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

Amanda J Holder; Rebecca Rowe; Niall P McNamara; Iain S Donnison; Jon P McCalmont

doi:10.1111/gcbb.12628

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

Glob Change Biol Bioenergy. 2019 Nov;11(11):1298-1317. doi: 10.1111/gcbb.12628. Epub 2019 Jul 26.

Authors

Amanda J Holder¹, Rebecca Rowe², Niall P McNamara², Iain S Donnison¹, Jon P McCalmont³

Affiliations

¹ Institute of Biological, Environmental and Rural Sciences (IBERS) Aberystwyth University Aberystwyth UK.
² Centre for Ecology & Hydrology Lancaster Environment Centre Lancaster UK.
³ College of Life and Environmental Sciences University of Exeter Exeter UK.

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 the 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 a geographic information systems interface was used to investigate implications for different bioenergy deployment scenarios. The study area was delineated into 855 sub-basins and 7,108 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% (2,192 km²) or 25% (1,096 km²) of existing improved pasture are quantified. Across the study area as a whole, only surface run-off 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 run-off 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 run-off reduced and baseflow increased, there could, depending on crop location, be potential benefits for flood and erosion mitigation.

Keywords: Miscanthus; bioenergy; evapotranspiration; flooding; hydrology; short rotation coppice; streamflow.