Study On Groundwater Recharge From Snowmelt Infiltration In Songhua River-Naoli River Basin Of Sanjiang Plain

The unique freezing-thawing process in seasonally frozen soil region has a great impact on regional hydrological process.Snowmelt infiltration is one of the important hydrological processes,it is important to study the groundwater recharge from snowmelt infiltration not only for understanding the hydrological process and groundwater resource evaluation,but also has reference significance for crop cultivation and snowmelt runoff research in seasonally frozen soil region.At present,the study on groundwater recharge from snowmelt infiltration mainly focuses on the monitoring of small-scale sites,while the study on the contribution of snowmelt infiltration to groundwater recharge and infiltration mechanism in large-scale seasonal frozen soil regions is relatively few.In this study,Songhua River-Naoli River Basin in Sanjiang Plain of China is taken as a typical research area.Based on the relevant data of temperature,precipitation,soil temperature and water content,snow depth and distribution,and groundwater level in the study area,the recharge response relationship between snowmelt infiltration and groundwater level dynamics during the freezing-thawing period was analysed.The recharge amount and influencing factors of snowmelt infiltration on groundwater were determined.The infiltration patterns of snowmelt infiltration to groundwater were analysed by using the isotope tracer technology,and the groundwater flow conditions under different recharge scenarios during the freezing-thawing period were predicted by numerical simulation.The details include:(1)Based on the long series monitoring data of temperature,precipitation,snow depth,soil temperature and groundwater level of observation point during the freezingthawing period in the study area from 2019 to 2020,the responses of climate change,snow distribution and melting,soil freezing-thawing process and groundwater level dynamics were analyzed.The results show that the groundwater level has an obvious response of receiving recharge during the thawing period,and the infiltration recharge of snowmelt water is the main reason for the rise of the groundwater level.(2)The water table fluctuation analysis method and spatial interpolation method were used to quantify the groundwater recharge from snowmelt infiltration during the freezing-thawing period.The results showed that 24%-43% of snowfall was in the form of snowmelt infiltration to recharge groundwater during 2016-2020.Under the same precipitation,the recharge amount of snowmelt infiltration to groundwater is even higher than that of rainfall infiltration in non-freezing period,indicating that spring snowmelt infiltration has significant recharge potential to groundwater.(3)The factors affecting groundwater recharge from snowmelt infiltration were analyzed on regional spatial scale and interannual scale respectively by using spatial feature analysis and correlation analysis.The results show that the spatial distribution of snowmelt infiltration intensity is dominated by geological lithology at regional spatial scale.On the interannual scale,the total snowmelt infiltration amount is dominated by annual total snowfall and surface soil moisture content before freezing.(4)The isotope tracer technology was used to analyze the recharge sources of groundwater in the study area,and the recharge pattern of snowmelt infiltration to groundwater was analyzed based on the significant difference of H-O stable isotope values among snowmelt water,soil water and groundwater.The characteristics of groundwater isotopes showed that the groundwater was recharged by surface snowmelt water.There are different infiltration patterns of snowmelt infiltration to groundwater under different geological lithology conditions.The snowmelt water in Songhua River Basin may recharge groundwater in two infiltration patterns: plug flow and preferential flow.The snowmelt water in Naoli River Basin mainly recharge groundwater in the form of preferential flow.(5)Based on the geological,hydrogeological,meteorological and hydrological data of the study area,the numerical model of groundwater flow during the freezingthawing period was constructed,and three recharge scenarios were set respectively to verify the influence of snowmelt infiltration on groundwater under different recharge conditions.The simulation results show that the fitting of simulated water level and measured water level under the centralized recharge of seasonal snowmelt is more realistic,and the fitting effect is better,indicating that considering the recharge of snowmelt infiltration on groundwater resources can improve the accuracy of groundwater resources evaluation in seasonally frozen soil region.Based on the above research on the groundwater recharge from snowmelt infiltration in Songhua River-Naoli River Basin of Sanjiang Plain is helpful to further understand the formation and evolution mechanism of groundwater resources in largescale seasonally frozen soil region,and can provide scientific basis for groundwater resource evaluation and management.