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Old ideas, new innovations

Nuevas Esperanzas has been building rainwater harvesting tanks in Nicaragua for over three years now, but even with the best ideas there is always scope for new innovations.  So for our latest projects, we decided to go  back to the drawing board to see how we can make our rainwater harvesting systems even better.  Two contrasting projects have given us an ideal opportunity to experiment with some innovative modifications.

The first modified tank has been built at the Escuela Waswalí Abajo in Matagalpa as part of a CARE International water and sanitation project for schools.  The aim of this project was not only to collect and store a clean and safe supply of drinking water for the school community, but also to make rainwater harvesting as user-friendly as being on the mains.  CARE’s idea for this project was to supply water to taps for hand washing and a laundry, as well as drinking water, creating a small distribution system so that the water can be delivered just like any mains water supply.  So with these requirements in mind, Nuevas Esperanzas set about designing some innovative new features.

The school was ideally located to make this possible.  Built on terraces on a sloping site, the school buildings were conveniently constructed at different levels which allows rainwater to be collected from the roofs of the two highest buildings and stored in a 71,000 litre tank below.  By gravity this tank supplies the taps and washing area built next to another school building on the next level down.  The purpose built hand-washing station has taps at the right height for the school students to wash their hands, as well as one for washing clothes and another to fill a bucket with water.  The durable self-closing taps used were specially designed in the UK to prevent wastage.  To guarantee quality, drinking water is filtered through clay water filters.  It has been tested and conforms to national and international standards. 

Our project partner CARE was also concerned that this rainwater system look smart, helping to convey the perception that rainwater harvesting is a clean and healthy option for water supply, so the final touch was to paint the tank blue and white, Nicaragua’s national colours.

Nearer to home, Nuevas Esperanzas has been busy with some other design modifications of a very different sort.  As part of the Mountain Rain project, Nuevas Esperanzas will be building 21 tanks over the next year in six remote communities on the hillsides of the volcanoes in the Maribios range, and up to 60 more in the next three years.  Access to these communities is difficult and the logistics of transporting materials up these mountain slopes are very challenging indeed.  So we decided to build an experimental tank to try out some modifications and to see how the process could be made as efficient as possible.  These tanks needed to be simpler, cheaper, quicker to build and, most importantly, require as little movement of materials as possible.  So we took a critical look at each stage of the construction process to find alternatives which improved efficiency. 

In the original tank design, steel reinforcement is carefully cut and arranged to support the floor, walls and roof of the tank.  This design works well, but with welded mesh now available locally we decided to simplify things by using prefabricated sheets.  We discovered that by using welded mesh for the walls of the tank, we were able to build the reinforcement structure in a matter of hours, and by replacing the heavy barbed wire to which the mortar adheres with a much lighter chicken wire, we were able to save money and weight as well as time.  The most important innovation, however, is the replacement of heavy and cumbersome timber and plywood formwork with nothing more than a roll of sacking material.  Instead of wrapping the reinforcement wire around wooden formwork, we can now erect the free standing welded mesh frame, wrap it in sacking and begin rendering from the inside.

This “wrap and render” technique was a great success in our experimental tank and will now be used for all future systems we build.  So instead of hauling timber and plywood sheets up the hillside we can take a light and compact roll of sacking which can be reused up to three times. 

Both these projects illustrate how good ideas can always be improved.  Nuevas Esperanzas actively encourages innovation and always seeks to promote appropriate technologies, from smart, user-friendly rainwater tanks for schools to simple “wrap and render” tank construction in hillside communities.

06/10/08