Ground Water Suveys and Development Agency, Pune | Un-Conventional Measures for Source Strengthening

Un-Conventional Measures for Source Strengthening

In Maharashtra, every year there is scarcity due to irregularity of rainfall. Drinking water scarcity is occur due to some dug wells becomes dry and water level of bore wells gets depleted. In spite of heavy rainfall in hilly area maximum rain water goes wasted due to runoff on steeper slope. In this area, porosity of land is poor, because of which less quantum of water gets recharged.In scarcity period, most of the villages water is supplied by water tankers or bullock carts, etc. Therefore to overcome the drinking water problem permanently of such villages, Government of Maharashtra started implementation of ambitious water conservation programe from year 1992-93 through Water Conservation Department. As one of the activity of water conservation programe, GSDA started to implement Unconventional programme to strengthen the drinking water sources.

  GSDA is implementing schemes to improve the performance of the existing ground water sources and strengthening the sources by unconventional measure.Sources strengthening by unconventional measures as on today 

1 Fracture Seal Cementation (FSC) 1001

2 Jacket Well Technique         (JW) 641

3 Bore Blast Technique  (B.B.T) 549

4 Hydro-Fracturing (HF) 19849

Principle and general description of the above technique is given below.

FRACTURE SEAL SEAL CEMENTATION :-

The groundwater migration through a network of shallow depth aquifer from the discharging location is arrested by this technique. It is suitable in disintegrated rock combined with fracture and granular porosity. After identifying the suitable area on the basis of geohydrological investigations, this technique is adopted. Under this process, normally one or two rows of suitable diameter boreholes are drilled to a depth of a little more than the deepest dugwell in the command area of stream or nalla. These rows across the stream are filled by injecting cement slurry under high pressure for sealing of existing fracture. This technique is useful to create an effect of “ Cut Off Wall “ as Underground bandha

                                                                      

 2. JACKET WELL :-

The construction of Jacket well around the dugwell in hardrock area increases effective diameter of the well artificially thereby increasing the storativity. Borewells of about 115 mm diameter and to a depth of open dugwell or to a shallow aquifer are drilled around the supply well, either in circular or semi circular or any other desired pattern depending upon the topographical and hydrological conditions. The blasting of these bores are carried out using slurry explosives, detonating cord and electrical detonators to create fractures and interconnection between the boreholes to cord and electrical detonators to create fractures and interconnection between the boreholes to increase the effective diameter of supply well and to create additional storativity of water.

  

3. BORE BLAST TECHNIQUE :-

Bore blast technique is adopted to create more storage space of Groundwater artificially in massive and crystalline hard rocks by fracturing the bed rocks. Hydrogeological survey is carried out to locate such area where the rock can be blasted to develop cracks below the zone of weathering. The no of boreholes is calculated depending on the quantity of water to be made available. Suitable type of slurry explosive is lowered in the boreholes and is blasted using detonating cord and electrical detonators. At a time about 5 to 6 boreholes are blasted. This technique is applied in assured rainfall areas and where landforms are mostly hilly. These are most suitable for small habitations of about 100 to 150 population, where drinking water shortage occurs.

     

4. STREAM BLASTING :-

Generally, drinking water wells are situated on nalla banks.However, at some places the groundwater flow through nalla bed is not connected to the well and therefore these groundwater goes waste as a runoff and the well being not connected becomes dry during summer months. Such wells are possible to be rejuvenated by technique known as “ Stream Blasting”.In this technique, the area of nalla bed in the vicinity of well is studied by geophysical and geohydrological survey. Then numbers of 115 mm borewells are drilled in the nalla bed to a depth of open dugwell. These drilled boreholes are further charged with explosives and blasted to artificially to create fractures joints etc. Such artificially created fractures are automatically get inter connected to the well and groundwater is made available thereby improving the drinking status of the well.

  

5. STORAGE PIT :-

Normally the hilly terrain in the state receives satisfactory Rainfall. But due to steep gradient, thin soil cover, limited weathered mantle and absence of joints and fractures in formation cause meager storability for groundwater. Ultimately the habitations located in such area face acute scarcity of drinking water in every summer. In such areas the conventional measures have limited utility due to technical and financial factors. The measures like “Storage Pit” is useful to collect water in required proportion with population. Small habitations ( Up to 200 souls ) are considered for this measure.In this project, size of pit is fixed by volumetric analysis in accordance with population. Quantity loss due to evaporation and other permissible seepages is also taken into account. Pit of required volume is excavated and curbed up to hard strata, same as dug well. To check the migration of stored water, pit wall at the down side is sealed by concrete lining. Normally the pits are open, but in cases to protect the pollution and evaporation, the pit is totally filled by coarse sand, pebbles and boulders as filter media. From the pit, water is pumped by shallow depth hand pump, which will be installed on safe distance from the pit to avoid pollution.These projects may be implemented in combination as per site requirements.

 

 

6. HYDRO FRACTURING :-   

This technique is applied for rejuvenation of poor yielding or Unsuccessful borewells. Some of the borewells in the villages are successful and fitted with pumping device. Poor yielding and dry borewells in the same village indicate that the fractures do not exist or if existing, they are not connected to the nearby bodies, and the fractures may be closed or sealed.By this technique very high hydraulic pressure is created between the confined sections of the borewell. This very high pressure is responsible for opening the closed or sealed fractures and further connecting it to nearby bodies. When confined section of borewell is not having existing network of fractures then the new fractures are created and these newly created fractures are further extended to connect the water bodies. In this way borewell yield is improved substantially    

                                                                                                                                        

National Rural Drinking Water  Programme (Coverage) :-

Ground Water Surveys & Development Agency (GSDA) is implementing the Solar/Electric Energy based dual pump mini piped water supply schemes under NRDWP, in the habitations totally depending on only Hand Pumps.  GSDA is also implementing the spring based mini piped water supply schemes under NRDWP in the hilly habitations where the natural springs are available nearby the habitations.Electric Energy based Dual Pump Mini Piped Water Supply Schemes -These schemes are implemented since the year 2008-09 as per the Govt. GR No. Grapapu-5310/ Pra. Kra.04/ Papu -15, Dated 11/01/2010 & revised Govt. GR NO. . Grapapu-5310/Pra. Kra. .04/ Papu -15, Dated 29/12/2011. In this scheme, 1 HP single phase electric pump is fitted along with the existing hand pump in the bore well having minimum yield 2000 liters per hour.  The water is collected in the 5000 liters capacity storage tank & it is then supplied to 30-40  households through tap water connections / public stand posts. The rain water harvesting structure for the bore well recharge is also included in the scheme.This scheme has maximum expenditure limit of Rs. 2.50 Lakhs each.Since the year 2008-09 to 2016-17, the total 2915 No. of schemes are completed so far