Summary
This paper brings together hydrologists, Critical Zone scientists, and Earth System Model developers to examine how hillslope-scale hydrological structures—particularly three-dimensional ridge-to-valley flow and aspect-dependent insolation contrasts—modulate water, energy, and biogeochemical cycling at the grid scale in global climate models. Current ESMs typically employ simplistic one-dimensional, shallow soil hydrology that cannot capture these organising processes. The authors hypothesise that explicit representation of hillslope hydrology in ESMs would increase simulated terrestrial water storage and residence time, thereby enhancing ecosystem buffering against seasonal and interannual droughts, whilst identifying critical knowledge gaps regarding subsurface water storage and release dynamics.
UK applicability
The hillslope hydrology framework presented is potentially applicable to UK upland and moorland systems, particularly in regions with pronounced topography (Scottish Highlands, Welsh uplands, Pennines) where terrain complexity, ridge-to-valley flow and slope-aspect effects significantly influence streamflow and ecosystem function. However, the paper emphasises critical knowledge gaps in subsurface characterisation globally, suggesting that UK-specific parameterisation and validation would be necessary before implementation in regional climate and hydrological models.
Key measures
Water storage and residence time; continental water buffering capacity; lateral ridge-to-valley flow pathways; slope-aspect insolation contrasts; subsurface water storage capacity; seasonal and interannual drought impacts; stream baseflow contributions; subsurface water dynamics; spatial heterogeneity in hillslope hydrology across global scales
Outcomes reported
The study identifies hillslope-scale terrain structures and hydrological processes that fundamentally organise water, energy, and biogeochemical fluxes at subgrid scales in Earth System Models. The authors hypothesise that three-dimensional lateral ridge-to-valley flow and insolation contrasts between slopes are primary organisers of water, energy, and vegetation fluxes at the hillslope scale, and that their implementation in ESM land models could increase simulated continental water storage and residence time. The paper identifies critical knowledge gaps in subsurface water storage and release mechanisms that affect terrestrial ecosystem resilience to drought and aquatic ecosystem baseflow dynamics.
Topic tags
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