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     10.   Special project studies.

      ·     Special project studies - Artificial recharge and
             conjunctive use projects

        
        
        

 
a)  Experimental Artificial Recharge Studies in Kolar 
      District, Karnataka.
                

      Ground water irrigation has gained importance during   the last decade in Karnataka through dugwells, dug-cum-borewells and borewells in some districts, especially in areas where perennial rivers are absent.  Kolar is one among such  districts which has experienced high stage of ground water development where a spurt in groundwater activity is seen during the past two decades.  The periodical monitoring of wells for the period 1973 to 1996 shows a declining trend in ground water levels.  The area showing declining trend in ground water levels are associated with higher degree of ground water development.

      Central ground water Board under Central Sector scheme has carried out  Experimental Artificial Recharge Studies (EARS) in Gauribidanur and Mulbagal taluks during 1993-94.

      The main activities carried out in the above taluks are:

      Desilting of two tanks and converting the same into Percolation tanks.

      Watershed treatment in two areas

      Construction of point recharge structures at 5 locations.

      Gravity recharge wells at 2 locations.

      Roof top rain water harvesting structure at Gauribidanur.

      Construction of Percolation Tanks:

      The existing defunct and silted up Minor Irrigation (M.I.) tanks at Errapothenahalli and Manchiganahalli were taken up for conversion to percolation tank after desilting.  Government of Karnataka had plans to take up desilting of M.I. tanks in Kolar district on a large scale and in this context the district level authorities emphasized the need to quantify the additional recharge through such desilting programme.  Keeping this in mind, it was planned to take up study of the tank bed seepage prior to desilting and after desilting and thereby quantifying  the  same.   

                                                  

      

      Watershed Treatment:                                                   

      Treatment of Basavapura and Bhovibikkanahalli micro-watersheds with traditional water harvesting structures to study the impact   the same on ground water recharge.  The studies were taken up as watershed development programme, which are being taken up in Karnataka on a large scale and the present study attempts to quantify the additional recharge by such programmes. Check dams are the major structures constructed under this programme.

      Point Recharge Structure (PRS)

      Five PRS were taken up in the district.  The construction of PRS involves two stages of work.  Firstly, the construction of a borewell for recharge and secondly, designing a filter bed around the recharge borewell.  The surface water either from the M.I. tank or from the nalla is allowed into the filter bed.  The silt free water from the filter bed will be let into the recharge borewell tapping fractured aquifer.  The drilling of recharge borewells together with observation wells (ie: recharge well field) were taken up by CGWB.  The five well fields are located at Hosur (two nos.), Bhakthara halli, Sonaganahalli and Manchiganahalli. 

      Gravity Recharge Wells:  

      Two gravity recharge well fields were constructed, one each at Belchikkanahali and Hussainpura.  A short duration injection test was conducted in these two well fields and tested for their intake capacity rates.  The source water for the tests was transported through pipe line from an existing irrigation borewell located about 700 meter away from the well field.

      Findings of Artificial Recharge Studies:

      Percolation tanks:

      Infiltration tests results carried out at Percolation tank beds prior to and after desilting showed an improvement in tank bed percolation. The infiltration rate ranged from 0.17 to 2.4 cm/hr prior to desilting whereas the rate has increased in the range of 1.8 to 8.8 cm/hr after desilting at Errapothenahalli.  At Manchiganahalli, it ranged from 1.2 to 5.8 cm/hr prior to desilting whereas the same was observed to be in the range of 10 to 16.8 cm/hr after desilting. The ground water level data during post desilting periods reveals a built-up in storage in the order of 2 to 4.5 m to the downstream of the tanks.

      Watershed treatment:

      It has revealed that the flow recorded is considerably reduced after the treatment and the construction of the structures.  A built-up in storage was observed to be in the order of 3 to 5 m in the phreatic zone. The treatment of Basavapura  microwatershed has shown watershed treatment can arrest flows during monsoon and enhance recharge to ground water.  This indicates that watershed treatment especially in the drought prone district of Karnataka can be taken up on a large scale  which can contribute greatly to recharging of ground water and retention of moisture for crop production.

      Point recharge structure:

      The recharge through point recharge structure has benefited the deeper aquifer to build-up storage locally and to improve the ground water potential and are effective in recharging deeper aquifer and can be applied in feasible areas of a drought prone district.      

      Gravity recharge experiments:                                  

 

      The experiments carried out at Belchikkanahalli and at Hussainpura have indicated 3 to 4 lps intake of the aquifer (weathered and fractured granite gneisses) with a possibility of creating additional storage using the excess water available in Bandihalla. This can be adopted successfully in similar environs having surplus source water.  The source water has to be clear and silt free before recharge. Stream flow and tank water are  ideal as source water.  

