Environment & EcologyGS319 September 2026

A Strengthening El Niño, a 15% Rainfall Deficit and a Record 269 GW September Power Peak

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The news

The Economic Times reports that the south-west monsoon has remained deficient this season while El Niño has strengthened during it, leaving parts of the country with lower soil moisture and raising concerns over reservoir status; States have been asked to assess district-wise residual soil moisture and reservoir and groundwater availability. The clearest measurement of that deficit appeared not in a hydrological bulletin but in the electricity market. Peak power demand hit a record 269 GW on September 10, which the paper describes as unusually high for the month. Indian Energy Exchange joint managing director Rohit Bajaj said that peak demand reached 269 GW on September 10 and attributed the strength to a 15% deficit in rainfall, the likely withdrawal of the monsoon from northwest India and higher temperatures, which together increased cooling and irrigation demand. On the supply side, he said lower hydro generation and temporary seasonal disruptions affecting coal availability had tightened supply and increased demand on the power exchanges; India has stepped up supplies from thermal power plants to meet the high-demand scenario driven by cooling and irrigation over the usual growth. The market registered the squeeze precisely. The High Price Day-Ahead Market on the exchange rallied through much of September, and IEX data for September 6-17 shows the HP-DAM daily market clearing price reaching its ceiling of ₹20 per unit, with most trade in time blocks of non-solar hours and a sharp rise in purchase bids. HP-DAM is the segment of the integrated day-ahead market designed for higher variable-cost generators — gas-based plants, imported-coal generation and battery energy storage systems. In the regular day-ahead market, purchase bids significantly exceeded sell bids in several recent trading sessions and the market clearing price reached ₹10 per unit in multiple time blocks; the average clearing price for September 1-17 was ₹7.83 per unit, more than double the figure for the same period a year earlier. Bajaj said HP-DAM is helping meet critical power requirements during this phase of tight supply.

The chain in one line: El Niño strengthens through the season → the south-west monsoon runs about 15% deficient and begins withdrawing from northwest India → higher temperatures and depleted soil moisture raise cooling and groundwater-pumping demand → reservoir inflows fall, so hydro generation drops just as demand peaks → peak demand touches a record 269 GW and supply shifts to thermal and high-variable-cost plants → exchange prices double and the high-price segment sits at its ₹20 ceiling in non-solar hours

Static syllabus linkage

El Niño is a phase of a coupled ocean-atmosphere oscillation, not a weather event. The El Niño-Southern Oscillation describes linked variation in sea-surface temperature and atmospheric pressure across the tropical Pacific. In the El Niño phase the central and eastern Pacific warm, the south-east trade winds weaken, and the Walker Circulation shifts eastward so that the ascending limb of convection moves away from the maritime continent towards the central Pacific. For India this statistically suppresses monsoon rainfall, but the relationship is probabilistic, not deterministic, and several El Niño years have produced normal Indian rainfall. La Niña is the opposite phase, and the Southern Oscillation Index, based on the pressure difference between Tahiti and Darwin, is the atmospheric measure of the same system.
The Indian Ocean Dipole is the second control and can cancel the first. The Indian Ocean Dipole is the difference in sea-surface temperature between the western Arabian Sea and the eastern Indian Ocean off Indonesia. A positive dipole, with a warmer western pole, is generally favourable to the Indian monsoon and can partly offset the suppressing effect of an El Niño; a negative dipole compounds it. The Madden-Julian Oscillation governs intra-seasonal active and break spells, and Eurasian and Himalayan snow cover is the classic third predictor. The India Meteorological Department’s seasonal forecasts combine statistical models built on such predictors with dynamical coupled ocean-atmosphere models, which is why a single El Niño reading never determines the official outlook.
How rainfall is officially classified, and when the monsoon leaves. Seasonal rainfall is expressed as a percentage of the Long Period Average: 96% to 104% of LPA is normal, 90% to 96% is below normal, and below 90% is deficient, with corresponding above-normal and excess categories at the upper end. The south-west monsoon normally sets in over Kerala around 1 June, covers the country by early July, and begins withdrawing from west Rajasthan around the middle of September — which is exactly the withdrawal the news refers to. The retreating monsoon then feeds the north-east monsoon from October to December, which is the principal rainy season for Tamil Nadu and the adjoining south-eastern coast.
A rainfall deficit becomes an energy problem through storage, not through rain. Reservoir live storage in the country’s major reservoirs is monitored by the Central Water Commission, and groundwater levels by the Central Ground Water Board; both are the stocks that a monsoon either replenishes or does not. Hydroelectric generation depends on that storage, so a weak monsoon reduces generation and also removes the flexible peaking capacity that hydro supplies. At the same time higher temperatures raise cooling load and drier soils raise electric pumping for irrigation. Electricity exchanges operate under the Electricity Act, 2003 and are regulated by the Central Electricity Regulatory Commission, which is why segments such as the day-ahead market carry regulated price ceilings.

