Moed Katan 1:2-3

Moed Katan 1:2

Rabbi Elazar ben Azariah says that one may not dig a conduit for water on chol hamoed or during the Sabbatical year. The Sages say that a new conduit may be dug during the Sabbatical year and a damaged conduit may be repaired on chol hamoed. Similarly, they may repair and clean water pipes that are in the public domain, as well as repair roads, public squares and reservoirs, and perform all public needs. They may likewise mark the locations of graves and send out agents to ensure that mixed species have been uprooted.

Moed Katan 1:3

Rabbi Eliezer ben Yaakov says that one may draw excess water from one tree to another so long as he does not water the entire field. Plants that were not watered before chol hamoed may not be watered on chol hamoed but the Sages permit it in both of these cases.