Disentangling the effect of climate and cropland changes on the water performance of agroecosystems (Spain, 1922–2016)

Abstract

The main type of consumptive water use is crop evapotranspiration. The historical evolution of crop evapotranspiration depends on climate and cropland changes. These two latter variables present complex interactions and are expected to continue changing in the future, but the coupling between these two processes is insufficiently addressed in the literature. The objective of this study is to disentangle the impact of historical climate and cropland changes on four water performance indicators of agroecosystems in a Mediterranean country (Spain) between 1922 and 2016: crop water requirements actual evapotranspiration, the net primary productivity-based water intensity and violet water, accounting for water stress. These indicators were estimated based on soil water balances and the effects of climate and cropland were unravelled through counterfactual scenarios. The results showed that climate change tended to increase actual evapotranspiration (9%), crop water requirements (14%) and net primary productivity-based water intensity (8%), its greatest impact being on violet water (increasing it by 34%). The cropland variable produced effects of different positive or negative signs according to the parameters considered (type of crop, crop management and point in space-time). In aggregate terms, however, the cropland effect pushed in the same direction as climate change, causing increases in actual evapotranspiration (11%), violet water (15%) and crop water requirements (3%), while reducing net primary productivity-based water intensity (−15%). This approach allows us to quantify and show the importance of agricultural industrialization on the water performance of agroecosystems. In this way, our results highlight great opportunities to manoeuvre to adapt agriculture to climate change through agronomic management and hydrological planning options. Complex interaction patterns between climate and cropland effects were shown. Moreover, geographical, crop-type and temporal evapotranspiration hotspots and drivers were uncovered, and interrelations among the water performance indicators were discussed, thus raising relevant points of discussion in the field.