Responses of arid and semiarid watersheds to increasing carbon dioxide and climate change as shown by simulation studies

Tiny openings on the surfaces of leaves, stomata, control the flux of CO 2 , water vapor, and other gases between the atmosphere and the earth's vegetated surface. An increase in atmospheric CO 2 could have an effect on stomatal openings, causing indirect changes in many surface hydroclimatogical variables that could be comparable in magnitude to the direct radiative effects. Increased atmospheric CO 2 is expected to increase water use efficiency in many plant types because of the closure of the stomatal openings on the leaf surface. The present study assesses this stomatal effect by doubling the stomatal resistance in two land surface schemes, the Biosphere-Atmosphere Transfer Scheme and the Land Surface Model, which are coupled to the National Center for Atmospheric Research's Community Climate Model version 3 atmospheric general circulation model, and by evaluating the resulting hydrometeorological responses, particularly for the western United States. Because the simulated reduction of stomatal openings restricts evapotranspiration, latent heat fluxes are reduced, causing global average annual and seasonal decreases in precipitation as well as increases in sensible heat flux, surface temperatures, runoff, and root-zone soil water. Global seasonal decreases in latent heat flux of up to 7% occur, corresponding to surface temperature increases of up to 0.5ЊC and precipitation decreases of up to 3%. Regional responses vary. A focus of this study was to examine how these changes affect runoff and stream flow in the southwestern United States. Contrary to a previous empirical study of this effect, which showed an 87% mean increase in Arizona basin stream flow, this coupled land surface-atmospheric model shows no significant changes in any of the variables examined for this region.

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“…Our results for the Colorado River basin are in agreement with a study done by Skiles and Hanson (1994)…”

Section: Discussionsupporting

confidence: 93%

Use of a Coupled Land Surface General Circulation Model to Examine the Impacts of Doubled Stomatal Resistance on the Water Resources of the American Southwest

1999

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“…Some earlier studies (e.g. Idso & Brazel, 1984) with stand-alone hydrological models probably overestimated the CO 2 effect due to simplifying assumptions; specifically, physiological changes in vegetation were emulated in these studies by only reducing evapotranspiration, while structural effects and other feedback mechanisms were not considered (see Skiles & Hanson, 1994).…”

Section: Discussionmentioning

confidence: 93%

Global effects of doubled atmospheric CO₂ content on evapotranspiration, soil moisture and runoff under potential natural vegetation

Leipprand

Gerten

2006

Hydrological Sciences Journal

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Rising atmospheric CO 2 concentration affects the water balance through climatic changes and through changes in transpiration, vegetation structure and distribution. This study quantifies CO 2 effects upon evapotranspiration, soil moisture and runoff under conditions of potential natural vegetation globally, using a biosphere model forced by observed climate . Isolated CO 2 impacts were inferred from a 2 × CO 2 scenario, assuming no climate change. Global effects are moderate: evapotranspiration reduces by 7%, whilst runoff and soil moisture increase by 5% and 1%, respectively. But the effects vary regionally and seasonally, owing to the complex interplay between water and vegetation dynamics. For example, reduced leaf-level transpiration is outweighed by increased transpiration resulting from enhanced vegetation cover in semiarid areas; and seasonal transpirational water savings result in year-round increases in soil moisture in boreal regions. Overall, CO 2 effects impart significant variability to hydrological processes at all scales, so they merit consideration in assessments of future water resources.

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“…Plants exert considerable effects on runoff via features such as albedo and interception (Eckhardt et al, 2003), stomatal behaviour and transpiration (e.g. Skiles and Hanson, 1994), rooting strategy (Milly, 1997), leaf area (Neilson, 1995;Kergoat, 1998), and phenology (Peel et al, 2001). It is well-known, for example, that a reduction in forest cover increases runoff by decreasing evapotranspiration, whereas reforestation usually lowers runoff (Bosch and Hewlett, 1982).…”

Section: Introductionmentioning

confidence: 99%

Terrestrial vegetation and water balance—hydrological evaluation of a dynamic global vegetation model

Gerten

Schaphoff

Haberlandt

et al. 2004

Journal of Hydrology

853

909

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Responses of arid and semiarid watersheds to increasing carbon dioxide and climate change as shown by simulation studies

Cited by 23 publications

References 31 publications

Use of a Coupled Land Surface General Circulation Model to Examine the Impacts of Doubled Stomatal Resistance on the Water Resources of the American Southwest

Use of a Coupled Land Surface General Circulation Model to Examine the Impacts of Doubled Stomatal Resistance on the Water Resources of the American Southwest

Global effects of doubled atmospheric CO₂ content on evapotranspiration, soil moisture and runoff under potential natural vegetation

Terrestrial vegetation and water balance—hydrological evaluation of a dynamic global vegetation model

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Responses of arid and semiarid watersheds to increasing carbon dioxide and climate change as shown by simulation studies

Cited by 23 publications

References 31 publications

Use of a Coupled Land Surface General Circulation Model to Examine the Impacts of Doubled Stomatal Resistance on the Water Resources of the American Southwest

Use of a Coupled Land Surface General Circulation Model to Examine the Impacts of Doubled Stomatal Resistance on the Water Resources of the American Southwest

Global effects of doubled atmospheric CO2 content on evapotranspiration, soil moisture and runoff under potential natural vegetation

Terrestrial vegetation and water balance—hydrological evaluation of a dynamic global vegetation model

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Global effects of doubled atmospheric CO₂ content on evapotranspiration, soil moisture and runoff under potential natural vegetation