Climate-induced historical drift of reference evapotranspiration in Mymensingh region of Bangladesh

Reference crop evapotranspiration (ETo) is essential for planning and management of irrigation to ensure optimum utilization of a region’s available water resources. ETo being an indicator of atmospheric evaporative demand provides a measure of the integrated effect of climatic parameters like solar radiation, wind, temperature and humidity. Variation of these climatic parameters over long period of time alters ETo. The modified ETo is crucial for periodic adjustment of irrigation planning and management. This study evaluated variation of ETo and contribution of the climatic parameters to ETo-variation in Mymensingh region of Bangladesh by analyzing climatic data of 28 years (1990–2017). ETo was determined by FAO Penman-Monteith method and trends of ETo and its governing climatic parameters were evaluated by MAKESENS trend model. The ETo-governing climatic parameters revealed contrasting trends, which also varied in different months of the year. Net radiation and wind speed showed decreasing trend, while temperature and saturation vapor pressure deficit showed increasing trend. In spite of contrasting contributions of the climatic parameters, their combined effect reduced ETo with a resulting decreasing trend of the monthly average daily ETo over the months of the year except July. These results enhance our understanding of the effects of climate change on ETo and can help correct-planning of water resources for irrigated agriculture. J. Bangladesh Agril. Univ. 17(2): 258–264, June 2019

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Time series analysis of reference crop evapotranspiration for Bokaro District, Jharkhand, India

Journal of Water and Land Development ◽

10.1515/jwld-2016-0021 ◽

2016 ◽

Vol 30 (1) ◽

pp. 51-56 ◽

Cited By ~ 2

Author(s):

Ratnesh Gautam ◽

Anand K. Sinha

Keyword(s):

Water Resources ◽

Water Resources Management ◽

Moving Average ◽

Arima Model ◽

Likelihood Method ◽

Data Series ◽

Crop Evapotranspiration ◽

Reference Crop Evapotranspiration ◽

Resources Management ◽

Reference Crop

AbstractEvapotranspiration is the one of the major role playing element in water cycle. More accurate measurement and forecasting of Evapotranspiration would enable more efficient water resources management. This study, is therefore, particularly focused on evapotranspiration modelling and forecasting, since forecasting would provide better information for optimal water resources management. There are numerous techniques of evapotranspiration forecasting that include autoregressive (AR) and moving average (MA), autoregressive moving average (ARMA), autoregressive integrated moving average (ARIMA), Thomas Feiring, etc. Out of these models ARIMA model has been found to be more suitable for analysis and forecasting of hydrological events. Therefore, in this study ARIMA models have been used for forecasting of mean monthly reference crop evapotranspiration by stochastic analysis. The data series of 102 years i.e. 1224 months of Bokaro District were used for analysis and forecasting. Different order of ARIMA model was selected on the basis of autocorrelation function (ACF) and partial autocorrelation (PACF) of data series. Maximum likelihood method was used for determining the parameters of the models. To see the statistical parameter of model, best fitted model is ARIMA (0, 1, 4) (0, 1, 1)12.

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High-resolution global grids of revised Priestley–Taylor and Hargreaves–Samani coefficients for assessing ASCE-standardized reference crop evapotranspiration and solar radiation

Earth System Science Data ◽

10.5194/essd-9-615-2017 ◽

2017 ◽

Vol 9 (2) ◽

pp. 615-638 ◽

Cited By ~ 14

Author(s):

Vassilis G. Aschonitis ◽

Dimitris Papamichail ◽

Kleoniki Demertzi ◽

Nicolo Colombani ◽

Micol Mastrocicco ◽

...

Keyword(s):

Solar Radiation ◽

Climatic Data ◽

Climatic Zones ◽

Reference Crop Evapotranspiration ◽

Weighted Averages ◽

The Usa ◽

Validation Procedure ◽

The Mean ◽

American Society ◽

Reference Crop

Abstract. The objective of the study is to provide global grids (0.5°) of revised annual coefficients for the Priestley–Taylor (P-T) and Hargreaves–Samani (H-S) evapotranspiration methods after calibration based on the ASCE (American Society of Civil Engineers)-standardized Penman–Monteith method (the ASCE method includes two reference crops: short-clipped grass and tall alfalfa). The analysis also includes the development of a global grid of revised annual coefficients for solar radiation (Rs) estimations using the respective Rs formula of H-S. The analysis was based on global gridded climatic data of the period 1950–2000. The method for deriving annual coefficients of the P-T and H-S methods was based on partial weighted averages (PWAs) of their mean monthly values. This method estimates the annual values considering the amplitude of the parameter under investigation (ETo and Rs) giving more weight to the monthly coefficients of the months with higher ETo values (or Rs values for the case of the H-S radiation formula). The method also eliminates the effect of unreasonably high or low monthly coefficients that may occur during periods where ETo and Rs fall below a specific threshold. The new coefficients were validated based on data from 140 stations located in various climatic zones of the USA and Australia with expanded observations up to 2016. The validation procedure for ETo estimations of the short reference crop showed that the P-T and H-S methods with the new revised coefficients outperformed the standard methods reducing the estimated root mean square error (RMSE) in ETo values by 40 and 25 %, respectively. The estimations of Rs using the H-S formula with revised coefficients reduced the RMSE by 28 % in comparison to the standard H-S formula. Finally, a raster database was built consisting of (a) global maps for the mean monthly ETo values estimated by ASCE-standardized method for both reference crops, (b) global maps for the revised annual coefficients of the P-T and H-S evapotranspiration methods for both reference crops and a global map for the revised annual coefficient of the H-S radiation formula and (c) global maps that indicate the optimum locations for using the standard P-T and H-S methods and their possible annual errors based on reference values. The database can support estimations of ETo and solar radiation for locations where climatic data are limited and it can support studies which require such estimations on larger scales (e.g. country, continent, world). The datasets produced in this study are archived in the PANGAEA database (https://doi.org/10.1594/PANGAEA.868808) and in the ESRN database (http://www.esrn-database.org or http://esrn-database.weebly.com).

