Being a coastal geomorphology, groundwater resources around the Delta are already pretty plagued by marine incursions leading to widespread contamination/salinisation. Scientific communities largely attribute this to the Mettur Dam (where Cauvery enters Tamil Nadu), which presumably alters the river's natural flow regime. This allows for saline transgressions, undermining the irrigational framework and agronomic production. According to the recent finds of the scientists of the ICSSR and MIDS (Madras Institute of Developmental Studies), well over 40 per cent of farmlands across the Delta have already been turned to "built-ups" owing to marine transgression, with the highest in Nagapattinum (56 per cent). Concurrently, the "wasteland" acreage (fallow lands) has soared as well (about 25 times in Nagapattinum between 1971 and 2014). Under the circumstances, a proposal for CBM-operations gravely threatens hydrologic sustainability, adding to the woes of the farmers.
But to get a grip on the matter, first it is imperative to understand how CBM-explorations operate. Very simplistically, CBM is natural gas trapped in the tiny interstices of coal laid down during its formative stages. Due to large internal surface area of coal, it can entrap huge volume of methane. But to get it out of it, large volumes (roughly about 103/well) of groundwater has to be pumped out first to take the overhead pressure off the seams and for methane to desorb and flow out. By nature, it is a highly water-intensive operation, taking a heavy toll on groundwater reserves.
Being the Rice Bowl of Tamil Nadu, the Cauvery Delta has a long illustrious legacy, adding innovations to the national agronomic excellence. But rice-cultivation, often double-cropped (Rabi and Kharif) across the Delta, is a highly water-demanding bargain in itself and the irrigation system in the Delta is sourced to the groundwater reserves. In addition, the potable water infrastructure heavily counts on groundwater. Under the circumstances, chances of additional groundwater depletion owing to CBM-exploration is apprehended as a threat to basic livelihood.
But is the apprehension grounded in science? Hard to tell, but a comparative assessment of similar CBM-operations run by the GEECL in the Raniganj Coalfields, West Bengal, might shed some light on the issue. Recent research carried out by the scientists of the CIMFR and ISM, Dhanbad in Raniganj Coalfield area, revealed alarmingly high concentrations of fluoride [>4 ppm, where the maximum permissible limit (MPL) is 1.5 ppm], nitrate (43-50 ppm; MPL = 44.5 ppm), TDS (>2000 ppm where MPL = 2000 ppm), and iron (>0.1 ppm; MPL = 0.03 ppm) in CBM-wastewater, alongside elevated levels of trace metals including manganese, zinc, strontium, and aluminum. Needless to say, all of the above have as much graver implication towards human health as they have to the irrigation water quality. The study strongly hinted at detailed investigations of the CMB-wastewater chemistry prior to disposal/reuse.
But this is an expensive proposition for the CBM-operators, as well as time-consuming, and thus often bypassed. Often, the highly saline-sodic CMB-wastewater is discharged just directly into 'unlined' holding ponds (without much of prior wastewater-treatment) which puts both the soil and regional groundwater quality at high risk.
Apart from vulnerability of freshwater quality, peasant communities of the Delta are apprehensive about freshwater availability itself. Already enraged by the legal clauses of Cauvery-water-sharing with neighboring Karnataka - which they believe have led to man-made droughts - it's borne deep in their hearts that the CBM-operations will heavily deplete freshwater reserves, turning a lush delta into a rugged desert. Along that line, recent assessments by the Central Ground Water Board (CGWB) in the Delta revealed: (i) appalling rates of groundwater drafting, with several blocks already labelled as 'overexploited', coupled with (ii) significant decline in groundwater levels between 1980 and 2009. Projected groundwater budget for 2035 appears grave for Nagapattinum –equating to well over 100 per cent groundwater development- which implies high likelihood of physical water scarcity even under the existing land use practices (agriculture). Under the circumstances, the peasants believe that with additional groundwater drafting for CMB, end result will only be frequent recurrence of droughts leading to rapid escalation in the number of suicides of the farmers.
But then a coin has got a flipside. India is a highly power-starved nation and Tamil Nadu aptly represents the situation. Globally, India is the 4th largest producer of coal, which implies huge potentials for having highly productive CBM reservoirs underground. In a tweet last year, the Union Minister for Petroleum and Natural Gas, Dharmendra Pradhan stated that CBM accounts for about 5 per cent of the nation's total natural gas production. Which roughly equates to an investment bag of about Rs. 10,000 crores by the CBM sector. In addition, the project promises lucrative opportunities of youth employment/development and local business across the Delta. Also, having power sources, such as CBM, in the vicinity is critical to sustain agricultural operations itself.
But as an alternative, the locals are resorting to the research of late Dr. G. Nammazhwar, a renowned and highly revered organic agriculturist from Thanjavur. Known as The Green Crusader, Dr. Nammazhwar innovated methods to extract methane from cow dung. But to tell the truth, the method is yet to be tested for mass production to meet growing needs.
So there are arguments against as much there are in favor. For example, counter-argument to apprehensions of water resources depletion is that, life cycle assessment (LCA) of CBM-operations from other regions of the world reveals that water discharge (drafting) only peaks in the initial stages (dewatering stage), gradually declining as production soars/stabilises. Which means, water resources depletion owing to CBM might be just a fleeting phenomenon.
Just recently another set of agitations has flared up in the Delta (Neduvasal Village, Tamil Nadu) at the possibilities of shale gas exploration as parts of the Discovered Small Fields (DSF) project, initiated by the Center only this past year. But be it CBM or shale gas, the core issue has always been the sustainability of the agrarian communities, in face of projected eco-hydrologic hazards due to hydrocarbon explorations.
If it has to materialise ever in future (in Tamil Nadu or elsewhere in the country), probably the best bet would be to drill a few pilot-scale wells to conduct a detailed EIA involving regional geology, hydrostratigraphy, topography, vegetation, climate, and land management practices to ascertain potential impacts of hydrocarbon on human dynamics. Holistically, it may call for multi-agency collaboration, with ample provisions left for site-specific inputs from the locals. The USGS in lieu with the USEPA, had been conducting similar studies since the late '90, which could be consulted should the need be. It will be imperative to draw up a detailed regional hydrologic budget, identifying exact sources and sinks. Based on that, 4-D (including time) hydrologic models need to be designed/simulated with projected land management changes, and climatic factors to evaluate potential impacts on sustainable development for future.
(Sriroop Chaudhuri is Assistant Professor at Jindal School of Liberal Arts and Humanities, and Adithyalakshmanan is a First-year Student in the same institution. The views expressed are strictly personal.)