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The Importance of the Mekong River During the Khmer Empire

  |   Mekong River

The Khmer Empire, or Angkor Civilization, was one of the most powerful and prosperous states in history, formed in the 9th Century and dominating Southeast Asia for the best part of 7 centuries. It covered an area that includes what is now Cambodia and parts of Laos, Thailand and Vietnam. The Khmer people are heralded today for their architectural prowess, eminent culture and engineering genius, leaving behind them a remarkable legacy. 

Many of Southeast Asia’s most spectacular historical sites still stand today as a testament to this extraordinary society, but what was it that made the Khmer Empire so successful? What did this pre-Cambodian population get so right that ensured its dominion for over 600 years? And what brought about its eventual demise?


The answer to all of these questions, according to historical research, is water. The Khmer people managed to harness the power of water to build and sustain their wealthy empire, but it was this same untameable energy that catalyzed their final downfall, with the unpredictable droughts and floods of the tropical monsoon climate. 

The mighty Mekong River played a key role in the Khmer Empire’s rise and fall. This fluvial artery is the world’s 12th longest river and the 7th largest in Asia. From its source in the Tibetan Plateau to its mouth in the South China Sea, it passes through six different countries including modern day Cambodia and Vietnam. Way back in the first century CE, Khmer ancestors settled on its banks in the form of the kingdom of Funan, whose heartland was the Mekong Delta. Excavations at famous archaeological sites such as Angkor Borei in southern Cambodia show that the Funanese made use of the strategic positioning between India and East Asia to form maritime trade connections, using the delta’s convenient natural canal system to establish mercantile monopolies that would later be emulated by the Khmer people.

Whiz forward a few centuries and you come to 802 CE, when a man called Jayavarman II officially founded the Khmer Empire. After conquering and uniting a series of smaller kingdoms, he settled further North, near the great lake of Tonle Sap. He declared himself not just leader, but ‘chakravartin’, or ‘god-king’, giving himself and his successors political and religious authority over all. The capital that he established was the city of Angkor, and this grew rapidly into what would become the largest urban structure of the pre-industrial world, marking the beginning of the Angkor Period. To put this into perspective, Angkor itself was even bigger than today’s New York City! 

Angkor Wat Ruins

The key to the empire’s success was without a doubt its advanced water management system, stretching over approximately 1200 square kilometers (460 square miles). During the wet season, when the Mekong River flooded, Tonle Sap lake acted as a natural flood water reservoir downstream of Phnom Penh. The network of man-made canals was used to channel water flowing from the swollen lake to a series of reservoirs called ‘barays’, where the water would be stored for use during the dry seasons when there was little rain. This meant that Khmer farmers could triple or even quadruple their yearly amount of rice harvests, giving agricultural stability in a volatile and unreliable climate. Inland agricultural areas expanded for large-scale rice production - it’s thought they harvested over 50 million rice paddies in the Mekong River basin. Canals filled with fish (such as the giant catfish), which in turn fed the population of farmers and laborers. The state’s economy strengthened, and with it came wealth and prosperity.

With the growth and successes of Angkor’s economy, even more laborers could be mobilized for the construction of canals, barays, and temples. The energy and power of the Mekong River were considered divine and the monsoon rains sacred, and moats were often built around religious buildings to regulate groundwater levels. Because of their careful and clever construction, hundreds of temples in the area surrounding modern day Siem Reap still remain today, including the spectacular temple of Angkor Wat, built by Suryavarman II, and that of Angkor Thom, a legacy of Jayavarman VII.

It wasn’t just agriculture and building however that the Mekong River helped with. It allowed trade and travel with people north and south of the area, and formed a vital commercial link to the outside world. It also created the ideal defense from invasion - only the local Khmer people knew how to safely navigate the constantly changing sandbanks and perilous currents. 

Mekong River Sunset

This golden period couldn’t last forever though, and the Khmer Empire eventually dissolved in the 14th Century. This decline was brought about by a number of factors. Civil unrest, foreign invasion, and a conversion from Hinduism to Buddhism are all thought to have contributed to a period of instability. However, scientists and historians believe that it was the breakdown of their water systems that brought about the final demise. 

With a rapidly growing population, increased strain was put on their irrigation system. Forests were cleared to allow for more farming, which increased surface run-off and clogged the canals and reservoirs with silt. Plagued by a series of cruel droughts and subsequent violent floods, the Khmer hydraulic engineering was put to the ultimate test. The damage that the reservoir system endured was dramatic and left the empire irreversibly vulnerable.

It is this intense relationship between the Khmer people and the Mekong River that makes the area such a fascinating place to visit now. The stories of this advanced society, that relied so heavily on the river for all aspects of their life can still be seen carved into the temple walls and stamped into the physical landscape. The Khmer Empire permanently altered the natural hydrology and catchment areas of the region and the likes of the sophisticated irrigation system of Angkor have never been seen before. It’s little wonder the temple complex of Angkor is at the top of so many travel bucket lists, remaining one of the most extraordinary feats of ancient engineering.  If you are looking into booking any fantastic experience with us at Rainforest Cruises, including seeing this spectacular destination on any of our Mekong Cruises, please contact us by sending us an enquiry or calling us at 1-888-215-3555.

About Rainforest Cruises

Rainforest Cruises is a boutique travel company specializing in Amazon river cruises, Galapagos Islands tours, and Southeast Asia cruises. We provide you with the finest collection of cruises in Peru, Brazil, Ecuador, Bolivia, Panama and Southeast Asia. As travel experts we have all the advice you need to help you find and book your dream cruise and an unforgettable adventure.