EVAPOTRANSPIRATION AND SOIL MOISTURE DYNAMICS ON A SEMIARID PONDEROSA PINE HILLSLOPE<sup>1</sup>

Brandes, David; Wilcox, Bradford P.

doi:10.1111/j.1752-1688.2000.tb05702.x

Cited by 35 publications

(39 citation statements)

References 19 publications

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“…From these simulations, it appears that groundwater recharge (percolation) at this location is not significant, which is consistent with the previous study of this site (Wilcox et al, 1997). The modelled average ET for the 3-year period is 95% of the total precipitation, which is in agreement with previous water balance analyses of the field data (Brandes and Wilcox, 2000). Simulated interflow during the 3 years is of trace amount, similar to what was observed (Wilcox et al, 1997).…”

Section: Root-water-uptake Model Calibration and Soil Moisture Partitsupporting

confidence: 90%

“…It is estimated that over 90% of soil water loss at the study site was due to ET (Brandes and Wilcox, 2000). It is therefore important to appropriately represent evaporation and transpiration processes in order to simulate soil water partitioning correctly.…”

Section: Evaporation and Transpiration Modellingmentioning

confidence: 99%

“…The sum of surface runoff and interflow through the soil was estimated to be 10-60 mm/year (Wilcox et al, 1997). The rest of the water was returned to the atmosphere through evapotranspiration (ET) (Brandes and Wilcox, 2000). A low-permeability barrier at or above the soil-tuff interface was hypothesized to impede downward movement of water into the highly permeable tuff (Wilcox et al, 1997).…”

Section: Introductionmentioning

confidence: 99%

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Modelling investigation of water partitioning at a semiarid ponderosa pine hillslope

Guan¹,

Šimůnek²,

Newman³

et al. 2010

Hydrological Processes

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Abstract:The effects of vegetation root distribution on near-surface water partitioning can be two-fold. On the one hand, the roots facilitate deep percolation by root-induced macropore flow; on the other hand, they reduce the potential for deep percolation by root-water-uptake processes. Whether the roots impede or facilitate deep percolation depends on various conditions, including climate, soil, and vegetation characteristics. This paper examines the effects of root distribution on deep percolation into the underlying permeable bedrock for a given soil profile and climate condition using HYDRUS modelling. The simulations were based on previously field experiments on a semiarid ponderosa pine (Pinus ponderosa) hillslope. An equivalent single continuum model for simulating root macropore flow on hillslopes is presented, with root macropore hydraulic parameterization estimated based on observed root distribution. The sensitivity analysis results indicate that the root macropore effect dominates saturated soil water flow in low conductivity soils (K matrix below 10 7 m/s), while it is insignificant in soils with a K matrix larger than 10 5 m/s, consistent with observations in this and other studies. At the ponderosa pine site, the model with simple rootmacropore parameterization reasonably well reproduces soil moisture distribution and some major runoff events. The results indicate that the clay-rich soil layer without root-induced macropores acts as an impeding layer for potential groundwater recharge. This impeding layer results in a bedrock percolation of less than 1% of the annual precipitation. Without this impeding layer, percolation into the underlying permeable bedrock could be as much as 20% of the annual precipitation. This suggests that at a surface with low-permeability soil overlying permeable bedrock, the root penetration depth in the soil is critical condition for whether or not significant percolation occurs.

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Section: Root-water-uptake Model Calibration and Soil Moisture Partitsupporting

confidence: 90%

Section: Evaporation and Transpiration Modellingmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Modelling investigation of water partitioning at a semiarid ponderosa pine hillslope

Guan¹,

Šimůnek²,

Newman³

et al. 2010

Hydrological Processes

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“…A previous analysis of soil water data from the lowdensity site indicated that the soil water dynamics were driven by annual periodicity that seemed related to winter soil water infiltration, followed by depletion through evapotranspiration (Brandes and Wilcox, 2000). Our results show that the winter soil water content increases in the high-density stands are greater than those in the lowdensity stands, although the high-density stands' water content never reaches the same absolute magnitude as that of the low-density stands.…”

Section: Discussioncontrasting

confidence: 71%

Soil water dynamics under low‐ versus high‐ponderosa pine tree density: ecohydrological functioning and restoration implications

et al. 2008

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Soil water dynamics reflect the integrated effects of climate conditions, soil hydrological properties and vegetation at a site. Consequently, changes in tree density can have important ecohydrological implications. Notably, stand density in many semiarid forests has increased greatly because of fire suppression, such as that in the extensive ponderosa pine (Pinus ponderosa Laws.) forests that span much of western USA. Few studies have quantified how soil water content varies in low-versus highdensity stands both by depth and years, or the inter-relationships between water content, stand density, and ecohydrological processes. Over a 4-year period, we measured the soil water content throughout the soil profiles in both low-density (250 trees/ha) and high-density (2710 trees/ha) ponderosa pine stands. Our results document significantly greater soil water contents in the low-density stands over a wide range of conditions (wet, dry, winter, summer). We observed substantial differences in water contents at depths greater than are typically measured. Our results also show that differences in monthly average soil water contents between the low-and high-density stands fluctuated between 0Ð02 and 0Ð08 m 3 m 3 depending on the time of year, and reflect a dynamic coupling between infiltration and stand evapotranspiration processes. The difference in soil water availability between low-and high-density stands is substantially amplified when expressed as plant-available water on a per tree, per biomass or per leaf area basis. Our findings highlight important ecohydrological couplings and suggest that restoration and monitoring plans for semi-arid forests could benefit from adopting a more ecohydrological focus that explicitly considers soil water content as a determinant of the ecosystem process.

