Geological report on importance of rain water harvesting in selected areas of Ranchi city,India.

Dependency on groundwater for drinking and domestic purpose has increased.

By

Dr. Nitish Priyadarshi

Geologist.

nitish.priyadarshi@gmail.com

Introduction:

Water is essential for life- all living organisms contain water. In fact most living organisms consist of over 60 percent water.

Through out his brief history on earth, man has depended on three basic natural resources for his survival: air, land and water. Of these three, none has been more abused and neglected by man than water. Yet without water, the land produces nothing; without water, life vanishes from the face of the earth. Civilizations arose and have prospered for millennia where water was abundant. The Nile valley is a prime example. When water disappeared, civilizations withered and died. Mesopotamia is a classic example.

The utter human dependence on water is exemplified by the fact that man can survive for five weeks without food, but he dies after only five days without water. If the water supply of a human being is cut off for just a few days, he will die of dehydration long before the water is completely evaporated from his body. Water vapor is lost with every breath, and we cannot avoid breathing.

In recent years due to increasing contamination of surface water bodies, dependency on groundwater for drinking and domestic purpose has increased many fold. But these water sources are now badly affected with global warming. Groundwater is depleting day by day due to effect of rising temperature and urbanization.

The excess soil moisture that saturates subsurface soil or rock and migrates downward under the influence of gravity. In the literal sense, all water below the ground surface is groundwater; in hydrogeologic terms, however, the top of this saturated zone is called the water table, and the water below the water table is called groundwater.

Ranchi the capital city of Jharkhand state of India is located at 23.350 N and 85.330 E. The total area covered by Ranchi-Municipal area is about 141 square kilometers and the average elevation of the city is 645 m above Mean Sea Level (MSL). As of 2001 India census Ranchi had a population of 846,454.

Water supply, in adequate quantity and at desirable quality, is essential for any sustainable urbanization. Water supply in Ranchi dates back to more than 50 years ago.

There are three main dams ( Hatia, Rukka, and Kanke dam) from where the water is supplied to the city. Surface water is always vulnerable to pollution. People of Ranchi are dependent more on purer source like groundwater. Of the total consumption more than 60% comes from groundwater storage. Due to increasing population more pressure has developed on groundwater from the aquifer beneath the city.

The process of urbanization and industrialization from last 20 years has caused changes in the water table as a result of decreased recharge and increased withdrawal. Many of the small ponds which were main source of water in the surrounding areas are now filled for different construction purpose affecting the water table. Lots of DEEP- BORING in the Ranchi city has also forced the water table to move down as well as Ranchi plateau.

Groundwater in Ranchi city:

Groundwater in Ranchi city is mainly stored here in secondary porosity features or void spaces developed as result of weathering, fracturing, jointing, shearing or faulting phenomena. The gneisses and granitic rocks with associated schists and quartzites constitute the main consolidated rock terrain of Ranchi district.

Major portion of Ranchi city which is part of the Chotanagpur Plateau occupied by hard rock which are devoid of primary porosity and occurrence and movement of groundwater is controlled by the joints, fractures and fissures present in them.

During the long span of geological history these rocks have been deformed and tectonised in many ways including deep erosion.

In Ranchi city water table in the consolidated formations is now at its lowest from April to June. Water table is at its highest peak during August, gradually stabilizing in the month of November.

Sources of groundwater recharge in Ranchi city and the other parts of Jharkhand State is the vertical percolation of rain water. Although city experiences about 1000 to 1200 mm rainfall annually, the rate of vertical percolation is hindered by the presence of highly weathered and metamorphosed rocks. The Ranchi plateau gradually slopes down towards south east into the hilly and undulating region of Singhbhum. Due to this uneven topography the rain water are lost through surface runoff resulting in less water percolation below the surface. The thin soil layer of Ranchi plateau which is becoming more thin due to weathering is gradually loosing its water retaining capacity, Moreover, present land development practices in the recharge area and natural canals or rivulets in and around the city is also reducing the natural recharge significantly. More than 40% of the rain water is lost in the form of surface runoff. The rate of decline ranges between 1m/year to 5m/year at different observation locations within the city.

As Ranchi is becoming one of the important business center in Eastern India there is a rampant increase in construction and expansion of city. Due to inadequate water supply from the dams, dependency on ground water is increasing. Over pressed zones are Upper Bazar, Main Road, Ratu Road, Piska More, Chutia, Hindhpirhi, Circular Road, Burdwan Compound, Lalpur and Harmu Road.

