面向流域水质安全预警的土地开发压力源评估方法及其应用

为适应水环境风险管理中压力源风险的快速识别需求,构建了土地开发压力源评估方法,并以三峡库区为案例区进行应用研究. 土地开发压力源评估方法首先是基于不同土地利用类型的排污参数来确定敏感土地利用类型和不利转移方向,再采用状态和趋势兼顾的原则筛选流域内敏感单元,然后根据各单元的实际特征逐一确定预警指标,以进行压力源评估和预警级别划分. 案例研究结果表明:重庆市辖区控制单元、涪陵区万州区控制单元和澎溪河开县控制单元是库区水质安全预警的3个敏感单元；其中,重庆市辖区控制单元和涪陵区万州区控制单元的预警指标均为敏感土地类型面积比例和发生不利转移的土地面积比例,其中重庆市辖区控制单元的2个预警指标值分别为42.17%、3.43%；涪陵区万州区控制单元分别为32.86%、1.74%；而澎溪河开县控制单元的预警指标仅为敏感土地类型面积比例,其值为32.31%. ③重庆市辖区控制单元、涪陵区万州区控制单元和澎溪河开县控制单元的预警指标最大超标率分别为163%、33%和19%,相应各单元土地开发压力分别为红色预警(重警)、橙色预警(中警)和黄色预警(轻警)级别. 从管理意义上,重庆市辖区控制单元和涪陵区万州区控制单元未来需要从优化当前土地利用方式、合理控制未来土地开发的双重角度来降低压力；澎溪河开县控制单元未来应重点关注和降低当前土地利用状况对水质安全的压力. 研究认为,所提出的面向流域水质安全预警的土地开发压力源评估方法具有可操作性,其案例研究结果可为三峡库区案例区水环境风险管理提供决策支撑. 

Method and Application of Land Exploitation Stressor Assessment for Water Security Early Warning

Abstract: Considering the requirement of fast recognition of stressor risks for water environmental risk management, using a case study of the Three Gorges Reservoir (TGR) area, a land exploitation stressor assessment was established and applied. The results indicated that:1) an evaluation for determining the pressure of land development on water quality, and warnings for adverse status and changes, has been proposed. Firstly, sensitive land use types and negative land use transitions were determined using pollutant output parameters of different land use types. The sensitive area units were selected, taking into account both the land use status and trends. Finally, the early warning indicators were ascertained to carry out stressor assessment and to rate the early warning level of each unit according to its actual characteristics. 2) For the case study areas, Chongqing municipal district control unit (CU1), Fuling-Wanzhou control unit (CU2) and Kaixian section of Pengxi River control unit (CU3) were sensitive area units of water security. The early warning indicator of CU1 and CU2 were the area proportion of sensitive land use types (42.17% and 32.86% for CU1 and CU2 respectively) and the area proportion of negative land use transitions (3.43% and 1.74% for CU1 and CU2 respectively). The early warning indicator of CU3 was the area proportion of sensitive land use types with the value of 32.31%. 3) As the maximum exceeded proportion of early warning indicators of CU1, CU2 and CU3 were 163%, 33% and 19%, the early warning levels of the indicators were at the red alert level (i.e., severe warning), orange alert level (i.e., moderate warning) and yellow alert level (i.e., mild warning), respectively. In view of watershed management, both the optimization of current land use modes and the rationalization of future land exploitation are needed to reduce the pressure of land development in CU1 and CU2. Reducing the pressure of current land use status should be focused on to mitigate the risk to water security in CU3.The study showed that the proposed method of land exploitation stressor assessment for water security early warning is feasible for supporting water environment risk management in the TGR area.