I'm unclear about the methods of irrigation described in the mishna. Specifically , Rebbi Yehuda , who the gemora says is the tanna of the mishna , allows one to water a bais hashalchin from a spring but not to divert water from a spring. What is the difference , and how is the irrigation effected ? Does one use a waterwheel a bucket or dig a trench to the field?
The Mishnah permits irrigating a field by opening the dike at the inlet of the waterway that leads from the spring. The springwater then enters the waterway and and waters the field. There is no need for the person to lift up water at all (if he has to lift up water, it is considered to be like the water of a cistern and is Asur).
In contrast, it is prohibited to re-direct ("l'Fanos") the waterway, by stopping-up the passageway in one area in order for the water to go up the banks of the waterway and run to another area (where there is not yet a waterway constructed). Some explain that "l'Fanos" means to clean out a waterway that become clogged.
Mordecai