Most Sensitive Parameters of Soil and Water Assessment Tool (SWAT) Hydrological Model: A Review

Hydrological models are becoming more and more important instruments for hydrological base infrastructure planning, design, and management. However, there is uncertainty on using because of the varying nature. The key to establishing the uncertainty of a quantitative model is to analyze the sensitivity test of a hydrological model. The determination of the most sensitive parameters was the key and first step for model calibration and validation at the watershed scale. It is the process of identifying the model parameters that exert the greatest influence on model calibration or on model predictions. The SWAT is a watershed scale, continuous-time, semi-distributed hydrological model that predicts stream flow, sediments, nutrient loading, and pesticide transport by incorporating meteorological data, soil properties, land cover/use, and management methods. The model requires calibration and validation. Before the calibration and validation works are started the sensitive parameters of the model has to be determined. The most sensitive SWAT hydrological model parameters are base flow alpha factor (ALPHA_BF), soil evaporation compensation factor (ESCO), available water capacity (SOL_AWC), groundwater delay (GW_DELAY), saturated hydraulic conductivity (SOL_K), initial curve number (II) value (CN2), shallow aquifer flow threshold (GWQMN), effective hydraulic conductivity in main channel alluvium (CH_K2), manning′s n value for the main channel (CH_N2) and surface runoff lag time (SURLAG). The sensitivity depends not only on the physiographic and meteorological characteristics of the study area, but also on the sensitivity analysis methodologies applied.

Keywords: Calibration and Validation; Hydrological Models; Sensitive Parameters; SWAT