Geography of Cambodia: Terrain, Climates, and Landscapes of a Kingdom Shaped by Water

Published on January 28, 2026 and written by Cyril Jarnias

Cambodia often comes to mind through the silhouettes of Angkor or the rice paddies of the central plain. But behind these images lies a far more complex geography, where terrain, monsoons, major rivers, and agricultural practices are tightly interwoven. Understanding the country’s geography means grasping how a nearly entirely tropical, basin-shaped territory has built its economy, cities, and landscapes around water.

A Basin-Shaped Country at the Heart of the Indochinese Peninsula

Cambodia occupies the mainland part of Southeast Asia, at the center of the Indochinese peninsula. Its position is almost central within the subcontinent, surrounded by Thailand to the west and northwest, Laos to the north and northeast, and Vietnam to the east and southeast. To the southwest, a few hundred kilometers of coastline open onto the Gulf of Thailand.

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The territory covers approximately 181,000 km², composed of land and water surfaces.

The heart of the terrain consists of a vast alluvial plain, encompassing the Tonlé Sap basin, the floodplains of the lower Mekong, and the Bassac River plain. Completely situated within the tropics, between 10° and 15° north latitude, almost the entire country is at low altitudes, with a highest point, Phnom Aural, rising to 1,810 meters in the southwestern mountains, and a lowest point at sea level on the Gulf of Thailand coast.

This basin configuration is decisive: water flows in, spreads out, and recedes with the rhythm of the monsoons, shaping soils, ecosystems, but also human settlement and the agricultural map.

Terrain: Central Plains and a Crown of Mountains

Cambodia’s physical structure rests on a clear contrast between a vast central plain and peripheral highlands. Three main regions stand out.

First, the central plain occupies the majority of the territory. An estimated 75% of the country consists of lowlands, dominated by the alluvial deposits of the Mekong and Tonlé Sap. This plain extends southeast to the Mekong Delta in Vietnam, forming a continuum of rice fields and flood zones.

Good to know:

Cambodian territory is framed by three major mountain systems. In the southwest, the Cardamom Mountains (culminating at over 1,500 m with Phnom Aural) and the Elephant Mountains border the coast. To the north, the Dangrek Range forms a natural border with Thailand. To the east, the foothills of the Annamite Range and the highlands of Mondulkiri and Ratanakiri constitute an area of higher elevations that is cooler than the plains.

Finally, a narrow coastal plain lies between the southwestern mountains and the Gulf of Thailand. This coastal strip, wooded and in places marshy, hosts mangroves, beaches and several bays, as well as a constellation of islands – more than fifty – scattered off the coasts of Sihanoukville, Koh Kong, Kampot, and Kep.

Note:

The physical geography of the territory imposes significant constraints on transportation, human settlement, and infrastructure. The southwestern mountains shield the interior from maritime influences and intercept precipitation, while the highlands of the north and east frame the central “basin,” where the majority of the population is concentrated.

A Geography Dominated by Water: Mekong, Tonlé Sap, and the Hydrographic Network

It is impossible to discuss Cambodia’s geography without mentioning the power of its hydrographic network. The Mekong, one of Asia’s great rivers, crosses the country from north to south for nearly 500 kilometers. It enters from Laos in Stung Treng province, widens and calms as it approaches the plain, then meets, at Phnom Penh, the Tonlé Sap and Bassac rivers in a vast river confluence known as the Chattomukh, “the four faces.”

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Exceptional maximum surface area of the Tonlé Sap lake in Cambodia during very wet rainy seasons, in square kilometers.

The phenomenon of flow reversal is world-renowned. When monsoon rains swell the Mekong, the river’s level exceeds that of the Tonlé Sap river, which then reverses its current and pours massive volumes of water into the lake. Once the flood subsides, the current reverses again and the Tonlé Sap gradually empties back into the Mekong. On average, some thirty cubic kilometers of water transit each year in this seasonal back-and-forth movement that irrigates the plains, recharges aquifers, and nourishes ecosystems of exceptional richness.

