The Silent Thief of Precious Waters: Evaporation?….by KBS Sidhu

On evaporation, seepage and the political convenience of blaming the sun

Delhi’s Chief Minister, Rekha Gupta, recently sought to explain the capital’s acute water crisis by claiming that, due to extreme summer heat, “the water that we distribute evaporates on the way, which is why there is a water shortage in Delhi.” The remark, picked up instantly by television and social media, has since been mocked, memed and dissected. Yet beneath the easy ridicule lies a serious question: how do we actually lose water in our systems, and what does it tell us about our politics and our priorities that “evaporation” is trotted out as the chief culprit?

To answer that, one has to step out of Delhi’s closed, piped network and travel to the open canals and vast reservoirs of Indian Punjab. There, seepage and evaporation are very real, quantified parts of the hydrologic and irrigation vocabulary. The problem is not that evaporation is never a concern; the problem is that it is being politically weaponised as an alibi where other, more uncomfortable truths ought to be confronted.

When evaporation is a convenient villain

In an urban water-supply system like Delhi’s, water travels through buried or otherwise covered pipelines from treatment plants to overhead tanks and household connections. Whatever is lost “on the way” is not wafting into the summer sky; it is leaking out of aged mains, seeping from corroded joints, gushing from bursts that go unrepaired, or disappearing through unauthorised connections and faulty meters. Engineers call this “non-revenue water” — water that is produced, treated and pumped, but never billed because it never reaches a paying customer.

The Delhi Jal Board has at various points estimated its non-revenue water at between 40 and 50 per cent of total supply, though independent analysts have questioned both the methodology and the disaggregation. The figure bundles together at least three distinct problems: physical leakage from deteriorating pipes; commercial losses from theft and unauthorised connections; and apparent losses from inaccurate metering. Each has a different remedy and a different political economy. Fixing leaks requires capital expenditure and contractor accountability; curbing theft requires enforcement and the courage to disconnect powerful vested interests; improving metering requires administrative will and, often, tariff reform. None of these is as comfortable to discuss as the weather.

To blame evaporation in this context is, quite simply, a category error. Evaporation becomes significant when water is exposed over large surface areas for extended periods — lakes, reservoirs, tanks and open canals. In a pressurised distribution network, surface exposure is negligible. The real thief is not the sun, but chronic neglect of maintenance, tolerance of theft, and the failure to invest in modern metering and pressure management.

That is where Punjab’s experience becomes a useful counterpoint. If one truly wants to talk about evaporation and losses, there is no better classroom than the great carrier canals and storied reservoirs that feed the Green Revolution fields.

The canal belt: where seepage really bites

Punjab’s major canals are classic examples of open conveyance. Water flows for tens and sometimes hundreds of kilometres through unlined or partially lined channels, exposed to sun and wind, bounded by earthen banks. Hydrologists dissect the losses along such systems into three broad streams: seepage through the bed and sides, evaporation from the water surface, and operational wastage from escapes, overflows and unauthorised outlets.

Of these, seepage is usually the dominant item. Studies across South Asian irrigation systems consistently show that unlined earthen canals can lose anywhere between 25 and 50 per cent of their discharge to seepage, depending on soil type, hydraulic conditions and the state of the channel. The Central Water Commission and state irrigation departments have their own reach-specific figures, but the broad order of magnitude is not in dispute. This is not an academic quibble: it is precisely why lining of canals, distributaries and watercourses has been a standing demand of engineers and farmers alike. Each cubic metre saved from seepage can be diverted to expand command area or stabilise existing irrigation.

Evaporation from the canal surface does occur, and it increases in the very conditions now gripping North India — high temperatures, low humidity, brisk winds. But, even in peak summer, evaporation along the relatively narrow strip of a canal’s water surface remains the junior partner compared to the volume silently slipping away into the subsoil. When you stand on a canal bund in June, the real, invisible leakage is lateral, not vertical.

Ironically, seepage has a double-edged impact. In some tracts, it recharges groundwater which farmers then lift with tubewells, effectively routing canal water through an inefficient and energy-intensive detour. In others, particularly in south-western Punjab, it has contributed to waterlogging and secondary salinisation, turning once-productive lands into sodic wastelands. Punjab, in that sense, pays thrice: first by losing canal water to the ground, second by degrading soil health, and third by bearing the ecological cost of remediation that has barely begun.

The great reservoirs: evaporation at scale

Where evaporation truly earns its place as a line item is on the sprawling surfaces of Bhakra (Gobind Sagar), Pong and Ranjit Sagar dams. These are not pipelines under the road; they are inland seas. Gobind Sagar alone spreads over roughly 170 square kilometres at full reservoir level. When an intense summer bears down on such expanses, millions of cubic metres of water are indeed lost directly to the atmosphere — estimates for Bhakra in a hot, dry year run to several hundred million cubic metres, though the figure varies considerably with wind speed and relative humidity. Reservoir operation models carry an explicit evaporation loss term, and rule curves are designed around the expectation of how much water will vanish before the next monsoon refills the basin.

