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Gaziosmanpaşa Üniversitesi (2016)

Determination runnoff and soil ersion by using WEPP Hillslope model

DEMİR Saniye

Titre : Determination runnoff and soil ersion by using WEPP Hillslope model

WEPP Hillslope modeli ile yüzey akış ve toprak kayıplarının belirlenmesi

Auteur : DEMİR Saniye

Université de soutenance : Gaziosmanpaşa Üniversitesi

Grade : Doktora Tezi 2016

Résumé
Soil erosion is an important form of lad degradation in Turkey. Soil erosion leads to desertification and nutrient depletion in arid and semi-arid regions. Modeling approach is valuable tool for predicting soil degradation and runoff under different agricultural practices. Therefore, soil degradation and runoff losses under different tillage practices were predicted in this study through using WEPP hillslope model. The already measured data relating to sediment yield and flow measured in different crops like wheat, lentil and tobacco, sown parallel and perpendicular to slope were used in model fitting and prediction success of WEPP model was assessed. The individual events, seasonal, annual and long term yearly averaged data predicted by model and those collected by actual measurements were compared. Model performance was evaluated in compliance with the conditions of Turkey for wet and dry years, and sensitivity analysis was also conducted for the model parameters. Monthly and yearly average rainfall values were evaluated with WEPP model and found close to the actually measured values. In the season related predictions ; model was more successful in predicting highly rainy days in spring season while dry average precipitation was successfully predicted in summer. K parcel, event-based runoff and soil loss data from actual and estimated values were 2.40 and 4.98 mm, and 0.09 and 0.28 kg /m2 whereas, were 15.25 and 23.50 mm, and 0.63 and 1.35 kg/m2 according to annual average values. Model was found to be more successful according to the K parcel predicted by using annual average values. Similarly, P parcel, event-based runoff and soil loss data from actual and estimated values were 3.05 and 7.26 mm, and 0.1 and 0.26 kg/m2 whereas according to annual average data the values were 7.62 and 5.07 mm, and 0.32 and 0.18 kg/m2. The model was also found highly successful in predicting P parcel through using annual average values. In the same manner, C parcel, event-based runoff and soil loss data from actual and estimated values were 1.67 and 3.97 mm, and 0.06 and 0.18 kg/m2 whereas the values were 8.67 and 16.08 mm, and 0.22 and 0.12 kg/m2 according to annual averaged data. The model was also found successful in P parcel with the use of annual average values. The model performance was also tested for wet, dry and normal years and model was found more successful for normal years. USLE and WEPP were compared and it was found that USLE predicted less soil losses compared to WEPP in the current study.

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Page publiée le 2 janvier 2023