Although it is difficult to summarize the significance of the hydro-irrigation facilities of Korea in one word, it is clear that they worked as a facility maximizing the productivity of agriculture, especially water production. In particular, it can be inferred from fragmentary records that significant population growth occurred in the ancient period. However, it is during the ancient period that huge embankments (such as those that formed the valley-type reservoirs that can commonly be seen around us) made an appearance, likely intertwined with social changes such as population growth and numerous wars in ancient society. In the end, it would not be an exaggeration to say that the ancient embankments provided the most basic foundations supporting ancient society, their appearance acting as an inflection point for maximizing land use strategies. An examination of the ancient embankments identified thus far in Korea reveals that not only are there so-called ‘valley-type reservoirs’ that were used to irrigate a large area downstream by blocking the upper reaches of narrow valleys in the mountains, there were also dams located in the middle of wide fields, close to the coast, as in the case of Byeokgolje, in Gimjae. There are some that appear to have been built to irrigate the swampy areas below. However, the irrigation efficiency(maximum irrigated area/reservoir area) of major ancient embankments was reviewed from the perspective that the larger the area that can be irrigated compared to the area that can be stored, the higher the efficiency of land use, thereby reflecting the intention of constructing such embankments. The irrigation efficiency of Uirimji (in Jecheon), located in the mountains, was the highest at 39.6; Byeokgolje (in Gimje) was the lowest at 1.20. It is conventionally thought that the agricultural productivity of the Honam region, which is spread over a wide expanse of lowland, overwhelms the other regions. According to the modern agricultural production data of the National Statistical Office, production at Gyeongsangnam-do Province, in fact, overwhelms that of Jeollanam-do Province. It is thought that this is not irrelevant to the irrigation efficiency of the ancient embankments, and it is necessary to re-evaluate not only the civil and historical significance of the so-called ‘Korean-style hydro irrigation system’ but also the impact it had on the foundations of ancient society.