Hydrological evaluation of the LPX dynamic global vegetation model for small river catchments in the UK



Assessments of water resources by using macro-scale models tend to be conducted at the continental or large catchment scale. However, security of freshwater supplies is a local issue and thus necessitates study at such a scale. This research aims to evaluate the suitability of the Land Processes and eXchanges dynamic global vegetation model (LPX-DGVM) for simulating runoff for small catchments in the UK. Simulated annual and monthly runoff is compared against the National River Flow Archive streamflow observations from 12 catchments of varying size (500–10 000 km2) and climate regimes.

Results show that LPX reproduces observed inter-annual and intra-annual runoff variability successfully in terms of both flow timings and magnitudes. Inter-annual variability in flow timings is simulated particularly well (as indicated by Willmott's index of agreement values of ≥0.7 for the majority of catchments), whereas runoff magnitudes are generally slightly overestimated. In the densely populated Thames catchment, these overestimations are partly accounted for by water consumption. Seasonal variability in runoff is also modelled well, as shown by Willmott's index of agreement values of ≥0.9 for all but one catchment. Absence of river routing and storage from the model, in addition to precipitation uncertainties, is also suggested as contributing to simulated runoff discrepancies.

Overall, the results show that the LPX-DGVM can successfully simulate runoff processes for small catchments in the UK. This study offers promising insights into the use of global-scale models and datasets for local-scale studies of water resources, with the eventual aim of providing local-scale projections of future water distributions. Copyright © 2013 John Wiley & Sons, Ltd.