Strategic Groundwater Management Using Aquifer Mapping: A Gram Panchayat Level Study in Tumkur district, Karnataka

Groundwater serves as a crucial resource, particularly in regions where surface water is either scarce, non-perennial, or polluted[1]. In such contexts, it acts as a lifeline for drinking water supply, agriculture, and overall socio-economic development. In semi-arid areas like Karnataka, India, groundwater becomes even more vital, given the erratic rainfall patterns and dependency on subsistence agriculture[2]. However, the over-extraction and mismanagement of groundwater resources have led to declining water tables, quality degradation, and increased vulnerability to water scarcity. While large-scale regional aquifer mapping provides a broad understanding of groundwater systems[3,4], village-level mapping and management are critical in addressing the unique challenges of Karnataka's diverse and localized hydrogeological conditions.

Regional studies often generalize these variations, making them inadequate for developing site-specific solutions. Village-level mapping allows for a micro-scale understanding of aquifer behavior, enabling tailored interventions based on local conditions.

To address these challenges, the concept of micro-level aquifer mapping and management at village level has emerged as a comprehensive approach to ensure sustainable groundwater use. This paper focuses on aquifer management strategies developed for Bukkapatna Gram Panchayat, located in Koratagere Taluk, Tumkur district, Karnataka.

Objective and Methodology of the study

The primary objective of the study is to ensure sustainable and equitable utilization of groundwater resources while addressing the challenges of water scarcity and drought resilience. This involves securing a reliable drinking water supply, enhancing irrigation facilities for agriculture, and identifying vulnerable areas with declining water levels or poor-quality water for targeted interventions. The study aims to promote groundwater recharge through site-specific measures, such as recharge wells and check dams, while encouraging efficient water use practices. By fostering community participation and awareness, the initiative seeks to empower local stakeholders to manage groundwater resources responsibly. Additionally, it supports policy implementation by providing granular data and actionable insights to inform sustainable water resource management, ensuring long-term water security and resilience in this semi-arid region.

Various information on ground water occurrence in

borewells, depth of casing, occurrence of fractures

and yield reported, water samples were collected through field study and analysed. The thematic maps of depth to water level, weathered zone, hydrogeology and artificial recharge points are prepared Arc-GIS software. Both supply and demand side groundwater management plan for study area has been prepared in accordance with the nature of the aquifer, its quality of water, and stress on the resource. The management plans can be implemented by the stakeholders/user agencies as per conditions.

Study area

Bukkapatna gram panchayat comes under Koratagere taluk, Tumkur district of Karnataka, India. It comprises of 08 villages namely:? Bukkapatna, Baraka, Gatlagolahalli, Gatlahalli, Hirejenahalli, Venkanahalli, Veerobanahalli, and Gondihalli. The spatial extent of the gram Panchayat is between 13.49? N to 13.54? N latitude and 77.150? E to 77.220? E longitude.

It comes under Survey of India Topo-sheet No. 57 G/2(1:50,000 scale). The total area of the Gram Panchayat is 28.90Sq.Km.The total population of the village is 6693 persons (Census 2011)[5].

The location map of the study area is given in Figure 1.
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Figure 2: Drainage and geomorphology map of Bukkapatna gram panchayat

HYDROGEOLOGY

Types of Aquifers:

i. Aquifer-I (Phreatic/Unconfined aquifer) comprising of weathered granite gneiss

ii. Aquifer-II (Semi-confined/Fractured aquifer system) comprising of fractured granite gneiss.

In the study area, the depth of weathered zone varies between 10.67 mbgl to 36.5m bgl (Figure 3). Phreatic aquifer is confined within this depth range. The total depth of the bore-wells varies between 137.16mbgl to 274.32mbgl. Most of the borewells have only one water yielding fracture zone. The fracture zones reported by the village watermen/farmers vary between 70m bgl to 244 m bgl. (Figure 4,5,6). The average discharge reported in the area is about 1.0-1.5 lps. Post-monsoon water level varies from 32.60m bgl to 52.77m bgl. The wells are used for drinking water purpose and irrigation.
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Figure 3: Depth to weathered zone map of Bukkapatna gram panchayat
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Figure 4: 3D aquifer model of Bukkapatna gram panchayat
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Figure 5: Location map of studied wells
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Figure 6: Strip logs of the studied wells

Quality of Water

Table 1:? Results of chemical analysis of water samples

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The values of pH, EC, cations and anions are within the permissible limit mentioned in Bureau of Indian Standards BIS (IS_10500 and revised module IS 10500:2012) for drinking water. Nitrate (found to exceed the permissible limit of 45mg/L) in one Gatlagollahalli village (100 mg/L) only. Groundwater quality, in general, is good and potable. It is suitable for domestic and irrigation purposes.

