Understanding the accuracy of modelled changes in freshwater provision over time

Gosal, Arjan S.; Evans, Paul M. ORCID: https://orcid.org/0000-0001-6706-420X; Bullock, James M. ORCID: https://orcid.org/0000-0003-0529-4020; Redhead, John ORCID: https://orcid.org/0000-0002-2233-3848; Charlton, Matthew B.; Cord, Anna F.; Johnson, Andrew; Ziv, Guy. 2022 Understanding the accuracy of modelled changes in freshwater provision over time. Science of the Total Environment, 833, 155042. 12, pp. https://doi.org/10.1016/j.scitotenv.2022.155042

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Official URL: http://dx.doi.org/10.1016/j.scitotenv.2022.155042

Abstract/Summary

Accurate modelling of changes in freshwater supplies is critical in an era of increasing human demand, and changes in land use and climate. However, there are concerns that current landscape-scale models do not sufficiently capture catchment-level changes, whilst large-scale comparisons of empirical and simulated water yield changes are lacking. Here we modelled annual water yield in two time periods (1: 1985–1994 and 2: 2008–2017) across 81 catchments in England and validated against empirical data. Our objectives were to i) investigate whether modelling absolute or relative change in water yield is more accurate and ii) determine which predictors have the greatest impact on model accuracy. We used the Integrated Valuation of Ecosystem Services and Tradeoffs (InVEST) Annual Water Yield model. In this study, absolute values refer to volumetric units of million cubic metres per year (Mm3/y), either at the catchment or hectare level. Modelled annual yields showed high accuracy as indicated by the low Mean Absolute Deviation (MAD, based on normalised data, 0 is high and 1 is low accuracy) at the catchment (1: 0.013 ± 0.019, 2: 0.012 ± 0.020) and hectare scales (1: 0.03 ± 0.030, 2: 0.030 ± 0.025). But accuracy of modelled absolute change in water yield showed a more moderate fit on both the catchment (MAD = 0.055 ± 0.065) and hectare (MAD = 0.105 ± 0.089) scales. Relative change had lower accuracy (MAD = 0.189 ± 0.135). Anthropogenic modifications to the hydrological system, including water abstraction contributed significantly to the inaccuracy of change values at the catchment and hectare scales. Quantification of changes in freshwater provision can be more accurately articulated using absolute values rather than using relative values. Absolute values can provide clearer guidance for mitigation measures related to human consumption. Accuracy of modelled change is related to different aspects of human consumption, suggesting anthropogenic impacts are critically important to consider when modelling water yield.

Item Type:	Publication - Article
Digital Object Identifier (DOI):	https://doi.org/10.1016/j.scitotenv.2022.155042
UKCEH and CEH Sections/Science Areas:	Biodiversity (Science Area 2017-)
ISSN:	0048-9697
Additional Information. Not used in RCUK Gateway to Research.:	Open Access paper - full text available via Official URL link.
Additional Keywords:	water yield, InVEST, human impacts, model validation, ecosystem services, anthropogenic impact
NORA Subject Terms:	Ecology and Environment
Date made live:	25 Apr 2022 11:36 +0 (UTC)
URI:	https://nora.nerc.ac.uk/id/eprint/532530

Item Type:

Publication - Article

Digital Object Identifier (DOI):

https://doi.org/10.1016/j.scitotenv.2022.155042

UKCEH and CEH Sections/Science Areas:

Biodiversity (Science Area 2017-)

ISSN:

0048-9697

Additional Information. Not used in RCUK Gateway to Research.:

Open Access paper - full text available via Official URL link.

Additional Keywords:

water yield, InVEST, human impacts, model validation, ecosystem services, anthropogenic impact