Rain Water Harvesting Plant

INTRODUCTION

Rain water harvesting is one of the most effective methods of water management and water conservation. It is a term used to indicate the collection and storage of rainwater used for human,animal and plant needs. It involves collection and storage of rain water at surface or in sub-surface aquifer, before it is lost as surface run-off. The augmented resource can be harvested in the time of need. Artificial recharge to ground water is a process by which the ground water reservoir is augmented at a rate exceeding that of natural conditions of replenishment. The collected water is stored and pumped in a separate pipe distribution. This is a very useful method for a developing country like India in reducing the cost and the demand of treated water and also economizing the treatment plants operation, maintenance and distribution costs.

NECESSITY OF THE PROJECT

To overcome the inadequacy of surface water to meet our demands within the campus and decrease dependence on ground water.
To enhance availability of ground water and utilize rain water for sustainable development.
To increase infiltration of rain water into the subsoil.
To improve ground water quality by dilution.
To improve ecology of the area by increase in vegetation cover
Overall, to make the campus an Eco-friendly one. .

THE CRITICAL SCENARIO IN KOLKATA

The actual number of private deep tube wells in Kolkata is yet to be known. However, the withdrawal of ground water has increased to a great extent during the last two decades.

This has resulted in two major groundwater problems:

Depletion of water level to the tune of 10-12mbgl at places.
Deterioration of ground water quality.

Geologically and geomorphologically Kolkata belongs to the lower deltaic plain of the Ganga-Padma river system. The surface material is clay and clay loam. This clay extends up to a depth of 10 to 25 m bgl in most areas: Below this clay bed a fine sand bed is found which extends up to a depth of 30-to 35-metre bgl. Below this level another clay layer, dark brown to greyish brown in colour, occurs up to a depth of 60 to 100-metre bgl. From this depth another sand zone occurs which comprises fine, medium and coarse sand and extends up to a depth of 120 to 180 metrebgl. Below this sand zone lies a gravel bed. Tertiary black and sticky clay occur at the bottom of the sand and gravel zone.

Due to unique geological setting, rainfall in Kolkata does not percolate downwards to recharge thegroundwater regime. Rainwater is totally wasted and poses a serious problem like water-logging and sewageoverload.

To combat all such problems related to the water supply and demand, and also for combating problems due to over withdrawal of groundwater, scientists are advising the utilization of rainwater in urban areas.

PROBABLE BENEFITS OF THE PROJECT

The cost of recharge to sub-surface reservoir is lower than surface reservoirs.
The aquifer serves as a distribution system also.
No land is wasted for storage purpose and no population displacement is involved.
Ground water is not directly exposed to evaporation and pollution.
Storing water under ground is environment-friendly.
This storage type increases the productivity of aquifer.
This also effects rise in ground water levels.

POTENTIAL AREAS

Where a huge population has to be fed on a limited water resource.
Where ground water levels are declining on a regular basis.
Where substantial amount of aquifer has been de-saturated
Where availability of ground water is inadequate in lean months.
Where due to rapid urbanization, infiltration of rain water into subsoil has decreased drastically and recharging of ground water has diminished.

DO'S AND DON'TS

Harvested rainwater is used for direct usage or for recharging aquifers. It is most important to ensure that the rainwater caught is free from pollutants. Following precautionary measures should be taken while harvesting rainwater.

Roof or terraces uses for harvesting should be clean, free from dust, algal plants etc.
Roof should not be painted since most paints contain toxic substances and may peel off.
Chemicals, rusting iron, manure or detergent on the roof should not be stored.
Nesting of birds on the roof should be prevented
Terraces should not be used for toilets either by human beings or by pets
Gratings should be provided at mouth of each drainpipe on terraces to trap leaves debris and floating materials.
Provision of first rain separator should be made to flush offfirst rains.
Polluted water must not be used to recharge ground water.
Ground water should only be recharged by rainwater.
Before recharging, suitable arrangements of filtering should be provided.
Filter media should be cleaned before every monsoon season.
During rainy season, the whole system (roof catchment, pipes, screens, first flush, filters, tanks) should be checked before and after each rain and preferably cleaned after every dry period exceeding a month.
At the end of the dry season and just before the first shower of rain is anticipated, the storage tank should be scrubbed and flushed off all sediments and debris.

THE BEGINING

The plant started working under leadership of Dr. Dipak Kumar Kar, Principal, Asutosh College, and Dr. Sayani Mukherjee, Associate professor in Geography. The Plant has been running in deep association with Dr.Sudip Dashgupta, GLI in Geography and Dr. Subhayan Datta, SACT in Environmental Science, from 2013. The Government of West Bengal planned to fund one rainwater harvesting project in each district and following this, the cost of setting up of this Bhasa Campus project was sponsored by the state government, a venture for the district South 24 Parganas.

PRESENTWORKING MEMBER OF THE PLANT (2017 ONWARDS)

Conveners:

Dr. Sayani Mukhopadhyay, Associate Professor in Geography
Dr. Indira Halder, Assistant Professor in Geography
Dr. Sudip Dashgupta, GLI in Geography

Members:

Dr. Rwiti Basu,Assistant Professor in Geology
Sri Subhadip Gupta, Assistant Professor in Geography
Dr. Shramana Roy Barman, Assistant Professor in Environmental Science
Smt. Moumita Singha, Assistant Professor in Communicative English
Dr. Subhayan Datta, SACT in Environmental Science
Dr. Sayanti Poddar, SACT in Geography
Dr. Gourab Bera, SACT in Geography
Dr. Pampiya Chowdhury, SACT in Geology
Smt. Debasmrity Mukherjee, SACT in Geography
Dr. Indrajit Ghosh,SACT in Environmental Science
Dr. Tanmay Bhowmik, SACT in Chemistry

PLACE AND DETAIL OF THE PLANT

There are a few criteria behind the selection of Bhasa Campus as a unit of Rain Water Harvesting:

Large open Space
Close to Nature
Green campus
Eco-Friendly Initiative
To serve local residents in and around the campus
To solve the problem of fresh water crisis to some extent

DEVELOPING HISTORY

The main project was developed in the strip of land behind the Ladies Hostel just besides the draining channel. Initially the land was elevated to the height of the drain which meant that the water could not be drained out. Four pillars were set and raised up to the height of near about 3 feet and keeping those pillars as base, a platform was built and again after that those pillars were elevated. A platform was again constructed and upon that four tanks was set up for rainwater harvesting. The whole area is approximately 5meters * 12 meters.

IMPACT

Rainwater harvesting is gaining impact because of its minimum environmental impact. Areas that experience high amounts of rainfall will benefit the most from the system and will be able to distribute water to dry lands with ease. Even an area experiencing lesser rainfall or inadequate water resource can be benefitted from this method, particularly the highly populated residential areas, institutions which support a greater number of students, etc.

PRESENT ACTIVITIES (2016 ONWARDS)

Currently the rainwater harvesting project of the college campus caters to the following needs:

Washing and cleaning of the campus building floors.

Washing of utensil used daily by the resident students

Supplying the water for the regular needs of the campus garden plants

Watering the valuable medicinal plants grown in a part of the medicinal plant garden in campus ground.

Providing essential water for the basic vegetable cultivation carried out in the campus area for the consumption of resident students.