Simplify the following text for a Grade 11 native English-speaking person.
Original: The work , which included dredging and bolstering the banks of the stream and building the bridges , was carried out every 2 ~ 3 years during this period from the reign of Taejong , the third king of the Joseon Dynasty .
Simplified: Therefore , King Taejong , the third king of the Joseon Dynasty , firstly beginned river training work by starting construction work for an open channel . After that , King Yeongjo , the 21st king of the Joseon Dynasty , conducted the overhaul of the stream in earnest by dredging the stream , building stone banks and changing a waterway .