2,000-year-old water supply system uncovered in Jerusalem
“The Lower Aqueduct was originally built more than 2,000 years ago by kings in the Hasmonean dynasty, who ruled Judea and its surrounding regions from about 140 B.C. to 37 B.C., and preceded King Herod the Great.”
Seems that there was lots of water to fill the many large pools in Jerusalem. No difficulty performing multiple baptisms by immersion, even the three thousand on the Day of Pentecost.
G. N. Barkman