Five methods of computing reference evapotranspiration from a reference crop (Penman, radiation, Blaney-Criddle, Hargreaves and pan evaporation) have been studied for their applicability under different climatic conditions. The Penman method was taken as the standard and the other four methods were compared against this method. Good correlation was obtained between the values estimated by the four methods and the Penman method although differences in magnitude were found. Regression equations were developed to correct those differences in magnitude. The method suitable for the estimation of reference evapotranspiration for each climatic condition is also suggested. © 1991 Taylor and Francis Group, LLC.

S. Mohan

Department Of Civil Engineering

BLANEY-CRIDDLE METHOD

evapotranspiration

HARGREAVES METHOD

Pan evaporation

PENMAN METHOD

Radiation

Fulltext

IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

IIT Madras has been ranked as the top engineering institute in India for four years in a row by the National Institutional Ranking Framework of the MHRD

It currently offers undergraduate, postgraduate and research degrees across 16 disciplines in Engineering, Sciences, Humanities and Management. About 596 faculty belonging to science and engineering departments and centres of the Institute are engaged in teaching, research and industrial consultancy.

IIT Madras

Intercomparison of evapotranspiration estimates

Hydrological Sciences Journal

Evapotranspiration (ET) is an important parameter needed by water managers for the design, operation and management of irrigation systems. Since there are many methods to compute ET, based on climatic data, an inexperienced engineer or hydrologist is perplexed with the selection of an appropriate method. In this context, an expert system (ES) would be of great use to aid in selection of a suitable ET estimation method, given the location, data availability and climatic conditions. In this paper an intelligent front-end expert system (ETES), that has been developed to select suitable ET estimation methods under South Indian climatic conditions, is presented. Ten meteorological stations located in different climatic regions and thirteen ET estimation methods have been considered in this ES. Like a human consultant, the system asks the user for detailed information regarding the details of the project site such as location, season, climatic zone, and data availability. It then makes a recommendation based on this information and the system's own knowledge of such a situation. Along with the recommended method, ETES will also suggest suitable correction factors for converting the resulting ET values to those of methods that result in accurate estimation. The developed ES would be of much potential use in irrigation management in developing countries like India. © 1995.

Computers and Electronics in Agriculture

An intelligent front-end for selecting evapotranspiration estimation methods

Meteorological and lysimetric data for a period of nine years were used to develop crop coefficients for rice grown under lowland conditions in a sub-humid tropical climate in India. The estimated crop coefficients were found to be higher than those values recommended by FAO. A crop coefficient model with basal coefficient, moisture availability coefficient and surface wetness coefficient terms has been proposed and found suitable. On most counts, the moisture availability coefficient was found to be near unity and the wetness coefficient was found to be significant. The basal crop coefficients for lowland rice have also been presented for practical use with the proposed models. © 1994 Kluwer Academic Publishers.

Irrigation and Drainage Systems

Irrigation crop coefficients for lowland rice

Crop coefficients (Kc) were estimated for cotton, sorghum and millet for tropical South India based on lysimeter measured actual evapotranspiration (ET) and reference crop ET computed by the modified Penman method. The estimated crop coefficients were 0.46, 0.70, 1.01, and 0.39 in the four crop stages for cotton. Kc value of the last stage was significantly lower than the FAO Kc value. The estimated Kc values were considerably lower than FAO crop coefficients in the third and fourth stages for sorghum, for which the estimated stagewise Kc values were 0.42, 0.71, 0.62 and 0.23. For millet, the estimated Kc values for four stages were 0.51, 0.78, 0.87 and 0.50 and found to differ markedly from FAO Kc values. Crop coefficient relationships with respect to time were developed using mean crop coefficients derived from multi-year data. The developed crop coefficients and relationships would be of great use for the estimation of crop water requirements under tropical climatic conditions. © 1994.

Agricultural Water Management

Crop coefficients of major crops in South India

CIGR Handbook of Agricultural Engineering Volume I Land and Water Engineeering

CIGR Handbook of Agricultural Engineering, Volume I Land and Water Engineering, Chapter 5 Irrigation and Drainage, Part 5.1 Crop Water Requirements

Journal of Irrigation and Drainage Engineering

Hourly ET Model Calibration with Eddy Flux and Energy Balance Data

Soils in granitic alluvium in humid and semiarid climates along Rock Creek, Carbon County, Montana

Applied Engineering in Agriculture

Reference Crop Evapotranspiration from Temperature

Erratum: “Application of Penman Equation Wind Function” by Richard H. Cuenca and Martin T. Nicholson (March, 1982)

Intercomparison of evapotranspiration estimates [La comparaison des estimations de l’évapotranspiration]

Journal	Hydrological Sciences Journal
ISSN	02626667
Open Access	Yes