Project Title: 
Evolution of Cost Effective and Sustainable Management Scheme of Water Resources in Baiarasagara Watershed, Kolar District, Karnataka.

Thematic Area:
Watershed Management 

Location:
* Latitude: 13o32'20" -- 13o41'24" North
* Longitude: 77o39'25" -- 77o45'15" East
* Bairasagara Wtershed covers an area of 120 sq. km of Chikaballapur and Gudibanda Taluk, Kolar district, Karnatka, app. 60 km north of Bangalore City, having undulating topology and lies within 880m to 2000m contours. (Figure 1)
* Average rainfall at kolar is 717 mm. The rainfall recorded from 1990 to 2002 is shown in (Figure 2).
* Belongs to the Dharwar super Group of Archan age (Figure 3). It is mainly composed of granites, granitic gneiss, which is exposed in the form of hillocks. Granite schists are also recorded at few places like Gudibanda, Mandikal, etc.

Objective: 
* To develop and implement a scheme for sustainable development of groundwater resources in the watershed, to meet the groundwater demand for industrial, agriculture and domestic purposes.
* To monitor water levels during post-monsoon and pre-monsoon periods, to identify the groundwater regime.
* To delineate potential zones, in order to develop and implement sustainable groundwater scheme.

Abstract:
Geo-Electrical Investigations
Electrical resistivity technique makes use of variation in electrical resistivity of the ground. The resistivity of material is defined as the resistance offered by a unit cube when a unit current passes normal to its surface and the potential obtained across its opposite faces is unity, The units are expressed in Ohm-m. The resistivity is computed, by passing electric current (in milli- amperes) into the ground through two electrodes (iron stakes) and measuring the potential drop (in milli volts) resulting from the resistance offered by the ground with the help of two other potential electrodes placed co-linearly and symmetrically about the center of the electrode arrangement. Non-polarizable electrodes are used for potential measurements in order to eliminate the polarization potential. The apparent resistivity is given by
ra =K. DV/I
Where, K is a geometrical factor, DV is the potential in milli-volt and I is the current in milli-ampere.
The most commonly used Schlumberger configuration, has been deployed in the present survey, is
K= p(LL - l2)/2l
The geometrical factor K for Schiumberger configuration is:
L is one half of the current electrode separation in meter and l is one half of the potential electrode separation in meter.
Electrical resistivity investigations were carried out in Bairasagara Watershed mainly for conceptualizing aquifer geometry. It has been covered by 47 vertical electrical soundings (VES) almost on a grid pattern with a maximum current electrode separation of 400 meters. 

Fence Diagrams
Fence diagrams are the most useful means of displaying the sub-surface lithology. The lithology of the study area in the present instance has been displayed with the help of fence diagrams - which exhibit the complete aerial view. The litho-units have been inferred from the interpretation of sounding data. The Figure (Figure4) depicts north to south view and this displays various litho-units down to bedrock.
The study area can be divided into four geo-electrical zones:
Zone 1: eastern part of the area is more fractured (93 - 261 Wm) and extended to the depth of 28m.
Zone 2: western part of the area possesses more thickness (fractured, 80 - 185 Wm) and extended up to a depth of 35m.
Zone3: western part of the area is more weathered (~ 60 Wm) while eastern part is more fractured.
Zone 4: the weathering (~ 60 Wm) is limited to a shallow depth of 10 m.

Quality of GroundWater
The chemical, physical and bacterial characteristics of water determine its usefulness for domestic, irrigation and industrial purposes.
In present study 30 groundwater samples were collected from different part of study area to study the quality and assess the usefulness for domestic irrigation and industrial purposes. 

