(Mishnah): One may water an irrigated field on Chol HaMoed and in the year of Sheviis, both from a new and an old spring (due the financial loss involved if he refrains from watering)...

But one may not water from collected rainwater or from underground water pits.

One may not make Ugiyos (water collection gullies) around vines.

(Gemara): It is understandable that one may water from an old spring, but does it not involve excessive labor to water from a new spring?

The Mishnah follows R. Meir who said that one may even water a rain-watered field from a new spring.

R. Yosi: The Mishnah follows all opinions - the case is when there was originally one spring and it now became two. Alternatively, the spring originally flowed in a trickle and it now gushed.

Support (Beraisa): R. Meir - One may even water a rain-watered field from a new spring.

Chachamim: One may only water with it an irrigated field that formerly had a spring that was destroyed.

According to R. Meir, one can use this spring to water a rain-watered field (in which there is no financial loss if it would not be watered) and only if it does not involve toil.

According to Rabbanan, one can only use this spring in a case of financial loss, and only if it does not involve toil.

Question: What do the Rabbanan rule in a situation of financial loss that involves toil?

Answer - Beraisa: Any case of loss is considered an irrigated field. If it stopped losing value (when without water), it is considered a case of a rain-watered field where there is a dispute between R. Meir and Rabbanan.

Question: If he refrained from watering it for two or three days beforehand, can it now be considered like an irrigated field and permitted to water on Chol Hamoed?

Answer from here: There was a ditch that was full of water that dried up three days before the festival and then became refilled on Chol Hamoed.

Rav Chuna ruled that those seeds that will depreciate should be watered and those that will not, should not be watered.

R. Yona and R. Yosi permitted the people of Mikras Detziliya to harvest their barley on Chol Hamoed in order to prevent the barley from swelling and becoming ruined.