Effects of different land use types on potential evapotranspiration in the Beijing-Tianjin-Hebei region, North China

Potential evapotranspiration (ET0) is vital for hydrologic cycle and water resource assessments as well as crop water requirement and irrigation demand assessments. The Beijing-Tianjin-Hebei region (Jing-Jin-Ji)an important, large, regional, economic community in China has experienced tremendous land use and land cover changes because of urbanisation and ecological restoration, affecting the hydrologic cycle and water resources of this region. Therefore, we analysed ET0 in this region using climate data from 22 meteorological stations for the period 1991-2015 to understand this effect. Our findings show that ET0 increased significantly at a rate of 7.40 mm per decade for the region. Based on the major land use type surrounding them, the meteorological stations were classified as urban, farmland, and natural stations using the 2015 land use dataset. The natural stations in the northern mountainous area showed a significant increase in ET0, whereas most urban and farmland stations in the plain area showed a decrease in ET0, with only a few of the stations showing an increase. Based on the different ET0 trends for different land use types, these stations can be ranked as follows: urban stations (trend value: -4.663 to -1.439) > natural stations (trend value: 2.58 to 3.373) > farmland stations (trend value: -2.927 to -0.248). Our results indicate that land use changes affect meteorological parameters, such as wind speed and sunshine duration, which then lead to changes in ET0. We noted that wind speed was the dominant parameter affecting ET0 at all the natural stations, and wind speed and sunshine duration were the dominant parameters affecting ET0 at most of the urban stations. However, the main controlling parameters affecting ET0 at the farmland stations varied. These results present a scope for understanding land use impact on ET0, which can then be applied to studies on sustainable land use planning and water resource management.