| Mountainous areas are key water sources for the plain areas and provide valuable fresh water sources for cities where most of the water is consumed and are natural ecological barriers.They are responsible for regulating the climate and maintaining biodiversity.The evolution of the mountain water cycle process not only directly influences the quality and stability of its own ecosystem,but also transmits this impact to the downstream plains and cities.Since the spatial heterogeneity and the dominant vertical zonal characteristics are inherent in the mountain water cycle process,how to quantify the associated hydrological and water resources effects,accurately evaluate and predict the spatial-temporal patterns of water resources is of great significance to the sustainable development of regional economic society.Aiming at the influence mechanisms of spatial heterogeneity and vertical zonality of climate,topography,soil and vegetation on the water cycle process in mountainous areas,the paper designed an improved scheme with the combination of distributed hydrological model with the remote sensing technology and climate models.This paper selected the Taihang Mountain(TMR)as the research region,systematically analyzed the vertical zonalities of topography,climate,soil and vegetation,constructed a WEP-L model considering horizontal and vertical characters,and analysed the temporal and spatial patterns of water resources.The main conclusions obtained are as follows:(1)The vertical zonal characteristics of the climate,soil and vegetation of the TMR were summarized.The gradient of monthly precipitation in the TMR along the elevation was between-5.20 and 6.72 mm/hm.The monthly average temperature gradient was between-0.66 and-0.48 ?/hm,but there are apparent differences in different slope directions.The FVC in the mountainous areas is significantly higher than that in other months from May to September.The FVC was the highest in August,and the spatial variation ranged from 14 to 100%,the lowest in February,and the FVC ranged from 0.8 to 97.8%.The leaf area index of each month showed a decreasing pattern from southeast to northwest,with a range of 0.1?7.0.The saturated water content varied from 40%to 46%,the water holding capacity in the field varied from 17.4%to 29.3%,the water content of wilting varied from 7.7%to 15.5%,and the water content of single molecule varied from 3.5%to 6.6%.The saturated hydraulic conductivity varied from 0.0007cm/s to 0.0025cm/s,and the wet front suction varied from 6.1cm to 11.24cm.(2)An integrated distributed water cycle simulation scheme for mountainous areas considering spatial heterogeneity and vertical zonality was proposed.The vertical zonality of precipitation in the TMR was described by the gradient of monthly mean precipitation along the elevation.The vertical zonal distribution of vegetation was described by the spatial statistical results of the monthly FVC and LAI of the 500m resolution by the contour belt.According to the percentage of soil texture of the 1km resolution,a linear weighted method was used to generate the rasters of the saturated water content,field water holding capacity,residual water content.saturated hydraulic conductivity,single molecular soil moisture content and wet front soil suction.The vertical zonalities of soil physical parameters were described by the spatial statistics of these rasters by contours.According to the relationship between the soil thickness and the slope obtained from the Chongling watershed,the soil thickness of the TMR was generalized to 30-80cm in combination with the spatial distribution of the slope of the mountainous terrain.The improved WEP-L model was calibrated and validated:the validation results of the monthly simulated and reverted runoff of the 4 controlled hydrological stations showed that the constructed WEP-L model well simulated the macroscopic water cycle process in the TMR.The result that the runoff processes of several hydrological stations on the upper and lower reaches of the Qin River were simultaneously well simulated,and the correlation between simulated and remote sensing evapotranspiration was improved showed that the improvement scheme considering the vertical zonality was effective.(3)The evaluation and spatiotemporal pattern of the blue water and green water were analysed based on the improved WEP-L model.The average precipitation in the TMR from 1956 to 2016 was 70.22 billion m3,the blue water was 11.82 billion m3,the green water flow was 57.81 billion m3,and the high-efficiency green water was 37.49 billion m3.The ranks of the amount of seasonal precipitation,blue water,and green water flow in the TMR in descending order are summer,autumn.spring,and winter,while for the high-efficiency green water,the rank is summer,spring,autumn,and winter.The rank of the inter-annual volatilities in descending order is blue water,precipitation,high-efficiency green water and green water flow.The rates of the change of the precipitation,blue water and high-efficiency green water are-178 million m3/a.-92 million m3/a.and 190 million m3/a,respectively.The Hurst indices of precipitation,blue water and high-efficiency green water are 0.61.0.73 and 0.82.respectively.The precipitation time series has a higher degree of randomness,while the high-efficiency green water series has a lower degree of randomness.The Hurst indexes of blue water and high-efficiency green water are greater than 0.5,indicating that the probability of blue water attenuation and high-efficiency green water increase is greater in the future.The blue water in the TMR is more active than the high-efficiency green water,and the blue water is more sensitive to meteorological factors in the Haihe River Basin Part(HRBP)than in the Yellow River Basin Part(YRBP).(4)The impact of climate change on the temporal and spatial patterns of water resources in the TMR was analyzed.Compared with the historical average value(1956?2015),the RCP4.5,RCP6.0 and RCP8.5 climate scenarios predict that the annual precipitation in the TMR will increase-1%,3%and 11%in the future(2016?2050),respectively.The spatial variation rates of the estimated annual precipitation are 0.21?0.38mm/a,0.21?0.40mm/a and 0.23?0.42mm/a,respectively,and the variation slope is higher in the high altitude area.The annual average temperature in the TMR will increase 0.78?,0.51? and 0.79? in the future(2016?2050),respectively.The spatial variation rates of the average temperature are 0.0028?0.0075?/a,0.0027?0.0074?/a and 0.0028?0.0076?/a,respectively,and the variation slope is higher in the low altitude area.Under the three climate scenarios,the blue water is expected to show a decreasing trend compared with the historical average value,with amplitudes of-27.4%,-1 7.1%and-2.6%,respectively.The high-efficiency green water is expected to show an increasing trend,with amplitudes of 36.6%,40.7%and 48.8%,respectively.The analysis results of vertical bands show that the blue water attenuation phenomenon is more prominent in low-altitude areas,and the increase of high-efficiency green water in high-altitude areas is more apparent.The simulation results based on the RCP8.5 climate scenario show that the blue water in the TMR will be close to the historical average when the predicted precipitation in the future is 11%more than the average value from 1956 to 2015.The main innovations of this paper are as follows:(1)a scale downscaling correction method for satellite precipitation based on the fusion dataset is proposed,which enriches the precipitation distribution technology considering vertical zonality;(2)An improved scheme considering spatial heterogeneity and vertical zoning is proposed.The original related modules and parameterization schemes of the WEP-L model are specificly reconstructed,which improves the simulation effciency of the vertical water cycle process in the mountainous area;(3)Based on the WEP-L model,the temporal and spatial patterns of the green and blue water in the TMR are analysed,as well as the prediction of water resources situation under the climate change. |
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