Water bodies such as lakes, rivers, and streams were the source of water to drink during the ancient times. However, it is the same water bodies where human wastes were deposited. Therefore, in rivers became so polluted that the these ancient cultures needed to construct aqueducts in order to obtain clean drinking water.
The main reason for this water pollution was that human waste found its way to rivers and streams. Cesspools likewise found a way to water bodies and made many people ill.