Example:

Cambodia possesses a dense hydrographic network, with secondary rivers like the Sen, Sreng, Sangkae, Pursat, Sisophon, and Mongkol Borei draining the highlands and plateaus toward the Tonlé Sap lake or the Mekong River. These watercourses contribute to considerable renewable water resources, estimated at over 470 km³, primarily used for agriculture.

This river geography explains the concentration of the population along the rivers, in the alluvial plains, and around Tonlé Sap lake. It also forms the foundation of the country’s primary wealth: floodplain rice fields and inland fisheries, which remain central to national food security.

A Hot, Humid Monsoon Climate with Regional Contrasts

Cambodia enjoys a tropical monsoon climate, hot and humid year-round. Two seasons structure the calendar: a dry season, from November to April, dominated by northeast winds, and a rainy season, from May to October, under the influence of moisture-laden southwest winds.

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Extreme temperatures can exceed 40°C (104°F) during the hottest months, particularly in the interior plains.

Rainfall distribution is far from uniform. The approximate annual average of around 2,000 mm masks major disparities. The central plains and major cities like Phnom Penh or Siem Reap receive between 1,300 and 1,800 mm per year, with heavy downpours concentrated between June and September. The coastal fringe and seaward-facing slopes in the Cardamoms are among the wettest regions in all of Southeast Asia: accumulations can exceed 3,000 mm, even 5,000 mm on some exposed slopes.

Tip:

East of Phnom Penh and on some plateaus, annual precipitation may only reach around 1,000 mm. These areas experience more pronounced dry periods, posing challenges for agriculture that is still largely rain-fed.

The combination of these factors – constant heat, marked dry/wet season alternation, rainfall gradients according to terrain – shapes the landscapes: dense, evergreen forests on the humid highlands; savannas and deciduous forests in the plains; mangroves on the coast; mosaics of rice fields and dryland crops in the central basin.

Forests, Savannas, and Mangroves: A Mosaic of Tropical Ecosystems

For a long time, almost the entire territory was forested. Although deforestation has deeply eroded this vegetative cover, Cambodia remains one of the countries in the region with the highest forest coverage rate. It is estimated that in 1990, over 73% of the national surface was forested, compared to about 46% in 2020. This rapid decline is due to agricultural expansion, economic land concessions, legal and illegal logging, and infrastructure development.

The geography of this forest cover reflects the diversity of environments. The southwestern mountains, often called the region’s last large, nearly intact tropical forest massif, harbor humid montane forests, with trees sometimes towering over 40 meters. The slopes most exposed to rain are covered in dense forests, while the summits host pine forests adapted to higher altitudes.

Geographic Description

In the plains and transition zones, deciduous and semi-evergreen forests alternate with tall grasslands, scrublands, and rice fields. These savanna landscapes are particularly present in areas with poor or sandy soils, as well as in parts of the eastern plateau.

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Mangrove swamps occupy over 60,000 hectares along the Cambodian coastline, notably in Koh Kong province.

This vegetal richness is matched by a remarkable animal biodiversity: over 200 mammal species, more than 500 bird species, hundreds of reptile and fish species. Wild elephants, gibbons, various feline species, and abundant aquatic fauna still bear witness to this heritage, even though many species are now classified as threatened or critically endangered.

A Human Geography Centered on the Plain and Rivers

Cambodia’s geography is not limited to terrain forms or major ecological units. It is also read in the distribution of populations and activities. Approximately two-thirds of the inhabitants live on the great central plain, around the Mekong, Bassac, and Tonlé Sap. Over 80% of the population is concentrated in a few regions: the Mekong plain, the Tonlé Sap basin, and the coastal fringe.

Good to know:

The Cambodian population is concentrated in the alluvial plains, where soils are fertile and water facilitates transport, fishing, and irrigation. The eastern plateaus and southwestern mountains are less populated and host a greater diversity of indigenous ethnic groups, often referred to as “Khmer Loeu.”

