| The Qinghai-Tibet Plateau is known as the “third pole” and is known as the “Asian Water Tower”.Its hydrological cycle and changes in water resources have an important impact on the surrounding areas.Runoff is the main factor reflecting the function of water tower.Runoff coefficient is the basic factor to study the change of runoff,and observation of runoff on slope is the fundamental way to quantify the coefficient of runoff.The Selin watershed is located in the hinterland of the Qinghai-Tibet Plateau.The local water cycle plays a key role in explaining the water circulation mechanism of the inflow zone of the Qinghai-Tibet Plateau and its connection with water resources around the Qinghai-Tibet Plateau.However,due to its special geographical location and harsh environment,it is domestically There are no relevant reports on the observation of the runoff process on the slope of the Selin watershed,and there is no relevant measured data.Accurate observation of the runoff process on the slopes of the alpine steppe and quantitative disclosure of the changes in the runoff coefficient of the alpine steppe have important scientific significance for the interpretation of the water cycle and simulation of the inflow zone of the Qinghai-Tibet Plateau.Therefore,this study selects the typical alpine grassland slope in the Selin watershed as the research object.Through the observation of slope rainfall observation,evaporation observation,soil moisture observation and runoff process,the characteristics of runoff in the alpine steppe are discussed,and the slope precipitation is interpreted.-Infiltration-storage-flow generation mechanism;combined with soil water content,underlying surface properties,rainfall characteristics,rainfall and other rainfall characteristics,the main factors affecting slope runoff are analyzed.Provide observation verification and parameterization scheme for the color flow simulation of Selin,and contribute to the study of the “Asia Water Tower” change related to the “Belt and Road” strategy.The main findings of this paper are as follows:(1)Based on the discontinuity and extreme lack of ecological hydrological data of the color forest in the Qinghai-Tibet Plateau,a perfect flow observation system has been established on the slope of typical alpine grassland:A perfect flow observation system including precipitation observation,evaporation observation,soil temperature and humidity observation and slope runoff process observation was established on the typical alpine grassland slope in the Selin watershed of the Qinghai-Tibet Plateau.Based on the observations,precipitation,evaporation and Soil temperature and humidity characteristics.The results show that the rainfall in the study area has gradually increased in recent years,which is consistent with the “warm and humid” characteristics in the context of climate change.During the year of distribution,rainfall is mainly concentrated in May-September,accounting for 98% of the annual rainfall.The comparison of quantity and size shows the characteristics of July > August > September > May > June.In addition,the rainfall types in the study area are mainly medium and small rain characterized by formation and intermittent type.By comparing the soil evaporation characteristics under different vegetation coverages,the higher the vegetation coverage,the smaller the soil evaporation.The characteristics of evaporation diurnal variation were found to be the largest cumulative evaporation of soil during 12:00-16:00,accounting for the evaporation of the day.43%,the smallest 16:00-20:00,accounting for 13% of the day’s evaporation,which is basically consistent with the daily variation of solar radiation.By comparing the soil moisture content of each layer at different times of the day,it was found that the soil water content appeared at 320 cm,followed by 160 cm and 5 cm,and the water content at 320 cm was significantly higher than other depths.It is 2.9 times the water content at 160 cm and 8.1 times the water content at 80 cm.(2)Based on the observation results of precipitation,evaporation,soil moisture and slope runoff,the slope runoff process and its characteristics under different rainfall types are systematically analyzed:Under the continuous rainfall type,due to the high frequency of rainfall,low evaporation and high soil water content,the runoff is easier to form.The rainfall infiltration process mainly occurs in the soil 0-20 cm;in the absence of rainfall-rainfall type,As the water content of the soil continues to decrease due to evaporation,the water is more involved in the water infiltration process after the start of the next rain,resulting in the formation of the flow later than the continuous rainfall,and the production flow is small.In the study of slope runoff process under different rainfall types,it is found that the runoff time and rainfall time of light rain,moderate rain,heavy rain and heavy rain have obvious hysteresis;in light rain,rainfall is 7.6 mm,runoff depth At 0.23 mm,the water infiltration is 2.63 mm;in moderate rain,the rainfall is 18.8 mm,the runoff depth is 0.68 mm,and the water infiltration is 14.65 mm;in heavy rain,the rainfall is 32.4 mm,and the runoff depth is 0.78 mm,water infiltration is 30.49 mm;in heavy rain,rainfall is 55.4 mm,runoff depth is 0.89 mm,water infiltration is 47.59 mm;light rain,moderate rain,heavy rain and heavy rainfall infiltration occur in the soil 0-5 cm,0-80 cm,0-10 cm,and 0-80 cm.(3)Clarify the minimum rainfall formed by the runoff and the runoff coefficient of the Selin watershed,and determine the main influencing factors of the runoff coefficient based on factors such as rainfall characteristics,initial soil water content and underlying surface properties:The analysis of slope runoff characteristics in the study area shows that the relationship between rainfall and runoff is exponential,and with the increase of rainfall,the correlation between rainfall and runoff is more significant,and rainfall is affecting runoff.An important factor.In the relationship between the initial water content of the soil and the rainfall at the beginning of the runoff,it is found that at low water content(about 5%),the minimum rainfall formed by the runoff is 5 mm;while in the high water content(about 8%)When the runoff is formed,the minimum rainfall is 1.8 mm.The runoff coefficient of the Selin co watershed typical alpine grassland slope is about 0.016,and the rainfall types are light rain,moderate rain,heavy rain and heavy rain.The runoff coefficients are 0.016,0.018,0.014 and 0.017 respectively.Rainfall,rainfall duration,rainfall intensity,maximum 10 min rainfall intensity Among the influencing factors such as initial soil water content,the maximum 10 min rainfall intensity and initial soil water content are the main factors affecting the runoff coefficient. |
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