Hierarchical approach to hydrological model calibration

Abstract

Hydrological models have been widely used for water resources management. Successful application of hydrological models depends on careful calibration and uncertainty analysis. Spatial unit of water balance calculations may differ widely in different models from grids to hydrological response units (HRU). The Soil and Water Assessment Tool (SWAT) software uses HRU as the spatial unit. SWAT simulates hydrological processes at sub-basin level by deriving HRUs by thresholding areas of soil type, land use, and slope combinations. This may ignore some important areas, which may have great impact on hydrological processes in the watershed. In this study, a hierarchical HRU approach was developed in order to increase model performance and reduce computational complexity simultaneously. For hierarchical optimization, HRUs are first divided into two-HRU types and are optimized with respect to some relevant influence parameters. Then, each HRU is further divided into two. Each child HRU inherits the optimum parameter values of the parent HRU as its initial value. This approach decreases the total calibration time while obtaining a better result. The performance of the hierarchical methodology is demonstrated on two basins, namely Sarisu-Eylikler and Namazgah Dam Lake Basins in Turkey. In Sarisu-Eylikler, we obtained good results by a combination of curve number (CN2), soil hydraulic conductivity, and slope for generating HRUs, while in Namazgah use of only CN2 gave better results.

Effect of Watershed Delineation and Climate Datasets Density on Runoff Predictions for the Upper Mississippi River Basin Using SWAT within HAWQS

“…The majority of studies reported that the delineation scenarios resulted in only minor or negligible effects on SWAT-predicted streamflow (Table 1). However, some studies described streamflow effects estimated with SWAT that were influenced by the various simulated delineation scenarios [11,15,20,22,[30][31][32]. Several of these studies noted that the effects on streamflow were relatively stable for more refined delineation schemes, but that the accuracy of the streamflow estimates declined for coarser HRU and/or subbasin subdivisions (e.g., [11,15,20]).…”

“…The size of systems analyzed in these studies ranged from 6.2 km 2 /6.3 km 2 to in Indiana/Germany to 17,941 km 2 in Iowa ( Table 1). The level of detail incorporated in these different assessments also varied considerably, with large ranges of HRUs and/or subbasins used in some studies (e.g., [13,14,16,27]) versus limited detail in other studies [12,31]. For small watersheds, the landscapes may not be complex enough to detect the runoff variation caused by different delineation schemes.…”

A fast and automated hydrologic calibration tool for SWAT

“…It also provides a platform to implement other algorithms. For example, a hierarchical approach to calibration was implemented on this software (Ozdemir et al, ). For future research, choosing the most sensitive parameters will be performed by automated analysis of flow patterns.…”

“…MATLAB is chosen for developing the tool since it allows to implement, test and debug algorithms easily, and to perform extensive data analysis and visualization. FACT was also used for implementing a hierarchical approach for calibration (Ozdemir et al, ).…”

Event-based model calibration approaches for selecting representative distributed parameters in semi-urban watersheds

“…Manuscript 6 entire catchment (lumped or distributed) parameters according to model predictive performance at the basin outlet assessed via single or multiple objectives. Some authors have proposed advancing the single site calibration with a sequential/hierarchical approach (Hay et al, 2006;Ozdemir et al, 2017;Singh & Bárdossy, 2015). While the first authors sequentially calibrate a model"s performance of potential evapotranspiration, water balance, and daily runoff , the second authors divided sub-basins into two hydrologic response units (HRU) and two further child HRUs based on influential parameters such as curve number and hydraulic conductivity.…”