喀斯特包气带渗透过程及其水文地质含义研究

Karst water is very important drinking water resources in China. With the twofold pressures of high speed growing of economic and urbanization in past three decades, karst water has been more or less impacted respect to quantity and quality. In Yunnan Province, the water supplying situations are extreme hard after a four year continuous drought (from 2009 to now). How to effective utilization karst water and management karst aquifer has become a main issue. Recharge estimation is important for understanding the water cycle, contamination transport and for water management. Vadose zone, especially epikarst, plays a critical role on karst water circulations. It controls the main recharge dynamic of aquifer. However, monitoring water in vadose zone and estimating groundwater recharge is one of the most challenging works. So far, the infiltration processes of water through vadose zone are not well understood yet. This project takes the circulations of karst water as a whole, Corry out a detail monitoring on rainfall-soil moisture-vary rites cave dripping waters-spring for two hydrological years in an upper vadose cave and spring. Besides the consecutive measurement of pH, EC,T, amounts of rainfall and the discharges of cave dripping waters(10 main observing sites ) and spring by data loggers, the water isotropy(18O and 2H) and hydrogeochemtry (Major ions, DOC, Sr2+) samples, following two stages of sampling strategies(one is long term sampling phase with interval 2 weeks; another is event sampling with interval 1 to several hours depend on the recharge envets for at least two events), also will be took and analyzed. Couple with vadose zone vertical dye tracings and Electrical Tomography methods, a systemically study implement to characterize water infiltration processes in vadose zone. The following topics will be detail studied: a)the responses of discharges of cave dripping waters and spring to the effective rainfall, to the moistures of soil; identify different percolation processes in vadose zone and their influence factors by multi-parametric approaches; and then, classification of dripping waters based on their hydrological responses of discharges and infiltration processes to effective rainfall, taking classes as end members to carry out an end-member mixing analysis of spring water ground on the supposition that all the dripping water from the cave flows out from the spring (has been proved by previous studies) following the principles of Christophersen & Hooper (1992) proposed. The EMMA results will be used for evaluating the contribution of every end-member for spring recharge and its temporal distribution. The findings of study will not only help us better understanding water circulation within vadose zone, but also enhance the capacity of us better managing karst aquifer under extreme climate conditions. The results could be applied for the field of stalagmite palaeoclimate research as well.

洞穴滴水是降水补给在包气带内部气-水-岩三相综合作用的结果。滴水水文地球化学及渗透过程对补给的响应直接或间接地反映了表层喀斯特带水贮存与运动特征。本项目运用现代观测分析手段，多参数方法与包气带示踪试验相结合，辅助地物手段，在昆明市阿子营乡老黄龙洞对降水、土壤温湿度、洞穴滴水和泉水等包气带地下水循环各个环节的水量、理化参数（T、EC、pH）、水文地球化学（8大离子、Sr+、DOC和水同位素）高分辨率观测基础上，系统研究滴水对降水时间分布和土壤湿度的响应过程；识别不同渗透过程及其影响因素；基于滴水和渗透过程对降水的水文响应，对滴水分类；视不同滴水类型为端元，运用端元混合分析方法（EMMA）分割老黄龙洞泉暴雨过程，探讨不同类型滴水的水文地质含义。成果对深入认识与量化表层喀斯特功能、深化含水层脆弱性认识有重要学术价值，同时对有效管理与保护喀斯特地下水、缓解喀斯特地区人畜饮水形势也有重要现实意义。

项目以云南省昆明市阿子营乡老黄龙洞为研究点，运用现代观测分析手段，多参数方法相结合，对降水、洞穴滴水和泉水等包气带地下水循环主要环节的水量、理化参数（T、EC、pH）、水文地球化学（8大离子、DOC和水同位素）高分辨率观测基础上，系统研究不同滴水对降水事件响应过程；识别不同渗透过程及其影响因素；基于滴水和渗透过程对降水的水文响应，对滴水分类；视不同滴水类型为端元，运用端元混合分析方法（EMMA）分割老黄龙洞泉水过程，探讨不同类型滴水的水文地质含义。初步研究成果表明老典龙洞滴水可分为5个类型：快速集中渗流水、快速滴水、慢速滴水、沿非碳酸盐岩夹层顺层渗透滴水、二次渗透滴水；各滴水类型对降水事件都有响应，具有不同的响应特征与方式；滴水裂隙的构造特征在很大程度上影响着滴水点的滴速；不同类型滴水滴率对降水事件响应响应有很大差异，降水阈值也不一样，与降水强度、降水前期土壤、上层包气带含水状况有关；在快速滴水点观测到滴水明显存在一个滴水速率快慢频繁变换时期，说明该滴水裂隙有其它含水裂隙补给。裂隙水快速滴下导致裂隙含水量减少滴水点滴率变慢，其它裂隙含水层水体补给使裂隙含水量在一定时间内蓄积到一定程度后，滴水由慢变快。滴水快慢转换持续时间类似一个阻尼震旦过程，如果没有新雨水补给，滴水将变为中速或慢速滴水；洞中CO2浓度变化很大程度上与滴水速率正相关；数据初步分析显示，枯季时近一半的泉水流量来自风化裂隙含水层补给。随着降水过程增加，泉水中喀斯特含水层补给成分增加；项目获取了1-3年以周为周期滴水水化学、理化参数、水同位素以及DOC和TOC数据：滴水连续（0.5-2h间隔）滴水水温和电导率数据和滴速数据；水位、水温和电导率连续数据；降水数据和降水水样同位素数据；4个洞内和洞外1个环境监测站气温、湿度、气压和CO2浓度数据，进一步成果将在近期产出；研制成功降水与滴水滴速记录和取样器。成果对了解喀斯特含水层补给过程有重要意义。