中国西北干旱区石羊河流域重点治理综合效应评价

Evaluating the comprehensive effects of the Key Master Plan of the Shiyang River Basin in arid areas of northwest China

2007年中国启动石羊河流域重点治理项目,旨在提高用水效率,改善区域生态环境,全面准确地评价石羊河流域重点治理效应对于当地政策的调整与完善具有重要意义。该研究分析了石羊河流域重点治理前后气象、水文、生态、社会经济等多项指标的时空变化,并采用压力-状态-响应框架构建了石羊河流域生态系统健康评价模型,定量评估了流域重点治理综合效应。结果表明,石羊河流域气候呈现暖湿化的趋势,蔡旗断面年径流量提升至4.01×108 m3。流域下游地下水超采状况得到改善,中游地下水埋深持续下降。流域耕地扩张与林地缩减趋势得到缓解。流域生态健康评价指数呈波动增加趋势,金昌市评价指数增长幅度略高于武威市,分别达到Ⅳ级0.353、Ⅲ级0.413,治理均取得积极效果。在重点治理的后续规划中,科学的水资源配置方案与农业灌溉用水规模控制是流域管理机构需要重点关注与推进的工作。

An ecological environment in arid areas is continuously deteriorating faster than expected,particularly under the dual influence of global climate and human activities.Active ecological restoration projects can be effective ways to curb ecological degradation.An accurate and rapid evaluation of ecological restoration projects can also greatly contribute to the decision-making on ecological restoration measures in arid areas in the future.For instance,the Key Master Plan of Shiyang River Basin was launched in the arid area of northwest China in 2007,in order to promote water use efficiency and regional ecological environment.Taking the Key Master Plan of Shiyang River Basin as the research object,this study aims to determine the typical indicators(including the ecology,climate,hydrology,and social economy)before and after the implementation of the project.An evaluation system of comprehensive effect was also established suitable for the regional ecological restoration projects using the pressure-state-response framework.The analytic hierarchy process was first used to determine the weight of indicators by integrating the opinions of decision-makers and experts.Then,the ecosystem restoration was quantitatively evaluated to clarify the positive impacts and potential risks.The results showed that the climate of the Shiyang River basin presented a trend of warming and wetting,where the annual runoff of the Caiqi section increased to 4.01×108 m3.There was an increased over-exploitation of groundwater in the lower reaches of the basin,while the depth of groundwater continued to decrease in the middle reaches.Furthermore,the sown area of crops remained stable in the basin except in Yongchang County.At the same time,the irrigation water consumption decreased year by year,with an average annual decrease of 1.51%.Specifically,the water-saving irrigation area reached 23.99×104 hm2 in 2020.94.6%of the regions showed an increasing trend of Gross Primary Productivity(GPP),which was mainly concentrated on the banks of the Shiyang River and the vicinity of Qingtu Lake.By contrast,the vegetation showed a trend of recovery in the mountainous areas of the upper reaches.The cropland expansion and woodland shrinking were alleviated to reduce the scale of grassland,where the wasteland was the fastest growing land type after the implementation of land management.The evaluation index of Jinchang City(Grade 0.353)increased faⅣster than that of Wuwei City(Grade 0.413),indicating a positive evolution.There was aⅢsignificant increase in the comprehensive evaluation of the Key Master Plan in the middle and upper reaches of the basin,as well as the coastal areas of Shiyang River,while only a slight increase was found in the lower reaches of Minqin County.The GPP(16.1%)and the utilization ratio of water resources(11.6%)were the main contribution indexes of ecological restoration in this region.Therefore,the water resource allocation can be expected to timely adjust in the follow-up planning of the Key Master Plan,according to social and economic development.Groundwater monitoring and water right trading should also be adopted to limit the increase in agricultural water use.The finding can also provide scientific suggestions for the decision-making on the measures in the next stage of ecological restoration in the arid areas.