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Open AccessArticle

How Ångström–Prescott Coefficients Alter the Estimation of Agricultural Water Demand in South Korea

1
Department of Agricultural and Biological Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
2
Division of Agro-system Engineering, Institute of Agriculture and Life Science, Gyeongsang National University, Gyeongnam 52828, Korea
3
Department of Rural Construction Engineering, Chonbuk National University, Jeonbuk 54896, Korea
*
Author to whom correspondence should be addressed.
Water 2018, 10(12), 1851; https://doi.org/10.3390/w10121851
Received: 17 November 2018 / Revised: 10 December 2018 / Accepted: 12 December 2018 / Published: 13 December 2018
(This article belongs to the Section Hydrology)
The Food and Agriculture Organization (FAO) Penman–Monteith equation, recognized as the standard method for the estimation of reference crop evapotranspiration ( ET 0 ), requires many meteorological inputs. The Ångström–Prescott (A-P) formula containing parameters (i.e., a and b) is recommended to determine global solar radiation, one of the essential meteorological inputs, but may result in a considerable difference in ET 0 estimation. This study explored the effects of A-P coefficients not only on the estimation of ET 0 , but also on the irrigation water requirement (IWR) and design water requirement (DWR) for paddy rice cultivation, which is the largest consumer of agricultural water in South Korea. We compared and analyzed the estimates of ET 0 , IWR, and DWR using the recommended (a = 0.25 and b = 0.5) and locally calibrated A-P coefficients in 16 locations of South Korea. The estimation of ET 0 using the recommended A-P coefficients produced significant overestimation. The overestimation ranged from 3.8% to 14.0% across the 16 locations as compared to the estimates using the locally calibrated A-P coefficients, and the average overestimation was 10.0%. The overestimation of ET 0 corresponded to a variation of 1.7% to 7.2% in the overestimation of the mean annual IWR, and the average overestimation of the IWR was 5.1%. On average, the overestimation was slightly reduced to 4.8% in DWR estimation, since the effect of A-P coefficients on the IWR estimation decreased as the IWR increased. This study demonstrates how the use of A-P coefficients can alter the estimation of ET 0 , IWR, and DWR in South Korea, which underscores the importance of their proper consideration in agricultural water management. View Full-Text
Keywords: design water requirement; irrigation water requirement; paddy irrigation; Penman–Monteith equation; reference crop evapotranspiration design water requirement; irrigation water requirement; paddy irrigation; Penman–Monteith equation; reference crop evapotranspiration
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Jeong, H.; Bhattarai, R.; Hwang, S.; Son, J.-G.; Jang, T. How Ångström–Prescott Coefficients Alter the Estimation of Agricultural Water Demand in South Korea. Water 2018, 10, 1851.

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