2001-2018年石羊河流域植被变化及其对流域管理的启示

植被是流域生态系统的重要指标，植被景观管理也是流域综合管理的重要内容。综合利用长时间序列MODIS反射率和归一化差值植被指数（NDVI）产品及Landsat卫星遥感影像，基于谷歌地球引擎（GEE）平台，利用计算机自动分类的方法，监测了2001-2018年间石羊河流域的植被（包括灌溉土地）的逐年变化，结合降水、径流量和地下水位地面监测数据，分析了全流域植被指数、植被面积、灌溉土地范围的变化特征及其与水循环之间的互馈关系。研究发现，2001-2018年间，石羊河流域的植被面积以每年约135 km²的速率增加，其中，自然植被和灌溉土地分别以每年60.5 km²和74.6 km²的速率增加。除了金昌区的植被增加以灌溉土地为主外，其他区域都以自然植被的增加为主。特别是民勤地区，由于十多年的持续调水和有效退耕，地下水位近年来开始抬升，自然植被开始恢复。但与此同时，中游凉州区和永昌县的生态风险加大。未来可从灌溉规模控制、地表与地下水统一调度、景观分级和配置技术发展、优化产业结构、强化与流域外的连通性等方面加强流域综合管理，提高流域社会系统弹性，增强可持续发展能力。

Temporal-spatial characteristics of vegetation change in Shiyang River basin from 2001 to 2018 and its implication for integrated watershed management

Vegetation is an important indicator of watershed ecological health, and vegetation landscape management is also an important part of integrated watershed management. In this paper, based on the Google Earth Engine (GEE) platform and the long time series MODIS reflectance and Normalized Difference Vegetation Index (NDVI) products and Landsat satellite images, the annual changes of natural vegetation and irrigated extent in Shiyang River basin (SRB) from 2001-2018 were monitored using an automatic classification method. Based on the ground-based data of precipitation, runoff and groundwater level, the temporal-spatial characteristics of natural vegetation and irrigation land change and their interaction with watershed water cycle variables include precipitation, runoff and groundwater level were analyzed. We found that the vegetation area in SRB increased with a rate of about 135 km² per year from 2001 to 2018. Natural vegetation and irrigated land increased with a rate of 60.5 km² and 74.6 km² per year, respectively. Except for Jinchang area, the increase of vegetation is dominated by natural vegetation in other areas. Especially in Minqin area, groundwater level has been rising in recent years and natural vegetation has begun to recover due to more than ten years of continuous water diversion and effective control of cultivated land. However, this reduces the amount of water available in the middle reaches, and thus causing the increased ecological risks in Wuwei (Liangzhou District) and Yongchang County. In the future, the integrated management of river basins can be strengthened by comprehensive measures include irrigation land control, unified regulation of surface water and groundwater, optimization of industrial structure, and strengthening connectivity with the outside of the river basin. All of these are beneficial to improving the resilience of social ecosystems in SRB and enhance the ability of watershed sustainable development.