nations.
US Green Building Council (1996-2026). Homes Table 8 Common runoff coefficients. https://www.usgbc.org/resources/homes-table-8-common-runoff-coefficients
Wainwright, C. M., Finney, D. L., Kilavi, M., Black, E., & Marsham, J. H. (2021). Extreme rainfall in East Africa, October 2019–January 2020 and context under future climate change. Weather, 76(1), 26-31. https://doi.org/10.1002/wea.3824
Wanyonyi, K. W., Wambua, R. B., & Mwangi, J. K. (2015). Rainwater harvesting in Kenyan schools: A case study of Machakos County. Journal of Water, Sanitation and Hygiene for Development, 5(3), 435–442. https://doi.org/10.2166/washdev.2015.169
WHO. (2006). Guidelines for the safe use of rainwater. World Health Organization.
WMO. (2022). State of the climate in Africa 2022. World Meteorological Organization.
 
Water Harvesting Research
Volume 9, Issue 1
Issue in Progress
2026
Pages 40-56

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