Sunday, December 12, 2010


Rainwater harvesting is done to:

· Ease the demand on the city’s water supply;

· To relieve the seriously depleting groundwater reserves and allow for their levels to rise; and

· Because it’s the purest form of water available requiring practically little or no treatment.

Some of the simplest design include a open basin with some kind of filtration unit. Over the years, rainwater harvesting has steadily gained importance and its designs have gained wide scale publicity. It’s main components include:

1. Catchment: Surface that receives water supply. A variety of plains may serve as catchment areas ranging from rooftops to paved and unpaved open spaces.

2. Coarse Mesh: A large spacing wire mesh is positioned at the entrance of the opening to filter out debris.

3. Guters: Semi-cylindrical conduits that channel water from sloping rooftops to appropriate piping or storage tanks. A 10-15% factor of safety is recommended with reinforcing to support the weight of water.

4. Pipes/Conduits: To transport collected water from one system to another.

5. First Flush Valve: To divert the first flush of water to drains to prevent contamination from settled dust and particulates.

6. Filteration System: A filter unit is required to remove all floatables and suspended particles. Sand filters are easy and economical to use that consist of a layer of coarse media followed by gravel and then sand. Such filters have an added advantage of disinfection as they target microorganisms.

7. Storage Tanks: Various options are available in the market.

International Trends:

Japan: A simple rainwater harvesting system is in place that collects water from rooftops, utilizes a sedimentation tank to settle heavier particles and then transfers the supernatant solution to a sump; from which water is withdrawn with a handpump.

Thailand: Thai harvest rainwater and store it in large jars. They prefer this to other sources of water particularly due to its superior taste.

Saturday, December 11, 2010

New Human Right!

Right to Clean Water and Sanitation for All

UN declared basic right to clean water and sanitation to all. Here is an excerpt from their homepage.

By a vote of 122 in favour to none against, with 41 abstentions, the General Assembly today adopted, as orally revised, a resolution calling on States and international organizations to provide financial resources, build capacity and transfer technology, particularly to developing countries, in scaling up efforts to provide safe, clean, accessible and affordable drinking water and sanitation for all.