| Due to the shortage of water resources in the Ebinur Lake Basin,a series of ecological problems have caused serious threats to the local ecological environment and socio–economic sustainable development.The ecological water requirement can quantitatively describe the amount of water needed to maintain ecological healthy development.It can be used to formulate water resources planning based on ecological water demand,which is of great significance to the management of water resources in the study area.Therefore,based on the SEBAL model,this paper used MODIS data and the DEM digital elevation model and combined with meteorological data to calculate the ET of the vegetation growing season?April to October?in the Ebinur lake basin from 2000 to 2017,and analyzed the temporal and spatial distribution of ET.In order to verify the estimation accuracy of the SEBAL model,the ET measured by the eddy correlation system?EC?was used to verify the estimated ET.Based on accurate estimation of ET,Landsat 8 images were used to classify the study area into five land use types:timber forest,shrub land,grassland,farmland,and water area.The ecological water requirement of the Ebinur lake basin was calculated based on the ET method.The results are as follows:?1?During the vegetation growing season,the daily ET in the Ebinur lake basin shows significant spatial and temporal differences,which showed an increase from April to August and a decrease from August to October,the ET is larger in June,July,August,and smaller in April,May,September and October.?2?Under five–year time steps,the vegetation growing season ET show a trend of increasing first,and then decreasing in the Ebinur lake Basin from 2000 to 2015,with the highest in 2005,followed by 2010,2015,and the lowest in 2000.?3?The grassland is the most widely distributed in five vegetaion types,mainly in the western mountainous regions of the basin;followed by farmland,which is distributed in the west and east;there are few timber forest and scattered distribution;shrub land has the smallest distribution area,mainly in the middle of the basin.During the period from 2000 to 2017,there were reductions in the area of vegetation and water area in the Ebinur lake basin.The reduction was grassland>timber forest>water area>shrub land and the water area.The area of farmland has more than doubled.?4?During the vegetation growing season,the ET of each vegetation type was higher in July and August,and lower in April and October.The ET in 2017 was generally greater than 2000.The average month ET of the timber forest(124.53 mm·m-1)>shrub land(121.24 mm·m-1)>grassland(119.98 mm·m-1)>farmland(116.79 mm·m-1).?5?During the vegetation growing season,the ecolagical water requirement showed a“double–peak”change trend.The peaks occurred in May and August,respectively,and July and August were relatively large.In 2000,the ecological water requirement was 2.45×109m3 higher than that in 2017,which was 22.62×109 m3 and 20.16×109 m3,respectively.In addition to farmland,the ecological water requirements of all vegetation types were reduced,and the amount of grassland decreased?4.64×109 m3?>timber forest?0.44×109 m3?>Water area?1.99×109 m3?>Shrub land?6.44×105 m3?,the ecological water requirement of farmland increased by 2.83×109 m3. |
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