Simplified Estimation of Reference Evapotranspiration from Pan Evaporation Data in California

Snyder, Richard L.; Orang, M.; Matyac, Scott; Grismer, Mark E.

doi:10.1061/(asce)0733-9437(2005)131:3(249)

Cited by 68 publications

(35 citation statements)

References 5 publications

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“…One of the simpler techniques is to directly measure the water evaporation in the field from an evaporation pan, which is an apparently simple integrated measurement of complex meteorological interactions, such as solar radiation, temperature, humidity, and wind speed. Although pan evaporation cannot fully represent lake evaporation, it has been found as proportional to actual evaporation of moist surfaces, such as lakes or irrigated fields (Kahler and Brutsaert 2006), and also calculated reference crop evapotranspiration (Brouwer and Heibloem 1986;Grismer et al 2002;Snyder et al 2005;Ertek et al 2006). Because pans of various designs have produced data for many regions throughout the world for long periods, attempts have also been made to use these data to estimate actual evaporation even in non-moist environments.…”

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confidence: 99%

A critical overview of pan evaporation trends over the last 50 years

Charles

2009

Climatic Change

122

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Despite the observed increases in global average temperature, observations across the world show that the rate of pan evaporation at a regional scale has been steadily decreasing over the past 50 years. This is known as the pan evaporation paradox. This paper reviews current reported pan evaporation trends, examines available theoretical explanations about this "paradox", and discusses current research gaps and priorities. It concludes that: (1) three major potential causes of pan evaporation, solar radiation, vapour pressure deficit (VPD) and wind speed, have been changing in the last 50 years. The magnitude of changes and importance of each of these three causes varies from region to region, as does the pan evaporation trend, although overall there is a decreasing trend. (2) Currently two existing theories explaining the pan evaporation trends have limits and are only valid in some specific regions and seasons. Neither of them provides a fundamental physical-based theory that could be applied everywhere. (3) Further investigations are needed before we can fully understand the global evapotranspiration trend in global warming scenarios.

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confidence: 99%

A critical overview of pan evaporation trends over the last 50 years

Charles

2009

Climatic Change

122

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“…In contrast, pan evaporation data are easily accessible. Therefore many studies have tried to recruit pan evaporation data to estimate evapotranspiration (Grismer et al 2002, Snyder et al 2005, Abdel-Wahed et al 2008, Xing et al 2008, Trajkovic 2009, Liang et al 2011). Raghuwanshi and Wallender (1998) also noted that more than 50 methods were proposed to estimate reference evapotranspiration based on different assumptions, among which pan evaporation received the most attention when comparing various methods of evapotranspiration estimation.…”

Section: Discussionmentioning

confidence: 99%

Dynamic factor analysis and artificial neural network for estimating pan evaporation at multiple stations in northern Taiwan

Chang¹,

Sun²,

Chung³

2013

Hydrological Sciences Journal

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Evaporation is an important reference for managers of water resources. This study proposes a hybrid model (BD) that combines back-propagation neural networks (BPNN) and dynamic factor analysis (DFA) to simultaneously precisely estimate pan evaporation at multiple meteorological stations in northern Taiwan through incorporating a large number of meteorological data sets into the estimation process. The DFA is first used to extract key meteorological factors that are highly related to pan evaporation and to establish the common trend of pan evaporation among meteorological stations. The BPNN is then trained to estimate pan evaporation with the inputs of the key meteorological factors and evaporation estimates given by the DFA. The BD model successfully inherits the advantages from the DFA and BPNN, and effectively enhances its generalization ability and estimation accuracy. The results demonstrate that the proposed BD model has good reliability and applicability in simultaneously estimating pan evaporation for multiple meteorological stations.

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“…ET rates for vegetated upland areas were presumed to approximate the CIMIS values calculated for grass cover. Evaporation for the sparsely vegetated wetland area was assumed to be 1.28 times that of the grass ET value (Snyder et al, 2005). ET volumes were calculated at 30-min intervals to account for fluctuations in the wetted surface area.…”

Section: Hydrologic Characterizationmentioning

confidence: 99%

Fate of nitrate in seepage from a restored wetland receiving agricultural tailwater

Brauer

Maynard

Dahlgren

et al. 2015

Ecological Engineering

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A B S T R A C TConstructed and restored wetlands are a common practice to filter agricultural runoff, which often contains high levels of pollutants, including nitrate. Seepage waters from wetlands have potential to contaminate groundwater. This study used soil and water monitoring and hydrologic and nitrogen mass balances to document the fate and transport of nitrate in seepage and surface waters from a restored flow-through wetland adjacent to the San Joaquin River, California. A 39% reduction in NO 3 -N concentration was observed between wetland surface water inflows (12.87 AE 6.43 mg L À1 ; mean AE SD) and outflows (7.87 AE 4.69 mg L À1 ). Redox potentials were consistently below the nitrate reduction threshold ($250 mV) at most sites throughout the irrigation season. In the upper 10 cm of the main flowpath, denitrification potential (DNP) for soil incubations significantly increased from 151 to 2437 mg NO 3 -N m À2 d À1 when nitrate was added, but showed no response to carbon additions indicating that denitrification was primarily limited by nitrate. Approximately 72% of the water entering the wetland became deep seepage, water that percolated beyond 1-m depth. The wetland was highly effective at removing nitrate (3866 kg NO 3 -N) with an estimated 75% NO 3 -N removal efficiency calculated from a combined water and nitrate mass balance. The mass balance results were consistent with estimates of NO 3 -N removed (5085 kg NO 3 -N) via denitrification potential. Results indicate that allowing seepage from wetlands does not necessarily pose an appreciable risk for groundwater nitrate contamination and seepage can facilitate greater nitrate removal via denitrification in soil compared to surface water transport alone.

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Simplified Estimation of Reference Evapotranspiration from Pan Evaporation Data in California

Cited by 68 publications

References 5 publications

A critical overview of pan evaporation trends over the last 50 years

A critical overview of pan evaporation trends over the last 50 years

Dynamic factor analysis and artificial neural network for estimating pan evaporation at multiple stations in northern Taiwan

Fate of nitrate in seepage from a restored wetland receiving agricultural tailwater

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