Effects of root water uptake formulation on simulated water and energy budgets at local and basin scales

Ferguson, Ian J.; Jefferson, Jennifer L.; Maxwell, R. M.; Kollet, Stefan

doi:10.1007/s12665-015-5041-z

Cited by 40 publications

(32 citation statements)

References 62 publications

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“…A number of studies using water isotopic tracers (Dawson & Pate, 1996;Zhang et al, 2017) and root excavations (Fan et al, 2017) have observed that maximum rooting depths often track the water table depth suggesting plants actively subsidize their water demands with older and deeper water pools. These observations support modeling results, which indicate that in order to accurately capture spatial patterns in transpiration and the response of terrestrial ecosystems to precipitation variability, it is imperative to account for precipitation from previous seasons or years (Ferguson et al, 2016;Maxwell & Condon, 2016;Maxwell et al, 2019).…”

Section: Introductionsupporting

confidence: 82%

Persistence and Plasticity in Conifer Water‐Use Strategies

et al. 2020

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The selective use of seasonal precipitation by vegetation is critical to understanding the residence time and flow path of water in watersheds, yet there are limited datasets to test how climate alters these dynamics. Here, we use measurements of the seasonal cycle of tree ring δ18O for two widespread conifer species in the Rocky Mountains of North America to provide a multi‐decadal depiction of the seasonal origins of forest water use. The results show that while the conifer tree stands had a dominant preference for use of snowmelt, there were multi‐annual periods over the last four decades when use of summer precipitation was preferential. Utilization of summer rain emerged during years with increased snowfall and tree growth, suggesting that summer rain enhanced the transpiration stream only during the periods of highest water use. We hypothesize this could be explained through shallowing of the root profile during wetter periods and/or through the influence of changing water table depths on the residence time of summer precipitation in the root zone. We suggest the tree ring proxy approach used here could be applied in other watersheds to provide critical insight into the temporal dynamics of plant water use that could not be inferred from short measurement campaigns. These data on the seasonal origins of forest water are critical for understanding forest vulnerability to drought, the processes that affect precipitation pathways and residence time in watersheds and the interpretation of tree ring proxy data.

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Section: Introductionsupporting

confidence: 82%

Persistence and Plasticity in Conifer Water‐Use Strategies

et al. 2020

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“…PF simultaneously solves the 3D Richards equation and shallow water equations to determine a pressure head in every cell (Kollet & Maxwell, 2006;Maxwell, 2013). CLM solves the surface energy budget, explicitly representing evaporation, transpiration, snow processes, heat fluxes, and radiation partitioning (Ferguson, Jefferson, Maxwell, & Kollet, 2016;Jefferson, Gilbert, Constantine, & Maxwell, 2015b;Jefferson & Maxwell, 2015). CLM and PF are connected across four subsurface layers to represent rooting depths and lateral water transfer in the variably saturated subsurface (Maxwell & Miller, 2005).…”

Section: Modelmentioning

confidence: 99%

Sensitivity analysis of hydraulic conductivity and Manning's n parameters lead to new method to scale effective hydraulic conductivity across model resolutions

Foster

Maxwell

2018

Hydrological Processes

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Hydrological modelling is an important tool for research, policy, and management, but uncertainty remains about parameters transferability from field observations made at small scale to models at the catchment scale and larger. This uncertainty compels the need to develop parameter relationships that are translatable across scale. In this study, we compare the changes to modelled processes as resolution is coarsened from 100‐m to 1‐km in a topographically complex, 255‐km2 Colorado River headwater catchment. We conducted a sensitivity analysis for hydraulic conductivity (K) and Manning's n parameters across four orders of magnitude. Results showed that K acts as a moderator between surface and subsurface contributions to streamflow, whereas n moderates the duration of high intensity, infiltration‐excess flow. The parametric sensitivity analysis informed development of a new method to scale effective hydraulic conductivity across modelling resolutions in order to compensate for the loss of topographic gradients as resolution is coarsened. A similar mathematical relationship between n and lateral resolution changes was not found, possibly because n is also sensitive to time discretization. This research provides an approach to translate hydraulic conductivity parameters from a calibrated coarse model to higher resolutions where the number of simulations are limited by computational demand.

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“…Parameters that are used to determine leaf area index, reflectance and transmittance and root distributions vary by land-cover type and are provided as inputs to the model using the 18 land-cover classes defined by the International Geosphere-Biosphere Programme (IGBP). For additional details on the numerical approach and analysis on the sensitivity of evaporation and transpiration within the CLM the reader is referred to Ferguson et al (2016) Jefferson and Maxwell (2015), Kollet and Maxwell (2008) and .…”

Section: Hydrologic Modelingmentioning

confidence: 99%

Systematic shifts in Budyko relationships caused by groundwater storage changes

Condon

Maxwell

2017

Hydrol. Earth Syst. Sci.

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Abstract. Traditional Budyko analysis is predicated on the assumption that the watershed of interest is in dynamic equilibrium over the period of study, and thus surface water partitioning will not be influenced by changes in storage. However, previous work has demonstrated that groundwatersurface water interactions will shift Budyko relationships. While modified Budyko approaches have been proposed to account for storage changes, given the limited ability to quantify groundwater fluxes and storage across spatial scales, additional research is needed to understand the implications of these approximations. This study evaluates the impact of storage changes on Budyko relationships given three common approaches to estimating evapotranspiration fractions: (1) determining evapotranspiration from observations, (2) calculating evapotranspiration from precipitation and surface water outflow, and (3) adjusting precipitation to account for storage changes. We show conceptually that groundwater storage changes will shift the Budyko relationship differently depending on the way evapotranspiration is estimated. A 1-year transient simulation is used to mimic all three approaches within a numerical framework in which groundwater-surface water exchanges are prevalent and can be fully quantified. The model domain spans the majority of the continental US and encompasses 25 000 nested watersheds ranging in size from 100 km 2 to over 3 000 000 km 2 . Model results illustrate that storage changes can generate different spatial patterns in Budyko relationships depending on the approach used. This shows the potential for systematic bias when comparing studies that use different approaches to estimating evapotranspiration. Comparisons between watersheds are also relevant for studies that seek to characterize variability in the Budyko space using other watershed characteristics. Our results demonstrate that within large complex domains the correlation between storage changes and other relevant watershed properties, such as aridity, makes it difficult to easily isolate storage changes as an independent predictor of behavior. However, we suggest that, using the conceptual models presented here, comparative studies could still easily evaluate a range of spatially heterogeneous storage changes by perturbing individual points to better incorporate uncertain storage changes into analysis.

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Effects of root water uptake formulation on simulated water and energy budgets at local and basin scales

Cited by 40 publications

References 62 publications

Persistence and Plasticity in Conifer Water‐Use Strategies

Persistence and Plasticity in Conifer Water‐Use Strategies

Sensitivity analysis of hydraulic conductivity and Manning's n parameters lead to new method to scale effective hydraulic conductivity across model resolutions

Systematic shifts in Budyko relationships caused by groundwater storage changes

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