      The total amount sanctioned under the EARS is Rs. 44.116 lakhs and this amount has been released to State Government by CGWB under the central sector scheme.  

      b) Jnanabharathi campus, Bangalore University.

 A micro water shed 
 in the south central 
 part of the university 
 campus has been 
 identified for artificial 
 recharge study 
 purpose. The annual 
 run of calculated 
 within the water shed 
 is to the tune of 0.056 
 MCM and in which 

      0.026 MCM of freshwater is discharged into Vrishabhavathi river, which is highly polluted. Two exploratory borewells drilled by CGWB under exploration programme have turned out to be high yielding which cater to the needs of University campus. A fall of 3 to 5 m in ground water level has been observed during the last four years resulting in indiscriminate pumping of the bore wells in the water shed. thus laying heavy stress on the aquifer system. In view of this, studies have been taken up for harvesting rainwater which goes as run off in the micro water shed of the campus. In this context, the rainwater harvesting is proposed through three check dams of which one is a combination structure consisting of a subsurface dyke and check dam.

      The scheme has been sanctioned during the year for an estimated cost of  Rs.13.75 lakhs.  Shri.Arjun Charan Sethi, Hon’ble Minister for Water Resources, Govt. India has launched the scheme during  Feb.'2001 in presence of other dignitaries from Govt.of India, Govt.of Karnataka, Central Ground Water Board and Bangalore University. The construction of the recharge structures were completed.

      c) Conjunctive Use Studies In Ghataprabha River Basin.

      Conjunctive use study of surface and ground water in  
      Ghataprabha river basin in parts of Belgaum and Bijapur 
      districts has been carried out covering an area of
      10,370Km2.  The data from CGWB and state agency have
      been utilised in this study. Ground water modelling studies
      were also undertaken during the project period.

      The study indicated that canal water utilisation in the left
      banks command is 1114 MCM and the total water utilisation
      is 2070 MCM leaving a balance of 1015 MCM for further use
      out of which 529 MCM is surface water.  By increasing the
      cropping intensity a conjunctive use plan can be drawn. 
      Non utilisation of ground water in upper reaches of the basin
      has resulted   the water logging condition.  In tail end area
      water deficit is experienced. 

      A conjunctive use plan has been drawn both for left and  
      right  bank canal command areas with optimal utilisation of
      surface and ground water.  Under this a suggestion put forth
      for left bank canal is that utilisation of surface water to a
      tune of 1068 MCM (84%) and ground water to a tune of 173
      MCM (16%) can boost up the cropping intensity to 200%
      likewise in the case of right bank canal a cropping intensity
      of 140% has been suggested by utilising surface water to a
      tune of 712 MCM and ground water to a tune of 223 MCM.

      A total investment of Rs 40.5 crores has been suggested
      for  construction of 20,691 borewells upto a depth of 80m
      covering 10 taluks of Belgaum and Bijapur districts.  The
      main crops suggested for the cultivation under the
      conjunctive use plan are Sugarcane, Cotton, Groundnut,
      Maize and Pulses.

      D) Pollution Studies:

      An area about 50 sq.km in and around Bhadravathi town in  Shimoga district  was studied to  assess the ground water quality and aquifer material  vis-a  -vis  the industries existing, agricultural practices and urbanisation. The area  is  drained by the perennial Bhadra River  and  the  major industries are M/s Mysore paper mill and M/s Visweshwariah  Iron and Steel limited.

     The  area  falls  in southern transition  agroclimatic zone  and receives a mean annual rainfall of 826.3 mm. Extensive irrigation from  Bhadra reservoir and Gondi channel, which  are  constructed across the river Bhadra is practiced around Bhadravthi. Premonsoon survey was carried out in June, 1994 during which  26 dug  wells  and  17 bore wells were identified  for water  level monitoring  and sample collection. Solely granites underlie the area.  The premonsoon water levels  ranged from 1.54 to 13.21 mbgl and post monsoon water levels ranged from 1.16 to 9.88 mbgl and the seasonal fluctuation (1994-95) ranged from 0.16 to 5.60 m.

     A  total of 44 water samples, 20 no from dugwells, 21 from  bore wells,  2 from Bhadra river and 1 from municipal water supply  in two  sets  were collected during pre-monsoon 1994.  One  set  was analysed  in SWR office for 13 parameters and the other  set  has been  sent  to  Kerala region, CGWB,Trivandrum  for heavy  metal analysis.

      During  post monsoon 1994, a total of 47 water samples were  col­lected  in 3 sets. Sources of sampling was 21 from  dugwells,  18 from  bore  wells, 2 from river Bhadra, 1  from  Municipal  water supply, 1 from canal and 4 no.s from effluent samples. One set of samples were analysed in SWR office, one set was sent to Kerala region,  Trivendrum  for heavy metal analysis and third set  was submitted to Sriram institute for industrial research,  Bangalore for analysing selected parameters.

