Delineating hydrological response units in a mountainous catchment and its evaluation on water mass balance and model performance

Savvidou, Eleni; Tzoraki, Ourania; Skarlatos, Dimitrios

doi:10.1117/12.2068592

Cited by 2 publications

(2 citation statements)

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“…Such watershed subdivision also aims to preserve the watershed's natural boundaries, flowpaths, as well as channels for realistic flow routing (Zhang et al 2004). With the development of GIS (geographic information system) technologies, several watershed subdivision approaches have been developed to investigate the impacts of watershed subdivision on modeling outputs (Savvidou et al 2014), including (1) critical source area (CSA) (Thieken et al 1999;FitzHugh & Mackay 2000;Kalin et al 2003;Di Luzio & Arnold 2004;Arabi et al 2006); (2) threshold drainage areas (TDAs) (Nour et al 2008); (3) aggregated simulation area (Lacroix 1999); (4) representative elementary areas (Wood et al 1988); (5) representative elementary watershed (Reggiani & Rientjes 2005); (6) hydrologic similar units (Karvonen et al 1999); (7) functional units (Argent et al 2006); and (8) hydrologic response units (HRUs) (Flugel 1995(Flugel , 1997. In the SWAT model, watershed subdivision is basically based on the TDA, which is the minimum upstream drainage area for a channel to originate (Aouissi et al 2013), or as a percentage of total catchment area (Di Luzio & Arnold 2004;Kumar & Merwade 2009).…”

Section: Introductionmentioning

confidence: 99%

Quantifying the effects of watershed subdivision scale and spatial density of weather inputs on hydrological simulations in a Norwegian Arctic watershed

Bui

Nie

2021

Journal of Water and Climate Change

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The effects of watershed subdivisions on hydrological simulations have not been evaluated in the Arctic conditions yet. This study applied the Soil and Water Assessment Tool and the threshold drainage area (TDA) technique to evaluate the impacts of watershed subdivision on hydrological simulations at a 5,913-km2 Arctic watershed, Målselv. The watershed was discretized according to four TDA scheme scales including 200, 2,000, 5,000, and 10,000 ha. The impacts of different TDA schemes on hydrological simulations in water balance components, snowmelt runoff, and streamflow were investigated. The study revealed that the complexity of terrain and topographic attributes altered significantly in the coarse discretizations: (1) total stream length (−47.2 to −74.6%); (2) average stream slope (−68 to −83%); and (3) drainage density (−24.2 to −51.5%). The spatial density of weather grid integration reduced from −5 to −33.33% in the coarse schemes. The annual mean potential evapotranspiration, evapotranspiration, and lateral flow slightly decreased, while areal rainfall, surface runoff, and water yield slightly increased with the increases of TDAs. It was concluded that the fine TDAs produced finer and higher ranges of snowmelt runoff volume across the watershed. All TDAs had similar capacities to replicate the observed tendency of monthly mean streamflow hydrograph, except overestimated/underestimated peak flows. Spatial variation of streamflow was well analyzed in the fine schemes with high density of stream networks, while the coarse schemes simplified this. Watershed subdivisions affected model performances, in the way of decreasing the accuracy of monthly streamflow simulation, at 60% of investigated hydro-gauging stations (3/5 stations) and in the upstream. Furthermore, watershed subdivisions strongly affected the calibration process regarding the changes in sensitivity ranking of 18 calibrated model parameters and time it took to calibrate.

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Section: Introductionmentioning

confidence: 99%

Quantifying the effects of watershed subdivision scale and spatial density of weather inputs on hydrological simulations in a Norwegian Arctic watershed

Bui

Nie

2021

Journal of Water and Climate Change

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“…A SWAT model is spatially distributed and therein the watershed is partitioned into a number of sub-watersheds connected by stream networks using digital elevation model (DEM) data before further subdivision into multiple hydrologic response units (HRUs) by overlaying spatial datasets including slope, land-use, and soil maps to represent the spatial heterogeneity of the watershed (Savvidou et al, 2014;Luo et al, 2019). Model computational time is nearly proportional to the number of HRUs, since HRU is the basic calculation unit (Wang et al, 2016).…”

Section: Introductionmentioning

confidence: 99%

Identification of Suitable Hydrologic Response Unit Thresholds for Soil and Water Assessment Tool Streamflow Modelling

et al. 2021

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Use of a non-zero hydrologic response unit (HRU) threshold is an effective way of reducing unmanageable HRU numbers and simplifying computational cost in the Soil and Water Assessment Tool (SWAT) hydrologic modelling. However, being less representative of watershed heterogeneity and increasing the level of model output uncertainty are inevitable when minor HRU combinations are disproportionately eliminated. This study examined 20 scenarios by running the model with various HRU threshold settings to understand the mechanism of HRU threshold effects on watershed representation as well as streamflow predictions and identify the appropriate HRU thresholds. Findings show that HRU numbers decrease sharply with increasing HRU thresholds. Among different HRU threshold scenarios, the composition of land-use, soil, and slope all contribute to notable variations which are directly related to the model input parameters and consequently affect the streamflow predictions. Results indicate that saturated hydraulic conductivity, average slope of the HRU, and curve number are the three key factors affecting stream discharge when changing the HRU thresholds. It is also found that HRU thresholds have little effect on monthly model performance, while evaluation statistics for daily discharges are more sensitive than monthly results. For daily streamflow predictions, thresholds of 5%/5%/5% (land-use/soil/slope) are the optimum HRU threshold level for the watershed to allow full consideration of model accuracy and efficiency in the present work. Besides, the results provide strategies for selecting appropriate HRU thresholds based on the modelling goal.

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Delineating hydrological response units in a mountainous catchment and its evaluation on water mass balance and model performance

Cited by 2 publications

References 29 publications

Quantifying the effects of watershed subdivision scale and spatial density of weather inputs on hydrological simulations in a Norwegian Arctic watershed

Quantifying the effects of watershed subdivision scale and spatial density of weather inputs on hydrological simulations in a Norwegian Arctic watershed

Identification of Suitable Hydrologic Response Unit Thresholds for Soil and Water Assessment Tool Streamflow Modelling

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