In national statistics, four major geographical regions are often distinguished: the Plain region, the Tonlé Sap region, the Coastal region, and the Plateau and Mountain region. These areas combine physical, climatic, and human specificities but share a common trait: the persistent weight of agriculture and, increasingly, activities related to tourism, light industry, and natural resource exploitation.

Cambodian Countryside: An Agricultural Territory Shaped by Rice and the Monsoon

Agriculture remains an essential pillar of Cambodia’s geography, both in terms of land use and employment. Nearly 4.3 to 4.5 million hectares are currently cultivated. During the 2023 agricultural census, over 1.85 million farms were counted, covering approximately 3.2 million hectares. The average farm size is modest, around 1.7 hectares, and nearly half operate on less than one hectare.

The way land is held also reflects a social geography: acquisition through inheritance remains the primary mode, with about 1.4 million inherited plots.

The distribution of agricultural land use in 2023 can be summarized as follows:

Among these crops, rice dominates overwhelmingly. Approximately 66.6% of all cultivated land is dedicated to rice paddies, confirming the central place of this cereal in rural landscapes. Historically, this dominance was even stronger: rice occupied nearly 86% of cultivated areas in the early 2000s, before gradually declining in favor of other cash crops like cassava, rubber, or cashew.

Good to know:

The dominant rice cultivation is favored by flood-prone lowlands, the Tonlé Sap plains, and the Mekong terraces, ideal for irrigated varieties. In drier or more elevated zones, one finds more rain-fed crops like cassava, corn, cashew trees, and rubber plantations.

Major Crop Types: From Rice to Cassava, Rubber, and Cashew Plantations

Within this agricultural territory, rice remains the king crop, deeply structuring the geography of the countryside. The country has mainly two rice-growing seasons: a monsoon crop, planted in May-July and harvested at year’s end, and a dry-season crop, more limited, planted from November in well-irrigated regions and harvested early in the year.

This double seasonality is not distributed equally across the territory. In plain areas well served by irrigation or benefiting from high flood levels, like around the Tonlé Sap or in some provinces bordering the Mekong, a larger share of land can be devoted to dry-season rice, which is more productive. Conversely, in more isolated or drier zones, especially on the eastern plateaus, farmers remain largely dependent on rains and concentrate their efforts on a single annual crop.

Rice in Land Use

Distribution of rice paddies by cultivated variety, from the 2023 census.

Non-Aromatic Rice

Largely destined for domestic consumption and bulk exports.

Aromatic Rice

More prestigious varieties on the international market.

These figures show how agricultural geography also follows quality and market logics. Aromatic varieties – highly prized in Europe or China – occupy more restricted areas but are strongly concentrated around the Tonlé Sap basin, in provinces like Battambang, Kampong Thom, or Siem Reap, where soil and water conditions are particularly favorable.

Beyond rice, other major crops feature in the landscape. Cassava, in particular, has become the country’s second crop: over 430,000 hectares were dedicated to it in 2023, with a production of nearly 4.73 million tons. These plantations are mainly spread across plateau areas and forest fringes, where lighter soils are less suited to rice but allow for large areas of rain-fed crops.

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Cashew plantations covered nearly 334,000 hectares in 2023, primarily concentrated in plateau and mountain zones.

Fruit crops (mango, banana, coconut, jackfruit) also cover vast swathes of the countryside, often associated with rice fields or vegetable gardens. Over 600,000 farms cultivate mango trees, and more than 660,000 produce bananas, mainly in well-watered plains or around the lake.

In this agricultural landscape, one also finds small areas of aromatic and spice crops – pepper, lemongrass, various vegetables – which enhance the diversity of cultivated environments. Pepper, for example, occupied around 7,300 hectares in 2023 and remains highly visible in emblematic terroirs like Kampot, whose pepper benefits from a protected geographical indication.

To grasp the scale of this diversification, some key 2023 crops can be summarized:

This diversity illustrates a gradual shift from an agriculture focused almost exclusively on rice toward a more diversified model, where cash crops and exports occupy a growing place, especially in the peripheral plateau and mountain zones.

