One of the requirements for a mikveh is that a body of water may not be artificially redirected or rechanneled. Does that mean, for example, that an entire river downstream of a dam, either for preventing floods, generating hydroelectric power, or asserting water rights, is invalid for use as a mikveh?

  • Please cite that this is one of the requirements – Double AA May 31 '16 at 1:04
  • This is a very interesting issue in way to learn what the possible artificial things are, what is a river, what is a mikveh. Who need spring water and who need mikveh. What is the status of rivers. BTW you certainly know that mikvaot in Jewish community are built. – kouty May 31 '16 at 4:16
  • Downstream means in the direction the water is flowing. Upstream means toward the source of the river. So no, a dam would affect all the water which flows through it, so the river downstream could be invalidated, since a dam no longer makes the river a natural mikveh. Right? – eternalsquire May 31 '16 at 4:40
  • Let's take Hoover Dam, for instance. The Feds can completely shut off the water any time they want to. However, this has never really been done. But since it could, the dam is still a constructed object, a vessel and therefore is not a valid mikveh. Since most rivers in the US are dammed for various purposes, that basically means a great many Jewish people are SOL as far as the access to mikveh outside an established community. – eternalsquire May 31 '16 at 4:49
  • "But since it could, the dam is still a constructed object, a vessel and therefore is not a valid mikveh." How do you know this? – Double AA May 31 '16 at 18:26

From a Rabbi Jachter article here:

[T]he Halacha provides for a number of ways to remedy the Mayim Sheuvim status of water that had been in a receptacle. One way is the process of Hamshacha, running the Mayim Sheuvim along the ground. The Gemara (Temura 12a) cites a Braita that teaches that if the Mikva has a base of more than twenty Saah of rainwater that went directly into the Mikva, then one may obtain the rest of the forty Saah by taking Mayim Sheuvim and running it along the ground on its way into the Mikva. The Rambam (Hilchot Mikvaot 4:8) and Shulchan Aruch (Y.D. 201:44) codify this Braita as normative Halacha. For a conceptual analysis of the process of Hamshacha, see Rav Yitzchak Zeev Soloveitchik in his commentary to Temurah 12b. We should note that the Radbaz (Teshuvot 1:85) writes that this process is acceptable only Bdiaved (post facto) and should not be relied upon Lechatchilah (initially). Rav Moshe Feinstein (Teshuvot Igrot Moshe Y.D.3:64:3) and Rav Yonatan Shteif (Teshuvot Mahari Shteif 142) rule in accordance with the Radbaz.

There are a number of major disputes that pertain to the process of Hamshacha. One debate is the status of a Mikva that is created entirely through the process of Hamshacha. The Rambam (Hilchot Mikvaot 4:9) cites an anonymous “few sages from the West” who believe that a Mikva is acceptable even on a Rabbinic al level even if the entire Mikva was created through the process of Hamshachah. Some argue that the Rif and Rashi subscribe to this view. The Rambam strongly rejects this view. The Chazon Ish (Y.D.130:14) writes that he believes that the Raavad believes that a Mikva is disqualified on a Torah level if all of its water entered via Hamshacha. Tosafot (ibid.) suggest an intermediate position that a Mikva whose water entirely consists of Mayim Sheuvim revitalized through Hamshacha is only disqualified on a Rabbinic level. Many (but not all) later authorities adopted this approach. These authorities include Teshuvot Tashbeitz (3:12), Teshuvot Maharit (Y.D.2:17), Teshuvot Divrei Chaim (introduction to Hilchot Mikvaot, number 5), Yeshuot Yaakov (201:15), and Chazon Ish (Y.D. 126:1 and 130:14).

Thus, it would appear that Hamshacha would not apply in a situation where the river water became She'uvim through being dammed.

  • Does that mean the water downstream of the dam is invalid? – eternalsquire May 31 '16 at 4:46
  • Yes. 15 characters. – ephraim helfgot Jun 1 '16 at 23:57
  • Please edit the answer to indicate this. – eternalsquire Jun 3 '16 at 15:36

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