Reliable estimates of irrigation water requirements are essential for agricultural water planning in the Senegalese part of the Senegal River Basin, where rainfall variability, high evaporative demand and agricultural intensification place increasing pressure on water resources. This study evaluated AgERA5 and NASA POWER for estimating reference evapotranspiration and quantifying gross irrigation water requirements for rice with 115-day, 125-day and 150-day cycles, onion and tomato over the 1984-2025 period. Reference evapotranspiration was calculated using the FAO-56 Penman-Monteith method, and product performance was evaluated against eight ground stations located in open environments or within irrigated schemes. Both products reproduced monthly reference evapotranspiration satisfactorily at the open synoptic stations, with AgERA5 providing the estimates closest to the observations. NASA POWER showed larger deviations during the hot dry season. Overestimation was more pronounced at stations located within irrigated schemes, particularly during the dry seasons, highlighting differences in spatial representativeness between local irrigated conditions and gridded climate data. Gross irrigation water requirements ranged from 7158 m3·ha？1 for 115-day rice in Upper Ferlo during the rainy season with NASA POWER to 22,269 m3·ha？1 for 150-day rice in the Middle Senegal Valley during the hot dry season with the same product. The effect of sowing date also varied according to crop cycle and climate product. The difference between the least and most water-demanding sowing dates ranged from 905 m3·ha？1 for 115-day rice during the hot dry season with AgERA5 to 3672 m3·ha？1 for 150-day rice during the same season with NASA POWER. Early-season sowings required less water for rainy-season rice and for onion and tomato during the cool dry season. Across all crops, seasons and management units, the mean absolute difference between AgERA5 and NASA POWER was approximately 997 m3·ha？1. During the rainy season, both products identified the Middle Senegal Valley as having the highest requirements and Upper Ferlo as having the lowest, whereas their spatial rankings differed more during the dry seasons. Sobol analysis showed that ET0 was most sensitive to wind speed during the dry seasons and to relative humidity during the rainy season. These findings demonstrate that AgERA5 and NASA POWER can
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