The impact of model resolution on the water balance of a dryland basin

Quichimbo Miguitama, E. A., Singer, M. B. ORCID: https://orcid.org/0000-0002-6899-2224, Michaelides, K., Rosolem, R. and Cuthbert, M. O. ORCID: https://orcid.org/0000-0001-6721-022X 2026. The impact of model resolution on the water balance of a dryland basin. Hydrological Processes 40 (10) , e70733. 10.1002/hyp.70733

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Abstract

The spatial and temporal resolution of hydrological models determine model performance and affect water partitioning into fluxes and water storage changes. This is especially important in dryland regions which exhibit dynamic hydrological processes (both spatially and temporally) driven by highly variable and heterogeneous rainfall events, and potential evapotranspiration which exceeds annual precipitation rates. However, it is still unclear how varying model resolutions may affect performance and introduce uncertainty in water balance partitioning. Here, we use a parsimonious dryland-specific process-based hydrological model, DRYP, to assess the impact of temporal and spatial resolution on the water balance fluxes and stores in a dryland basin. To achieve this, we performed numerical experiments using three model grid sizes (300 m, 1 km, 5 km) and three time-steps (15 min, 1 h, 1 day) with four different built-in infiltration equations (Philips, Green Ampt, Shaake, Upscaled Green Ampt). The analysis was performed in the Walnut Gulch Experimental Watershed, Arizona, USA, where long-term, high-resolution datasets are available for both model calibration and evaluation. Results showed that sub-daily time steps combined with spatial resolution of less than 1-km grid size yield the best representations (Nash Sutcliffe index, NSE > 0.55) of hydrological fluxes and stores such as streamflow, soil moisture, and actual evapotranspiration. Model parameterization also indicates that coarser spatial and temporal resolutions require lower effective saturated hydraulic conductivity, reflecting the smoothing of rainfall variability associated with spatial and temporal aggregation. The analysis also highlights the importance of near-channel processes, such as transmission losses in ephemeral streambeds and the role of the riparian zone in providing water for plants and for groundwater recharge. These results have important implications for the quantification of water partitioning in dryland environments in response to rainstorms, and provide guidance for how to parameterize large-scale models, which requires careful consideration to represent key hydrological processes of interest to the modeller.

Item Type:	Article
Date Type:	Publication
Status:	Published
Schools:	Schools > Earth and Environmental Sciences Schools > Physical, Chemical & Environmental Sciences
Publisher:	Wiley
ISSN:	0885-6087
Date of First Compliant Deposit:	19 October 2026
Date of Acceptance:	28 September 2026
Last Modified:	19 Oct 2026 14:15
URI:	https://orca.cardiff.ac.uk/id/eprint/190312

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