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Zhejiang University (2010)

Land-use and Land-cover Change and Its Impacts on Evapotranspiration in Inland River Basin of Arid Region


Titre : Land-use and Land-cover Change and Its Impacts on Evapotranspiration in Inland River Basin of Arid Region

Auteur : 陈耀亮;

Grade : Doctoral Dissertation 2018

Université : Zhejiang University

As the second largest inland river in China,Heihe river basin(HRB)has been paid much attention as a hot spot region of remote sensing,hydrology,ecology and land-cover research field.The quantitative detection of land-use,land-cover status and its change could be of great reference to the allocation of future land resources.Evapotranspiration(ET)plays a key role in the water balance and energy balance,especially in arid river basin.Previous studies had took substantial attention to detecting land-cover and simulating or estimating ET for different ecosystems,but little was focused on the impacts of land-cover change on the ET.The response of ET to land-cover change in HRB remains unclear.This study aims at quantitatively estimating the change of ET derived by land-use and land-cover change in HRB.Firstly,the land-use and land-cover changes from 1990 to 2016 were investigated by using remote sensing technique.Then,the water,heat and energy characteristics of different land covers were simulated by using EALCO model.Further comparison and analysis of ET for these different land covers were also conducted at different time scale.Thirdly,the spatial ET in 2000 and 2010 over the whole region were modeled respectively.Finally,ET response to the land-cover change from 2000 to 2010 was estimated.The results show that :(1)The ’hard’ and ’soft’ methods are proposed to classify the complex land-cover schemes in HRB.The overall accuracy of hard classification in 2016 is 89.87%.The area of cultivated land and impervious surface area(ISA)had been continuously increasing driving by the process of land reclamation and urbanization respectively.The area of permanent ice was substantially decreased because of the warmer climate in the up reach.There is a significant difference for the land-cover change between the period before the start year of water allocation(2000)and the period after 2000.The area of desert vegetation,populous forest and lake was dramatically decreased during 1990 to 2000 while their areas were generally recovering after 2000.(2)A promising method is proposed in detecting irrigation attributes such as frequency and timing which have not been explored in previous research.The overall accuracy of water supplement stage using the proposed method is 87%.Validation of the number of water supplement stages and possible dates of water supply with a "strict"(or "loose")assessment method show an overall accuracy of 55%(94%)and 59%(89%),respectively.The good accuracy of an additional independent validations for different years and sites demonstrates the robustness of the proposed method,suggesting the general applicability to other arid agricultural regions.(3)The good accuracy of simulated net radiation,latent heat and sensible heat at both half-hour scale and daily scale indicates EALCO model can well simulated the water,energy and heat exchange in HRB.The peak value of daily ET of non-desert vegetation is much higher than that of desert vegetation and non-vegetation.The length of ET peak days in the sites which does not suffer the stress of cold temperature or drought is longer than that in the sites which suffers those stress.The water consumption of crop and wetland through ET is much larger than that of other land covers which are slightly or merely affected by human activities.The difference of monthly ET among all the sites is also obvious.For example,wetland basically ranks the largest ET in each month.July has the largest ET at all the sites.For the yearly scale,wetland ranks the top position with 796 mm.Following with wetland,the cultivated site-Daman has yearly ET of 619 mm.The sand desert site,Bajitan,has the lowest ET with only 113 mm in the whole year.(4)Evaporation dominates before planting while transpiration dominates after planting in the irrigation mode.On the contrary,evaporation almost dominates the entire year in the non-irrigation mode,with only slight transpiration in the summer

Mots clés : Land use; Land cover; Irrigation; EALCO; Land surface model; Evapotranspiration;

Présentation (CNKI)

Page publiée le 5 avril 2019