Καλησπέρα,
Νομίζω ότι στη σελίδα που δίνεις δεν γίνεται αντιστοίχηση των δυο γιορτών. Αναφέρεται απλώς ότι την 13η Οκτωβρίου άρχιζαν τα Fontinalia, και η ίδια αυτή μέρα ήταν η τρίτη μέρα των Θεσμοφορίων. Την πρώτη μέρα της γιορτής, λοιπόν, το 54 μ.Χ. πέθανε ο Κλαύδιος και ανέλαβε την εξουσία ο Νέρωνας.
Όπως είπε και ο Μπιλ, δεν υπάρχει καμία άλλη σχέση μεταξύ των δύο γιορτών πέρα από το ότι συμπίπτουν περίπου χρονικά. Δίνω και μερικές ακόμη πληροφορίες από το Oxford Classical Dictionary:
s. festivals
....Periodic fertility rituals, many going back to the neolithic period, were often performed by women, often in secret. Some were genuine mysteries (as at Eleusis).
Those centred on agriculture naturally occurred at critical time in the farming cycle, e.g. at ploughing (Proerosia),
at seeding (Thesmophoria), and at harvest (Anthesteria), with rituals appropriate to the deity and crop in question.
s. Fontinalia
Roman festival on 13 October to Fons, god of springs (Varro, Ling. 6.22), outside the porta Fontinalis, perhaps a shrine dedicated by C. Papirius Maso (consul 231 BC). Fontus is dubious; some made Janus father of Fons by Juturna: Arn. Adv. Nat. 3.29.
s. Thesmophoria
a women’s festival in honour of Demeter, common to all Greeks, celebrated in the autumn, before the time of sowing. Men were excluded and the women camped out, sometimes at a little distance from the town, for three days. At Athens, the first day was the ἄνοδος, the second νηστεία, the third καλλιγένεια, referring to a goddess of Fair Birth. Pigs were thrown into pits or caves, such as have been found at some Demeter shrines. The putrified remains brought up by ἀντλήτριαι and placed on altars of Demeter and Kore, ensured a good harvest when mixed with the seed corn. The festival included obscenity and a sacrifice. Otherwise, the secrets of the Thesmophoria have been well kept, as Aristophanes’ uninformative play shows.
Όσο για τον Κρηνέα, δεν νομίζω ότι υπάρχει. Νομίζω οτι γίνεται αναφορά στις κρηναίες νύμφες (πβ. νύμφαι κρηναῖαι του Ομήρου).
Βλ. π.χ.
https://en.wikipedia.org/wiki/Nymph, εκεί όπου αναφέρονται οι water nymphs.