Abstract
Investigating the impact of land cover change in hydrological modelling is essential for water resources management. This paper investigates the importance of landcover change in the development of a physically-based hydrological model called SWAT. The study area considered is the Dodder River basin located in southern Dublin, Ireland. Runoff at the basin outlet was simulated using SWAT for 1993–2019 using five landcover maps obtained for 1990, 2000, 2006, 2012 and 2018. Results indicate that, in general, the SWAT model-simulated runoff for a chosen time-period are closer to the real-world observations when the landcover data used for simulation was collated as close to the time-period for which the simulations were performed. For 23 (20) years (from 27 years period) the monthly mean (maximum) runoff for the Dodder River generated by the SWAT model had the least error when the nearby landcover data were used. This study indicates the necessity of considering dynamic and time-varying landcover data during the development of hydrological modelling for runoff simulation. Furthermore, two composite quantile functions were generated by using a kappa distribution for monthly mean runoff and GEV distribution for monthly maximum runoff, based on model simulations obtained using different landcover data corresponding to different time-period. Modelling landcover change patterns and development of projected landcover in the future for river basins in Ireland needs to be integrated with SWAT to simulate future runoff.
Highlights
Major alterations in land cover indicate the significance of human and anthropogenic activities on land use, which have been deemed responsible for extreme floods and the associated devastations [1,2]
The watershed area estimated by the Office of Public Works (OPW), Ireland based on the topographic maps of Ireland is documented as 94.3 km2, indicating that the difference in the basin area obtained based on topographic maps and EU-digital elevation model (DEM) based soil water assessment tool (SWAT) model is around 2%, which as deemed acceptable for practical purposes
Five different SWAT models had been generated by using five land cover maps obtained for the years 1990, 2000, 2006, 2012 and 2018
Summary
Major alterations in land cover indicate the significance of human and anthropogenic activities on land use, which have been deemed responsible for extreme floods and the associated devastations [1,2]. Climate change and urbanization both lead to the generation of excess surface runoff which results in the more frequent occurrence of flood events [3]. Fragmented land cover areas caused by urban development have resulted in alterations to the hydrological cycle [4]. A recent report [5] stated that between one-half to one-third of our planet’s surface has been transformed by human development, leading to the rapid growth of urbanization. There is an increasing concern that urbanization, resulting in increased impervious areas responsible for the reduction in infiltration capacity of the soil and an increase in soil erosion, are causing increased flooding [6,7]. Previous studies reported that high rates of soil erosion are responsible for higher and quicker surface runoff [8,9,10]. The rate of surface runoff is dependent on various factors such as topography, morphology, river network [11,12] and the rainfall-runoff relationship [13]
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