A new study has pointed out that increased irrigation efficiency does not translate to more water availability for other uses at the watershed level. The subsidies for increasing irrigation efficiency are intended to increase crop production as well as more return flow from irrigated areas that can be allocated to urban, domestic and industrial uses. But this does not seem to be happening.
The study, published in the journal Science, by Quentin Grafton of Australia with co-authors from France, UK and the US underscores what has been observed in recent years. It cites Rajasthan as one of the examples where increased irrigation efficiency due to approaches such as drip irrigation has led to an increase in crop yields and agricultural incomes. At the same time, there is also an increase in irrigated area and water withdrawals.
While groundwater management is under the purview of state governments, the central government incentives to the state focus on irrigation efficiency as a step towards climate resilience. A 2017 study by the US geographer Trevor Birkenholtz had reported that farmers adopting drip irrigation are generally commercial-scale farmers who can afford the high costs and are also aware of increasing water demand from drip irrigation. Considering nearly 80 percent of water supply for both irrigation and domestic use is from groundwater, dependence on irrigation efficiency for groundwater sustainability may be misplaced.
The increased irrigation efficiency, in fact, reduces the usable return flows despite increased crop transpiration and reduced evaporation. The water availability at the watershed level decreases because subsidies for irrigation efficiency lead to an increase in irrigated areas and water withdrawals. This could also drive a choice for more water-intensive crops. This is clearly a critical concern for India considering the monsoon response to global warming.
Much has been written about the reduced total monsoon rainfall over India during the 20th century with a striking increase in rainfall extremes, spatial variability and a threefold increase in floods. Future projections indicate a continued drop in water availability and crop yields for most major crops. Consistent with the global trends, irrigation in India also accounts for well over 75 percent of the total water consumption.
In 1960-61, canals and traditional wells contributed nearly 60 percent of the water supply for irrigation with less than one percent water withdrawals from tubewells. By 2012-13, canals and traditional wells contributed only about 40 percent but withdrawals from tubewellsis up at 46 percent. Correspondingly, the total area under cropping systems has increased by about 45 percent but the area under irrigation has tripled during these decades. This shows up as nearly equal amounts of grain production in both kharif and rabi seasons whereas the kharif used to be the dominant cropping season in the 1960s with twice the annual production compared to rabi.
Despite an impressive increase in agricultural productivity, per capita food production shows a decline over the recent decades due to the increasing food demand and continued population growth. Electricity use is up for pumping groundwater. The depletion of groundwater tables is alarming in the northwest even though central-western India shows some groundwater recovery. Irrigation water use shows no decrease even during excess monsoon years which is a clear indication that the subsidies are not incentivising the farmers to produce more crops with less water.
If we want to deal with this dilemma of increased irrigation efficiency leading to increased water withdrawals, we need to establish data networks to track not only crop transpiration but also total inflows and recoverable outflows of irrigation water. We also need to know the losses to unrecoverable sinks such as evaporation. Explicit caps on extraction as well as irrigated areas are also recommended to ensure better irrigation efficiency.
The amount of water withdrawn for irrigation depends on crop selections as well as soil types. Risk perception by farmers based on weather forecasts, access to loans and crop insurance also play a role. The use of subsidies for water withdrawal must be combined with the weather and extended range forecasts as well as seasonal outlooks. This will need trust-building so that irrigation can be planned based on weather forecasts despite their uncertainties. Behavioural economics and other novel approaches can be brought to bear on maximising agricultural production with minimal water use instead of focusing on marginal increases in yields with unbounded water use.
Ensuring real increases in irrigation efficiency requires carefully combining subsidies with caps and trade-offs of water withdrawal, irrigated area, electricity use, crop selection, weather and extended range forecasts as well as seasonal outlooks and other market factors. (India Science Wire)
The writer is a professor of Atmospheric and Oceanic Science and Earth System Science at the University of Maryland, USA. He is currently a visiting professor at IIT Bombay.