American Journal of Civil Engineering and Architecture
ISSN (Print): 2328-398X ISSN (Online): 2328-3998 Website: Editor-in-chief: Mohammad Arif Kamal
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American Journal of Civil Engineering and Architecture. 2015, 3(3), 86-100
DOI: 10.12691/ajcea-3-3-5
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Modelling Rainwater System Harvesting in Ibadan, Nigeria: Application to a Residential Apartment

Omolara Lade1, and David Oloke2

1Department of Civil Engineering, University of Ibadan, Nigeria

2Faculty of Science and Engineering, University of Wolverhampton, United Kingdom

Pub. Date: July 23, 2015

Cite this paper:
Omolara Lade and David Oloke. Modelling Rainwater System Harvesting in Ibadan, Nigeria: Application to a Residential Apartment. American Journal of Civil Engineering and Architecture. 2015; 3(3):86-100. doi: 10.12691/ajcea-3-3-5


Reduction of water consumption associated water wastage in the residential sector is a rapid pressing issue. The residential sector is a substantial consumer of water in every country and therefore constitutes a focus of water consumption efforts. Since the water consumption, characteristics of the residential sector are complex and inter-related, comprehensive models are needed to assess the technical and economic impacts of adopting rainwater harvesting (RWH) as a sustainable system suitable for residential applications in developing countries. This paper has presented the hydraulic and financial modelling of a RWH system using a residential apartment in Ibadan, Nigeria. With a RWHS being site-specific, a Raincycle model was used to optimise tank size and savings. Sensitivity analysis and MonteCarlo simulation were also carried out. The analysis consists of a detailed assessment of the proposed system, taking into account 18 parameters. Seven of these are fixed parameters- catchment surface area, first-flush volume, storage tank volume, pump power rating, pump capacity, UV unit power rating and UV unit operating time while 11 are variable parameters- rainfall profiles, runoff coefficients, filter coefficients, additional inputs (if any), discount rate, electricity cost, mains water cost, water demand, disposal cost, capital cost and decommissioning cost. The RWH and water savings efficiency were assessed and payback period was estimated. Optimising tank size results reveals that the maximum percentage of demand that could be met was 70.6% with a tank size of 4 m3. Optimising saving analysis showed that there were four tank sizes with a potential long-term profit. The best was 4 m3 tank which was predicted to save $259 over 50 years and had a payback period of 21 years, which is typical for a current domestic system. The results show that significant reductions in the total fresh water consumption and the total cost can be obtained. A Monte Carlo simulation shows an important influence of a given set of conditions on the economic viability of RWH systems.

rainwater harvesting water savings payback period residential apartment Ibadan Nigeria

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