Water Demand for Crops Rise in Germany

To Reduce Future Demand for Water Under a Changing Climate, the Study Suggests that Farmers Grow Different Crops and Change Their Management Practices

In Europe, 44% of water taken from rivers and groundwater is used for agriculture. Thesewithdrawals affect EU Member States' commitments to achieve good status of water as laidout by the Water Framework Directive (WFD).

Under the WFD, the amount of waterabstracted must be controlled and Member States' River Basin Management Plans need tobe adaptable to the changing availability of water in the future.

This study investigated how climate change could affect irrigation to the year 2070, in termsof how much water will be needed per square metre of cropland. As case study, it focusedon the agricultural county ofUelzen,inGermany.

In this county an average of 73millimetres of water is applied per square metre of land (mm/m2) per year for irrigation.

Nomore than 79 mm/m2 can be extracted from groundwater for this purpose, under localauthority rules.

The researchers modelled future water requirements for crops under the RCP 8.5 emissionsscenario, the most extreme scenario described by the IPCC.

However, the study notes that ithas already been surpassed by actual observations.

They considered water demand under three possible temperature rises by 2070: ‘maximum'(daily averagetemperature that is 1.7°C higher than it was during 1991-2010), ‘medium'(+1.3°C) and ‘minimum' (+0.9°C).

They assumedthat current cultivation patterns would continue and that crops would be irrigated when thesoil's water content drops below 20% of its total capacity to store water.

The soil in thecounty is sandy and does not retain water well.

The results suggest that demand for water is likely to rise under the maximum andmedium temperatureincreases, and fall slightly under the minimum scenario.

It wouldexceed the maximum water allowance of 79 mm/m3in the years following 2064, but onlyunder the maximum temperature rise of 1.7°C. Fourteen millimetres more rainfall each yearis expected under the maximum scenario, but this would not be enough to make up for theextra 28.4 mm/yr of evapotranspiration in the higher temperatures.

Under this scenario, it is likely that crops would fail or be damaged more often. Localwetlands may beendangered by agricultural demand for groundwater.

Sugar beet andpotato in particular require large amounts of water. For instance, in the time period 2051-2070 under the maximum temperature rise, sugar beet could need around 100 mm/m2 ayear and potato around 90 mm/m2 a year on average.

Demand for irrigation water would also rise under the medium scenario of +1.3°C, butwould stay within regulatory limits. Annual rainfall is expected to rise by 45 mm under thesecircumstances but evapotranspiration would increase by 5.6 mm/yr.

Under the minimumtemperature rise scenario (+0.9°C), water demand may fall slightly because more rainfall(+44.7 mm/yr) and less evapotranspiration are predicted (-8.7 mm/yr) in this scenario.

To adapt to warmer conditions in future the study suggests growing water-efficient crops,moving sowing dates to earlier in the year when more rain is expected and using moreefficient irrigation technologies, such drip irrigation.

Source: European Comission

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• Agriculture
• Research
• Climate Change