| The Changbai Mountain Area(CMA)is located in the northeast of China which is an important water conservation area and ecological function area.It’s also the water source area of the Songhua River basin,the Tumen River basin and the Yalu River basin.As a typical mountainous cold region,the CMA is sensitive to climate change,and the regional water cycle is processes are changing inresponse.In this paper,we analyse the intra-year and interannual variability of meteorological and hydrological elements in the study area and sub-basins based on station observations.A bidirectional coupled meteorological-hydrological model(WRF/WRF-Hydro)was constructed and its applicability was evaluated in this study area.The coupled model was applied to simulate the water cycle processes in the study area during the historical period(1975-2020),and high-resolution data on water cycle elements were obtained for a long time series.The study revealing the spatial and temporal characteristics of the water cycle in the study area under changing scenarios based on the data.Based on the model,simulations were carried out to predict trends in the water cycle for 2021-2050 under the change scenarios(RCP4.5 and RCP8.5).The main conclusions of this study are as follows:(1)From 1975 to 2020,the multi-year average temperature in the study area was5.53°C,with an increasing trend of 0.038°C/a,and the average temperature of the Yalu River basin was the highest among the three sub-basins;the annual precipitation in the study area ranged from 550-1149 mm,with an increasing trend of 2.04 mm/a.The annual precipitation was mainly concentrated in summer(June-August).The precipitation of the Yalu River basin is the highest among the three sub-basins.The study area is characterised by double streamflow peaks in April-May and July-August,which is maily due to the supplementation of river flow by melting snow and ice in April-May and the supplementation of large amounts of precipitation in July-August,respectively.What’s more,the annual mean instantaneous flows at the hydrological stations in the study area tend to decrease.(2)Six important hydrological parameters have been calibrated by running the WRF-Hydro model offline and the simulation has been assessed using the NSE,CC and RSR.The results show that the overall modelling performance was good during the rate period(1975-1993),with the assessment results achieving an overall rating of good and above.During the validation period(1994-2020),all sites were assessed to be satisfactory and above,indicating that the model is suitable for simulating the water cycle in the CMA.(3)The coupled model was applied to carry out the simulations of hydrometeorological data for the historical period(1975-2020)in the study area to obtain high-resolution data on water cycle-related elements.On this baisis,the study revealing the evolutionary characteristics of the water cycle in the study area from the perspectives of spatial distribution and spatial and temporal changes.The average annual canopy water volume in the study area is 76 mm and the total evapotranspiration is 606 mm,of which 234 mm is plant transpiration,296 mm is soil evaporation and 76 mm is canopy evaporation.during the year,plant transpiration is the largest in summer and soil evaporation is the largest in the rest of the year.From the water cycle elements,all elements except surface runoff showed increasing trends to varying degrees.During this period there is a tendency for the freezing time of the topsoil in the study area to be delayed,an earlier trend during the thawing period and a gradual reduction in the annual freezing time.(4)The runoff coefficient in the study area increases with the elevation(0.017/100m),while the evaporation coefficient decreases with the elevation(0.029/100m),indicating that the higher the altitude the morer the runoff production.Among the different land uses,the highest runoff coefficient of 0.53 is found in towns and built-up areas,while the smallest runoff coefficient is found in broad-leaved forests at 0.38.The highest evaporation coefficient is found in cultivated areas at 0.62,while coniferous and mixed forests have smaller evaporation coefficients at 0.38 and 0.40 respectively.(5)Both the RCP4.5 and RCP8.5 scenarios show an upward trend in temperature and total evapotranspiration and a higher upward trend in the RCP8.5 scenario.Precipitation and runoff show an increasing trend under RCP4.5 and a decreasing trend under RCP8.5,and the spatial trends in precipitation and runoff are highly consistent across the scenarios,especially in the Yalu River basin where significant increases.The two-way coupled modelling approach adopted in this study can provide a reference for related studies in other watersheds,and the results of the study are of great value in providing water security and efficient use of water resources in the CMA... |
PDF Full Text Request