> Uruk was extremely well penetrated by a canal system that has been described as, "Venice in the desert."[13] This canal system flowed throughout the city connecting it with the maritime trade on the ancient Euphrates River as well as the surrounding agricultural belt.
> The original city of Uruk was situated southwest of the ancient Euphrates River, now dry. Currently, the site of Warka is northeast of the modern Euphrates river. The change in position was caused by a shift in the Euphrates at some point in history, which, together with salination due to irrigation, may have contributed to the decline of Uruk.
From 20,000 up until 8000 years ago, the Persian Gulf, where the Tigris and Euphrates rivers drain into, was continuously filling in, and thousands of square miles where people lived were disappearing beneath the waves.
Is it? "Silted up" would usually imply that the river moved, not that it disappeared. A river that isn't there can't deposit silt.
The article kind of suggests that the river in question was the Euphrates:
> Archaeologists found the boat in an area that, 4,000 years ago, would have been the bustling hinterlands of the largest city in the world: Uruk. Founded in 5000 BCE from the merger of two smaller settlements on the bank of the Euphrates River, Uruk was one of the world’s first major cities
The Euphrates is still around.