| The monsoonal temperature glacier is sensitive to climate change and is closely related with regional water resource and hydrological processes. Study on the hydrological processes of temperature glacier region is of great significance to the sustainable utilization of water resource. Selecting Lijiang-Yulong Mountain region as the study area, this paper mainly studied on the evolution of water geochemistry, the hydrological processes, the sources and recharge region of surface and ground water in the temperate glacier region based on the methods of hydrochemistry, hydrogeology. isotopic tracing and modeling.The temperature markedly increased in the drainage basin from1979to2006, and the increase of temperature in winter was higher than those in other seasons. The annual precipitation varied with a slightly upward trend in the same period, when the increase mainly occurred in spring and summer while the decrease occurred in autumn and winter. The streamflow at Yanggong River showed a significant increasing trend. During the four seasons, spring experienced the most significant increase. The distribution of runoff is very uneven during a year. Runoff in the flood period accounts for72.69%of the annual amount. The increasing trend in runoff was the results of variation of groundwater, ice-snow meltwater and precipitation caused by global climate change. The discharge was characterized by similar variation in a year for Sanshu river, Geji river and Shu river, which increased during the wet season and was stable in the other seasons. Moreover, the discharge of Baishui river varied obviously over the year, showing the special recharge of ice-snow melting water and precipitation. The discharge of Heilong spring in Lijiang basin showed obvious variation during1988-2006.The ion composition and variation in natural water of different altitude regions were studied to reveal the evolution of water geochemistry in typical temperate glacier basin and distinguish different factors effecting the hydrogeochemisty of different water. Natural waters were neutral to slightly alkaline from the high and low altitude area. The ion concentration of natural waters increased as the altitude decreased in the study area. Chemical variations for the major ion concentrations versus depth for the seven snowpacks are apparent. The spring snowpacks can reflect the high concentration of dust in Asian while the ions redistributed in summer snowpacks because of ion elution. The ice-snow melting water was of HCO3-Ca2+type with small seasonal variations and obvious spatial variations. The marine source was the most significant contributor of sea salt ions whereas the anions were related to human activites. The local terrestrial source was also important for alkaline earth ions.Both the river and ground water in the area were of the HCO3--Ca-2+-Mg2+type with similar ion compositions and showed small seasonal variations, normally high in the dry season and low in the wet season. From upper basin downward there was a general increasing trend for the total ion concentrations in the river and ground water. Water-Rock interactions were the significant contribution to water geochemistry while precipitation contribution is important in monsoon seasons. The correlationship of Mg2+/Ca2+versus Na+/Ca2+indicated that limestone and dolomite were the main end-members controlling the variations in chemical composition of river and spring waters.The results indicated different stable isotope composition in different water bodies in this typical temperate-glacier basin. The δ18O in new snow was characterized by obvious seasonal changes, which was high in pre-monsoon and was low during summon monsoon and the winter monsoon. The variations for δ18O versus depth were apparent in the winter monsoon and pre-monsoon. The post-deposition process led to redistribution of oxygen in snow layers. The overall δ18O composition ranged between-16.7%o and-11.1‰for the river waters and ranged between-15.13%o and-14.20%o with small seasonal variation. The comparison of δ18O in different waters indicated that the most significant seasonal variation was observed in rainwater while the least in river and spring water. The similarity of δ18O for both surface and groundwater samples was due to their frequent transformation in karst regions. The18O values revealed that groundwater was recharged by ice-snow melting water and precipitation in high altitude region (>2700m). Rivers around Mt. Yulong were recharged by melting water and precipitation, whereas rivers without glaciers in the drainage basins were recharged by groundwater.The hydrograph separation was applied in Baishui glacial basin to firstly assess different contributions of ice-snow melting water and rainwater to runoff. The results showed significant difference of oxygen-18existed among meltwater, rainwater, ground water and stream water, and significantly seasonal variation of precipitation occurred during the observed period. The streamflow of Baishui catchment was separated into components of ice-snowmelt and precipitation using oxygen-18. As shown by the result of the two-component mixing model, on average,53.4%of the runoff came from ice-snowmelt during the wet season, whereas the remaining46.6%were contributed by precipitation in the catchment. According to monthly hydrograph, the contribution of snow and glacier meltwater varied from40.7%to62.2%in wet season. Analyses suggested that the uncertainty in the measurement method was less important than that in the temporal and spatial variations of tracer concentrations. The uncertainty terms for precipitation was generally higher than80%of the total uncertainty, indicating that the δ18O values of precipitation accounts for the majority of uncertainty. The uncertainty was sensitive when the difference between mixing components was small. Therefore, the variation of tracers and the difference of mixing components should be considered when hydrograph separation was applied in one basin. |
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