高原山地—湖泊地区雨季地表水补给来源的空间格局及形成机制

Spatial pattern and formation mechanism of surface water recharge sources in plateau mountain-lake region during the rainy season

本文旨在解析中国西南高原山地—湖泊地区雨季地表水补给格局及其形成机制,基于2022年7—8月在洱海流域采集的多水体氢氧稳定同位素数据,利用贝叶斯混合模型和遥感技术,量化地表水的补给源和比例,并探究水体转化机制。结果表明:(1)洱海流域雨季降水受蒸发和季风气候等影响,其氢氧同位素值与地下水和地表水相比偏负。地下水δD、δ18O表明,在高海拔及富水性高的区域地下水氢氧同位素值偏负,d-excess值则表明不同含水岩组的蒸发差异。地表水氢氧同位素值随着水体从入湖河水经过洱海湖水到出湖河水的流动逐渐偏正,其中苍山东坡和南部区域同位素值较北部区域而言更偏正,就苍山东坡而言,其中游地区蒸发作用最为显著。(2)苍山—洱海间地表水补给来源的空间格局显示,地表水对其下游混合水体的贡献率最大。其中降水和地表水在苍山—洱海间各河段的贡献率皆表现为,在出山口以上河段的降水、地表水贡献率小于出山口之后河段;而地下水贡献率反之。(3)沿河流流向,其地形、地质条件、地表覆盖和水汽特征共同影响地表水补给来源的空间格局,植被覆盖状况好、地表温度高和实际蒸散量多的区域,降水对地表水的补给多;植被覆盖状况较差的区域,地表水的补给较多;地下水对地表水的贡献率则取决于含水岩组类型。

This research aims to decipher the patterns and mechanisms of surface water recharge during the rainy season in plateau mountain-lake region.Based on the stable hydrogen and oxygen isotope data of multiple water bodies collected in the Erhai Lake Basin from July to August 2022,and using Bayesian mixing models and remote sensing technology,the study quantifies the sources and proportions of surface water recharge and explores water body transformation mechanisms.The results indicate that:(1)Precipitation in the Erhai Lake Basin during the rainy season is influenced by evaporation and monsoon climate,resulting in hydrogen and oxygen isotope values that are more negative compared to groundwater and surface water.GroundwaterδD andδ18O indicate that in areas of high altitude and high water richness,the hydrogen and oxygen isotope values of groundwater are more negative,while dexcess values reveal evaporation differences among different aquifer groups.The hydrogen and oxygen isotope values of surface water gradually become more positive as the water flows from inflowing rivers through Erhai Lake to outflowing rivers,with the isotope values on the eastern slope and southern region of Cangshan Mountain being more positive compared to the northern region.For the eastern slope of Cangshan Mountain,the midstream area shows the most significant evaporation.(2)The spatial pattern of surface water recharge sources between Cangshan Mountain and Erhai Lake shows that surface water contributes the most to its downstream mixed water bodies.The contribution rate of precipitation and surface water in each river section between Cangshan Mountain and Erhai Lake is shown as follows:the contribution rate of precipitation and surface water in the river section above the mountain outlets is smaller than that in the river section below the mountain outlets;while the contribution rate of groundwater is vice versa.(3)Along the river flow direction,the spatial pattern of surface water recharge sources is jointly influenced by topography,geological conditions,surface cover,and water vapor characteristics.Areas with good vegetation cover,high surface temperatures,and high actual evapotranspiration receive more precipitation recharge;areas with relatively poor vegetation cover receive more surface water recharge and the contribution rate of groundwater to surface water depends on the type of aquifer groups.