Irrigation is by far the largest consumer of freshwater worldwide. Thus, effective water management in this sector is crucial to enhancing water productivity (WP). In this study, a physically based agrohydrological model, the Soil Water Atmosphere Plant (SWAP), was used to investigate the WP of the main irrigated crops and water balance in the Furfuro irrigation scheme, Ethiopian Rift Valley. The SWAP model requires meteorological, soil, crop, and water data to simulate soil moisture and crop growth. The meteorological data (1991–2020) was collected from the Ethiopian National Meteorology Agency. The physical properties of the soil were determined in the laboratories. The basic crop data for selected crops was collected from Food and Agricultural Organization (FAO) documents. Field experiments were conducted in the scheme command area in 2022–23 to collect data for the calibration and validation of the SWAP model. The field experiments were conducted on six experimental plots using the main irrigated crops (wheat, onion, and tomato) in the study area. The six experimental plots were categorized into two groups: Researcher plots and Farmer plots. Each group contains three plots, one for each crop type. Crop water requirements and irrigation scheduling were determined for researcher plots based on climatic, crop, and soil data of the area. All irrigation practices (amount and timing of application) and field management for farmer experimental plots were carried out by farmers based on their own experiences. However, the depth of irrigation water was measured during each irrigation at all six experimental plots using a 5.08*90 cm Cutthroat flume. Soil moisture content after each irrigation (for the wheat plot) was determined using the gravimetric method. Crop data such as leaf area, growth stage-based dry matter, and yield were collected from each experimental plot. The SWAP model was then calibrated and validated using soil moisture and crop growth data collected from experimental plots. The water balance components (rainfall, irrigation, transpiration, evaporation, and percolation) of the experimental plots were simulated using the calibrated SWAP model. The WP of the main crops grown in the study area was then determined using the simulated water balance components and measured yield in the experimental plots. The results indicated that the simulated irrigation depth at both researcher and farmer plots accurately represented the field condition. There was no significant difference between the researcher and the farmer plots in the evapotranspiration of the same crop. The percolated depth was 210.9 and 308.5 mm for wheat, 167.1 and 252.6 mm for onion, and 169.8 and 253.9 mm for tomato at the researcher and farmer plots, respectively. The physical and economic WP of researcher plots was greater than that of farmer plots at all water balance components. The physical and economic WP of wheat was lower than that of onion and tomato in both researcher and farmer plots, and tomato demonstrated higher physical and economic WP in both researcher and farmer plots. The findings in this study can provide technical assistance for effective irrigation water management to save irrigation water and enhance WP.