Soil Water Assessment Tool (SWAT) simulated hydrological impacts of land use change from temperate grassland to energy cropsa case study in western UK

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Type Article
Original languageEnglish
Pages (from-to)1298-1317
Number of pages20
JournalGCB Bioenergy
Volume11
Issue number11
Early online date22 May 2019
DOI
Publication statusPublished - 01 Nov 2019
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Abstract

When considering the large scale deployment of bioenergy crops it is important to understand the implication for ecosystem hydrological processes and the influences of crop type and location. Based on potential for future land use change (LUC) the 10,280 km2 West Wales Water Framework Directive River Basin District (UK) was selected as a typical grassland dominated district, and the Soil Water Assessment Tool (SWAT) hydrology model with GIS interface was used to investigate implications for different bioenergy deployment scenarios. The study area was delineated into 855 sub‐basins and 7108 hydrological response units based on rivers, soil type, land use, and slope. Changes in hydrological components for two bioenergy crops (Miscanthus and short rotation coppice, SRC) planted on 50% (2192 km2) or 25% (1096 km2) of existing improved pasture are quantified.

Across the study area as a whole, only surface runoff with SRC planted at the 50% level was significantly impacted, where it was reduced by up to 23% (during April). However, results varied spatially and a comparison of annual means for each sub‐basin and scenario revealed surface runoff was significantly decreased and baseflow significantly increased (by a maximum of 40%) with both Miscanthus and SRC. Evapotranspiration was significantly increased with SRC (at both planting levels) and water yield was significantly reduced with SRC (at the 50% level) by up to 5%. Effects on streamflow were limited, varying between ‐5% and +5% change (compared to baseline) in the majority of sub‐basins.

The results suggest that for mesic temperate grasslands adverse effects from the drying of soil and alterations to streamflow may not arise, and with surface runoff reduced and baseflow increased there could, depending on crop location, be potential benefits for flood and erosion mitigation.

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Keywords

  • hydrology, miscanthus, short rotation coppice, flooding, bioenergy, streamflow, evapotranspiration