Why UPSC loves this

The monsoon is the most reliably examined physical phenomenon in the syllabus. GS1 carries “important geophysical phenomena” and the climate of India; ENSO, the Indian Ocean Dipole, the jet streams and the mechanism of onset and withdrawal recur in Prelims almost every cycle. The examiner asks for mechanism — why the Walker Circulation shift matters — rather than for the season’s numbers, so the physical chain is what must be memorised.
Climate-energy-water linkage is where GS1 and GS3 now meet. GS3 carries energy, infrastructure and conservation. A story in which a rainfall deficit reduces hydro generation while raising cooling and pumping demand is exactly the kind of cross-sectoral chain the paper has begun to favour, because it cannot be answered from any single standard chapter.
Adaptation has displaced mitigation as the examinable question. Earlier questions asked about India’s emission commitments and international negotiation. The more recent framing asks how a system absorbs a climate shock — which is what a record September peak, a depleted reservoir and a price ceiling being touched actually describe. Answers that treat climate purely as an emissions accounting problem now read as dated.

Prelims nuggets

The El Niño-Southern Oscillation is a coupled ocean-atmosphere phenomenon of the tropical Pacific; in the El Niño phase the central and eastern Pacific warm, the trade winds weaken and the Walker Circulation shifts eastward, statistically suppressing the Indian south-west monsoon.
The Southern Oscillation Index measures the atmospheric pressure difference between Tahiti and Darwin and is the atmospheric component of ENSO; La Niña is the phase opposite to El Niño.
The Indian Ocean Dipole is defined by the sea-surface temperature difference between the western Arabian Sea and the eastern Indian Ocean near Indonesia; a positive phase is generally favourable to the Indian monsoon and can partly offset an El Niño.
The India Meteorological Department expresses seasonal rainfall as a percentage of the Long Period Average: 96% to 104% is normal, 90% to 96% is below normal, and below 90% is deficient.
The south-west monsoon normally sets in over Kerala around 1 June and begins withdrawing from west Rajasthan around mid-September; the retreating monsoon gives the north-east monsoon of October to December, the principal rainy season for Tamil Nadu.
Live storage in India’s major reservoirs is monitored by the Central Water Commission, and groundwater levels by the Central Ground Water Board; both function under the Ministry of Jal Shakti.
Power exchanges function under the Electricity Act, 2003 and are regulated by the Central Electricity Regulatory Commission; the High Price Day-Ahead Market is the segment of the integrated day-ahead market meant for higher variable-cost generators, including gas-based plants, imported-coal generation and battery energy storage systems.

Analysis

The electricity market is the fastest and least-managed instrument for measuring a monsoon failure. Rainfall departure figures are seasonal and reservoir bulletins are weekly, but the exchange prices a rainfall deficit every fifteen minutes. An average day-ahead clearing price of ₹7.83 per unit for September 1-17, more than double a year earlier, and a high-price segment sitting at its ₹20 ceiling in non-solar hours, are statements about hydrology written in rupees. Nobody is managing those numbers for presentational effect, which is precisely what makes them useful. A candidate who can read a power-market figure as a climate indicator is doing something more sophisticated than reciting the season’s rainfall percentage.
Hydro failure is a double loss, and the second half of it is the one that hurts. A weak monsoon reduces hydro energy, which is the obvious loss. The less obvious and more serious loss is flexibility: hydro is despatchable within minutes and is what a system leans on at the evening peak. When storage is low, that peaking capacity is withdrawn at exactly the moment demand is highest, so the system must call on gas, imported coal and storage — which is the description of the HP-DAM segment itself. The price at the ceiling is therefore not merely scarcity; it is the cost of replacing flexibility, not just energy.
“Non-solar hours” is the single most structurally revealing phrase in the report. Most HP-DAM trade clustered in non-solar hours. India has added very large solar capacity, which flattens the midday problem and concentrates the difficulty into the evening ramp when solar output collapses and demand does not. A monsoon deficit stresses precisely that window, because cooling load persists after sunset and hydro is unavailable to cover it. The lesson generalises beyond this season: as the solar share rises, the binding constraint moves from energy to timing, and storage rather than capacity becomes the correct policy answer.
Irrigation pumping is a maladaptive feedback loop and should be named as one. Less rain means less soil moisture, which means more groundwater pumping, which means more electricity demand, which in a tight year is met by thermal generation. The response to a climate shock therefore raises the emissions that drive the shock, while simultaneously drawing down the aquifer that is the buffer against the next one. This is an adaptation trap, and it is invisible in any framework that counts only rainfall or only emissions. The honest qualification is that the alternative — not pumping — is not available to the farmer, so the fix has to be in pump efficiency, solarised pumping and groundwater regulation rather than in exhortation.
Attributing a 15% deficit to El Niño is plausible but not demonstrated, and the distinction matters. ENSO suppresses Indian monsoon rainfall statistically, and India has recorded normal rainfall in El Niño years and deficits in neutral ones. A strengthening El Niño alongside a 15% deficit is consistent with the relationship; it does not establish it for this season, because the Indian Ocean Dipole, intra-seasonal variability and the timing of withdrawal all contribute. The counter-view is worth stating plainly: treating every deficit as an El Niño event encourages a fatalism about forecasting that the science does not support, and it obscures the years when the deficit had a different cause and a different remedy.
The price signal stops before it reaches the people who could respond to it. Exchange prices doubled, but the household running an air conditioner and the farmer running a pump saw a regulated retail tariff, often heavily subsidised for agriculture. The scarcity was absorbed by distribution companies rather than transmitted to demand, so the one mechanism that could have moderated consumption in a tight fortnight was switched off by design. There is a real defence of that design, since exposing households to a ₹20 ceiling would be both regressive and politically impossible. But the consequence should be stated rather than assumed away: in a climate-stressed year, India manages peak demand almost entirely on the supply side, and that is a choice with a cost.

