Model parameter transfer for streamflow and sediment loss prediction with SWAT in a tropical watershed

Abstract

Distributed hydrologic models are increasingly used to describe the spatiotemporal dynamics of water and sediment fluxes within basins. In data-scarce regions like Ethiopia, oftentimes, discharge or sediment load data are not readily available and therefore researchers have to rely on input data from global models with lower resolution and accuracy. In this study we evaluated a model parameter transfer from a 100 hectare (ha) large subwatershed (Minchet) to a 4800 ha catchment in the highlands of Ethiopia using the Soil and Water Assessment Tool (SWAT). The Minchet catchment has long-lasting time series on discharge and sediment load dating back to 1984, which were used to calibrate the subcatchment before (a) validating the Minchet subcatchment and (b) through parameter transfer validating the entire Gerda watershed without prior calibration. Uncertainty analysis was carried out with the Sequential Uncertainty Fitting-2 (SUFI-2) with SWATCup and ArcSWAT2012. We used a similarity approach, where the complete set of model parameters is transposed from a donor catchment that is very similar regarding physiographic attributes (in terms of landuse , soils, geology and rainfall patterns). For calibration and validation the Nash-Sutcliff model efficiency, the Root Mean Square Error-observations Standard Deviation Ratio (RSR) and the Percent Bias (PBIAS) indicator for model performance ratings during calibration and validation periods were applied. Goodness of fit and the degree to which the calibrated model accounted for the uncertainties were assessed with the P-factor and the R-factor of the SUFI-2 algorithm. Results show that calibration and validation for streamflow performed very good for the subcatchment as well as for the entire catchment using model parameter transfer. For sediment loads, calibration performed better than validation and parameter transfer yielded satisfactory results, which suggests that the SWAT model can be used to adequately simulate monthly streamflow and sediment load in the Gerda catchment through model parameter transfer only. Vincent

An accurate evaluation of water availability in sub-arid Mediterranean watersheds through SWAT: Cega-Eresma-Adaja

“…Modellers look for the balance between several factors: the objective function, the function weight, the initial and boundary conditions, and the type and length of measured data used to calibrate (Abbaspour, 2012). Consequently, the parameter-combination band is very complex in large watersheds; other research at daily time scale and large watershed also refers to values in the range of our P-factor and R-factor results (Begou et al, 2016;Roth et al, 2016). Further study is needed on a sub-basin scale to expand on details to reach higher performance values of the uncertainties.…”

Assessing sediment yield and streamflow with SWAT model in a small sub-basin of the Cantareira System

“…SWAT was developed to assess the impact of management and climate on water supply, sediment production, and agricultural chemical yields for large river basins. However, the model has also been applied in small catchments, mainly to estimate average monthly streamflow (Spruill et al, 2000;Fukunaga et al, 2015;Roth et al, 2016). Usually, SWAT model calibration is carried out with outlet streamflow and sediment load data, even in the studies that calibrate parameters related to hillslope soil losses (Arnold et al, 2012;Roth et al, 2016;Zuo et al, 2016).…”

Spatial and Temporal Variability in Hydrological Responses of the Upper Blue Nile basin, Ethiopia

“…In addition, most studies incorporated the data of only a few weather stations for a few years in their model and calibrated and validated it with data from one or two gauging stations along the upper Blue Nile Basin. More detailed discharge modelling was conducted by many studies at the catchment level in different watersheds in the upper Blue Nile basin [22][23][24][25][26][27][28][29]. Lemann et al [30] showed the different hydrological responses to different rainfall patterns and different meteorological conditions in the upper Blue Nile basin, but only at the sub-basin level.…”