From rain-fed to irrigated agriculture? Projecting the future irrigation water demand in Germany using a hydro-economic multi-agent system model

Climate change increases the frequency and severity of droughts in Central Europe and thereby threatens food production in the German agricultural sector, which is mostly rain-fed and heavily dependent on precipitation. Farmers need to adapt to these changing conditions, for instance by shifting to irrigated production systems. This increases the future agricultural water demand and may result in competition for water use and higher groundwater depletion. Simultaneously, farmers adapt their land-use patterns towards an optimal crop mix, responding to changes in climatic and economic conditions. This land-use adaptation also affects the irrigation water demand.

To project the future irrigation water demand in Germany considering land-use adaptation, we present the spatial multi-agent system (MAS) model DroughtMAS which simulates agricultural land-use adaptation of the 8 major field crops using a positive mathematical programming (PMP) approach. Each agent captures the behavior of farmers in one of Germany’s 401 NUTS-3 regions, is individually calibrated to the observed production conditions for a 20-year historic average, and is empirically validated for the same period. Therefore, the agent-based structure portrays the agroeconomic and biophysical heterogeneity of Germany. To consider uncertainties concerning future climate change levels and socioeconomic developments, we project the future land-use adaptation and irrigation water demand using integrated RCP-SSP scenarios. To this end, the MAS model is coupled to a statistical crop yield model driven by meteorological indicators and soil moisture, derived from the mesoscale Hydrologic Model (mHM). Projections of the agricultural crop prices are based on the SSP scenarios. The integrated hydro-economic model consequently reflects the adaptive behavior of agents responding to changing crop yields and prices.

The results emphasize the importance of accounting for land-use adaptation to accurately project farmers’ irrigation water demand and to consider changes in biophysical and socioeconomic variables simultaneously. Such estimates are crucial in planning for future agricultural water demands to prevent user conflicts and water resource depletion.