Largely Rain-Fed Agriculture, on the Front Line Facing Climate

Despite the rise of these cash crops and improvements in some irrigation systems, Cambodian agriculture remains highly dependent on monsoon rains. Barely over one-fifth of farms reported using irrigation in 2023. In concrete terms, this means the majority of farmers remain exposed to the vagaries of the rainy season: late onset, dry spells mid-season, excessive floods, or premature flood recession.

Note:

The country is one of the most vulnerable in Southeast Asia to natural disasters, notably floods and droughts. These phenomena, sometimes linked to El Niño or La Niña, manifest as intense rains causing floods and landslides, or as droughts jeopardizing planting and crop growth, leading to harvest losses.

Long-term climate data shows a warming trend, with an average temperature increase of about 0.18 °C per decade since the 1960s. Projections for the coming decades predict a continuation of this rise and greater variability in precipitation, which could intensify contrasts between very wet years and dry years.

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This is the share of water withdrawals in France destined for agriculture, a sector occupying nearly 20 to 27% of the national territory.

Tonlé Sap and Mekong: A Geographical Foundation for Fisheries and Seasonal Floods

Beyond agriculture, the geography of inland waters also structures the country’s major fisheries sector. Cambodia has one of the highest per capita fish consumption rates in the world, and inland fisheries – particularly in the Tonlé Sap, Mekong, and their floodplains – represent a pillar of food security.

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This is the estimated quantity, in tons, of fish that Tonlé Sap lake could supply annually, thanks to its role as a nursery for hundreds of species.

But the geography of this resource is fragile. The decline of flooded forests, increasing fishing pressure, changes in flood regimes linked notably to dams built upstream on the Mekong and its tributaries, and climate change have already caused a decline in catches in some areas. Scientists anticipate a significant decrease in capture fisheries within a few decades if current trends continue.

Good to know:

The floodplains of the Mekong and Tonlé Sap offer fertile land for rice cultivation but regularly expose populations to floods. Many villages in Kandal, Prey Veng, and Svay Rieng provinces are flooded for several weeks each year. The cities of Phnom Penh and Siem Reap are also vulnerable during heavy rains combined with rising rivers.

This geography of risk requires rethinking developments: dikes, canals, retention basins, water storage policies, but also urban and rural planning to limit population exposure.

Coastline and Islands: A Small but Strategic Maritime Facade

While most of the territory faces inland and the river network, the Gulf of Thailand coastline represents another facet of the country’s geography. Approximately 440 to 450 kilometers long depending on sources, this coastal strip hosts a mosaic of landscapes: dense mangroves in estuaries, sandy beaches, rocky capes, small sheltered bays, and archipelagos of islets.

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Annual precipitation often exceeding this threshold in millimeters on exposed slopes in Cambodia’s coastal provinces.

This geography has enabled the development of maritime ports – notably Sihanoukville, the country’s main deep-water port – and an expanding coastal tourism around resorts like Sihanoukville, Kep, or nearby islands. It has also favored the presence of mangroves and seagrass beds, essential for marine biodiversity, but vulnerable to urbanization, intensive aquaculture, and mining activities (like sand extraction).

In the longer term, this maritime facade is also on the front line facing sea-level rise and risks of tropical storms, although Cambodia is relatively less exposed to direct typhoons than its Pacific neighbors.

Cities and Countryside: A Network Dominated by Phnom Penh and a Few Secondary Hubs

Cambodia’s human geography contrasts a vast rural majority, occupying the plains and plateaus, with a handful of expanding urban centers. While the urbanization rate remains modest compared to neighbors, urban growth is rapid and gradually transforming landscapes.

Phnom Penh, located at the heart of the alluvial plain, at the confluence of the Mekong, Tonlé Sap, and Bassac, embodies this movement. Built on an ancient, slightly elevated alluvial levee, surrounded by flood zones, the capital has expanded onto reclaimed marshlands or filled-in lakes. This location makes it particularly vulnerable to flooding and raises questions about the interplay between urban expansion, drainage, and wetland conservation.

