Managing the periphery – Water and sanitation design for BangaloreNovember 25, 2012
The peripheral areas of cities are seeing an unprecedented growth and Bangalore is no exception. Land use is changing from agricultural to non-agriculture use and sites are being developed in ‘layouts’ all across. While infrastructure like roads and electricity can and will eventually reach the layouts the case of water and sanitation infrastructure is more difficult.
The Bangalore Metropolitan Regional Development Authority assisted by 11 Local Planning Authorities is the planning approval authority for over 8000 square km. of area around the city of Bangalore.
Since no more water is likely to be pumped from the Cauvery River with the completion of the Phase IV Stage 2 it is groundwater that most of the peripheral development must depend on. Ground water is however getting increasingly overused in the surrounding semi-arid areas of the city where the rainfall is 700 mm on an average.
How can the authority make sure that the people who move in to these developments have water and sanitation in the future? One good way to begin is to get the layout developer do a yield test for the bore-wells dug or available on site. If this is done in summer it is likely to give a better understanding of reliable yield for the entire layout. A quality test of the bore-well waters would also establish potability or otherwise. Water treatment plants may become necessary if the water is hard or contaminated. This should be basic information with the authority as well as what potential buyers of sites or buildings should demand from the developer.
No individual bore-well should be permitted to be drilled and only common use of groundwater under metered and tariff conditions should be encouraged in the layouts.
While rainwater harvesting is insisted upon by the entire local planning authorities a more detailed implementation and design would help both the authority and the consumer. For example it should be made conditional that all homes and flats have rainwater harvesting structures to store or recharge 60 mm of rainfall .
It should also be made conditional that all storm-water falling on non private plot area is completely recharged in to the ground. The recharge structures should be site specific and should be based on infiltration and recharge data from each site. Only in case where recharge is not possible should storage and reuse be permitted. In any case each layout should be designed as a zero run off area for rainwater.
However all conditions imposed should be easily implementable, should bring tangible benefits to the occupiers, should be easy to monitor and should have clear ownership so that it is maintained in the long run and is therefore sustainable.
At the macro-level, the BMRDA would be better off generating a detailed micro-watershed map of the area under its jurisdiction. It should then be able to push for the maintenance of these tanks and other water bodies plus their inter-connectedness through adequate policy, legislative and fiscal incentives.
The BMRDA should also map the aquifers and detailed sub-aquifer maps overlapping with the micro-watershed maps should be generated so that groundwater situation is better understood and managed with the development that will take place inevitably in the megalopolis area.
Sanitation: The Karnataka State Pollution Control Board insists on a sewage treatment plant for each development in the BMRDA zone. While this is motivated with a need to prevent water pollution and to add to reuse and recycling of water, the practical aspects of what happens to these treatment plants and who maintains them should be studied. Resident Welfare Associations and Flat owner associations find it difficult to maintain these units. As units or houses are built incrementally, it is difficult for the treatment plants to become fully functional until occupancy is at least 50 % and above.
As a matter of choice individual on-plot sanitation systems like septic tanks and baffled reactors with the right design should be permitted. These have the benefits of being maintained by individual owners and also they demand much less water than piped sewerage. A dual system of grey-water disposal and back water disposal on plot should be permitted.
While on-plot sanitation systems can be maintained with as low as 70 lpcd of water, piped sewerage will demand at least 135 litres per person per day especially for self cleansing velocity requirements.
The sustainable management of water and sanitation outside the BWSSB influence zone is a challenge. The BMRDA has to think wisely and move ahead quickly so as to avert a serious water shortfall situation.
This would be water wisdom for a city.