(1) And the children of Israel, even the whole congregation, came into the wilderness of Zin in the first month; and the people abode in Kadesh; and Miriam died there, and was buried there. (2) And there was no water for the congregation; and they assembled themselves together against Moses and against Aaron. (translation from Sefaria.org)

The congregation had no water--From here [we learn] that for all 40 years they had the well through the merit of Miriam

(6) Ten things were created on the eve of the [first] Sabbath at twilight, And these are they: [1] The mouth of the earth [that swallowed Korach in Numbers 16:32 ], [2] The mouth of the well [that accompanied the Israelites in the Wilderness in Numbers 21:17], [3] The mouth of the donkey [that spoke to Balaam in Numbers 22:28–30 ], [4] The rainbow [that served as a covenant after the Flood in Genesis 9:13 ], [5] The manna [that God provided the Israelites in the Wilderness in Exodus 16:4–21 ], [6] The rod [of Moses], [7] The Shamir [worm that helped build the Temple without metal tools], [8] The letters, [9] The writing, and [10] The tablets [of the Ten Commandments]. And some say: Also the destructive spirits, And the burial place of Moses, our teacher, And the ram of Abraham, our father. And some say: Also the [first human-made] tongs, made with [Divine] tongs. (translation from Sefaria.org)

R. Yosi son of R. Y'hudah objected saying, "Three great leaders stood for Israel and these are them: Moshe, Aharon, and Miriam. Three great gifts were given through them and these are them: the well, the cloud, and the manna. The well-through Miriam's merit, the pillar of cloud-through Aharon's merit, the manna-through Moshe's merit. When Miriam died, the well disappeared as it is said, "Miriam died there..." and it is written after, "There was no water for the congregation" (Num. 20:1-2). It returned through the merit of the [other] two. (my translation)

The well was due to the merit of Miriam, who [because] she said the song upon the waters as it is said, "Miriam chanted for them (Vata'an) 'Song to G!d'" (Ex. 15) and at the waters of the well "Israel sang this song, 'Rise, well! Sing to it (Enu lah)... (Translation from Shira Lenza)

And the well was due to the merit of Miriam. For what does Scripture say? And Miriam died there, and was buried there (Num. 20:1). And what is written after that? And there was no water for the community (Num.20:2)…

How was the well constructed? It was rock-shaped like a kind of bee-hive [or sieve], and wherever they journeyed it rolled along and came with them. When the standards [under which the tribes journeyed] halted and the tabernacle was set up, that same rock would come and settle down in the court of the Tent of Meeting and the princes would come and stand upon it and say, Rise up, O well (Num.21, 17), and it would rise. (Translation from Rachel Adelman)