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“…Para monitoramento da umidade do solo foram instalados blocos de resistência elétrica, que fornecem leituras de tensão da água no solo (Irmak & Haman, 2001), em 12 pontos na microbacia, nas profundidades de 20, 50 e 80 cm, sendo 8 na área ocupada por pastagem e 4 na área plantada com eucalipto. Amostras em cada ponto e profundidade foram coletadas para determinação das respectivas curvas características; os dados de tensão também o foram a cada 2 dias, convertidos em umidade volumétrica e transformados em umidade relativa do perfil do solo, segundo Brandes & Wilcox (2000): em que: θ r é a umidade residual (PMP), θ s , a umidade de saturação e , θ v a umidade volumétrica média no perfil do solo.…”

Section: Características Morfométricas E Monitoramento Hidroló-gico Dunclassified

Simulação do deflúvio e vazão de pico em microbacia hidrográfica com escoamento efêmero

Mello¹,

Lima²,

Silva³

2007

Rev. bras. eng. agríc. ambient.

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RESUMOA predição da resposta hidrológica em microbacias hidrográficas a partir de diferentes usos do solo é de fundamental importância para nortear ações de manejo ambiental, razão por que se objetivou, neste trabalho, desenvolver, em primeira mão, uma modelagem hidrológica para predizer o deflúvio total e a vazão de pico em uma microbacia hidrográ-fica experimental, de escoamento efêmero, ocupada por eucalipto e pastagem, e após esta etapa, aplicá-la a diferentes cenários de ocupação da microbacia por ambas as coberturas vegetais, estimando-se as respostas hidrológicas das situações simuladas. O monitoramento hidrológico foi realizado entre novembro/02 e abril/03, por meio de estação meteorológica e calha Parshall, conjugada a linígrafo automático. A umidade do solo foi monitorada a cada 2 dias, em 3 profundidades (20, 50 e 80 cm), em 8 pontos na área ocupada por pastagem e 4 na área com eucalipto. A modelagem mostrou-se precisa e eficaz aos objetivos propostos de predição em diferentes cenários de uso e ocupação do solo. Verificou-se que, se a microbacia for ocupada por 80% de eucalipto, haverá redução do deflúvio em 29%, constatando-se ainda, redução substancial da vazão de pico; verificou-se também que a umidade do solo é fundamental no processo, especialmente para pequenas vazões, no início e no final do período chuvoso e após veranicos e que, para vazões mais elevadas, as características da precipitação são determinantes.Palavras-chave: hidrologia, uso do solo, umidade do solo Surface runoff and peak discharge simulation in ephemeral watershed ABSTRACTThe prediction of hydrological responses in a microbasin from different soil uses is of fundamental importance to develop actions to minimize environmental impacts. This work aimed to develop and to apply hydrological modeling for predicting surface runoff and peak discharge in experimental tropical ephemeral watershed occupied by eucalyptus and grasses, creating different soil use scenarios. Hydrological monitoring was performed between November/2002 and April/2003, using, respectively, gauge and climatologically stations. Soil moisture was monitored every 2 days, at 3 depths (20, 50 and 80 cm), at 8 distributed spatial points in the grass area and 4 points in the eucalyptus area. The modeling has presented a high precision, thereby showing to be very effective for application for the proposed goals. In scenarios which eucalyptus area is larger than the grass area there will be surface runoff reduction of up to 29%, when the microbasin would be occupied by 80% of this vegetable cover. Also, a substantial reduction in peak discharge was verified. The modeling showed itself to be precise and effective in relation to the proposed prediction objectives in different scenarios of soil use and ocupation. It was verified that, if the microbasin was occupied by 80% eucalyptus, there would be a reduction in surface runoff of 29%, and furthermore, a substantial reduction in peak discharge. Also verified was that soil water is fundamental in the process, especially for ...

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EVAPOTRANSPIRATION AND SOIL MOISTURE DYNAMICS ON A SEMIARID PONDEROSA PINE HILLSLOPE¹

Cited by 35 publications

References 19 publications

Modelling investigation of water partitioning at a semiarid ponderosa pine hillslope

Modelling investigation of water partitioning at a semiarid ponderosa pine hillslope

Soil water dynamics under low‐ versus high‐ponderosa pine tree density: ecohydrological functioning and restoration implications

Simulação do deflúvio e vazão de pico em microbacia hidrográfica com escoamento efêmero

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EVAPOTRANSPIRATION AND SOIL MOISTURE DYNAMICS ON A SEMIARID PONDEROSA PINE HILLSLOPE1

Cited by 35 publications

References 19 publications

Modelling investigation of water partitioning at a semiarid ponderosa pine hillslope

Modelling investigation of water partitioning at a semiarid ponderosa pine hillslope

Soil water dynamics under low‐ versus high‐ponderosa pine tree density: ecohydrological functioning and restoration implications

Simulação do deflúvio e vazão de pico em microbacia hidrográfica com escoamento efêmero

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EVAPOTRANSPIRATION AND SOIL MOISTURE DYNAMICS ON A SEMIARID PONDEROSA PINE HILLSLOPE¹