But even here, perspective matters. Evaporation is one component in a larger water balance: inflows from the Satluj, Beas and Ravi; releases for irrigation and power; spills in exceptional monsoon years; seepage and bank storage; and, finally, evaporation. In drought years, the dominant story is deficient rainfall and reduced inflows. Evaporation worsens the situation; it does not single-handedly create it.

There is a deeper irony. The very reservoirs that suffer evaporation losses are also the backbone of regulated, assured irrigation that allowed a water-hungry crop like paddy to spread across Punjab’s semi-arid plains. The bigger structural leak in this story is not physical but policy-driven: we chose, and have continued to choose, cropping patterns that are fundamentally at odds with our agro-climatic reality.

Delhi’s pipes versus Punjab’s canals

Placing Delhi next to Punjab clarifies the mischief in the “evaporation on the way” remark.

In Punjab’s open canals and reservoirs, one can legitimately discuss seepage and evaporation as separate, quantifiable hydrologic processes, debate what lining or operational changes might reduce each, and design engineering and policy responses accordingly. In Delhi’s closed network, the vocabulary should shift to leak detection, metering reform, demand management, network extension to unserved settlements, and the politically fraught question of inter-state water allocation. To pretend that a Delhi Jal Board pipeline behaves like a Rajasthan Feeder canal is to muddle science in the service of spin.

At one level, it is an honest enough error — evaporation is, after all, something every Dilliwala experiences viscerally in May and June — and it may not have been uttered in bad faith. But the effect, whatever the intent, is to deflect attention from questions that carry political cost: why underground assets have not been mapped, why repairs take weeks rather than days, why tariff reform remains untouchable, and why investments in metering technology repeatedly stall.

From flood to drip: plugging the real leaks

If one is truly worried about “water that disappears on the way”, the most cost-effective and climate-wise place to look is not the last kilometre of Delhi’s pipelines but the last kilometre of Punjab’s fields.

For decades, the prevailing irrigation method for paddy has been flood irrigation: water released into a field until it stands ankle-deep, repeatedly, across the growing season. Some of this water is needed to maintain puddled conditions and suppress weeds. A great deal simply percolates beyond the root zone or evaporates under the fierce sun. The economics have long been perverse: free or heavily subsidised power for tubewells, combined with assured minimum support price procurement, has meant that farmers have had little financial reason to count drops. The rational response to a zero-price input is to use as much of it as the crop and the season will absorb.

Modern agronomy and irrigation engineering offer alternatives. Direct seeded rice has, in controlled trials in Punjab, reduced water consumption by 20 to 30 per cent compared to conventional puddled transplanting. The alternate wetting and drying technique — intermittently flooding and drying the paddy field rather than keeping it continuously inundated — has shown comparable water savings in field demonstrations by the Punjab Agricultural University and international research bodies, without significant yield penalties when managed well. Drip irrigation for paddy, though still uncommon in India, has produced dramatic efficiency gains in pilot projects.

Yet these methods have not scaled. The reasons are not mysterious and deserve to be stated plainly rather than glossed over. Power for tubewells is free, so the cost of over-irrigation is invisible to the farmer. Procurement policy rewards paddy volume, not water efficiency. Extension services are thinly spread and often focused on input distribution rather than technique. And there is, understandably, a risk premium: a farmer who has cultivated one way for thirty years is not easily persuaded to experiment on his entire holding. Saving water in Punjab’s fields is as much a problem of political economy as of agronomy, and any serious policy conversation has to engage honestly with the subsidies and procurement architecture that currently work against it.

Lining of field channels and on-farm laser levelling can further reduce wastage at the margins and, unlike the larger structural changes, face fewer political obstacles. They deserve to be pushed harder and faster than they currently are.

The politics of invisible water

Water losses are, by their nature, invisible. Seepage slips underground, evaporation rises without a trace, leakage disappears into the soil or someone else’s pipe. This invisibility makes them perfectly malleable for political storytelling. Leaders can invoke or downplay them at will, confident that most citizens cannot see the flows for themselves, and that the gap between physical reality and political narrative is wide enough to accommodate almost any claim.

The responsibility of serious public discourse is therefore twofold. First, to insist on basic physical accuracy: canals and reservoirs lose water differently from pipelines; evaporation is not an all-purpose excuse; and different loss pathways demand different remedies. Second, to hold political executives to account for the choices they make — on whether to modernise distribution, line canals and watercourses, reform crop patterns and power subsidies, or continue pretending that nature, not policy, is the main culprit.

If there is a “silent thief of precious waters” in North India today, it is not evaporation alone. It is a compound offender: obsolete infrastructure, perverse incentives, neglect of maintenance, and a studied indifference to efficiency at every stage from dam to field to tap. Evaporation does its bit, of course, particularly on the broad backs of Bhakra, Pong and Ranjit Sagar. But the greater theft occurs in our blind spots — in the subsidies we dare not touch, the reforms we perpetually defer, and our abiding preference for the comfort of easy explanations over the discomfort of hard ones.

Perhaps the next time a chief minister reaches for evaporation as an all-purpose alibi, the public conversation can firmly but fairly redirect the lens: yes, let us talk about invisible losses — but let us begin with the ones we can actually fix, and with the political choices that keep them invisible.

June 7, 2026