Abstract

An adequate supply of water and nutrients is vital in crop cultivation to conserve water, prevent shortages, minimize production losses, and curb excessive utilization of water resources. This study aimed to estimate the water demand of major irrigated crops using open-access portals, such as satellite and reanalysis datasets within the Koga irrigation scheme. We collected climate data from the local weather station, WaPOR, and ERA5-Land open-source datasets. The Koga Irrigation Development Office provided the field data for the entire irrigation system. The Modified Penman-Monteith equation was employed to compute the reference evapotranspiration. The single-crop coefficient approach was applied to determine crop evapotranspiration (ETC). The result indicated a strong correlation between the measured and predicted values. Additionally, it was also found that the ETC tended to peak during the mid-stage of the crops, and a robust relationship between the measured and estimated values was examined on a monthly scale. The seasonal average water requirements for wheat were 532 mm, 510 mm, and 542 mm, whereas maize had mean values of 603 mm, 589 mm, and 636 mm. Potato water needs averaged 549 mm, 529 mm, and 564 mm, and for tomatoes, the water requirements were 540 mm, 532 mm, and 583mm based on observed, satellite, and model-based estimations, respectively. Remarkably, the maize crop consistently had the highest ETc value across all estimation scenarios, indicating that maize is more susceptible to water stress, has a longer growing season, a large leaf area index when mature, and transpires at a higher rate than wheat, potato, and tomato. According to our research, the model-based estimation was 5.9 to 8.7% and 1.9 to 7.4% higher than the satellite-based estimates and the measured values, respectively. 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.