Almeria's Greenhouses Cut Water per Tonne 59% - Yet Total Use Tripled
A farming system can become dramatically more efficient with water and still consume much more of it. A new peer-reviewed reconstruction of greenhouse agriculture in Campo de Dalias, Almeria, puts unusually clear numbers on that paradox.
Published on 24 October 2026 in npj Sustainable Agriculture, the study finds that water consumed per tonne of produce fell 59% between 1975 and 2018. Over the same period, greenhouse area expanded 231%, output rose 666% and total water consumption increased 213%. In other words, water productivity improved while absolute pressure on the aquifer more than tripled.
The analysis, by Wan Izar Haizan Wan Rosely and Nikolaos Voulvoulis, is available in the open-access paper Campo de Dalias and the 'Almeria miracle': a cautionary tale of the value of water in agriculture. It combines historical production, water-use and cost evidence with a counterfactual model. It is not a randomized field trial, and its scenarios should be read as analytical estimates rather than direct observations of an alternative history.
A spectacular efficiency gain that did not conserve the aquifer
The production gains are real and important. Yield per hectare increased 131%, while modern greenhouses, drip irrigation, fertigation and improved crop management sharply reduced the water required for each tonne sold. The study's central finding is that these relative gains were overtaken by growth in scale and intensity.
Water per tonne: down 59%. This is the familiar efficiency measure used to show that farms produce more with less water per unit of output.
Yield per hectare: up 131%. This captures higher land productivity inside the greenhouse system.
Greenhouse area: up 231%. More land was brought into the intensive production model.
Total production: up 666%. Output expanded far faster than either land area or water efficiency changed.
Total water use: up 213%. This is the basin-scale result that determines pressure on groundwater reserves.
Those figures do not prove that efficient irrigation alone caused the expansion. Export demand, infrastructure, finance, labor, protected cultivation and regional policy also shaped Almeria's growth. They do show why a project-level efficiency statistic cannot be treated as evidence of water conservation unless total withdrawals are also measured.
How the irrigation rebound works
The pattern is often called a rebound effect. When technology reduces the water needed for each kilogram or tonne, it can lower the effective water constraint on production. Farmers may intensify a crop, shift into higher-value horticulture or expand the irrigated area. If those responses are large enough, the water saved per unit is absorbed by additional output.
That distinction matters for irrigation policy. A subsidy can improve farm margins and make a business more resilient without reducing basin withdrawals. Both outcomes may be worthwhile, but they are not the same policy result. A water-saving program therefore needs an explicit accounting rule: was the objective higher productivity, lower abstraction, or both?
Campo de Dalias is an extreme but valuable case because the changes unfolded over several decades. The long record makes visible a risk that shorter technology trials often cannot capture. A drip system may save water on a plot during a season, while the regional production system responds over years through investment and expansion.
The aquifer became hidden capital
The researchers estimate groundwater abstraction increased from 7.45 cubic hectometres a year in 1975 to about 60.19 cubic hectometres by 2008. One cubic hectometre equals one million cubic metres. Their central estimate of sustainable annual abstraction is about 50 cubic hectometres, although the paper discusses a wider range of 30 to 60 and tests a narrower sensitivity band of 45 to 55.
That comparison suggests the production system was drawing down a natural asset even as surface indicators such as yield, exports and revenue improved. Groundwater made rapid expansion possible because it could be accessed before a fully enforced basin-wide allocation system was in place. The study also describes weak control of abstraction and illegal wells as part of the governance problem.
The environmental consequences extend beyond a falling water table. The paper records seawater intrusion in the coastal aquifer and nitrate pollution above 100 milligrams per litre in affected areas. Salinity can damage crops and soils, while high nitrate concentrations raise treatment and public-health concerns. Once a coastal aquifer is degraded, recovery can be slow and expensive.
Desalination kept production viable, but changed the cost structure
Almeria increasingly substituted desalinated seawater for groundwater. The study says desalinated water's share rose from roughly 50% to 80% over two decades. That reduces dependence on an overdrawn aquifer, but it connects irrigation more tightly to electricity prices, treatment capacity and the economics of blending different water sources.
The paper's melon example shows why water intensity matters commercially. It estimates that premodern production used about 673 cubic metres of water per tonne, compared with about 65 cubic metres after modernization. At an illustrative groundwater price of EUR 0.16 per cubic metre, the old system's water cost would be around EUR 108 per tonne. At EUR 1 per cubic metre for desalinated water, the modern system's water cost would be around EUR 65 per tonne.
That is a striking result: a much more expensive cubic metre can still produce a lower water bill per tonne when physical efficiency improves enough. It also explains how high-value greenhouse horticulture can tolerate water prices that would be uneconomic for lower-value field crops.
The trade-off is exposure to energy. The study places desalinated water at about EUR 0.60 to EUR 1.00 per cubic metre, with prices reaching EUR 1.20 in March 2022, and says energy accounts for more than half of operating cost. Producers and water authorities therefore need to watch electricity markets, desalination efficiency, renewable-power contracts and the cost of moving water inland.
What the counterfactual actually shows
The researchers model what might have happened if modernization had arrived earlier. They estimate annual abstraction could have been around 14 cubic hectometres lower and the sustainable threshold breach could have been delayed. But the modeled efficiency gain did not prevent depletion when the production trajectory was held constant.
That assumption is crucial. Holding output growth constant isolates the water-intensity effect, but it does not simulate how farmers, investors or markets might have responded to different prices, quotas or technology. The counterfactual is useful evidence about scale, not a forecast and not proof that every irrigation upgrade produces the same rebound.
Why the Almeria result matters beyond Spain
Water-scarce regions across the Mediterranean, Middle East, North Africa, western North America, South Asia and Australia are promoting precision irrigation, protected cultivation and higher-value crops. Almeria shows why those investments should be evaluated at two levels: the farm and the water body.
At farm level, better irrigation can raise yield, reduce water per tonne and help a producer survive higher water prices. At basin level, the same change can fail to conserve water if irrigated area and output keep expanding. Policymakers need both accounts before describing a program as water saving.
The practical policy package is less glamorous than a new irrigation device. It includes enforceable abstraction caps, metering, transparent water rights, timely monitoring, penalties that actually deter illegal pumping, and prices that reflect scarcity without ignoring farm viability. Diversified supply can include recycled water and desalination, but new supply should not become a reason to postpone demand management.
For lenders and agribusiness investors, the lesson is equally direct. A profitable greenhouse can still depend on a deteriorating aquifer or subsidized energy-intensive water. Due diligence should test exposure to future pumping restrictions, salinity, treatment costs, electricity prices and the capital needed for alternative supply.
What to watch next
The most revealing indicators are absolute groundwater withdrawals, aquifer levels, salinity and nitrate concentrations, not only litres per kilogram of crop. Greenhouse area and production volume should be tracked alongside these physical measures so that rebound becomes visible early.
Water pricing also deserves close attention. The gap between groundwater and desalinated water can influence crop choice, investment and pressure for public support. Any comparison should state whether power, capital repayment, distribution and subsidies are included.
Finally, enforcement matters. Technology can measure and deliver water with increasing precision, but only governance determines whether saved water remains in the aquifer, supports environmental flows, or is reassigned to additional production.
Sources and methodology
Agrilinkage based this analysis on the authors' peer-reviewed, open-access study published on 24 October 2026: read the full paper and methods. Percentage changes, historical abstraction estimates, water-cost examples and the counterfactual result are reported by the study. Agrilinkage did not conduct interviews or field observations for this article.
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