One argument put forth by some for a northern Silwan/City of David location for the Temple is the location of the Gihon spring. This is based not on any explicit statement that the Temple was built above or by the Gihon. Rather it is based on allegorical interpretation conflating the eschatological River of Life following from the Temple with the Gihon Spring.
First, it is important to note that the Gihon is never explicitly connected with the Temple in any way. It is likely that the Gihon is not the original Jebusite name of the spring (unless one assumes the Jebusites had parallel oral traditions to those of the Israelites about the names of the Rivers of Paradise). Rather, the Israelites probably renamed the spring Gihon after their conquest of the city, based on one of the four Rivers of Paradise described in Gen 2:13. (Likewise, the traditional Arab name of the spring is ʿAyn Sittī Maryam = “The Spring of Lady Mary”; the Israelis renamed it with the old biblical name when they gained power in Jerusalem.) At any rate, the only explicit ritual context that mentions the Gihon is the crowning of Solomon (1 Kgs 1), before the Temple had been built. (The other two major references to the Gihon—Hezekiah in 2 Chr 32:30, and Manasseh in 2 Chr 33:14—are about military engineering to supply the city with water.) In 1 Kgs 1:28-53 we read that David, on his death bed, ordered his prophets, priests and ministers to crown Solomon king before he died in order to thwart an attempted coup of Adonijah. They were commanded to “go down to Gihon” (1:33) and crown Solomon there. Zadok, the High Priest “took the horn of oil from the Tent (ʾohel) and anointed Solomon” (1:39). This is presumably the Tabernacle, or, more likely, a restoration of the Mosaic Tabernacle. Remembering from the discussion in our previous section that David had placed the Ark in “the Tent (ʾohel) that David had pitched for it” (2 Sam 6:17) in the “City of David” within the walls of old Jebusite Jerusalem, the most obvious interpretation here is that Zadok took the horn of oil from the restored Tabernacle/Tent in the City of David on the Silwan ridge and “went down to Gihon” to anoint Solomon. In other words, the supposed cosmic relationship between the Gihon spring and the Temple was, in reality, established as a relationship between the restored Davidic Tabernacle in the City of David, which was set up directly above the Gihon spring, which was probably renamed Gihon at the time to reemphasize the cosmological relationship between Eden and the Tabernacle. Remember, too, as discussed in the previous section, that Solomon did not build the Temple where David had pitched the Tent for the Ark, since “Solomon gathered the people together ‘to bring up (haʿălôt) the Ark of YHWH’s covenant from Zion, which is the city of David’ to Solomon’s new Temple (1 Kgs 8:1), after which ‘the priests took the Ark, and they brought up (yaʿălû) the Ark of YHWH’ to the Temple (1 Kgs 8:3-4).” Thus Solomon’s Temple was not built in the City of David, but in a place higher (meaning further north up the ridge) than the City of David. The cosmological relationship, however, had been established earlier between David’s Tent in the City of David and the Gihon.
There are also a number of eschatological passages in the Bible that speak of the River of Life flowing from the Temple to restore the world. The most important passages in this regard are Ezek 47.1-12, Zech 14.8, and Rev 22.1. Ezekiel describes the water flowing from the threshold of the Temple, past the altar (47:1-6). Zechariah describes half the waters flowing west (14:8). Revelation describes the waters flowing from the Throne of God (22:1). Of course none of these can be equated literally with the waters of the Gihon since even if the Temple had been built on the Silwan ridge directly above the Gihon, the waters would still not be flowing from within the Temple itself, but from a spring near the base of the ridge. Thus insisting that the Temple must have been literally over the Gihon ignores the evidence of the relationship between David’s Tent and the Gihon, and engages in special pleading by insisting that part of the River of Life passages must be understood as literally related to the existing Gihon, while other parts of the same passage must be eschatological or metaphorical.
Another important association of water with the Temple comes from the Letter of Aristeas (c. 200-150 BC), sections 89-91. (See Harward, The Jewish Temple, 28 for text, 31-32 for commentary; and Charlesworth, Old Testament Pseudepigrapha 2:18.) Aristeas wrote “there is an endless supply of water [at the Temple], as if indeed a strong flowing natural spring were issuing forth from with [it].” If, indeed, the Gihon were directly connected with the Temple, as Silwan theorists claim, why would he say “as if” instead of “because.” He goes on to say “there exist marvelous and indescribable reservoirs underground—as they showed me—for five stades [a stade is about 200 yards] around the foundation of the Temple; and each of them had numberless channels such that the streams join up together with each other from different sides.” First, it is important to note that five stades is about 1000 yards. Allowing for hyperbole and assuming it was roughly 500 yards north and 500 years south of the Temple, this description encompasses the massive know complex of underground tunnels and cisterns on the current Temple Mount. (Gibson, Shimon, and David Jacobson. 1996. Below the Temple Mount in Jerusalem: A Sourcebook on the Cisterns, Subterranean Chambers and Conduits of the Haram al-Sharif. Oxford: Tempus Reparatum.) On the other hand, no similar massive conduit or cistern system has been discovered on the Silwan ridge. These waters, in fact, literally flowed from underneath the Temple itself, precisely as the eschatological texts mentioned earlier describe. This water system was used in part to wash away the sacrificial blood (Aristeas 90).
Taken together, then, the evidence of the site of the Gihon, the cosmic waters of Life, and the archaeologically identifiable system of channels and cisterns, the Temple Mount once again matches all the known data—both textual and archaeological—better than the Silwan Ridge.