The Torah does not give details as to how the Bnai Yisrael got water in the desert. Given that there were 600,000 men between twenty and sixty (about 2 - 3 million people total) they could not have lined up at a single source to collect water. Hashem could have arranged for a rain storm every day to allow enough water for the people to collect (like the man) but did not. What did He do?
Note that when the people complained, he had Moshe and the elders go ahead in the journey to hit the rock. Some say the rock was at Har Sinai (about six weeks travel ahead). What exactly happened and how did it provide enough water for the entire people for the entire trip. Note that the people had to "wash their clothes" at Har Sinai, implying that there was no difficulty in everyone getting enough water for all their needs, It also implies that they did not have to ration water as they did the manna nor was its use restricted as to time.