Objective:

The main objectives of Rain Water Harvesting are:-

• Increasing the availability of ground water during periods of requirement.

•Preventing depletion of ground water reservoirs in areas of over exploitation.

• Improving quality of ground water through dilution.

Rainwater harvesting is the collection, storage and injecting precipitation  down in the earth of  for later human use. This project focuses on the selection of the site and rainwater harvesting system located at the different rickshaw pullers garage located in different areas of Ratu road and Piska more in Ranchi city. The information collected  from this project will be used to build a template for designing a rain water harvesting system that can be placed in the selected areas.

                                    Fig.1 Depletion of ground water.

                                  Fig. 2. Structure of rain water harvesting.

Fig.3. Depleted water in a well in Piska More, Ranchi.

Rickshaw pullers are the most affected people as they are more dependent on surface and well water which is polluted and gets dry in summer season.

Till about thirty years back, the areas surveyed used to be unpaved and the rain falling on these areas would percolate into soil and remain there for being drawn through shallow open wells. With the proliferation of flat complexes, these areas been covered, resulting in stopping of percolation of rain water into the soil. But on the other hand the use of ground water has risen immensely. With Increase in the number of deep bore wells, the shallow wells started drying up. The reason is that no sincere attempt was made to re- establish the ground water table to its original level during monsoons.

Rooftop rain water harvesting was suggested in the surveyed areas. Out of 30 sites 10 sites were selected as the rickshaw pullers were using dug well waters for their daily purpose. Rooftop catchments is  the most basic form of this technology, rainwater is collected in simple vessels at the edge of the roof. Variations on this basic approach include collection of rainwater in gutters which drain to the collection vessel through down-pipes constructed for this purpose, and/or the diversion of rainwater from the gutters to the settling  tanks/percolation tank or absorption tank  filled with sands and cobbles and pebbles working as water filters. As the rooftop is the main catchment area, the amount and quality of rainwater collected depends on the area and type of roofing material. Reasonably pure rainwater can be collected from roofs constructed with galvanized corrugated iron, aluminum or asbestos cement sheets, tiles and slates.  Roofs with metallic paint or other coatings are not recommended as they may impart tastes or color to the collected water. Roof catchments should also be cleaned regularly to remove dust, leaves and bird droppings so as to maintain the quality of the water.

Settling tanks for collecting rainwater harvested using guttering may be either above or below the ground. Precautions required in the use of se tanks include provision of an adequate enclosure to minimize contamination from human, animal or other environmental contaminants, and a tight cover to prevent algal growth and the breeding of mosquitoes.

Sr.No	Garage Name	Garage owner name	Address	No.of rickshaw pullers staying  in the garage	Water Harvesting status	Remarks	Date of visit
1	Vijay	Vijay Tirkey	Near Krishi Bazar, Pandra, Ranchi	50	Yes; Important		29-01-2018
2	Amit	Amit kr. Bhagat	Piska More	70	Yes; Important		29-01-2018
3	SLK	Suresh Kachhap	Piska More	15	No	Shed not much and well is not owned by owner but garage owner has himself made some water harvesting system.	29-01-2018
4	Pawan	Pawan Sharma	Piska More	40	Yes		29-01-2018
5	BPK	Suresh	Karam toli	40	No	Has naturally available water resources which maintains the water level.	29-01-2018
6	JPB	Jagdish Bagla	Piska More	20	Yes; Important		30-01-2018
7	Guddu	Rajiv Agarwal	Near Uphar cinema, Ratu road	30	No	Consist of self built water system which maintains water level	30-01-2018
8	Mitu	Jayant Agarwal	Near Uphar cinema, Ratu road	30	No	Land too low so naturally land absorbs water, sheds are not available in much	30-01-2018
9	MPS	Madhukar Singh	Near Pahadi Mandir	25	No	No well; no boring and monthly rented land	30-01-2018
10	Sunil	Sunil Yadav	Near Pahadi Mandir	50	No	Less possibility of holding rain water	30-01-2018

Acknowledgement:

This survey was carried out with the help of Mrs. Aprajita Mishra and Smita Dasgupta of Maitri India, Ranchi.