Arsenic in groundwater

Threat to Agriculture
Last Updated 18 March 2019, 18:50 IST

Over the last three to four decades, the dependence on groundwater as a source of irrigation burgeoned and consequently the problems of groundwater over-exploitation have been a focus area for policymakers.

As per the latest assessment of groundwater resource availability and utilisation by the Central Ground Water Board (CGWB), the net annual groundwater availability is 411 billion cubic metres (bcm), annual groundwater draft is 253 bcm, amounting to a stage of groundwater development of 62%. Based on an assessment of the stage of groundwater development at the level of blocks/mandals/taluks/firka, the CGWB has categorised 1,034 assessment units as ‘over-exploited’, 253 as ‘critical’ and 681 as ‘semi-critical’ out of a total of 6,584 such units.

Exploiting the energy-groundwater nexus through energy pricing, enhancing water use efficiency through incentivising use of technological innovations (drip and sprinkler irrigation) and non-technological measures (controlling the timing of paddy transplantation) have been some of the important policy instruments to tackle the receding water table.

Issues related to consumption of poor or contaminated water are also increasingly being recognised and actions are being taken to ensure safe drinking water to affected populations. Arsenic, for instance, which had been found in well water in West Bengal during the early 1980s has been taken up as a serious public health issue. Although grassroots-level reach of government measures in creating awareness and ensuring safe drinking water for the affected population remains questionable, there seems to be some concrete action in the right direction. However, the aspect that has not received due attention is the implications of contaminated irrigation water on agriculture.

Arsenic is now known to be widely prevalent in the floodplains of rivers with their origin in the Himalayas and has its coverage across the states of West Bengal, Jharkhand, Bihar, Uttar Pradesh, Assam, Manipur and Chhattisgarh. Numerous research studies based on scientific experiments have confirmed deterioration in fertility of soil and decline in yield of crops when arsenic-concentrated water is applied for irrigation. The impact on yield varies across crops, variety of crop grown, soil type and soil conditions. Moreover, another well-known fact is that extraction of groundwater in contaminated zones increases the mobilisation of arsenic from rocks into the aquifer.

The cause for concern stems from the fact that having utilised the yield potential as well as the irrigation potential in north-western states, the government has directed attention towards the relatively water-abundant eastern states to bring about a second Green Revolution in order to meet India’s growing food requirements. Such a shift became explicitly visible with the introduction of the ‘Bringing Green Revolution to Eastern India’ scheme launched in 2011 under the Rashtriya Krishi Vikas Yojana.

Continuing with this UPA government plan, Prime Minister Narendra Modi on several occasions reiterated the need for a second Green Revolution. In an address at Burnpur, West Bengal, in May 2015, Modi remarked, “East India needs to be strengthened…I clearly see the second Green Revolution happening here…East India has abundance of water, land and people. It can usher in the revolution.”

The question that needs to be asked is, is this the right step forward if, on the one hand, we talk of ‘sustainable groundwater management’ and ‘sustainable agriculture’ and, on the other, we push for increased groundwater usage in areas where its extraction and usage would be detrimental to the resource itself as well as diminish the possibilities for agriculture in the long run.

Without doubt, the resource is a crucial component of the country’s agriculture sector, with nearly 80% of irrigated agriculture being supported by groundwater, and hence it is a significant contributor to achieving the goal of food security.

At the national level, particularly, we observe a lack of due attention towards the status of groundwater quality, its larger implications, and so towards initiatives in the right direction. In fact, significant increase in groundwater use in so-called ‘groundwater-abundant’ areas without proper appraisal of the available resource in terms of quantity, quality and other environmental conditions is noted.

Groundwater protection zones

Although the latest Model Bill for the Conservation, Protection, Regulation and Management of Groundwater, 2016, laid out by the central Ministry of Water Resources, to be appropriately modified and implemented by each state government has provided a good set of guidelines, it will be beneficial only if those provisions are implemented with the right force and spirit. It suggests the demarcation of areas affected by arsenic, fluoride and salinity ingress under ‘groundwater protection zones’. This is in line with its mandate of protecting groundwater from depletion, deterioration, biological and chemical pollution.

The Model Bill further includes a section on the need for undertaking environmental impact assessment, specifically on the short-term and long-term impacts on quantity and quality of groundwater, impacts on agricultural production and so on. Similar such bills have been presented previously in 1992, 1996, 2005 and 2011. However, to date, only 14 states have enacted a legislation for groundwater resource management.

Sustainable use of groundwater needs to be encompassed and imbibed in an all-pervasive sense by managing both quantity and quality deterioration of the resource. It further calls for understanding the long-term implications of extracting contaminated groundwater on the groundwater quality itself, on human health as well as on agricultural production. For instance, arsenic concentration in aquifer may increase with groundwater pumping and its usage over long periods can render agriculture unsustainable. Rainwater harvesting, tapping deeper arsenic-free aquifer or finding alternative irrigation sources are some of the possible solutions whose feasibility may be assessed and accordingly implemented.

(The writer is a PhD scholar at the Centre for Economic Studies and Policy, Institute for Social and Economic Change, Bengaluru)

(Published 18 March 2019, 18:45 IST)

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