I am an architect practicing in Cochin, Kerala. Currently we are involved in a residential project, the site of which is next to a back-water canal (saline water). Our basic motive in the project is to make the intervention as energy self-sufficient as possible; in terms of water, power, waste management, use of materials, etc.
I have some queries about the way water is to be managed on site, mainly along two issues:
1. Rain water harvesting:
The ground water on site is saline (as observed from ponds and wells in the vicinity). We want to be independent of municipal water supply, as far as possible. For the purpose of drinking and bathing, we intend to build a rain water harvesting pond of an approximate capacity of 1.5 lakh litres.
We thought that making a roofed pond which is amply ventilated from all sides would be appropriate since it would reduce evaporation. Is this assumption correct?
Secondly, we thought of introducing certain varieties of fish in the pond (and the required vegetation) so that it does not become a breeding place for mosquitoes. Is this appropriate?
Also, as mentioned earlier, there might be seepage of saline water into the pond from the ground. Would stone walls (basalt or laterite) and an earth floor be sufficient for the construction of the pond, or is concreting necessary (also keeping in mind the fish and the required vegetation)?
As far as further processing for intended uses is concerned, we had thought of a sand-charcoal filter for bathing purposes and a further RO treatment of the same for drinking purposes.
2. Treatment of saline water from canal for agricultural purpose:
The concerned site is quite large (2 acres) and the construction area very less. There is a lot of salt water ingress from the canal into a large part of the site as this part is below the canal high tide level. The soil though, seems quite fertile. As of now, only coconut tress are grown in this part, and it is more or less marshy. We intend to make this part useful for other kinds of tress as well. For this, we thought of channeling the salt water first into a catchment area where we could introduce certain kinds of vegetation to reduce its salinity and then divert it over the concerned field.
This is something that I have only read about a year ago in local newspaper coverage, but have not been able to find any information thereafter. Could somebody please guide me on this matter? What kinds of vegetation reduce the salinity levels of water, and over how much period of time?
We do not have a lab report of the water quality of the site or the ground water.
Most of the above is through empirical observations.
Kunjan.
kunjangarg@yahoo.co.in