URBAN areas especially in the developing countries are known to suffer serious water deficiency due to the dearth of financial capacity to develop elaborate water infrastructure.
But a poster displayed at the World Water Week celebrations in Stockholm, Sweden in August puts forward a novel idea that could significantly change this for the good of urban dwellers as a result of rainwater harvesting.
The concept, a case study at the University of Nairobi titled Rainwater Harvesting as Part of Urban Water Demand Management, aims at promoting rainwater harvesting as a tool for urban water demand management.
It was the result of a pilot demonstration at the Kenyan university’s main campus encompassing two student hostels (Mamlaka A and B) and a students’ kitchen and dining unit.
The study by Teshamulwa Okioga, in collaboration with Dr. Zablon Isaboke Oonge, Maimbo Malesu and Andre Dzikus established water demand for the study area by use of questionnaires and meter readings
A detailed water demand management strategy, which included rainwater harvesting as an integral part, was developed. Another method used was carrying out of rainfall analysis over a 32-year period using the average rainfall data from three nearby meteorological stations.
The roof catchment areas were calculated from measurements of roof plan dimensions and potential rainwater was determined as a function of the catchment area. The team also used rainfall amount and run-off coefficient
The tank capacities required were obtained as the largest difference between the cumulative rainwater supply and cumulative uniform demand that could be met for every month
Various results were achieved including the establishment of an annual rainfall, percent probability rainfall by Gumbel’s distribution per year and the total available roof area. The roof run-off coefficient and the total potential supply over a period were realized.
The study revealed the various benefits that could accrue from this method. It resulted in reduction of water bills by 25 percent. It led to more sustainable use of ground water and reduced drawdown of water level. Change of attitude and increased ownership towards water demand management by students and university administration was realized. It also resulted in increased awareness on benefits of rainwater harvesting.
The study recommends the building of capacity to encourage and up-scale rainwater harvesting within large institutions. It also calls for promotion water demand management by the following measures:
? hardware measures to include repair of leaking /broken taps, retrofitting shower heads, and replacement of the automatic urinals with user-activated flushing mechanisms
? software measures for study area to include awareness campaign for the residents of the hostels as well as regular water audits.
Rainwater harvesting, it concludes, has proven itself as a tool which can complement water demand management strategies in urban areas.