Preks – What are they anyways?

So what are Preks anyways?

One term that crops up literally all the time that I write about my PhD project is ‘Prek’. But what is a Prek? God knows it took me a while to figure that out! So here’s the run-down.

Strictly speaking, Preks are man-made channels that diverge perpendicularly from a river course. Like so:

The beginning of a Prek from above

Their profiles are regular, generally trapezoidal. However, due to erosion and sediment deposition, many channels have experienced bank collapses and clogging. They have lost much of their original forms.

But what is the purpose of the Preks? To answer this question, it’s first essential to know the topology of the landscape in the Cambodian Mekong Delta.

In a word: It’s flat. Only less so in some places than in others.

In a configuration that may seem counter-intuitive to many Europeans (including me), the land is actually raised higher than elsewhere along the river courses. That’s because the annual monsoon flood deposited sediments here year after year for centuries. As a result, the river banks are raised and then slope gently downwards towards the floodplains in the backlands.

The raised land along the watercourses is also known as Chamkars. Due to the accumulation of deposited sediments in the past, these areas are very rarely flooded nowadays. Consequently, they are hubs of human settlements. For this reason, the villages and roads are all directly on the river banks. Crops that are sensitive to being flooded are grown here.

The low-lying floodplains, on the other hand, are called Boeungs. These Boeungs are flooded regularly, and since many areas remain submerged for more extended periods, they are practically marshlands.

The arrangement of Chamkars and Boeungs in the landscape

Initially, the purpose of the Preks was to pierce the raised river banks, providing a connection to the floodplains. The effect? Water could flow freely from the river to the floodplains and back during the yearly Monsoon cycle. This had several consequences:

  • Sediments were deposited along the Prek channels – and new Chamkar areas were formed.
  • During the first half of the flood, water could freely flow from the river to the floodplains, inundating them regularly, and attenuating the flood peak in the river.
  • During the flood recession, water could drain from the floodplains back from the river, leaving them dry and ready for rice cultivation earlier in the season.

Many of the Preks go back to the period of French colonisation of the area and even before – feel free to check out this post for more details!

Today, the Preks have fulfilled their primary purpose of raising land. New Chamkar areas have been created along them. The closer to the villages on the original Chamkars they are, the higher they are raised, sloping gently into two directions – towards the floodplains, and laterally away from the Preks. The crops grown on these Chamkars are arranged according to the likelihood of certain areas being flooded.

Over time, Preks have also acquired a multitude of other functionalities. People use them to travel between floodplains and villages by boat, use the plants that grow on their banks for food and construction materials, and pump the Prek water to their fields for irrigation during the dry season. There is a large variety of ecosystem services provided by the Preks.

However, as I also explain in this post, it’s necessary to take a more holistic perspective. Everything in this landscape is interconnected. And while the word ‘Prek’, strictly speaking, only refers to the water channel, the ‘Prek System’ that I study during my PhD encompasses the entirety of the landscape by the shaping hydrological processes – Prek channels, Chamkars and Boeungs.

But there’s an additional layer of complexity to the Prek system. Like I mentioned above, many Preks have faced erosion and sedimentation and have thus been limited in their functionalities. In some places, the natural inflow of water into the Preks only happens during a few months of the year. During the rest of the time, water needs to be pumped into the Preks if the people want to make use of them. This has led to water shortages and limited agricultural production due to a lack of irrigation.

Since the early 2000s, several development agencies, in partnership with the Cambodian ministries, have implemented rehabilitation projects. In most cases, that means that the Prek profiles have been restored through large-scale earthworks, new roads have been built along the Preks, and additional infrastructure such as gates has been installed. The purposes were to enable inflow into the Prek during longer periods during the year, and, in the case of gates, to make a regulation of inflow (and outflow) possible. In many cases, these projects have been fraught by problems, as I explain in more detail in a future post.

A gate that was built during a rehabilitation project in 2017

The bottom line, however, is that Preks are not only channels that are a typical element of the landscape of the Cambodian Mekong Delta. They are also a catalyst for landscape-shaping hydrological processes. And the Prek System encompasses not just the channels themselves, but also the landscape elements that they help shape – Chamkars and Boeungs.

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