Since the borewell from which sample was collected in Gatlagollahalli village is located close to agricultural field, Nitrate contamination is occurring in the aquifer due to some point source like agricultural runoff, indicating anthropogenic origin.

Piper diagram (Figure 7) plotted for the samples indicates the following:

1. In terms of cations, the water samples show no dominant type
2. In terms of anions, the water samples are dominantly bicarbonate type
3. Overall, the ternary diagram indicates that the groundwater of the study area is dominantly of Calcium-Magnesium-Bicarbonate type.
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Irrigation sector

There are two agricultural seasons, namely Kharif (June ? October) and Rabi season (Mid October ? Mid February), apart from summer crops. The extraction of ground water for irrigation is 292.6ham.

During field study, it was observed that, most farmers in this gram panchayat had not adopted micro-irrigation practices yet. They were extensively following the normal flood irrigation. Erratic and deficient rainfall in preceding years and traditional farming practices leads to severe water crisis during Rabi season.

Domestic Consumption

The Gram panchayat has a population of 6693 persons with 1555 households. The livestock population is about 8000 consist of cows/ buffaloes, sheep, goat, poultry. The annual domestic demand is 14.21ham. Around 450 households have been provided with piped water supply connections. There are 4 Over Head Tanks of 50,000cc to 1,00,000cc in 3 villages and 61 cisterns and 58 public taps in the gram panchayat.? There are 13 deep bore wells with average pumping duration at 6 hrs/day.

MANAGEMENT PLAN

The gram panchayat being agriculture-based economy, groundwater is mostly utilized for irrigation. Since it is in over-exploited category, it requires strict regulation in use. In order to maintain sustainability of this resource, both supply side and

demand side management practices need to be followed.

Demand and Supply-side Issues

The issues plaguing the study area are as follows:

• Drying up of source of domestic water supply & irrigation wells due to over extraction of resource, erratic rainfall, nature of terrain and improper disposal of garbage.
• Drying up of tanks due to silt accumulation which reduces storage capacity
• Lack of proper maintenance recharge structures
• Point source of contamination of groundwater
• Wastage of water due to leakage/absence of taps in standpost, leakage in water supply channels and not switching off pumps even after cistern gets filled.

Supply-side Management measures

• Desiltation of tanks/Renovation of tanks: Bukkapatna gram panchayat has 5 big lakes. They are mostly ephemeral and have little water during summer. The lead channels and foreclosure to the tanks are filled/ utilised for other purposes. Hence inflow is reduced. Besides, the tanks also get silted up in due course of time leading to reduced storage reservoir. Removing the silt will improve storage capacity and groundwater recharge [7].
• Augmentation of the resources: Suitable artificial recharge structures like checkdams, farm ponds with recharge pits, recharge wells are to be constructed in the gram panchayat (Figure 8,9) [8]. Since this gram panchayat is located in the foothills, sufficient scope exists to harvest the surface runoff after rainfall. Periodical maintenance of artificial recharge structures should be implemented. The abandoned dug wells and bore wells may be converted into recharge wells.
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• Construction/Maintenance of Rainwater Harvesting structures like farm ponds, step wells, tanks and roof top rain water harvesting structure for government building.
• Proper operation and maintenance of water supply structures and systems is required. All leakages/ other faults should be rectified at the earliest to avoid loss and wastage of water. Proper training is to be imparted to village watermen.
• Interaction programmes to sensitise people about the importance of this dwindling resource and involving them in water conservation programmes.?

Demand side management measures suggested:

Apart from recharge of groundwater, steps need to be taken to decrease the volume of water consumed.

• Since the study area is surrounded by hillocks, there are several ?Talapariges? (point where the underground water oozes or springs out) seen during field work. The farmers have made small dugwells of 1m*1m*1.5/2m dimension in the field which automatically gets filled with groundwater after monsoon (Figure 10)[9][10]. The water is used for domestic purposes like washing, cleaning and bathing as also for ragi, vegetables and fodder grass cultivation. Such practices are to be encouraged and taken up more intensely.
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