Using abandoned mines to augment water supply

The growing population in our country led to an increase in the demand for natural resources such as water, minerals, land etc. Groundwater supports nearly 50 per cent of agriculture and about 80 per cent of freshwater demand for domestic, industrialisation, green revolution, urban development use etc, and is absolutely essential for the entire world. As a result, there is incessant pressure on the groundwater resources.

Karnataka has numerous gold mines functional and dysfunctional. Some of them date back to more than 2,000 years and testify to the widespread nature of the gold mining industry.

There are about 400 ancient and modern gold and copper mines in Karnataka. Some of these have reached a depth of average 200 metres. Kolar Gold Mine (KGF) is worked up to 3.20-km depth, and in Hutti Main Gold Mine, it is up to 1.10-km depth.

In KGF, all the shafts, drives, cross-cuts, winzes, raises etc put together would run to 1,900 km. There are 55 shafts on the surface and 26 shafts underground. After the closing of mining activities in KGF and in other abandoned underground mines of the state, the equipment, stoped out areas, underground mines excavated areas etc got inundated with water.

According to an estimate, 18-20 million cubic metres of water has been accumulated in KGF. During the operations of all KGF mines, an average of 95,40,000 litres of water was pumped out daily. Mangalur Gold Mine in Yadgiri district was suspended due to heavy inflow of groundwater (52,000 ltr/hour).

Groundwater inflow plays a significant role in underground mines in both the active and abandoned stages. By nature, underground mines are huge rainwater harvesting and natural recharge structures. In Karnataka, several occurrences of gold and copper have been prospected/explored and for some reason or other were later abandoned. Therefore, it is necessary to integrate the water management system into them to make it beneficial to the industry as well as to the common man.

It is a fact that in most parts of the world, mining companies are exposed to some kind of risk related to the availability of water. Either there is a lack of water or the contrary, there is too much water. Both circumstances can cause significant effects on the mining operations and on the environment. The important key factors which need attention from the authorities for mine water management are:

An understanding of hydrogeological and hydrological processes within the aquifer system embedded in the mining zone.

Capacity building on mine water management with the approaches of mathematical and physical modelling etc.

Data monitoring on groundwater occurrence, distribution, groundwater level and quality of water and development of a database to share with like-minded organisations so that water management strategy can be developed for each mine with reference to different stages of the mining process.

Integration of water balance of different operations by taking into account both mine area, surrounding environment and management to process control system of the mine.

Feasibility studies on the utilisation of underground mine water by studying the old maps, plans and sections of the underground mines.

Statutory and safety clearance for the utilisation of underground mine water.

Detailed studies on the water-rock–mineral interaction, suitability of underground mine water for various sectors should be tested/established using standard tools (MoEF, CPCB, CGWB etc) i.e. treatment, reuse, re-cycle, and monitoring of the quality of mine water.

The use of Information and Communication Technology (ICT) helps to deploy the application for water exploration, exploitation, quality and management.

The utilisation of underground mine water for hydroelectric/thermal power generation.

Installation of motors/pumps of higher capacity in mine and design of Canal Network.

Safety, eco-friendly and sustainability with the state-of-art technology in utilisation of underground most precious resource, the mine water.

As it is well-known fact that the underground excavations behave as large natural sinks and create a hydraulic gradient towards the mine. In response to the differential pressures, water flows toward the mine. The inflow is directly proportional to the mine depth, underground excavations, aquifer parameters, hydro-meteorological factors etc.

With the underground mine water harvesting and aquifer development, the mine area gets converted into a sustainable groundwater resource zone. By adopting detailed feasibility studies and adopting proper quality measures, about 400 abandoned underground mines can be converted.

The existing water sources like rivers and wells are proved to be insufficient to meet the water demand. An alternative is the underground mine water which can be one of the perennial sources. This will lead to the development and protection of mine water and will benefit the socio-economic status of the mining community and will form the base for the uplift of the local populace.

Abandoned underground mines located in various districts of Karnataka where the mine water storage and distribution can be adopted are as follows:

BELLARY: Ettinahatti; BIJAPUR: Ilahal; CHICKMAGALUR: Jalagargundi, Siddarhalli, Nandi, Ajjampur, Bukkambudi; CHITRADURGA: Halekal, Honnemaradi, Gonur, Bodimaradi, Nalabaigudda, Mallebennur, Dindivara, Ingaldhal-Kunchiganhal, G R Halli; DHARWAD and HAVERI: Chinmulgund, Jalligeri, Hirevadvatti, Ganjur, Karjgi & Mangalgatti; GULBARGA & YADAGIRI: Manglur, Higgandoddi, Godigira, Naganur, Mudgota, Thintanni and Mangihal; HASSAN: Yelvari, Kempinkote, Gollarhalli, Karadihalli, Kalyadi and Aladahalli; MANDYA: Nagamangala, Kalinganahalli, Bellibetta, Karimuddanhalli, Sonnahalli, Amble, Woolargiri, Porsedyke and Hadabanatta; RAICHUR: Kadoni, Wondalli, Buddinni, Hutti Main Mine, Topaldoddi, Chincherki, Maski, Ramaldini, Udbal, Sonbal, Uti, Hira-Buddinni, Hirenaganoor, Kallur, Machanur and Chikhonnakuni

KOLAR: Champion, Mysore, Mannighatta, Balaghat, Nandidurg, Oorgum & Bisnatham

GADAG: Hosur-Shirunj, Yelisirur-Venkatapura, Nagavi-Beldadi-Nabhapur, Kabuliyatkatti-Attikatti and Mysore-Sangli; SHIVAMOGA: Honnali, Kudrekonda, Palavanhalli, Honnehatti and Tambadihalli; TUMKUR: Ajjanhalli, Javanhalli, Bellara, Honnebagis.

Treatment and reuse of abandoned underground mine water are essential to meet the ever-increasing water demands.

(The writer, a former executive director, Hutti Gold Mines Co. Ltd., is currently with National Institute of Advanced Studies, Bengaluru)