«GROUND WATER INFORMATION BOOKLET MANDYA DISTRICT, KARNATAKA SOUTH WESTERN REGION BANGALORE AUGUST, 2012 FOREWORD Groundwater is an essential ...»
4.1.2 Depth to water levels Out of 41 national hydrograph stations in Mandya district, during May 2011, 2 stations were dry and during November 2011 no stations were dry. The depth to water levels in the national hydrograph stations (dug wells) recorded during May/2011 was in the range of 0.38 to 21.28 m bgl. The depth to water levels in the national hydrograph stations (dug wells) recorded during November /2011 were in the range of 0.20 in Sivasamundram to 23.41 m bgl in Hebbani. In the district there are totally eight piezometers national hydrograph stations. The water levels in the four measured piezometers ranges from 0.20 to 18.53 m bgl during May 2011 and the water level in the five peizometer ranged from 0.03 to 17.67 m bgl during November 2011.
Pandavapur and major part of S.R.Patna taluk the weathered thickness is more than 10m.
Depth to water levels of May and November 2011 are shown in fig- 4 and 5 respectively.
4.1.3 Seasonal water level fluctuation The seasonal water level fluctuation for the year 2011 was in the range of 0.6 to 5.73 for water level raise category and was in the range of –2.58 to –0.47 m for water level fall category. The seasonal water level fluctuation for the year 2011 is available for piezometer hydrograph network stations in the range between 0.20 to
4.1.4 Long-term water level trends (from year 2001 to 2010) Out of 29 pre monsoon Long term water level trend data for the period from year 2002 to 2010 available for national hydrograph network stations, 26 are showing rising trends in the range of 0.056m/year to 1.055/year and remaining 3 are showing falling trends in the range of 0.149 m/year to 0.324 m/year. Out of 31 post monsoon long term water level trend data for the period from year 2002 to 2010 available for national hydrograph network stations, 20 are showing rising trends in the range of 0.029 m/year to 0.844m/year and the remaining 11 are showing falling trends in the range of 0.005 m/year to 0.638 m/year.
4.1.5 Results of Ground water exploration On the basis of the hydro geological surveys followed by resistivity surveys, a total of 26 sites were recommended for the drilling of exploratory wells to a depth of 100m bgl in the first phase of ground water exploration in Mandya district. The depth of the wells ranged from 15.95 to 92.50 m bgl. The discharge during PYT ranged from 0.095 to 6.1 liter per second (lps). The transmissivity during PYT ranged from
1.2 to 126m2/day. The drilling results indicated that 35% of the wells, discharge during PYT was 3 lps. In the second phase of ground water exploration in Mandya district total of 26 exploratory wells were drilled to a depth maximum of 200m bgl.
The depth of the wells ranged from 123.24 to 200.00 m bgl. The drilling discharge ranged from 0.014 to 16.4 lps The discharge during PYT ranged from 55.2 to 438 lpm. The transmissivity ranged from 0.276 to 291m2/day. The drilling results indicated that 65% of the wells, the drilling discharge was 3 lps. The deep fractures were encountered at a depth 150 to 200 mbgl. The locations of the exploratory wells constructed by CGWB are show in fig 6.
Fig - 4 Fig - 5
4.2 Ground Water Resources The ground water resource estimation shows that, (Fig 7 and Table 6) total annual ground water recharge is 99520 HAM and net annual ground water availability is 91343 HAM as on year 2010. Existing gross ground water draft for domestic and industrial water supply uses is 2751 HAM and for irrigation purposes the draft computed is 37364 HAM. Total existing gross ground water draft for all uses is 40114 HAM. The net ground water availability for future irrigation development is 53841 HAM, after allocating 5047 HAM of ground water for domestic and industrial uses for the next 25 years.
Thus the taluk wise ground water development stage and % in taluk area falling in various categories can be summarized as KR pet : 63% (In terms of taluk area 79%is safe and 21% is over exploited ) Maddur : 47% (In terms of taluk area 70% is safe and 30% is semi critical) Malavalli : 58% (In terms of taluk area 60% is safe, 25% is semi critical and 15% is over exploited.) Mandya : 32% (In terms of taluk area 99% is safe, 1% is over exploited) Nagamangala: 59%, (In terms of taluk area 50% is safe, 50% is over exploited) Pandavapura: 25%, (In terms of taluk area 70% is safe, 30% is over exploited) Srirangapatna: 24% (In terms of taluk area 99% is safe, 1% is over exploited) For the year 2008-09, the unit area annual ground water resource of the taluks of Mandya district is calculated (Fig 8) in m. It is calculated to be 0.25 to 0.50m for Pandavpura taluk, o.15 to 0.25 m for Srirangapatna and 0.10 to 0.15 m in the remaining taluks.
