| 28 Jul 2026
A flexible open-source modular framework for ecohydrological modeling: Application and validation of GEOSPACE-1D
Abstract. Ecohydrology is a rapidly evolving interdisciplinary field. It explores the interactions among the variety of hydrological processes and ecosystems, specifically water controls on the biota. Advances in measurement techniques and modeling frameworks have enhanced our understanding of key processes, such as vegetation-rainfall interactions, soil moisture dynamics, water-borne disease infections, and the impacts of landscape evolution on streamflow. However, most existing ecohydrological models rely on rigid, predefined components and parameterisations, which limit their flexibility to diverse case studies and datasets. Addressing these limitations requires the implementation of open-source modular frameworks that facilitate customization, comparison, and integration of several modeling components.
The present study introduces and validates GEOSPACE (Soil-Plant-Atmosphere Continuum Estimator), a flexible, open-source ecohydrological framework within the GEOframe system. GEOSPACE employs object-oriented programming principles to model mass and energy fluxes within the critical zone, focusing on processes such as evapotranspiration, soil water dynamics, and vegetation water uptake. Its modular architecture offers multiple alternative formulations for key processes, allowing researchers to tailor simulations to specific scenarios, compare different models, and extend the capabilities of the model. The study uses data from a previous experiment to demonstrate the effectiveness of GEOSPACE in simulating ecohydrological processes under diverse conditions. GEOSPACE is therefore identified as a valuable tool for addressing critical ecohydrological challenges, paving the way for innovative and reliable solutions in a changing environmental context.
The manuscript describes the application and evaluation of the GEOSPACE ecohydrological model with data from the «Spike II» lysimeter experiment. The study is well-organized and clearly written, addressing an important topic in ecohydrological modeling. The authors provide a thorough description of the experimental setup and demonstrate the model's capacity to replicate various components of the soil-plant water balance. The study is generally suitable for publication. However, in my opinion, the manuscript has several major and minor shortcomings that should be addressed before publication.
Major comments
Minor comments
L41 There is some inconsistency in the wording of the definitions of evaporation and transpiration. The listed approaches do not explicitly estimate transpiration. The PT equation is for potential evaporation. The H method is a simple way to estimate reference evapotranspiration. The PM equation is used to estimate actual evapotranspiration.
L43 (Penman and Keen, 1948). It is one of the possible references to the Penman equation. Actually, if you like to refer to the Penman-Monteith equation for potential evapotranspiration, you need to choose another reference. Refer to J. Monteith.
L45 (D’Amato and Rigon, 2025) Actually, there are a number of much more sophisticated models.
L150 A more detailed description of the models is required.
L151 PM for evapotranspiration
L155 However, LAI and LAD can be recalculated using, for example, biomass on foliage, or they can be obtained using a hemispherical photo.
L161 The stomatal conductance of the leaf was derived from the Jarvis parameterization. How was the tree (bulk) stomatal conductance calculated? Did you recalculate the leaf to surface big-leaf stomatal conductance in your study?
L175 What about estimating the intercepted evaporation (i.e., the rainwater that was intercepted)?
L188 big-leaf approach? for individual tree?
I see there are a variety of different approaches to evapotranspiration simulation in your model frameworks. It is actually necessary to proceed with great caution when synthesizing models that differ in their approach to vegetation cover structure and physiology. Directly exchanging parameters can lead to significant errors in flux estimates.
L195 Once again, it’s not entirely clear what the authors mean by the terms “evaporation” and “evapotranspiration.” Generally, they refer to the same thing - they’re almost synonyms. Evapotranspiration, or total evaporation, is the amount of water that is released into the atmosphere as vapor as a result of transpiration and physical evaporation from the soil and the moist parts of vegetation.
Or perhaps this was calculated based on the difference in measurements from various lysimeters... But this is a relatively rough estimate... The direct extrapolation of moisture fluxes (i.e., soil evaporation) between lysimeters with different vegetation types can lead to serious errors in attributing the contribution of soil to total evaporation, for example. The same applies to grass cover....
L196-197 This looks like a discussion
L198 How was transpiration actually measured in your study? For example, was it calculated based on the soil surface's contribution to evaporation?
L220 It sounds like an advertisement for a software product... given the assumptions made in the model... such claims aren't very trusted. You should avoid making such statements in the article.
L231 The Priestley-Taylor equation is used to calculate potential evaporation (not potential evapotranspiration). Evaporation from a water surface or a wet grass surface.
L237 PT constant may vary depending on the LAI and the amount of water on the leaf surfaces.
Fig 8 These are very high transpiration rates. They are 3–5 times higher than the daily evaporation rate of a humid tropical forest.
L268 The question still remains about how to determine transpiration and how accurate that determination is.
L273 What is the statistical significance of R2 estimates?
L283 This was under conditions in a single lysimeter. How can this data be extrapolated to a real vegetation canopy?
L301 Once again, the Priestley-Taylor equation was considered a simplification of the Penman equation for a water-covered or wet surface... under conditions of minimal advection... The air entering your lysimeter has properties that are quite different from those formed near the vegetation in the lysimeter. Drier air can lead to increased transpiration and physical evaporation. So, using lysimeters for such tasks is a very risky business.
L320 Such a combination of modeling approaches should not be treated in a purely formal manner; instead, one must take into account the purpose of the models, the assumptions underlying each modeling approach, and the potential errors associated with those assumptions.
L338 Based on the results of measurements in four lysimeters and the modeling of flow within them, this is undoubtedly a very bold claim. It’s hard to believe.
L354 Heatwaves seem to have been left out of the article… The results make no mention of changes in evaporation due to high temperatures. Or was it just a passing remark?
L366 The results for the grassy plots and the lone tree hardly support such promising claims.