丽江黑龙潭地下河系统的水均衡分析与预测评价

Equilibrium analysis and prediction evaluation of the Heilongtan groundwater system in Lijiang of northwestern Yunnan Province

滇西北丽江黑龙潭流量大幅减少、间歇式断流问题日趋频繁,已成为地方经济社会发展的重要制约因素。在对丽江盆地区域水文地质条件和黑龙潭地下水系统动态调查的基础上,考虑社会经济发展过程中人类工程活动的影响,以近70年的数据为基础,采用水均衡法定量分析黑龙潭地下水系统流量的动态变化及其影响因素,得出不同时段黑龙潭断流的主要原因,并根据近年黑龙潭断流的影响因素及变化趋势,预测未来黑龙潭流量的变化趋势,2021—2030年,黑龙潭将成为季节性泉水,2030年之后,黑龙潭泉群将长期处于断流状态。该认识可为黑龙潭的地下水动态恢复和丽江城区地下水水资源开发及环境保护提供依据。

The karst water system is a dynamic system controlled by the degree of karst development and the underlying geological conditions.It constantly evolves with changes in climate,human activities,and many other factors.As one of the main driving forces of environmental change,human activities have caused the change at the rate and intensity far exceeding that of natural succession in a short period of time.The environmental effects and induced hydrogeological problems resulting from human activities are extremely difficult to distinguish and quantify,and hence have been the working focus of local governments and scholars at home and abroad.The Lijiang basin is a typical covered and semi-covered karst water system developed in the strong uplift zone of the late Cenozoic crust,which has given birth to the Heilongtan spring,the Xiguanlongtan spring,the Jiudinglongtan spring and other karst springs(spring groups).These springs are not only important water sources for Lijiang City,but also the city's highlights of tourism resources.Among them,the Heilongtan groundwater system is the most important karst water subsystem in the groundwater system of the Lijiang basin.However,the primary discharge point of this system,the Heilongtan spring,has currently experienced a significant reduction in flow and increasing intermittent drying up,which have become important factors restricting local economic and social development.Based on the comprehensive analysis of data over the past 70 years,the investigation of hydrogeological conditions in the Lijiang basin area,and the dynamic monitoring of the Heilongtan groundwater system,we quantitatively evaluated the dynamic flow change of and its influencing factors on the Heilongtan groundwater system with the method of water equilibrium.Fully considering the impact of human engineering activities in socioeconomic development,we summarized factors for the drying-up of the Heilongtan groundwater system as follows.(1)From 1951 to 1990,human engineering activities that replaced and reduced regional vegetation increased natural evaporation capacity and continuously increased evaporative discharge by 10,827,400 m^(3),accounting for 87.00%of the total decrease in the resources of the Heilongtan groundwater system(12,445,400 m^(3)).This is the main reason for the dryingup probability and the increasing span of Heilongtan spring.(2)From 1991 to 2018,with the recovery of vegetation,the evaporative discharge continuously decreased by 18,303,400 m^(3),compared with that in the 1980s,which was beneficial to the recovery of Heilongtan spring.However,the factors such as human mining,leakage from the surface river system,and urban development and rereconstruction have caused a total decrease of groundwater resources by 50,586,900 m^(3),which is unfavorable to the recovery of the Heilongtan spring and is also the cause for its drying up.Among these causes,urbanization and human groundwater extraction reduced groundwater resources by 45,805,200 m^(3),which accounted for 90.54%of the overall decrease and was another primary cause of the drying-up.According to the change of influencing factors of the Heilongtan spring in recent years,the future changes of its flow predicted by the method of water equilibrium shows that:(1)From 2021 to 2030,the Heilongtan spring will change into a seasonal spring and become drying up during median water year and low flow year.(2)After 2030,the Heilongtan spring groups will remain drying up for a considerable amount of time with a very slim chance of reproduction.This study research can serve as a foundation for the dynamic recovery of Heilongtan groundwater,and the development and environmental protection of the groundwater resources in the urban area of Lijiang.