Satellite and Model-based Estimation of Crop Water Requirement of Major Irrigated Crops in the Koga Irrigation Scheme, Ethiopia

Alebachew Tiruye1

Pakorn Ditthakit1,Email

Quoc Bao Pham2

Warit Wipulanusat3

Uruya Weesakul4

Suthira Thongkao5

Nand Lal Kushwaha6

1Center of Excellence in Sustainable Disaster Management, School of Engineering and Technology, Walailak University, Nakhon Si Thammarat 80161, Thailand. 
2Faculty of Natural Sciences, Institute of Earth Sciences, University of Silesia in Katowice, Będzińska Street 60, 41-200, Sosnowiec, Poland.
3Department of Civil Engineering, Thammasat University Research Unit in Data Science and Digital Transformation, Thammasat School of Engineering, Thammasat University, Pathumthani 12120, Thailand.
4Thammasat University Research Unit in Climate Change and Sustainability, Department of Civil Engineering, Faculty of Engineering, Thammasat School of Engineering, Thammasat University, Pathumthani 12120, Thailand.
5School of Languages and General Education, Walailak University, 222, Thaiburi, Thasala, Nakhon Si Thammarat 80160, Thailand.
6Division of Agricultural Engineering, ICAR-Indian Agricultural Research Institute, New Delhi, 110012, India.

Abstract

An adequate supply of water and nutrients is vital in crop cultivation to conserve water, prevent water shortages, minimize production losses, and curb the excessive utilization of water resources. This study aimed to estimate the water demand of major irrigated crops using open-access portals and reanalysis datasets within the Koga irrigation scheme. Climate data were obtained from the local weather station, water productivity through open-access remotely sensed derived data (WaPOR), and ERA5-Land datasets, while field information was obtained from the Koga Irrigation Development Office. The Penman-Monteith equation was applied to compute the reference evapotranspiration. A single-crop coefficient approach was used to determine the crop factor (kc). The water requirements for wheat, maize, potato, and tomato were then calculated. A strong correlation between measured and predicted values was observed in the time series analysis. Monthly crop evapotranspiration peaked during mid-growth stages, and a robust relationship between measured and estimated values was found at monthly scales. The seasonal average water requirements for wheat were 532, 510, and 542 mm, respectively, whereas maize had mean values of 603, 589, and 636 mm, respectively. Potato water needs averaged 549, 529, and 564 mm, and for tomatoes, the water requirements were 540, 532, and 583 mm, based on observed, satellite, and model-based estimations, respectively. Remarkably, the highest crop evapotranspiration (ETc) value was consistently obtained for maize crops for all estimation scenarios, suggesting that it has physiological traits that enable efficient water use, but also results in higher overall water consumption due to its rapid growth and large biomass in comparison to wheat, potato, and tomato. Our findings indicated that the model-based estimates exceeded the satellite-based estimates by 5.9 to 8.7% and surpassed the measured values by 1.9 to 7.4%. In conclusion, our research highlights the importance of utilizing satellite and model-based data to calculate crop evapotranspiration in irrigation schemes and benefits decision-makers, water managers, agronomists, stakeholders, and irrigation operators.

Satellite and Model-based Estimation of Crop Water Requirement of Major Irrigated Crops in the Koga Irrigation Scheme, Ethiopia