Archemedies's screw was essentially a large screw, open at both ends and encased lengthwise in a watertight covering that could be used to raise water up to 1 to 1.5 meters.
It was invented by, as the name suggests Archemedies around 280 B.C. and then extensively used ancient irrigation, such as to draw up water from the river into the surrounding elevated farmlands.
While its modern days were too numerous to describe.
Alexander was quite happy to be reminded of this vital equipment because it really was an extremely useful tool, especially for agriculture in mountainous areas.
Using it here could be revolutionary!
Hence he planned to have his smithies forge the product in vast numbers and send it to Thesalie.
That was why he simply asked the engineers to continue proceeding as they were, while also planning to undertake quite a few more irrigation projects around these lands after it was produced.