| Natural-artificial oasis ecosystems are widely distributed in inland river basins of Northwest China,but water shortage is the restrictive factor for the maintena nce and development of oasis ecosystems.The precipitation in the arid area of Northwest China is less,and the runoff in main yield region of alpine is the direct water resource for the oasis in the middle and lower reaches.The precipitation in mountaino us area and ice-snow melt-water played an important role in the composition of water resources in the region,and is also the main recharges source of streamflow.The transformation and transportation of the various hydrology factors in the process of runoff-producing and converging in the inland river basin are a complicated process,which is also an important problem to be solved in the field of hydrology.The impact of global climate change on the hydrological cycle is also one of the hot issues in the current international water science research field.Global climate change,land use and overlay changes have a profound influence on the dynamic equilibrium process of the hydrological cycle in the basin.Climate change will cause changes in hydrological factors such as precipitation,evaporation,and glacial melting,which in turn will lead to the redistribution of water resources in time and space;The change of land use type will directly affect the hydrologic elements such as precipitation,evaporation,soil moisture content and seepage amount in the canopy of vegetation,and it will also obviously affect the runoff river display and the water balance process in the basin.The Manasi River Basin is the study area,through making use of meteorology and hydrology observation data and multi-source remote sensing data,combined with routine statistics method,spatial analysis of GIS and RS technology,the hydro-climate conditions in all the elevation zones were grasped preliminary in the basin,this study analyzed the variation of glacier ablation in the area of runoff formation and the spatial heterogeneity of underlying surface.By improving and application of GIS-based distributed SWAT Hydrological Modeling,the suitability and simulation precision are improved,and the eco-hydrological process and runoff producing mechanism of different landscape belts are revealed.About four aspects of hydrological regime,glacier variation,the evolution of vegetation landscape pattern and hydrological processes modeling,the main contents of this study include the following aspects:(1)Hydrological Regime.In the past 60 years,the annual mean runoff of the Manasi River Basin has increased significantly,and showed an obvious abrupt change in 1995.The annual runoff distribution in a year is non-uniformity,which is summer half year and winter half year account for 87%and 13%of the total,respectively.The increase in temperature has accelerated the melting of snow and ice in high and cold areas,and the increase in precipitation has resulted in a significant increase in runoff in the study area.In the period2000-2016,the inclination rate of temperature was 0.12°C/10a,and the annual temperature at different altitude of the whole mountainous area was-0.32°C/100m.The vertical lapse rate of air temperature at different elevations also showed significant differences in season.The average annual precipitation amount is 1611.8mm,and the change rate is about 13.23mm/10a.Precipitation is gradually increased with altitude in low mountainous region,the maximum value(414mm)at about 3000-3500m,and above 3500m is gradually decreasing with altitude in the alpine area.(2)Glaciers Area and Ice Volume.In the period1990-2016,the area of glaciers in the Manasi River Basin has been greatly reduced,about 32.5%of the glaciers have disappeared,and the annual changing rate in ice volume was1.6%.In terms of the number and area of glaciers,small glaciers appear to be very sensitive to climate change.Glacier development depends on the combination of mountain temperature and precipitation.The increase in glacier area at high altitudes(>4600m)may be because glacier accumulation caused by increased precipitation is greater than glacier melting caused by rising temperatures.(3)Changes on vegetation landscape pattern.The underlying surface in the study area is mainly covered by various grasslands;with the large-scale glaciers and a certain area of forests constitute the landscape pattern of the subject.In the past 26 years,the meadows,bare rocks and residential areas in the study area have shown a significant increase,while the grassland and sparse grassland area presented a decreasing tendency with fluctuation.The heterogeneity and degree of fragmentation of the landscape in the whole study area are increasing,and the proximity of the same type of landscape patches is gradually decreasing.The distribution of landscape types is aggravated by the dispersion.(4)Hydrological Processes Modeling.The average annual runoff volume of glacial meltwater in the study area was 4.95×10~8m~3,which accounts for about 37%of the average annual runoff of mountain-pass,and presented a decreasing tendency with fluctuation.Glaciers melt water accounts for 94%of the total amount in all year from May to September,and the recharge process of glacial runoff showed remarkable seasonality.The order of the amount of water produced by the underlying surface to the runoff is as follows:glacier/firn>meadow>grassland>sparse forest>evergreen coniferous forest>sparse grassland.Within the period of this study,the drought year and rainy year distribute at intervals,and the water balance in the basin is a dynamic equilibrium process of various water bodies for many years.When the precipitation in the research area increases,the runoff increases obviously,and the temperature increases will reduce the depth of surface runoff,but it accelerates the melting of glaciers and fills part of the runoff lost due to evaporation.In the future,the runoff of the Mahe River basin will continue to increase under the climate scenario.The innovations of this paper include the following two aspects:(1)Based on the inversion of MODIS and TRMM data,the temperature and precipitation data for the study area are achieved.Through the statistical downscaling method and GIS spatial analysis technology,the space-time characteristics of key meteorological elements at high and cold area are objectively described.Meanwhile,the study on the vertical change law of temperature and precipitation in the mountain area of the Manasi River Basin is a beneficial supplement.(2)The glacial material balance model is embedded in the SWAT distributed hydrological model.From the main hydrology factors such as precipitation,glaciers melt water,actual evaporation,interflow and shallow groundwater,the dynamic process of water balance in the study area is analyzed to reveal the runoff yield and concentration mechanism. |
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