Have digged and drunk ... and dried up - The meaning seems to be - “Mountains do not stop me - I cross them even in my chariots. Deserts do not stop me - I dig wells there, and drink the water. Rivers do not stop me - I pass them as easily as if they were dry land.”
The rivers of besieged places - Rather, “the rivers of Egypt.” The singular form, Mazor (compare the modern Misr and the Assyrian Muzr), is here used instead of the ordinary dual form, Mizraim, perhaps because “Lower Egypt” only is intended. This was so cut up with canals and branches of the Nile, natural and artificial, that it was regarded as impassable for chariots and horses. Sennacherib, however, thought that these many streams would prove no impediments to him; he would advance as fast as if they were “dried up.”