4.3 Ground water Quality Water samples are collected from selected dug wells (National Hydrograph monitoring Stations) annually for chemical analysis. The analysis result indicates that in general the quality of ground water is potable for drinking and suitable for irrigation purposes. However high concentration of fluoride (1.5 mg/lit) is observed around Nagamangala and Maddur as small patches. High concentration of nitrates (45 mg/lit) is observed in major parts of all taluks except Malavalli taluk where it is seen as small patches in the southern part. This may be attributed to more use of fertilizers and canal irrigation. High chloride concentrations are observed in eastern part of Mandya and around Maddur. Electrical conductivity is in permissible range in general. In the western part of the district the Electrical conductivity values are less than 1000 micro mhos, whereas In southeastern part the electrical conductivity values varies from 1000 to 3000 micro mhos, especially in canal command areas of the district the EC values are more than 2000 micro mhos /cm.
Ground water quality map of the district is shown in Fig -9.
4.3.1 Groundwater Vulnerability area
Groundwater being a dynamic resource, getting recharged annually, primarily from the rainfall, is vulnerable to various developmental activities and is prone to deterioration in quality and quantity. The vulnerability is high in certain areas while in other areas it is comparatively stable. Based on it’s susceptibility to various stress factors the Mandya district vulnerability map is prepared on a regional scale considering the following factors viz.
Area under high stage of ground water development falling in over exploited (generally with stage of development more than100%) and critical (generally stage of development within 85-100%) category as on March 2009.
Area having intensive cultivation/ area falling under canal command, thus prone to pollution from fertilizers / insecticides or water logging.
Area having fluoride above maximum permissible limit of 1.5ppm Area having nitrate above maximum permissible limit of 45ppm. (Even though nitrate is point source pollution due to anthropogenic activity and as such area cannot be demarcated, for the convenience of the user group, area having high incidence of pollution is marked. Within the marked area there may be points devoid of high nitrate and vice-versa.) Fig-9 Fig-10 Industrial cluster as identified by Central Pollution Control Board, prone for pollution from industries.
In the district, the groundwater is vulnerable to fluoride and nitrate contamination and to fertilizer and pesticide because of intensive agriculture its application of (Fig 10). Hence precaution is to be practiced in command areas.
4.4 Status of Ground Water Development The ground water is a major source for drinking purpose. The farmers with small acreage of land depend mainly on the rainwater and water available in the shallow wells within their premises. The abstraction structures, dug-wells and bore wells constructed/existing are mainly tapping the aquifers within depth range 8.00 to
12.00mbgl and 150 to 200mbgl respectively. As per the record of 31.3. 2006, the domestic water requirement is supplied through 1132 numbers of Mini-water supply schemes, 932 numbers of piped water supply schemes through bore wells along with 9902 number of bore wells installed with hand pumps.
The 4th Minor Irrigation census was carried out in 2006-07 which included both ground and surface water. The Ground Water Schemes consists of Dug wells, Shallow Tube wells and Deep Tube wells. As per the census, there are 3119 dug wells (88 are not is use) and 35709 bore wells (546 are not in use). The taluk wise status of dug well and bore well is given in Table 7.
5. Ground Water Management Strategy.
5.1 Ground water development Sustainability of ground water resource and its judicious use should be given prime importance while making development strategy. In critical and over exploited areas, artificial recharge and rainwater harvesting measures are recommended to augment to ground water system. About 91343 ham of ground water resource is available in the district for further development. The development is recommended only in area categorized as safe and semi critical while avoiding the parts of over exploited blocks of Nagamangala, Pandavpura, KR pet and Malavalli. In such areas, potential aquifers can be located by hydrogeological surveys aided by geophysical methods. Dug wells and filter points are recommended only in river and valley banks where sufficient thickness of valley fill is available which gets saturated during rainy seasons. The ground water development in other feasible areas should be done by bore wells. Spacing norm of 200 m may be strictly adhered to avoid interference. Aquifer should be pumped as per crop water requirement.