Analysis of water samples has been done by following parameters:
* PH Values: The intensity of the acid and alkaline condition of any solution of liquid is expressed in terms of PH and is a measure of hydrogen ion activity. For low PH Values below than 7, water sample is categorized as acidic and alkaline for higher than 7. Allowable values of PH range from 6.5 to 8.5 for drinking and domestic purposes. The analysis shows that all water samples falls within the limit 7.5 to 8.26, which shows slightly alkaline nature and suitable for drinking and domestic purposes.
* Specific Conductance: The conductance of groundwater is a function of temperature and type of various ions present and also the concentration of various ions. The specific conductance (the ability of a cube of one centimeter to conduct electric current) readings are usually adjusted to 250 c, so the variation in conductance are a function of only the concentration and types of dissolved constituent present. Pure water has a electric conductivity of less than 100 micro mhos/cm. The ocean water conductance varies from 45,000 to 55,000 micro mho/cm, which indicates the water is highly saline. The normal groundwater conductance varies from 100 to 2,000 micro mhos/cm. The collected water sample conductance varies from 330 to 800 micro mhos/cm except a few. 
* Total Dissolved Solids: It is a measure of total amount of solids, in mg/ltr that remains when a water sample is evaporated to dryness. Measuring the electrical conductance of a groundwater sample can make the TDS. Based on the TDS, groundwater has been classified into four categories, namely Fresh, Brackish, Saline and Brine, which ranges 0-1,000; 1,000-10,000; 10,000-100,000 and >1000,000 respectively. Water sample analysis shows that generally Fresh water, of TDS value ranges from 211 to 524, is present in study area. 
* Calcium Carbonate and Bicarbonate: The primary source of carbonate and bicarbonate ions in groundwater is the dissolved carbon dioxide in rain, which, as it enters the soil, dissolves more carbon dioxide under usual conditions. CaCO3 is absent in the study area. The bicarbonate concentration ranges from 100 to 800 ppm, but from 200 to 500 from potable stand point. The bicarbonate ranges in the study are within the limiting value ranges from 92 to 280, which is suitable for drinking and domestic purposes.
* Chloride: According to WHO drinking water quality standards, the chloride concentration should not exceed more than 250 mg/l. Water analysis shows that at Battalahalli village chloride concentration is beyond the permissible limit which is 420 ppm. And in other portion, chloride concentration is under permissible limit, which ranges from 24 to 190.
* Fluoride: Fluorine occurs widely with an average concentration in the earth's crust of about 300-ppm. Fluorspar, cryolite and fluorapatite are seen as the main sources but substitution in OH sites of hydrous minerals such as biotite, muscovite and amphibole, from which leaching believed to be relatively easy, may locally be important. The safe limit of Fluoride concentration varies from 0.5 to 1.5 mg/l for portable water. Excess of fluoride causes florosis, bone and dental disorders and muscular pains. The analysis indicate that the fluoride concentration is within the safe limit, varies from 0.19 to 1.44.
* Nitrate: Nitrate can be formed naturally in the soil by the microbial degradation of nitrogenous organic material, such as protein. Ammonium ions are produced first and these are biologically oxidized to nitrate via nitrite. Higher than normal levels of nitrate are usually, accompanied by high faecal bacteria counts. The limiting value of nitrate as N concentration for potable water varies from 0 to 10 mg/l. From the water samplke analysis that the concentration of nitrate has exceeded the limiting value at Addagal, Kammaguttahalli, Lagumenahalli, Nemeliguriki, Chikkanarappanahalli, chhota Timmanahalli, Gudibanda (Rural), Battalahalli, Gundla Mandikal, Jiganahalli, Paiyuru and Mandikal. There, Nitrate concentrations are 11,05, 11.72, 10.72, 11.06, 14.16, 11.29, 13.75, 68.36, 27.50,20.63, 11.86 and 10.64 respectively.
* Sulphate: The limiting value of sulphate for potable water is 250 mg/l. Excess of sulphate concentration cause bitter taste and bad odor. In the present study water samples show the sulphate concentration within the safe limit, which varies from 5 ton 86 ppm.
* Sodium: If the sodium concentration in the groundwater exceeds 50 mg/I, the water becomes hard and causes corrosion. Most sodium salts are readily soluble in water but it is chemically non-reactive. Hence the boiling of water is helpful for the reduction of Na concentration in water before consumption. The water sample analysis indicates that the Na concentration in the study area is more at Nallakadirenahalli (65 ppm), Brahamarahalli (115 ppm), Nemeliguriki (110 ppm), Gudibanda (101 ppm), Battalahalli (207 ppm), and Gundla Mandikal (55 ppm).
* Potassium: Potassium concentration, in potable water, rangesfrom 1 to 3.8 ppm. From analysis, the K concentration is more at few places like at the villeges nallakadirenahalli (4 ppm), Indrahalli (5 ppm) and Battalahalli (6 ppm).
* Calcium: Limiting value of Ca content should not exceed 200 ppm according to WHO standard. The analysed water samples indicate that the Ca concentration in this watershed is within the permissible limit that varies from 8 to 184 ppm.
* Magnesium: The magnesium in potable water is generally 40 ppm, but according to WHO and ISI standard, it should not exceed 150 ppm. In analysis, the mg concentration, in the study area, is within the permissible limit, which ranges from 12 to 58 ppm.
* Hardness: The hardness of water is derived from the solution of carbon dioxide, released by bacterial action of soil, in percolating rainwater. The analyzed water samples indicate that the groundwater in this area is, in generally hard. But, at some places, it is very hard, viz. Mandikal (420 ppm), Kammaguttahalli (320 ppm), Battalahalli (680 ppm) and also at some pleces, it is moderately hard, viz. Yadaralahalli (140 ppm), Kotturu (128 ppm), Lagumenahalli (112 ppm), Chinnappali (136 ppm), Nemeliguriki (140 ppm), Gandlavarahalli (120 ppm).
* Sodium Absorption Ratio: Soils containing a large portion of Na with carbonate as predominant anion are termed alkali soils; and those with chloride and sulphate as the predominant anion are saline soils. The classification of the water quality for irrigation purposes are defined based on SAR parameter, 0 to 10 as excellent, 10 to 18 as good, 18 to 26 as fair and for greater than 26 poor. Particularly, this area having excellent water quality for irrigation purposes ranging from 0.74 to 4.07.

