Models of soil moisture dynamics in ecohydrology: A comparative study

Guswa, Andrew J.; Celia, Michael A.; Rodrı́guez-Iturbe, Ignacio

doi:10.1029/2001wr000826

Cited by 192 publications

(199 citation statements)

References 19 publications

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“…Thus drainage can be ignored when considering drying intervals on a timescale of days, as is documented by the 1-3 day SMAP soil moisture observations (Chan et al, 2016). Assuming drainage is negligible outside of rainy intervals is a common assumption in models of soil moisture dynamics (Federer et al, 2003;Guswa et al, 2002;e.g., Laio et al, 2001;McColl et 10 al., 2017a;Porporato et al, 2004). We make this assumption here.…”

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confidence: 99%

Controls on surface soil drying rates observed by SMAP and simulated by the Noah land surface model

Shellito¹,

Small²

2017

Preprint

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Abstract. Drydown periods that follow precipitation events provide an opportunity to assess the mechanisms by which soil moisture dissipates from the land surface. We use SMAP (Soil Moisture Active Passive) observations and Noah simulations from drydown periods to quantify the role of soil moisture, potential evaporation, vegetation cover, and soil texture on soil drying rates. Rates are determined using finite differences over intervals of 1 to 3 days. In the Noah model, the drying rates are a good approximation of direct soil evaporation rates. Data cover the domain of the North American Land Data 10 Assimilation System phase 2 and span the first 1.8 years of SMAP's operation.Drying of surface soil moisture observed by SMAP is faster than that simulated by Noah. SMAP drying is fastest when surface soil moisture levels are high, potential evaporation is high, and when vegetation cover is low. Soil texture plays a minor role in SMAP drying rates. Noah simulations show similar responses to soil moisture and potential evaporation, but vegetation has a minimal effect and soil texture has a much larger effect compared to SMAP. When drying rates are 15 normalized by potential evaporation, SMAP observations and Noah simulations both show that increases in vegetation cover lead to decreases in evaporative efficiency from the surface soil. However, the magnitude of this effect simulated by Noah is much weaker than that determined from SMAP observations.

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confidence: 99%

Controls on surface soil drying rates observed by SMAP and simulated by the Noah land surface model

Shellito¹,

Small²

2017

Preprint

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“…However, field experiments are time consuming, 61 relatively expensive and difficulties in up-scaling from limited numbers of observations are readily 62 apparent (Singh et al, 2006). To overcome this, process-based models that link hydrology and plant 63 ecophysiology have been developed that provide useful tools to investigate interactions amongst 64 4 energy, water and momentum balances of the soil-vegetation-atmosphere system across multiple 65 spatial and temporal scales (Baird et al, 2005;Guswa et al, 2002;Laio et al, 2001; Zhang et al, 66 1996). Studies of modelling these coupled behaviours have been attempted previously (Gerten et al, 67 2004; Kucharik et al, 2000).…”

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Modelling vegetation water-use and groundwater recharge as affected by climate variability in an arid-zone Acacia savanna woodland

Chen

Eamus

Cleverly

et al. 2014

Journal of Hydrology

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19(1) For efficient and sustainable utilization of limited groundwater resources, improved 20 understanding of how vegetation water-use responds to climate variation and the corresponding 21 controls on recharge is essential. This study investigated these responses using a modelling approach. 22The biophysically based model WAVES was calibrated and validated with more than two years of 23 field experimental data conducted in Mulga (Acacia aneura) in arid central Australia. The validated 24 model was then applied to simulate vegetation growth (as changes in overstory and understory leaf 25 area index; LAI), vegetation water-use and groundwater recharge using observed climate data for the 26 period 1981−2012. Due to large inter-annual climatic variability, especially precipitation, simulated 27 annual mean LAI ranged from 0.12 to 0.35 for the overstory canopy and 0.07 to 0.21 for the 28 understory. These variations in simulated LAI resulted in vegetation water-use varying greatly from 29 year-to-year, from 64 to 601 mm pa. Simulated vegetation water-use also showed distinct seasonal 30 patterns. Both climate variability and vegetation dynamics exerted significant controls on annual 31 recharge. The simulated annual recharge ranged from 58 to 672 mm when only climate effects were 32 considered; but this range was greatly reduced to 0 to 48 mm when vegetation water-use was 33 accounted for. Understanding such effects under the observed historical climate conditions gave 34 significant insight into assessing potential impacts of interactions amongst climate variability and land 35 use/land cover change on groundwater resources management in arid and semi-arid regions. 36 37 3 Introduction 38(2) Groundwater is a valuable natural resource, which not only supports human activities, but also 39 has a key role in sustaining the health of wide-spread groundwater dependent ecosystems (Eamus et 40 al., 2006;Jha et al., 2007). Sustainable water resource management is a major challenge for water 41 resource managers in arid and semi-arid regions (Fernandez et al., 2002), where excessive and 42 unsympathetic groundwater abstraction can degrade vegetation health (Clifton and Evans, 2001, 43 Donohue et al., 2007). Vegetation dynamics in arid and semi-arid regions largely depend on soil 44 water availability, which in turn, result in a number of complex hydrologic processes (Gee et al., 1994; 45 Porporato et al., 2002; Scanlon et al., 2005;Garcia et al., 2011). Climate variations, which lead to 46 changes in vegetation structure and/or its water-use, can have a follow-on impact on recharge to 47 groundwater under vegetation. With increasing demand for water and a changing climate regime, it is 48 crucial to better understand the hydrological role of vegetation for developing sustainable 49 groundwater management and mitigating the environmental impacts of groundwater development. A 50 key aspect of this role is that of transpiration, a major component of catchment water balances, to 51 which biological productivi...