Possible Mains question

“In a climate-stressed year the failure of the monsoon is registered as much in India’s power system as in its reservoirs.” Explain the physical mechanism linking an El Niño-driven rainfall deficit to electricity demand and supply in India, and examine what this linkage implies for climate adaptation. (250 words, 15 marks)

Model approach

Introduction. Open with the mechanism, not the season. One sentence defining ENSO and the eastward shift of the Walker Circulation that suppresses monsoon convection over India, and one sentence stating that the relationship is statistical rather than deterministic. That qualification, placed early, signals that you understand the science rather than a headline about it.
Body — carry the chain from the Pacific to the grid. Warming of the central and eastern Pacific and weakened trade winds; suppressed monsoon rainfall and early withdrawal from northwest India; depleted soil moisture and reduced reservoir live storage; falling hydro generation; rising cooling load and groundwater pumping. Use the concrete anchors — a 15% rainfall deficit and a record peak demand of 269 GW on 10 September — as illustration, not as the argument.
Body — explain why the system strains at particular hours. Distinguish energy from capacity and from flexibility. Hydro is lost as both energy and despatchable peaking power; solar covers midday but not the evening ramp, which is why the high-price segment clusters in non-solar hours; the marginal supply becomes gas, imported coal and battery storage. This paragraph is where most answers will stop at “demand rose”, and where marks are available.
Body — draw out the adaptation implications, including the uncomfortable ones. Name the feedback loop: a rainfall deficit raises pumping, which raises thermal generation, which raises emissions while the aquifer buffer is drawn down. Note that regulated retail tariffs mean the scarcity price does not reach consumers, so adaptation is almost entirely supply-side. Mention storage, solar pumping, irrigation efficiency and groundwater regulation as the structural responses.
Conclusion. Conclude on measurement and institutions rather than on exhortation: India’s climate exposure is now visible in coupled indicators — reservoir storage, groundwater levels and peak demand together — and adaptation planning should be organised around that coupling rather than around any single ministry’s data. Avoid ending with a list of schemes.

Administrator's brainstorm

You are the District Collector of a district with a rainfall deficit of about 15%. Borewell deepening applications are rising sharply and the power utility reports load on agricultural feeders at record levels. What do you do?

Recognise that deepening is a rational individual response producing a collective disaster, so an appeal to restraint will fail. Get the observation-well data and identify the blocks where the water table has fallen fastest, and treat those differently from the district as a whole rather than issuing one uniform order. Coordinate with the utility on feeder-level supply scheduling, because fixed, announced hours for agricultural feeders reduce the wasteful pumping that uncertainty produces and are easier to enforce than a restriction on pumping itself. Protect drinking water sources first and in writing, since the competition between drinking and irrigation demand is the one that will reach you as a law-and-order problem. And record the deficit and the groundwater trend formally now, because whatever relief framework is invoked later will depend on documentation created in these weeks.

As Collector you must decide priority for releases from the district’s main reservoir in a deficit year: drinking water, irrigation, or the hydro station that the State grid is depending on at the evening peak. How do you approach it?

Start from the position that this is not your discretion alone to exercise — reservoir operation follows an approved rule curve and inter-departmental protocol, and a Collector who improvises on it creates a precedent that will be used against the next Collector. Within that, drinking water has first claim and should be stated as non-negotiable at the first meeting so that the rest of the negotiation happens honestly. Ask the water resources department for the storage trajectory to the end of the dry season rather than the current level, because a release that is affordable today may not be. Make the decision in a recorded meeting with the utility, water resources and irrigation present together, and publish the reasoning; in a scarcity year, the perception that the allocation was made quietly does more damage than the allocation itself.

The State is preparing a climate adaptation plan and asks you what the district actually needs. You know that the usual answer is a list of schemes. What do you send?

Send indicators before interventions. Ask that the district be assessed on coupled data — reservoir storage, groundwater depth by block, and agricultural feeder load — because each of those alone conceals what the others reveal, and no existing report puts them on one page. Then propose a small number of things that change the physical system rather than fund activity: solarised and efficient pumps in the blocks with the steepest water-table decline, restoration of the specific tanks that recharge those blocks, and a groundwater management plan with a legal basis rather than an advisory one. Be candid that adaptation in this district is mostly about water and electricity behaving as one system, and that a plan written by either department alone will miss it.