Recharge Estimation
To estimate the amount of rainwater infiltrated into the ground, tracer i.e. artificial tritium is injected into the ground (tracer injection method). The water, added to the first/uppermost layer, pushes the equal amount of water to the next layer and second to third and so on. Thus an equal amount of water is added to the water table/zone of saturation. The whole system is supposed to work as piston, termed as "Piston Flow Model".

Injected Tracer Studies
Tritium injection technique deals with piston flow model and works on the principle that the soil moisture moves downward in discrete layers through unsaturated zone under the force of gravity. The tritium is tagged below the shallow root zone before the onset of monsoon rains and collected after monsoon. The displaced position of tracer is indicated by the peak in its concentration distribution, which corresponds to spot natural recharge to groundwater over the time interval between the injection of tritium and collection of soil core profile. Moisture content (%) and tritium activity of samples of each site was plotted against depth. The displacement of the tracer was determined and that was used to estimate the recharge.
In the study area, tritium injections were made during June 200l at 36 locations, a small amount (2.5 ml) of tritiated water (HTO) having an activity 10 mC/ml was injected at 80cm depth in a 1.25cm diameter hole made using drive rod. The hole was filled back by local soil.


Highlights/Findings:
* The large-scale exploitation of groundwater for industrial as well as agricultural purposes has lead to deepening of water level as well as deterioration in groundwater quality.
* The central part of the basin has suffered more weathering and fracturing.
* The area around Ramapatana, Nallaakadirenahalli, Yadarahalli and Oundla Mandikal are having thicker aquifer zones and in these areas, the recharge also has been found to maximum. Hence these are the zones, which could be considered to be most potential zones for the sustainable groundwater development.

Data Used:
* Integrated hydro-geological and geophysical studies, to delineate potential aquifer zones and estimate the recharge potential.
* The photogeological map, to carry out geo-electrical investigation and recharge estimation. 
* The tritium injection technique, for recharge estimation
* Few sites, to tap groundwater resources in the watershed.

Output:
* Recharge was found varying from nil to 200mm. Some of the typical tritium profiles (Figure 5) depict nil and low and some (Figure 6) depict moderate and high recharge sites.
* Comparative study of recharge and geo-electric parameter show that wherever, resistivity of the topsoil is low, the natural recharge is also low. (Figure 7)
* In the northern part, where resistivity of the weathered layer is low, the recharge values are also low. At the same time in the southern region, the resistivity of the weathered layer is high and recharge is also very high. (Figure 8)
* As depth to basement increases the thickness of weathered zone and soil column above the weathered zone also increases, which can cause more recharge. (Figure 9)
* In Figure10,
· A linear relationship of recharge with depth to basement was found. An attempt has been made to get empirical relation using least square fitting and arrival at the following relation:
Re=0.0034*D+19
Where, D is depth to basement (cm) and Re is recharge (cm).
· A good co-relation has been between recharge and water level fluctuation. Data of water level fluctuation plotted against recharge is found, to be governed by the following equation:
Re=0.0042*L+3
Where, L is fluctuation in water level (cm).
* Recharge map of the study area has been prepared by general conventional polygon method. (Figure 11)

Date of project completion:
June' 2003 

Project Investigator:
S. C. Jain,
National Geophisical Research Institute, 
Hyderabad.