How Much Water Does the Swiss Agricultural Sector Need for Irrigation?

To date, figures on agricultural water use for irrigation in Switzerland have been quite patchy. In response, Agroscope has developed a method for estimating consumption volumes on behalf of the Federal Office for the Environment.

Until now, Switzerland has seldom been associated with water shortages. Increasingly, however, local bottlenecks have led to bans on surface-water withdrawal for agricultural irrigation. In the absence of comprehensive information on agricultural water consumption, the extent to which such problems will grow in future remains unclear.

The aim of the SwissIrrigationInfo Project carried out by Agroscope and the HAFL on behalf of the FOEN was to develop a method for gauging annual water consumption for agricultural irrigation in Switzerland. The method is based on a model approach of the FAO (FAO56) rooted in climate, soil and crop information. For ten crops and crop groups (annual and perennial berries, vegetables, potatoes, maize, apples, grapes, tobacco, grassland and sugar beet), the model was parameterised based on the literature, expert knowledge and real-life data to estimate customary irrigation practice.  

Highest water consumption for vegetables, fruit and grassland

Using these models for the various crops as well as climate, soil and land-use data available throughout Switzerland, water consumption for agricultural irrigation was estimated for the years 2021 to 2023. Accordingly, a consumption of around 9.5 mn m³ was estimated for the wet year of 2021 and of 41 mn m³ and 31 mn m³ for the warm, dry years of 2022 and 2023, respectively. The crops with the highest water consumption were vegetables, fruit and grassland. The results are largely congruent with the estimates of the Swiss Federal Statistical Office for 2023, which are based on random surveys.  

Comparisons of the model estimates with regionally recorded water withdrawal volumes for irrigation in Schaffhausen and Thurgau show that the model-based method substantially underestimates irrigation for the wet year of 2021. For the warm, dry years of 2022 and 2023, the modelled values were relatively congruent with the recorded withdrawal volumes, provided that information was available on the share of irrigated croplands for the respective region.

Without climate protection, irrigation demand could rise by around 20% by 2100

Future irrigation consumption was modelled on the basis of the CH2018 Climate Scenarios and extrapolated to the whole of Switzerland, with the assumption of no changes in land use. According to the said projections, by the end of the century water consumption would rise by around 21% without climate protection measures (RCP8.5) and by 6% with moderate climate protection measures (RCP4.5). These increases show that agricultural water management is confronted with growing challenges.

The reference information on real-life irrigation practices was invaluable for the project, allowing for optimal comparison of the model estimates with reality. However, it also emerged that there was a very high variance in the data on real-life irrigation, which could not be explained with the model. This variance resulted from the fact that irrigation decisions do not depend solely on soil moisture and plant water requirements, but that various business and personal considerations are also determining factors.