Solar energy has become a sacred icon of the Greens. Thus, to combat this, one of my roles in my day job is to present material showing that solar is far from "ecologically sustainable," and in some cases is harming the environment. In the case of India, solar pumps have enabled farmers to expand production, since they do not have to pay for petrol or diesel fuels. What could go wrong? This increase in the intensity of pumping is leading to the fast depletion of groundwaters. The very success of solar pumps is "threatening the viability of many aquifers already at risk of running dry," according to Soumya Balasubramanya, an economist at the World Bank. As the Wired.com article concludes, "An innovation that initially looked capable of reducing fossil-fuel consumption while also helping farmers prosper is rapidly turning into an environmental time bomb." The depletion of groundwaters seems unstoppable, since it will be difficult for the government to regulate pumping now that the genie is out of the bottle. There will be no water reserves in time of severe drought, making agriculture more vulnerable.
This is an example of how even when solar seems to work well, it has unintended destructive longer-term effects. The cost of fossil fuels at least put a barrier to excessive water use.
"There is a solar-powered revolution going on in the fields of India. By 2026, more than 3 million farmers will be raising irrigation water from beneath their fields using solar-powered pumps. With effectively free water available in almost unlimited quantities to grow their crops, their lives could be transformed. Until the water runs out.
The desert state of Rajasthan is the Indian pioneer and has more solar pumps than any other. Over the past decade, the government has given subsidized solar pumps to almost 100,000 farmers. Those pumps now water more than a million acres and have enabled agricultural water use to increase by more than a quarter. But as a result, water tables are falling rapidly. There is little rain to replace the water being pumped to the surface. In places, the underground rocks are now dry down to 400 feet below ground.
That is the effective extraction limit of the pumps, many of which now lie abandoned. To keep up, in what amounts to a race to the bottom of the diminishing reserves, richer farmers have been buying more powerful solar pumps, leaving the others high and dry or forcing them to buy water from their rich neighbors.
Water wipeout looms. And not just in Rajasthan.
Solar pumps are spreading rapidly among rural communities in many water-starved regions across India, Africa, and elsewhere. These devices can tap underground water all day long at no charge, without government scrutiny.
For now, they can be great news for farmers, with the potential to transform agriculture and improve food security. The pumps can supply water throughout the daylight hours, extending their croplands into deserts, ending their reliance on unpredictable rains, and sometimes replacing existing costly-to-operate diesel or grid-powered pumps.
But this solar-powered hydrological revolution is emptying already-stressed underground water reserves—also known as groundwaters or aquifers. The very success of solar pumps is "threatening the viability of many aquifers already at risk of running dry," Soumya Balasubramanya, an economist at the World Bank with extensive experience of water policy, warned in January.
An innovation that initially looked capable of reducing fossil-fuel consumption while also helping farmers prosper is rapidly turning into an environmental time bomb.
For much of the 20th century, artificial irrigation of farmland boomed thanks to state and World Bank investment in reservoirs and in networks of canals to bring water to fields. Irrigation watered the "green revolution" of new high-yielding but thirsty crops, keeping a fast-growing world population largely fed.
But many systems have reached their limits. Rivers are being emptied, and new investment has dried up. So in the past three decades, hundreds of millions of farmers in hot arid regions, from Mexico to the Middle East and South Asia, have switched to getting their water from underground.
Boreholes sunk into porous water-holding rocks now provide 43 percent of the world's irrigation water, according to a study last year by the World Bank. Irrigation is responsible for around 70 percent of the global underground water withdrawals, which are estimated at more than 200 cubic miles per year. This exceeds recharge from rainfall by nearly 70 cubic miles per year.
Monitoring of individual underground reserves is patchy at best. They are too often out of sight and out of mind. But a study of historical data from monitoring wells in 1,700 aquifers in 40 countries, published in January, reported that "rapid and accelerating" declines in reserves were widespread.
Scott Jasechko, a hydrologist at the University of California, Santa Barbara, found water tables dropping by 3 feet or more every year in India, Iran, Afghanistan, Spain, Mexico, the United States, Chile, Saudi Arabia, and other countries.
The implications of this for the future are profound. "Groundwater depletion is becoming a global threat to food security, yet … remains poorly quantified," says Meha Jain, who studies the sustainability of farming systems at the University of Michigan. But rather than calling a halt to groundwater withdrawals, policymakers are upping the ante by promoting solar power as a means of delivering yet more and cheaper underground water to fields.
The solar revolution on farms is happening with the best of intentions and is using a technology widely seen as environmentally beneficial. Farmers love the fact that their photovoltaic (PV) pumps do not require expensive and polluting diesel fuel or grid connections. Once installed, they can run all day at no cost, growing more food crops, or allowing their owners to expand their businesses—growing water-intensive cash crops, or earning income from selling spare water to neighbors. Many farmers also keep their old diesel or electric pumps to continuing pumping when the sun goes down.
Development agencies and governments are equally keen. They subsidize solar pumps to boost food production, reduce poverty, cut emissions from fossil fuels, and curtail growing demands on overstretched electricity grids. But the long-term downside of this solar revolution looms large."