Accurately estimating how much water plants need is crucial for planning irrigation projects. In Melkassa, Ethiopia, researchers used five different methods to calculate how much water plants in the area need. They looked at factors like temperature, sunlight, humidity, wind, and solar radiation. The Thornthwaite method overestimated water needs, while the Blaney-Criddle method underestimated them. The Modified Penman method, which considers both energy and aerodynamic factors, provided a good estimate. The Radiation method also performed well when wind speed and humidity data were available.