Most visitors soon learn that the topography of Cambodia consists mostly of a large basin that sits in the tropics and lacks the four distinct seasons normally associated with temperate climates. But in lieu of marked seasons, the climate of Cambodia pivots upon the arrival of the monsoon which drench the basin with torrential rains and downpours and heralds Cambodia’s “wet“ season. This mega annual event, which traditionally begins in May and ends in October, is accompanied with towering temperatures (which at times can soar to 38c) and high levels of humidity. Conversely, the “dry” season traditionally begins in November and ends in April and is characterized by cooler temperatures (as low as 30c) and less humidity. And although typhoons can hit Cambodia at any time, they are mostly concentrated along the coast of Vietnam.
Few people have described Cambodia’s landscape better than Jean Delvert, a geographer, “(most of) Cambodia consists of a great depression or basin studded with isolated heights with few rising over 100 meters. Such island-like promontories, called phnoms, dot the great basin.” But Cambodia’s topography also consists of mountains that border the basin on all sides but the east and rarely and exceed 1,000 meters in height. . Heading the list is the 150 kl. long Cardamon Range(or Kravan Davreiin Khmer), Cambodia’s longest mountain range and home to the country’s highest peak, Phnom Aural(1813 mts.). Then on the north, we find the Dangrek Range whose steep escarpments define the natural border between Thailand and Cambodia and whose antiquity dates back to more 600 million years! And on the east, we find a small strip of the Annam Mountains, Vietnam’s legendary mountain range.
The Mekong and the Tonle Sap River
From the lofty height of the Tibetian Plateau, the Mekong River begins its arduous jaunt towards the South China Sea logging some 4,300 kl.,in the process. That makes the Mekong, or “The Mother of all Rivers” in Khmer, the largest river in Southeast Asia. Through its turbulent geological past, the river has created some of the most spectacular jewels of Southeast Asia. They include scores of steep valleys teeming with exuberant vegetation; a collection of picturesque rapids, cataracts and water falls including the majestic Khone Falls in Laos; an extensive flood plain that nourishes over 500 species of fish; a unique lake (Tonle Sap) with an unsurpassed fluvial wealth and a fertile delta consisting of nine distinct canals flanked by interminable rice fields and much more. So it is not surprising that the river’s bounty contributes to the welfare of some 60 million people. Most of which live in the river’s immense and multi-national flood plain (shared by six nations). But, as explained below, much of the Mekong’s bounty depends on the annual monsoons that swell the river’s bank and expands the size of the Tonle Sap Lake four-fold! Let us see how this event plays out every year (beginning in May) resulting in an interminable abundance of rice and fish that feeds millions!
The Tonle Sap Lake
And from its headwaters in the Phnom Kulen Hills(some 30 kl. northeast of Angkor), the Tonle Sap River begins its trajectory towards its notable lake, the Tonle Sap Lake, or the “Great Lake” in Khmer. It then continues its course terminating at the confluence with the Mekong River. All told, it logs a paltry 300 kl. But while it does not measure up in length, it scores high in its ability to expand and shrink in size in concert with the annual monsoons. In May, when the monsoon season begins, the torrential rains overwhelm the banks of both the Mekong and the Tonle Sap rivers and, like an overloaded septic system, it reverses the flow of the Tonle Sap river upstream towards the Tonle Sap Lake! This dramatic annual event, which normally starts at the confluence of the Mekong and the Tonle Sap River, expands the Great Lake’s flood plain four-fold to some 10,320 sq. kl., creating a vast inland sea complete with thunder and storms, a phenomenon that endures until late October. Then in December, when the river resumes its normal flow, it shrinks its elaborate flood -plain and reduces the level of the water trapping tons of fish and creating an unsurpassed opportunity for rice farming and fishing! Remarkably, some 300,000 tons of fresh-water fish are caught here annually ranging in size from the finger-size silver fish to the mighty giant cat – fish underscoring an age-old proverb of the lake: “”…when the water is high, the fish eats the ants, when the water is low, the ants eat the fish.”To be sure, this bounty represents the lifeblood of some 1.5 million people, including thousands of Vietnamese who reside on the ubiquitous floating villages that dot the 125 kl., long lake. Unfortunately the lake’s ecological balance, already threaten by unmanageable demographic growth and overfishing, is facing an even greater threat: the incessant drive for dam building. China alone has built half-a-dozen dams in the upper Mekong during the last two decades! If these uncontrollable forces continue, it will disrupt the Mekong’s natural flow and with it, the delicate conditions that makes the lake Great.