1. The Babylonian zodiac has another 'river' sign, viz. Eridu:

However, the ends of these 'rivers' cannot be seen.

Considering the location of the ancient city-state of Eridu far down in the Sumerian south, the position of the sign Eridu in the zodiac (close to summer solstice) probably reflects the position of Eridu down on earth:

Wikipedia: "According to the Sumerian kinglist Eridu was the first city in the world. The opening line reads,

'[nam]-lugal an-ta èd-dè-a-ba

[eri]du^ki nam-lugal-la'

'When kingship from heaven was lowered,

the kingship was in Eridu.'

In Sumerian mythology, it was said to be one of the five cities built before the Deluge occurred ...  Because of accumulation of silt at the shoreline over the millennia, the remains of Eridu are now some distance from the gulf at Abu Shahrain in Iraq.

In Sumerian mythology, Eridu was originally the home of Enki, who was considered to have founded the city, later known by the Akkadians as Ea. His temple was called E-Abzu, as Enki was believed to live in Abzu ('Deep Ocean'), an aquifer from which all life was believed to stem."

I remember having read that fresh water is welling up from a few spots on the sea bed in the Persian Gulf.

Possibly the invisible ends of the river signs of the constellation Eridu are meant to indicate how south of the city Eridu was only endless water. The rivers flowing from the high region in the north disappeared into the ocean at Eridu.

In the text of G we can compare with Ga1-29, where rima aueue at left (in the past) also is drawn with an invisible end:

Ga1-21 (22)	Ga1-22	Ga1-23	Ga1-24	Ga1-25 (*90)	Ga1-26

Ga1-27	Ga1-28	Ga1-29	Ga1-30

Counting from Sirrah and the present spring equinox north of the equator tagata rima aueue in Ga1-29 will be just beyond summer solstice (i.e. at a position not far away from the season of the constellation Eridu in the Babylonian zodiac).