Amud 77a

תוס' ד"ה דאגר

He hired workers to irrigate, and rain came; it is the workers’ loss - דאגר אגורי לדוולא ואתא מטרא פסידא דפועלים

Summary:
Regarding irrigation and rain; the workers receive only according to their work; while אריסים receive whatever was negotiated.

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תוס' ד"ה ואתא

And rain fell at night; it is the workers’ loss - ואתא מיטרא בלילה פסידא דפועלים

Summary:
Rain can render irrigation unnecessary more than it can make plowing impossible. We therefore need both rulings of רבא. There are two views whether the פסידא דפועלים by דוולא is only if סיירא or even if לא סיירא.

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תוס' ד"ה ופסק

And the river dried up at noon - ופסק נהרא בפלגא דיומא

Summary:
Rivers tend to dry up during midday if it is used for irrigation.

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תוס' ד"ה עביד

If it usually dries up it is the owner’s loss - עביד דפסיק פסידא דבעל הבית

Summary:
Fields with irrigation canals indicate that they expect the river to overflow (but will not necessarily irrigate all the fields). The entire city is aware when the river dries up.

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תוס' ד"ה יד

The worker has the upper hand - יד פועל על העליונה

Summary:
יד פועל על העליונה here means that the יד פועל is not על התחתונה (as ר"ד maintains).

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