Model calculations show how climate change will affect the water requirement for different crops grown on the Swiss Central Plateau. This will allow us to proactively plan for crop irrigation and adaptation to the changing climate.
As climate change progresses it will become warmer, and less rain will fall during summer. Consequently, farmers can expect more water deficits. These deficits could be reduced by irrigation, provided that sufficient water resources are available.
Model-based estimates of irrigation needs
Using the FAO method for estimating crop-specific irrigation needs, the changes in irrigation requirement that might be expected for the future were modelled based on current climate projections. The changes were investigated for various locations on the Swiss Central Plateau (Aigle, Basel, Bern, Changins, Güttingen, Payerne, Reckenholz) and for various vegetable, field and grassland crops.
More irrigation needed, especially in the summer and autumn
The projections without climate-change mitigation (RCP8.5) show an increasing demand for irrigation for all crops and locations. For the investigated potato, iceberg lettuce and ryegrass crops, the estimated percentage increase by the time horizon of 2045–2074 is around 20%, and by 2070–2099 around 35%.
In absolute figures, the greatest irrigation needs are forecasted for the already-more-arid locations of Aigle, Changins and Payerne. From a seasonal perspective, irrigation needs rise the most in the summer and autumn months, whilst few changes are to be expected on average in the spring months.
Benefits of planning climate-adaptation measures
The applied method offers a wide variety of options for use, e.g. in the planning of irrigation infrastructure projects, or for the development of alternative climate-adaptation measures such as the cultivation of more-drought-resistant varieties or crops. Far-sighted planning could reduce future water-use conflicts and prevent bad investments.
Inclusion of field data and weather extremes essential
Further studies must take a closer look at existing model uncertainties and gradually reduce these through the inclusion of field data. In addition to changes in average irrigation needs, the effects of the increasing frequency of weather extremes must be examined further.
- Without climate-change-mitigation measures, the Swiss agricultural sector’s water requirement on the Central Plateau will generally rise according to the model estimates.
- For the crops discussed, the estimated percentage increase by the time horizon of 2045–2074 is around 20%, and around 35% by 2070–2099.
- The increases in irrigation needs are particularly noticeable in the summer and autumn months.
- The operationalised FAO method for estimating crop-specific irrigation needs offers potential for use in the planning of adaptation measures (e.g. irrigation infrastructure projects).
- Validations and model improvements aim to reduce uncertainties of the projections.