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Université de l’agriculture de Chine (2017)

Modeling Hydrological Processes in Oasis of Heihe River Basin Based on Landscape Units

李江

Titre : Modeling Hydrological Processes in Oasis of Heihe River Basin Based on Landscape Units

Auteur : 李江

Grade : Doctoral Dissertation 2017

Université : Université de l’agriculture de Chine

Résumé
The middle reaches of Heihe River basin are located in the arid region in Northwest China.There are several severe problems in this region,such as water shortage and serious water conflicts.The oasis in this region is one of the major grain producing areas in China.The agriculture in the oasis is dominated by irrigation,where the hydrological process is strongly influenced by human activities.Because the hydrological process in this region is typically characterized by dissipative type,direct application of the traditional hydrological model based on runoff processes is no longer suitable.Therefore,developing a corresponding hydrological model for this region is essential to quantify the main hydrological transformation terms,as well as to evaluate the effects of human activities on hydrological processes and to promote the scientific management of local water resources.In this study,an oasis hydrological process model considering different landscape units in the middle reaches of Heihe River Basin was established,and on the basis of which the actual hydrological processes were simulated and scenario predictions were conducted.The main work and results are listed as follows :(1)Firstly,geostatistical analysis of groundwater level spatial distribution in the middle reaches of Heihe River Basin was conducted.Based on the comparison of the ordinary Kriging method,the Yamamoto correction method of Kriging smoothing effects and the universal Kriging method,it was found that the best accuracy was gained by the ordinary Kriging method and that the smoothing effects in Kriging method could be minimized by the Yamamoto correction method.Although all the three methods worked well,the ordinary Kriging method was selected to describe the spatial distribution of initial groundwater levels in this study due to the small spatial variation of groundwater level.(2)Secondly,farmland lateral seepage test was conducted in the typical maize field in the middle reaches of Heihe River Basin.The lateral seepage ratio(i.e.,the ratio of lateral seepage amount to total irrigation)under different irrigation quotas,farmland area and soil textures was simulated using HYDRUS-2D.Results showed that the lateral seepage ratio had a positive relationship with irrigation quota while negative relationship with farmland areas.Furthermore,the lateral seepage ratio could also be affected by layered soil texture.The ratio would decrease when coarse-textured soil was covered by fine-textured soil in the root zone.In terms of the general farmland length and soil texture in the study area,lateral seepage caused by irrigation could be neglected and only the vertical movement of soil water was included for the development of oasis hydrological process model.(3)Thirdly,the water balance models in vadose zone for farmland were developed and the simulated results were compared and validated with the results calculated by the dynamic model HYDRUS-1D.In the validation,the soil water dynamics under different conditions of phreatic water depths and irrigation quotas during the growing season of main crops in vadose zone were analyzed.A good coherence was shown between the simulated results of the water balance models and HYDRUS-1D model in soil water storage,evapotranspiration,the water recharge from root zone and deep percolation to groundwater.Above all,these results indicated that the water balance models were suitable to simulate the soil water movement in the study area.(4)In addition,a comprehensive hydrological model which could describe the water balance(such as evaporation/transpiration,deep percolation,etc.)in the vadose zone and regional groundwater flow dynamics,as well as their interactions was established.This model loosely coupled the water balance models in the vadose zone considering various landscape units(including farmland,grassland,bare soil,etc.)with the groundwater flow model FEFLOW under GIS,and was validated by comparing the simulated results(evapotranspiration,groundwater levels and the total water balance in the oasis)with remote sensing results,previous studies and monitored data(2000-2010).Results showed that the model was feasible to be used for simulating and predicting the hydrological processes in the middle oasis of Heihe River basin.(5)Finally,the coupled model was utilized to simulate the hydrological processes under various scenarios of water-saving activities.Results showed that along with the decrease of irrigation quota,the increment of water storage in vadose zone as well as evapotranspiration in the study area was decreased.If canal lining ratio was raised to 90%while the groundwater exploitation quantity remained unchanged,the groundwater recharge would be reduced and the groundwater deficit would be aggravated.However,it would be beneficial to help maintain the local groundwater balance when the canal lining ratio was improved while the groundwater exploitation was reduced

Mots clés : Middle reaches of Heihe River basin; Soil moisture; Groundwater; Hydrological model; Evapotranspiration;

Présentation (CNKI)

Page publiée le 8 septembre 2017