In areas, which are categorized as critical and over exploited, growing crops like paddy, sugarcane etc, having high water requirement may be avoided. Farmers should be encouraged to go for less water requirement crops. Advance irrigation methods like drip and sprinkler irrigation may be practiced.
In the command areas, conjunctive use of surface and ground water may be practiced to avoid long-term hazards like water logging and ground water as well as soil salinity problems.
5.2 Water conservation and Artificial Recharge The ground water development in KR pet taluk is 63% (21% taluk area is over exploited) and Nagamangala is 59%, (50% taluk area is over exploited). Water level in these is taluks showing downward trend. In such a situation there is a need to augment ground water recharge by artificial recharge structures and rainwater harvesting structures to harvest noncommittal surface runoff.
In the western part of the district where the topography is hilly and rugged artificial recharge structures like nalla and gully plugs contour bunds and contour trenches and nallabunds may be constructed and in comparatively plain areas percolation tanks and point recharge structures like recharge shafts recharge pits and recharging through existing dug/bore wells may be practiced. In semi-urban areas in the district, lot of roof area is available for rooftop rainwater harvesting. So in these semi-urban areas rooftop rainwater harvesting practices may be encouraged. This will help in reducing the load on urban water supply systems. In the district headquarter i.e. Mandya town, rain water harvesting is to be encouraged in all the government departments and educational institutions.
Moreover from the year 2001-02, Central Ground Water Board was also involved technically with NABARD and concerned state government departments in dug well recharge scheme, where 4677 nos. of structures and 91 small and marginal structures were surveyed. Out of the total 4768 nos. of structures, 1660 structures were approved by SLSC, district agencies and NABARD. Till date as on 31.3.2012, only 12 nos. of structure are in progress and an amount of 50 lakh has been released so far. As a part of the scheme, trainings, workshops, capacity buildings are also organized in Mandya district.
Fig- 11 shows the area feasible for artificial recharge structures in the district based on Master Plan of Artificial Recharge of Karnataka prepared by CGWB. According to the master plan, 1836 nos. of check dam, 310 nos of percolation tanks, 83 nos. of point recharge structures and 9 nos. of sub-surface dykes construction are feasible in the Mandya district.
6.0 Ground water related Issues & Problems There is over exploitation of ground water resource in parts of K.R.Pet taluk, Malavalli taluk, Nagamangala and Pandavpura taluk. This has resulted in the decline of water level. Therefore, immediate artificial recharge measures are required to be taken up in these taluks to achieve sustainability of ground water resources.
Fluoride concentration of more than permissible limit exists as small pockets in parts of Maddur and Nagamangala taluks of the district. Ground water in younger granites has more fluoride content than the gneisses. The fluoride content increases with depth in same aquifer. The shallow aquifers are having comparatively low concentration of fluoride. In order to reduce or control the problem, it is recommended to recharge ground water by way of artificial recharge structures like percolation tank, desilting of silted tanks, check dams, nalla bunds, farm ponds and subsurface dykes. Nitrate concentration of more than permissible limit exists all over the district. This may be due to indiscriminate use of fertilizer and biological contamination from decaying vegetation. Judicious use of fertilizer and proper care in disposing the biological waste can reduce the problem. Regulated use of fertilizer and pesticide is required in the command and vulnerable areas.
7. Awareness and Training Activity
7.1 Water Management Programmes (WMTP) Training program on Ground water management was organized for TOT at Cauvery Auditorium, ZP Office, Mandya during 26.7.2003 to 28.7.2003.
Sri.S.S.Chauhan Chairman, CGWB presided over the function. Sri B.P.Kaniram, IAS, DC, Mandya District inaugurated on 26.7.03. Sri K.H.Ashwathnarayana Gowda, IAS, CEO, ZP, Mandya participated as Guest of Honour. Sri C.S.Ramasesha R.D, CGWB, SWR, welcomed the gathering and Sri.K.Keerthiseelan, Suptdng Hydrogeologist gave vote of thanks. 32 trainees from various State Government Departments, NGOs, and Educational Institutions from Mandya district participated in the training programme. Officers of CGWB presented seven lecture topics on the theme. One-day field visit was arranged to Bangalore University and trainees were apprised of the artificial recharge scheme implemented in the university campus.