Comparative Study On Remote Sensing Evapotranspiration And Ecological Water Consumption In Typical Small Watersheds Of South And Northern Xinjiang

Evapotranspiration,including surface evaporation and plant transpiration,is an important parameter of surface water heat balance.Accurate estimation of regional evapotranspiration has important application value in the rational allocation and utilization of water resources and agricultural production practice.Using meteorological data and Landsat 8 images,combined with the SEBS model,we calculated monthly mean evapotranspiration for the 12 months of 2016 in the typical small watersheds of South and Northern Xinjiang,Hutubi County and Qira County,and analyzed the temporal and spatial distribution of the evapotranspiration and conducted Comparative analysis.The precision of evapotranspiration estimated by the evapotranspiration model was verified using the calculation results of the Penman formula,micro-lysimeter and vorticity correlation instrument.Analyze the correlation between meteorological or remote sensing factors such as temperature,atmospheric pressure,wind speed,sunshine duration,NDVI,and other factors affecting evapotranspiration,and evapotranspiration.Based on the remote sensing inversion of evapotranspiration combined with land use,the evapotranspiration method was used to calculate the ecological water consumption of typical grassland basins in Hutubi County and Qira County in south and northern Xinjiang,and a comparative analysis was conducted.Research indicates:(1)From a timescale perspective,the overall changes in the monthly average evapotranspiration for the 12 months of 2016 in Hutubi and Qira County showed a trend of first increase and then decrease.The monthly average evapotranspiration in Hutubi County in2016 was an upward trend in January-August and peaked in August,with a downward trend in August-December and a clear seasonal change.The average monthly evapotranspiration in Qira County in 2016 showed a fluctuating upward trend from January to July,and it reached a maximum in July and a downward trend from July to December.The average monthly evapotranspiration for the 12 months of 2016 in Qira County was higher than that in Hutubi County,and the change was larger.The maximum and minimum evapotranspiration spans were 2.929 mm.The maximum monthly average evapotranspiration in Qira County in 2016 occurred in July,while the maximum monthly average evapotranspiration in Hutubi County in2016 occurred in August;the minimum values of both occurred in January.(2)From the perspective of spatial distribution,the evapotranspiration in both Hutubi and Qira counties is closely related to the geographical units of the county.Both of them are divided into three parts: southern mountainous area,central plain and northern desert.Due to the wide distribution of grassland and rivers in the southern mountainous areas,there is ample supply of water and the largest amount of evapotranspiration.Due to the distribution of farmland and evapotranspiration in the central plain is smaller than that in the southern mountainous areas;the supply of desert water in the northern desert is low,and the vegetation coverage is low and the evapotranspiration is the smallest.Due to the influence of cloud cover in remote sensing images of Qira County,the evapotranspiration in the northern desert is high.In general,the spatial distribution of evapotranspiration in both Hutubi County and Qira County shows a trend of southern> central> northern.(3)The main environmental factors affecting the monthly average evapotranspiration in Hutubi and Qira are air temperature and air pressure.Among them,the monthly average evapotranspiration in Hutubi County is negatively correlated with the air pressure.In addition,Hutubi Monthly average evapotranspiration was also significantly affected by sunshine hours,followed by NDVI and wind speed,while monthly average evapotranspiration was not related to NDVI,wind speed,and sunshine hours in Qira county.(4)The ecological water consumption per unit area of woodland in Hutubi County is greater than the ecological water consumption per unit area of grassland.The ecological water consumption per unit area of grassland in the Qira county is greater than the ecological water consumption per unit area of the forest land,and the ecological water consumption per unit area of grassland in the Qira county is greater than the ecological water consumption per unit area of the grassland in Hutubi county.