Browsing by Author "Juma, Kashinde Abdulla"

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    Sensitivity analysis and auto calibration using SWAT Model: a case study of 1dd1 catchment
    (Unversity of Dar es Salaam, 2006) Juma, Kashinde Abdulla
    A complex hydrologic model is generally characterized by a multitude of parameters. The success of a manual calibration essentially depends on the experience of the modeler and their knowledge of the basic approavhes and interactions in the model. A manual calibration therefore always is subjective to some extent. Moreover, it can be extremely time consuming. Parameters identifiability was conducted using Sensitivity analysis based on sampling strategy that is a combination of Latin-Hyperrcube and one-factor at a-time sampling which built-in physically based model SWAT. An automatic calibration based on SCE-UA which is incorporated into SWAT model, was used for parameter optimization. Available daily stream flow data for six years (i.e 1977-1982) and four years (i.e 1970-1973) were used for model calibration and validation respectively. The sensitivity analysis has identified six (6) most sensitive parameters. Such parameters are Curve Number (CN2), surface Runoff lag time (Surlag), minimum threshold depth of water for ground flow to occur (GWQMN), Recharge to deep aquifer (RCHRG-DP). Overland Slope (SLOPE), and Soil depth (SOL-z). besides, it was found that surface runoff parameters are mostly influencing rainfall-runoff transformation in the catchment. Calibration and validation on a daily basis gave satisfactory results with Nash-Sutcliffe coefficient of efficiency R2= 54% and R2-64% respectively.