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Alluvial fans have been proven to have great utilisation potential in QTP, but to what extent they are suitable for agricultural development is unknown. Therefore, using the alluvial fan in the Lhasa River Basin (LRB) as a case study, this paper established an evaluation system of land suitability for agriculture (LSA). Principal component analysis (PCA) and the exhaustive method (EM) were used to define the minimum dataset (MDS) and then the LSA of the alluvial fan in the LRB was evaluated using a comprehensive index of LSA. Two scientific approaches were implemented to improve the LSA using a scenario simulation. The results showed that the MDS assessed by the EA was more representative compared to the PCA. Alluvial fans with suitable grades are mainly distributed in the Lhasa River's middle and lower reaches. Developing facility agriculture and repairing roads accessing the alluvial fans are effective approaches to improve the LSA, which can increase the suitable-grade area from 58.62% to 97.82% and 63.85%, respectively. Therefore, most alluvial fans in the LRB are suitable for developing agriculture, and under the influence of human activities, there will be more alluvial fans suitable for developing agriculture. Our research provides scientific methods for the sustainable development of land in alpine regions. [ABSTRACT FROM AUTHOR]

• Water erosion on the Qinghai-Tibet Plateau decreased from south to north. • Water erosion decreased from 1982 to 2015 but slightly increased since 2007. • Climate variability enhanced erosion and human activity reduced it from 1982 to 2015. Climate variability and human activities cause changes in precipitation and underlying surface conditions, which are the main driving forces of changes in water erosion, especially in the Qinghai-Tibet Plateau (QTP). In this paper, the water erosion on the QTP from 1982 to 2015 was quantified by the Revised Universal Soil Loss Equation (RUSLE), and the response of water erosion changes to climate variability and human activities was investigated. The results indicated that the distribution of water erosion gradually decreased from south to north during 1982–2015. Areas of severe erosion were mainly distributed along the Yarlung Tsangpo River and in the western Hengduan Mountains. The years of the abrupt change in water erosion were 1989 and 2006. Compared to 1982–1989, the amount of water erosion was mitigated in both 1990–2006 and 2007–2015, with a 19.5% and 6.2% decrease, respectively. The contribution of human activities to the decrease in water erosion was 25.4% and 16.7% for each of these periods, respectively, and the contribution of climate variability to the increase in water erosion was 5.9% and 10.5%. However, water erosion increased by 16.5% from 2007 to 2015 compared to 1990–2006. The contribution of climate variability was 4.9% and the contribution of human activities 8.4%. The increase in water erosion due to human activities may be attributed to the construction of the Qinghai-Tibet Railway and associated human activities. It is therefore important to draw attention to the influence of human activities on the QTP on erosion, to prevent potential future risks. This study is the first attempt to research the relative contributions of variation in climate and human activities to changes in water erosion on the QTP. It would be beneficial for carrying out ecological environmental protection work on the QTP. [ABSTRACT FROM AUTHOR]