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“…This ability was recognised by Ferná ndez et al (1991Ferná ndez et al ( , 1997 in olive trees and by Rana et al (2004) in vineyards, as a process that allows trees to get their water supply during drought periods. Modelling studies show that predicting ET c based only on root zone averaged soil moisture may be an oversimplification, particularly if plants can compensate for a portion of their roots being in dry soil (Guswa et al, 2002). REW decreased gradually to a value of 0.39 in the middle of June, only to increase to a value of 0.93 after the irrigation events at the beginning of July.…”

Section: 2mentioning

confidence: 99%

Water use, transpiration, and crop coefficients for olives (cv. Cordovil), grown in orchards in Southern Portugal

Ramos

Santos

2009

Biosystems Engineering

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To improve the scheduling of irrigation for low-density olive trees (Olea europaea L.) grown in a typical Mediterranean environment of Southern Portugal, and to clarify the mechanisms of water uptake by trees, transpiration, soil water status and stomatal response to water deficit were measured in an olive orchard. Olive trees of cv. Cordovil were subject to three irrigation treatments: full-rate irrigation, sustained deficit irrigation (SDI) providing for approximately 60% of water applied at full-rate irrigation, and a regulated deficit irrigation (RDI) with water applied at periods during three critical phases: before-flowering, at beginning of pit-hardening, before crop-harvesting to replenish soil moisture to field capacity. There was also a dry-farming treatment. Trees responded differently to summer rainfall and irrigation water: full-rate irrigation, which received 880 mm of irrigation and 240 mm of rainfall, used 704 mm for transpiration; SDI, which received the same amount of rainfall and 448 mm of irrigation water, used 745 mm of water for transpiration; RDI, which received 69 mm of irrigation water and 240 mm of rainfall, used 638 mm of water for tree transpiration; dry-farming, which received no irrigation, benefited from 240 mm of summer and early autumn rain and used 404 mm of water for transpiration. The results support the hypothesis that trees under RDI and dry-farming satisfy most of their early atmospheric evaporative demand by extracting water from outside of the area wetted by drip irrigation. Scaled-up orchard transpiration was used to define orchard crop and water stress coefficients. With full-rate irrigation and SDI the results showed that during summer droughts olive trees slow down their physiological mechanisms to conserve water, regardless of amount applied. The derived crop coefficient results also indicated that SDI was the most appropriate for scheduling the irrigation of cv. Cordovil orchards in Southern Portugal although applying RDI helped sustain orchard transpiration and yields. Irrigation accounted for 11% of total water used in transpiration, with the balance extracted by roots in the large volume of soil lying in the areas between the trees. However, using the RDI scheme to schedule irrigation appears to be appropriate only in wet years with well distributed late summer rainfall or where there is a shortage of farm irrigation water. In general, and particularly in years with no summer and early autumn rains as can often occur in this region, the SDI regime appears to be more appropriate for scheduling irrigation.

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Models of soil moisture dynamics in ecohydrology: A comparative study

Cited by 192 publications

References 19 publications

Controls on surface soil drying rates observed by SMAP and simulated by the Noah land surface model

Controls on surface soil drying rates observed by SMAP and simulated by the Noah land surface model

Modelling vegetation water-use and groundwater recharge as affected by climate variability in an arid-zone Acacia savanna woodland

Water use, transpiration, and crop coefficients for olives (cv. Cordovil), grown in orchards in Southern Portugal

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