The 40-volume Commentary to the River Classic, with a total of 32,000 characters, records 1,252 rivers. With the rivers as the key links, the book gives detailed descriptions of the history, geography, economy, culture, and social customs, and so on of the areas where the rivers pass by. Hence, it is not simply a commentary, but rather, it is a recreation that boasts great importance and high scientific value in the history of ancient geography.

The book provides comprehensive information on the 1,252 rivers, large or small, including the river source, the size of the mainstreams, the distribution of tributaries, the width of river valleys, the depth of riverbeds, the length of the river flows, the direction, the seasonal changes in the volume of water, and the flood season, and so on. More detailed description of the northern rivers is provided, which shows the author Li Daoyuan's familiarity with these rivers. The book not only has records on rivers with water in them, but also 24 ancient rivers without water, providing clues in the search for underground water.

There are also accounts of floods in history in the Commentary to the River Classic, including information on the time and scale. Li Daoyuan collected most of the materials through field investigation, and some from ancient records in books or stone carvings. These records are of enormous reference value for today's flood prevention and disaster salvage. Besides, the book contains specific information on various types of lakes.

In terms of geology, Li Daoyuan elaborated on the effect of flowing water on geological formations, such as erosion, removal, and sediment, which is of great significance in the geological history. Also, many fossils are recorded in the book, including the fossils of both animal debris and relics.

Records can be found in the book of 31 hot springs , with comparatively detailed description of the features, the temperatures, the minerals, and the living things of different hot springs. Regarding the living things, records are provided of the animals and plants around the rivers mentioned in the Commentary to the River Classic.

There are comprehensive records of the agriculture geographical situation in the book, covering such areas as cultivation, pasturage, fishing, and hunting. Materials are also included on a great many farmland and irrigation projects, among which are 28 well-known projects, such as Dujiang Yan and Baiqu. The book provides more detailed and richer information on the construction reason, process, and scale than its predecessors.

A famous geographical work in ancient China, the Commentary to the River Classic cast tremendous impact on the later generations after its publication. Many scholars, while carrying out geographical research, referred to the book.

Between 1735 and 1820 in the Qing Dynasty (1644-1911), some 20 scholars carried out a systematic research of the book, making it a specialized study -- the study of Li (Li Xue). The research has been carried on to date, and spread to the foreign countries, giving rise to many experts in "the study of Li."

Author: Jessie