If as stated in this article in these regions during menstruation:
1) The woman uses dirt, sand, ash and rags which are never sterilized but just reused month after month.
2) 70% of all pregnancy related medical issues can be tied back to this lack of hygene
Then its not unreasonable to say that the women are unclean in this period and should not have contact with the village water supply... its actually good sense.
