Multimethod assessment of evapotranspiration shifts due to non-irrigated agricultural development in Sweden

SummaryDuring the 20th century, Sweden underwent a persistent agricultural development. In this study, we use and combine historical hydroclimatic and agricultural data to investigate how this large scale change of land use, and subsequent intensification of crop production, affected regional hydrology in two adjacent Swedish drainage basins. We find a main increase of evapotranspiration (ET) as cultivated area and/or crop production increased during the period 1901-1940. Thereafter, ET stabilized at a new higher level. Comparison between the data given, water balance constrained ET quantification (ETwb), and a range of different comparative estimates of purely climate driven ET (ETclim) shows that only 31% of the steep 1901-1940 increase of ETwb can be explained by climate change alone. The remaining 69% of this ETwb shift, which occurred in both investigated drainage basins, is instead explainable to large degree by the regional land use conversion from seminatural grasslands to cultivated land and associated enhanced productivity of herbaceous species.

► We use historical hydroclimatic and agricultural data for the 20th century. ► Non-irrigated agricultural development affected regional hydrology. ► We find shifts in evapotranspiration when cultivated area and production increase. ► Evapotranspiration increase is not explained by concurrent climate change. ► Productivity boost of herbaceous crops may alone alter regional evapotranspiration.