1)
Why does it say "Aso"?
1.
Radak, Malbim: They should make pits [to hold the water that will come]. Radak - this is Makor (like an infinitive) in place of a command.
2)
What are "Gevim Gevim"?
1.
Rashi: They are pits full of water.
2.
Radak: They are pits. The Targum is Patzidin Patzidin, like the Targum of "Afikav 1 " (Yeshayah 8:7) 'Patzidohi'.