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High resolution global grids of revised Priestley-Taylor and Hargreaves-Samani coefficients for assessing ASCE-standardized reference crop evapotranspiration and solar radiation

10.5194/essd-2016-59 ◽

2016 ◽

Author(s):

Vassilis G. Aschonitis ◽

Dimitris Papamichail ◽

Kleoniki Demertzi ◽

Nicolo Colombani ◽

Micol Mastrocicco ◽

...

Keyword(s):

High Resolution ◽

Solar Radiation ◽

Climatic Data ◽

Climatic Zones ◽

Reference Crop Evapotranspiration ◽

Weighted Averages ◽

Validation Procedure ◽

The Given ◽

Reference Crop ◽

Statistical Criteria

Abstract. The objective of the study is to provide high resolution global grids of revised annual coefficients for the Priestley-Taylor (P-T) and Hargreaves-Samani (H-S) evapotranspiration methods after calibration based on ASCE-standardized Penman-Monteith method (ASCE method includes two reference crops: short clipped grass and tall alfalfa). The analysis also includes the derivation of global grids of revised annual coefficients for solar radiation Rs estimations using the respective Rs formula of H-S. The analysis was based on global gridded climatic data of the period 1950–2000. The method for deriving annual coefficients of P-T and H-S methods was based on partial weighted averages (p.w.a.) of their mean monthly values, which eliminate the effect of monthly coefficients that occur during periods where ETo and Rs fall below a specific threshold. Five resolution global grids (30 arc-sec, 2.5, 5, 10 arc-min and 0.5 deg) of annual coefficients for each method were developed. The new coefficients were validated based on data from 140 stations located at various climatic zones of USA and Australia with expanded observations up to 2016. Nine statistical criteria including Taylor diagrams were used in the validation procedure. The validation procedure for ETo estimations of short reference crop showed that the P-T and H-S methods with the new revised coefficients outperformed in comparison to the typical methods reducing the ETo RMSE of estimated values by 39 % and 36 %, respectively. The estimations of Rs using the H-S formula with revised coefficients reduced the RMSE by 30% in comparison to the typical H-S radiation formula (the given results are based on the finer resolution grid). All the statistical criteria indicated better performance of the revised coefficients of all resolutions versus the typical coefficients used in the original methods. Finally, a raster database was built consisting of: a) global maps of revised annual coefficients for the ETo methods of P-T and H-S for both reference crops and the Rs H-S formula, b) global maps which indicate the optimum locations for using the original P-T and H-S methods and their expected error based on reference values. The provision of the database aims to improve ETo and Rs estimations which are used in hydrologic/climatic applications when climatic data are limited. The datasets produced in this study are archived in PANGAEA database (doi:10.1594/PANGAEA.868808, doi:10.1594/PANGAEA.868808) and in ESRN-database (http://www.esrn-database.org or http://esrn-database.weebly.com/).

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Reference crop evapotranspiration database in Spain (1961–2014)

10.5194/essd-2019-64 ◽

2019 ◽

Author(s):

Miquel Tomas-Burguera ◽

Sergio M. Vicente-Serrano ◽

Santiago Beguería ◽

Fergus Reig ◽

Borja Latorre

Keyword(s):

Spatial Interpolation ◽

Climate Models ◽

Drought Indices ◽

Watershed Scale ◽

Climate Variables ◽

Evaporative Demand ◽

Reference Crop Evapotranspiration ◽

Climate Studies ◽

Reference Crop ◽

Water Science & Technology ◽

10.2166/wst.1985.0187 ◽

1985 ◽

Vol 17 (6-7) ◽

pp. 879-890 ◽

Cited By ~ 1

Author(s):

Edwin E. Herricks

Keyword(s):

Water Quality ◽

Water Resources ◽

Environmental Quality ◽

Habitat Management ◽

Aquatic Habitat ◽

Water Quality Criteria ◽

Water Resources Planning ◽

High Quality ◽

Planning And Management ◽

Resources Planning

With increased emphasis on environmental quality objectives in water resources planning and management, past practices of simply considering water quality as the only environmental quality objective are inappropriate. Expanded environmental quality objectives include maintenance of high quality aquatic habitat. Water resource systems must provide both physical and chemical conditions appropriate for the propagation and maintenance of healthy diverse aquatic communities. Managing water resources to provide high quality habitat involves planning to meet both water quality and water quantity objectives. Existing technology based water quality controls and stream based water quality criteria can now be supplemented by aquatic habitat management. An approach to aquatic habitat management is illustrated by use of the Incremental Methodology developed by the U. S. Fish and Wildlife Service. The Incremental Methodology uses measures of aquatic habitat to assess instream flows required for by aquatic life. Thus the range of environmental quality objectives in resources planning and management is expanded by application of these methods to include aquatic habitat as well as water quality management. Methods used to determine instream flow needs for rivers in Illinois are reviewed, and the use of this information in developing regulations limiting water extraction for off stream use are described. Aquatic habitat based management is shown to provide workable methods to meet expanded environmental quality objectives in water resources planning and management.

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