The Interactive Impact of Land Cover and DEM Resolution on the Accuracy of Computed Streamflow Using the SWAT Model
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The Interactive Impact of Land Cover and DEM Resolution on the Accuracy of Computed Streamflow Using the SWAT Model Mahmoud Al-Khafaji & Fouad H. Saeed & Nadhir Al-Ansari
Received: 28 May 2020 / Accepted: 13 July 2020 # The Author(s) 2020
Abstract Twenty daily time step–based SWAT simulation models for the Duhok, Adhaim and Dokan dam watersheds, in Iraq, were implemented using five land cover (LC) and digital elevation model (DEM) of different resolutions. The optimal LC and DEM for computing the most accurate streamflow for each watershed were specified. Results indicated that delineation of the flat watersheds is significantly affected by the DEM resolution and there was no evident trend on the computation of watersheds’ total areas, boundaries, number of subbasins and stream networks. Moreover, there is no significant trend between the increase in LC and DEM resolutions and accuracy of the computed streamflow. The most accurate streamflows for the Duhok, Adhaim and Dokan watersheds were computed using LC (DEM) of 30 m, 1000 m and 1000 m.
Keywords Interactive impact . LC . DEM . SWAT
M. Al-Khafaji Civil Engineering Department, University of Technology, Baghdad, Iraq e-mail: [email protected] F. H. Saeed Ministry of Water Resources, Baghdad, Iraq e-mail: [email protected] N. Al-Ansari (*) Lulea University of Technology, Lulea, Sweden e-mail: [email protected]
1 Introduction Most human activities are related to water resources, the management of which requires accurate calculations. The hydrologic models are useful tools developed to simulate the total or partial hydrologic cycle. Recently, digital image data such as land cover (LC), digital elevation model (DEM) and soil data are utilized to implement hydrologic simulation models. These data are produced with a certain degree of accuracy and temporal and spatial resolution. Currently, the SWAT (soil and water assessment tool) is the most useful and commonly used tool for implementing the watershed simulation models. Comprehensive understanding of the implications of utilizing the available satellite data of different spatial resolutions on the behaviour of hydrologic simulation models is important. In general, the accuracy and reliability of the modelling results increase with increasing precision of the input data (Booij 2005; Katrin et al. 2011; Casper et al. 2011). Wolockm and Price (1994), Romanowicza et al. (2005) and Tan et al. (2015) indicated that the DEM and LC source, resolutions and the DEMs resampling technique have a significant impact on the results from hydrologic models. Chaubey et al. (2005) studied the Moore’s Creek watershed in the USA (18.90 km2) using the SWAT model. Seven DEM resolution scenarios (30, 100, 150, 200, 300, 500 and 1000 m) were considered. They concluded that the DEM spatial resolutions between 100 and 200 m cause less than 10% of error, in the computed streamflow. Chaplot (2005) examined the DEM at spatial resolutions ranging between 20 and 500 m; the result of this investigation indicated that
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