Abstract:[Objective] The spatial-temporal changes and associated driving forces of land use in the Beiluo River basin were investigated in order to provide a scientific basis for the optimization of land resources, the improvement of environmental quality and further exploration on runoff-sediment dynamics in the area.[Methods] Based on the google erath engine (GEE) platform, we sorted and processed six-phase remote sensing images acquired in 1970-2019 for the Beiluo River basin. The characteristics of land use change in the basin were captured from the perspectives of temporal variation, dynamics attitude, transfer direction and spatial structure, and the associated driving factors were explored.[Results] During the study period, the land use types in the Beiluo River basin were mainly woodland, cultivated land and grassland, and the quantitative structure changed from 1:1.1:0.6 before 2000 to 1:2.7:0.7 after 2000. During 1970-2019, cultivated land, grassland and water area in the basin decreased by 16.6%, 6.7% and 0.1%, respectively, while contrarily woodland and construction land have increased by 19.9% and 1.3%, respectively. The patches of cultivated land and grassland in the basin tended to be dispersed and simple, while the woodland tended to be aggregated and complicated. Land use transfer mainly occurred as the conversion of cultivated land to woodland and construction land, and the conversion of grassland to woodland. The comprehensive land use dynamic attitude of the basin increased firstly and then decreased, reaching a peak during 2000-2010. In the basin, the upstream hilly and ravine area saw the most significant change of land use structure, followed by Ganquan, Yijun, Huachi and Heshui counties in the middle reaches.[Conclusion] The evolution of national policies, socio-economic development and population growth determine the direction and extent of land use change, and natural factors are long-term auxiliary influencing factors.

Abstract:[Objective] The objective of this paper is to explore the spatial and temporal characteristics of evapotranspriation(ET) in the Beiluo River basin, and provide theoretical basis for the study of ecological benchmark and ecological water requirement and the effect of returning farmland to forest. [Methods] Based on MOD16 remote sensing image data, meteorological and hydrological date during 2000—2014, and the land use date in 2011, we used river basin water balance method, method of mean value, the standard deviation method and the linear trend method to analysis the spatial and temporal variation characteristics of evaporation. [Results] The mean annual evapotranspiration of Beiluo River basin increased slowly with values ranged from 395.4 to 517.4 mm, and average evapotranspiration during the past 15 years was 446.74 mm. The monthly variation of evapotranspiration within the year show a unimodal pattern, it was mainly concentrated in the period from May to September, and its peak value occurred in August. The average relative error was 12.04% between spatial interpolation results based on measured rainfall and estimates based on MOD16-ET, the correlation coefficient was 0.81. The profile line of ET changed greatly from upstream to downstream of the Beiluo River basin, which presented the irregular “wave curves”. The spatial variation of annual ET was obvious in the basin. The ET showed an increasing trend in the midstream and upstream, while it showed a decreasing trend in the downstream. [Conclusion] In the recent 15 years, the evapotranspiration in Beiluo River basin showed an increasing trend, and human activity was the main driving force, especially the implementation of grain for green project and soil and water conservation project.