      The  key wells were got surveyed to determine (1)reduced  levels of  ground water levels to know flow direction and (2) to  estab­lish  the relationship of river Bhadra with the ground  water  in the area. The study shows that elevation of W.T lies between  565 to 611 m above sea level and the river Bhadra in this section  is effluent  in  nature and receives water from  surrounding  ground water reservoir.

MULTI DISIPILINARY  PROJECT  STUDIES                       

        (a) Karnataka

               A multi disciplinary ground water project was carried out with Canadian Assistance (1971 – 1975) envisaged to develop methods of ground water resource evaluation, mainly for granitic and basaltic terrains covering parts of Andhra Pradesh and Karnataka which covers an area of 505 sq.km in parts of Gulbar­ga and Bidar districts of Karnataka.

              Vedavathi River Basin Project (VRBP) was taken up during 1975-80 covering an area of 19,000 sq.km.  falling in parts of Chitradurga, Chikamagalur, Hassan, Shimoga, Bellary and  Tumkur districts. The aims of the project studies were to develop methodology for scientific and rational development  of ground water in crystalline terrain and for  quantifica­tion  of  ground water resources and determination  of  Specific yield percent of the formation and minimum rainfall required  for recharging the ground water body.

             Ground water  evaluation was carried out during 1979-81 in trap Bhima crystalline  fringe areas and Kaldgi formation (sandstone, shales and  limestones) in Gulbarga and Bijapur districts by drilling wells. The studies helped in locating fractures in different depths in the area.

      Hydrology project

      Under the World Bank assisted hydrology Project constructed piezometers for continuous monitoring of ground water levels using digital water level recorders were taken up.     

      CGWB along with MGD, Govt.of Karnataka have drawn a plan to construct 805 Piezometers in Karnataka.  The CGWB participation involves analysis of NHS for water level and water quality data.  The basis for selection of sites for the piezometers construction is as follows.

                       a. Topography

b. Hydrogeological condition

c. Optimisation study for PZ density location

d. Depth of existing NHS location

e. Water level changes over a period of time.

f. Dark and grey blocks

g. Agroclimatic conditions.

h. Quality considerations in respect of fluoride and nitrate.

      Based on the analysis of historical data of water levels the optimum number of observa­tion station decided for CGWB in Karnataka is 305 Piezometers.

      URBAN GROUND WATER MANAGEMENT

      Dharwar and Hubli urban area: Ground water studies in Urban agglomeration has become essential, since the demand of the growing population and high growth rate of industries is creating a remarkable change of scenarios in the present environment.  Hence urban ground water management studies have been taken up. An area of 190sq.km was covered covering Dharwar and Hubli cities in Dharwar district. The area is characterized by semiarid climate with an average annual rainfall of 838mm and it is underlain by schistose formations(Schists, Grewackes, shales and ferruginous quartzites) of Dharwar super group of Archaean age. Ground water occurs under water table conditions in weathered zones and under semi confined conditions in deep-seated jointed formations. Depth of weathering varies from 5 to 35 meters.

      Twenty-five key observation wells have been established all over the urban area for repeat measurements of water levels 4 times in a year to know the changes in the ground water regime. The premonsoon water levels vary from 3.5 to 16.54 mbgl and postmonsoon water levels vary form 1.81 to 14.19 mbgl. There are 6 NHS in the twin cities. The general trend of water levels in these NHS shows that two stations show falling trend and other stations maintain steady trend. 

      To understand the quality of ground water 32 water samples were collected and submitted for chemical analysis. The general quality of ground water is good and potable for domestic purposes.

      INLAND GROUND WATER SALINITY STUDIES

      An area of 2800 sq.km out of geogrpahical area of 2829 sq.km of Navalgund , Dharwad district and Nargund and Ron taluks of Gadag district(Under district ground water management studies) was selected for inland ground water salinity studies.. In order to have precise information on the extent of saline aquifers a total of 54 water samples were collected from ground water abstraction structures for detailed chemical analysis. During the course of study it is found that certain factors which might have influenced the relative ground water salinity in the aquifers of study area. They are :

1.  Net balance between annual evaporation, precipitation and run off.

2.  Rate of local rock weathering and solution with resultant formation in the soil of water-soluble salts forms the decomposed product.

3.  Salt content transported in the region by streams and rain from outside sources.

4.  Permeability and hydraulic gradient of the aquifer.

5.  The rate of groundwater circulation and rate of salt accumulation in the aquifer body from infiltrating water.

6.  Poor permeability of the soil with major area covered by black cotton soil.

                                 

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