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Universiteit Gent (2012)

Evaluating in-situ water conservation practices with a fully-coupled surface/subsurface process-based hydrological model in Tigray, Ethiopia

OPOLOT Emmanuel

Titre : Evaluating in-situ water conservation practices with a fully-coupled surface/subsurface process-based hydrological model in Tigray, Ethiopia

Auteur : OPOLOT Emmanuel

Université de soutenance : Universiteit Gent

Grade : Master of Science (MS) Physical Land Resources 2012

Résumé
Agricultural food production should considerably increase to feed the ever growing population. Land degradation in form of soil erosion, overgrazing and deforestation remains a major challenge to food production particularly in developing countries. The situation is aggravated by negative climatic effects in which rainfall is erratic and highly variable making rain-fed agriculture more susceptible to droughts and seasonal water logging. In situ soil water conservation (SWC) practices are a promising intervention especially if developed to suit a given climate, soil type as well as crops. This study was designed to evaluate the potential of using a fully coupled surface-subsurface process based model (HydroGeoSphere) to simulate the effects of terwah+ (TER+) and derdero+ (DER+) in situ SWC practices currently under study in Tigray, Ethiopia and to evaluate the treatments in terms of rainwater partitioning. In TER+ practice, contour furrows of about 0.2 m wide and 0.1 m deep are created at 1.5 m intervals to collect excess water while in DER+, permanent raised beds of 0.6 m width with furrows of about 0.2 m wide and 0.1 m deep are created to prevent water logging and collect excess water that would otherwise runoff. The plus sign (+) in both practices represents retaining at least 30% of crop residue after a cropping season. Comparison was done with the conventional tillage practice (CT) in which no contour furrows are made and at least three tillage practices are carried out with complete removal of crop residue. The effects of these practices on runoff, soil moisture content and overall soil water balance were simulated using the model. Model parameters were obtained from the field measurements as well as from literature. Field measured surface runoff and moisture content were used for model parameter optimization and calibration. The model accurately reproduced measured surface runoff (DER+ : RMSE 1.15 mm, E 0.7 ; TER+ : RMSE 2.02 mm, E 0.79 ; CT : RMSE 3.09 mm, E 0.23 mm) and soil moisture content (DER+ : RMSE 0.03 cm3cm-3, E 0.83 ; TER+ : RMSE 0.03 cm3cm-3, E 0.16 ; CT : RMSE 0.04 cm3cm-3, E 0.80). Simulated runoff depth was lowest under DER+ (59 mm) followed by TER+ (102 mm) and significantly higher in CT (165 mm). Simulated soil moisture content was highest under DER+ practice, followed by TER+ and least under CT. Transpiration, evaporation and drainage water balance components were all higher under DER+ and TER+ compared to CT. The study concludes that DER+ and TER+ have positive effects on runoff reduction but recommends improvement of these practices. A detailed study is also necessary to collect a complete data set necessary for full validation of HydroGeoSphere model.

Source : Pedon 24 - Physical Land Resources - Universiteit Gent

Page publiée le 25 décembre 2015, mise à jour le 25 janvier 2018