Monday, 12 May 2014

No more dry spells at DHOBI GHAT.

No more dry spells at DHOBI GHAT.

All good omens for the dhobi ghat and the residents of Malleshwaram area in Bangalore.

Of the many dhobi ghats in Bangalore, the one is Malleswaram is spread over six acres. It lies in the downstream of Sankey Tank. This dhobi ghat was once a natural water body. Decades ago, it was converted into a dhobi ghat, where 250-300  workers wash clothes in shifts. Earlier, the sources of water were streams of the Vrushabavathi River.  

 With time, these streams dried up because of the proliferation of open wells and borewells in the vicinity. Houses and establishments upstream discharged sewage into the storm water drain which ran right through the dhobi ghat. Left with little choice, the washer men had to use polluted water, which they collected in huge ponds. They added hefty quantities of detergents and chemicals into cement-ring tanks with their bare hands, leaving them vulnerable to burns and infection. The clothes with chemicals were rinsed in the huge ponds, leaving the water even more murky and contaminated. The ponds were drained by unplugging valves at the bottom once in three-four days. The dirty water was released in to the Vrushabhvathi.

 The dhobi ghat had a huge well, which went dry 20 years ago. The BBMP got four borewells dug 18 years ago but all went dry within no time. Water was then pumped from a public borewell behind Kadu Malleswara Temple in Malleswaram and piped to dhobi ghat. Fights broke out between the washermen and the local residents. Soon, even this water yield began to decline.
Distraught, the dhobis approached Government. Government requested the Karnataka State Council for Science & Technology to come up with a solution.

 The solution

The dhobi ghat has a steep slope from east to west and north to south. The tanks are built in the valley at the lowest level. The highest ridge is on the eastern side and a huge open well is located at this point. As the rainwater collection area inside the dhobi ghat is not conducive for systematic collection, it was decided to harvest runoff water from the stormwater drain on 15th Cross of Malleswaram, starting from Bashyam Circle in Sadashivnagar. The paved road on 15th Cross has a stormwater drain on either side that carries rainwater from east to west.
 The upstream stormwater from the stormwater drain on the roadside at the north-eastern corner of the dhobi ghat is collected with a system of first flush separator, leaf slide, silt trap and a pebble filter for subsequent storage. The huge quantity of stormwater is systematically processed.

 During low rainfall and lean flow periods, water in the storm water drain (which carries pollutants) is not allowed into the water storage system.
 During periods of heavy rainfall and higher flow, the debris, leaf litter and suspended particles such as plastic covers are allowed over the leaf slide and relatively cleaner water percolates to silt traps. The silt settles in these traps and clean water passing through the filter bed is allowed to flow into the open well in the dhobi ghat which is 60 ft deep.

 The rainwater harvested in this manner is temporarily get stored in the open well and it also recharges the ground water. The overflow from the well is connected to 4 underground sumps (of 1 lakh litre capacity each) which are built strategically in the open space located beside and behind a temple inside the dhobi ghat. The extra rainwater from one of the underground sumps is allowed to flow into one of the existing borewells for ground water recharge.

The stored water from the underground sumps is directly piped, without pumping, into the wash area as these tanks are located at an elevation.
This intervention has mitigated the water crisis to a large extent. The 60 ft deep well, which had gone dry, is now full of water through the year. Two of the four borewells have been recharged. All good omens for the dhobi ghat and the residents of the area.