Where is Xi 'an? South of Weihe River is "Yin". How can it be ancient Xianyang? Old ancestors wouldn't make such a mistake, would they? Don't talk nonsense if you don't understand. That sounds ridiculous.
The present Xianyang city and the ancient Xianyang city are not completely coincident. The site of Xianyang ancient city is located in the site of Epang Palace, the palace of Qin Shihuang in the east of Xianyang, which is under the jurisdiction of Xi 'an on the south bank of Weihe River, but there was no such city as Xi 'an at that time.
There are many examples where the old city and the new city do not overlap. Many Chang 'an in Han Dynasty and Chang 'an in Tang Dynasty do not completely coincide with Xi 'an now. Now Xi and the city wall are new cities established in the Ming Dynasty. The ruins of the ancient city are located in the suburb of Xi 'an now, and there are too many related examples, but it cannot be denied that this is not a continuation of the ancient city.
In order to answer this question, please add more knowledge of history and geography. As a descendant of the dragon, it is ridiculous to say such nonsense.
PS As for why the Qin people were located in the north of Weishui and the Han people were located in the south of Weishui, it is not difficult to find that Qin had just risen when Xianyang was established. The main threat comes from the six eastern countries. If you attack Xianyang, you will cross the Weihe River from south to north, which will become a natural barrier (it is not difficult to find that Xianyang is located in the strategic position of Hetao). After the Han Dynasty, including the threat of the capital of the Tang Dynasty, the main source was the northern nomads, and the site was located in the south of Weihe River, which became a barrier to prevent the northern nomads.