I've been reading through The Memoirs of Cleopatra: A Novel, by Margaret George, which is historical fiction, and I just came to the bit (page 114 - I borrow liberally from her language) where Arsinoe's general Ganymedes tries to drive Cleopatra, Caesar, and his men out of the palace by thirst. Alexandria's water supply comes from underground tunnels that channel Nile water through the city, and Ganymedes had divided the water supply, protecting his own, and constructing giant waterwheels to draw seawater up to higher ground so as to pump it into the palace's water supply.
Caesar responds by having his men dig for a few hours in the beaches so as to tap into the veins of fresh water there, thus thwarting Ganymedes tactic.
Or, if you wish to see it inside:
This was done long before Caesar. As I discussed in an earlier post on parshat Va'era, in Shemot 7, we have the plague of blood, in which God turned the waters of Egypt to blood, and the fish died and fouled the water. This seems to have been done to all the water of Egypt, including pools, ponds and streams. Hashem thus cuts off their water supply.
In response to this, as verse 24 notes,
|כד וַיַּחְפְּרוּ כָל-מִצְרַיִם סְבִיבֹת הַיְאֹר, מַיִם לִשְׁתּוֹת: כִּי לֹא יָכְלוּ לִשְׁתֹּת, מִמֵּימֵי הַיְאֹר.||24 And all the Egyptians digged round about the river for water to drink; for they could not drink of the water of the river.|
That is, they have Caesar's response to the cutting off of their water supply.
Now, as I noted in that earlier post, there are two possible ways of reading the psukim in this perek. One is that the Egyptians were successful, and they other is that they were not successful, since those waters too were blood.
At any rate, it is clear that Hashem was waging war on the Egyptians, using a military tactic, and the Egyptians at the least attempted to respond in kind. In light of this, Ganymedes tactic, while smart, is someone derivative, while Caesar's response was logical and known already to at least some Egyptians. (This all happened about 48 BCE; comparatively, some date the Exodus from Egypt to 1280 BCE, and Ezra and Nechemia are 458-420 BCE.)