Example:

While Phnom Penh polarizes national flows, several secondary cities play key economic and regional roles: Battambang (rice-growing center of the Northwest), Siem Reap (tourist pivot for Angkor), Sihanoukville (port and seaside crossroads), Kampong Cham (river hub in the eastern plains), and plateau towns like Banlung or Senmonorom, which serve as gateways to mountainous areas.

These cities are part of a network structured by major road arteries radiating from Phnom Penh toward the Thai, Lao, and Vietnamese borders. Major infrastructure – special economic zones, industrial zones, new airports, expressways – is gradually altering the geography of goods flows and internal migration.

Soils, Resources, and Constraints: A Decisive Underlying Geography

Beneath the visible landscapes, geology and soils impose their own constraints. The central plain largely rests on recent deposits of sand, silt, and clay laid down by the Mekong and its tributaries. These soils are generally suitable for rice, but their fertility varies according to flood frequency and intensity, groundwater depth, and sediment supply.

Good to know:

On these highlands, the substrates are mainly granite, sandstone, and ancient sedimentary rocks. The derived soils, often Acrisols, have low natural fertility. They can exhibit aluminum toxicity, which limits agricultural yields without significant fertilizer inputs or the adoption of suitable agroforestry practices.

These pedological characteristics partly explain why some regions remain dominated by forest or extensive crops like cassava or rubber, rather than intensive rice cultivation. They also condition the distribution of economic concessions, often located on forest margins for industrial plantations, with significant impacts on ecosystems.

Furthermore, the country’s subsoil holds a diversity of natural resources – timber, minerals, offshore hydrocarbon potential – which have increased pressure on once-isolated areas. The opening of mines or oil projects in the mountains or offshore in the Gulf of Thailand could reshuffle the economic geography cards, but also poses major environmental and social challenges.

Contemporary Challenges: A Geography Under Pressure

Cambodia’s geography finds itself at a pivotal moment. The large structures – plains, mountains, rivers, Tonlé Sap lake – remain the same, but their internal balances are shifting under the combined effects of demographic growth, rapid urbanization, the rise of export crops, logging, and climatic transformations.

Good to know:

The alluvial plains, the traditional heart of rice cultivation, are seeing their crops diversify (cassava, cashew, sugarcane) and are subject to urban sprawl. The eastern plateaus, once sparsely populated, are becoming pioneering zones for agriculture and mining. Finally, the forests of the southwestern mountains, although preserved, are increasingly fragmented by road infrastructure, hydropower dams, and agro-industrial projects.

The rivers, especially the Mekong, are suffering the cascading effects of dams built upstream, which alter flood regimes, reduce sediment supply, disrupt fish migrations, and affect the Tonlé Sap’s dynamics. This new hydrological reality impacts fisheries, plain fertility, and the frequency of floods or low water levels.

Good to know:

In Cambodia, geography is a central element of public policy. It directly influences agricultural strategies (irrigation, diversification, land management), energy strategies (hydropower, dam construction), and territorial planning (controlling the expansion of Phnom Penh and secondary cities). It is also at the heart of conservation imperatives for ecosystems like forests, mangroves, and wetlands.

The country’s “basin” shape, its dependence on the monsoon, the central place of the Mekong and Tonlé Sap, the fragility of its forests, and the concentration of the population in a few low plains combine their effects to make Cambodia a territory both richly endowed with natural resources and particularly sensitive to environmental imbalances.

Therefore, understanding Cambodia’s geography means measuring how the slightest variation in rainfall, the slightest upstream dam, the slightest expansion of rice fields or plantations can, in the long run, reshape the landscapes, livelihoods, and ecological balance of an entire kingdom.

Cyril Jarnias

Cyril Jarnias is an independent expert in international wealth management with over 20 years of experience. As an expatriate himself, he is dedicated to helping individuals and business leaders build, protect, and pass on their wealth with complete peace of mind.

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