It was my English colleague-friend who told me about the meromictic lake in Penang State Park.

I can’t remember now why I contacted him in the first place. Or perhaps it came about because he replied an old email or something when I was already in Penang? Anyhow, I was in Penang for its street art when he told me about it. He had discovered the lake hiking in the forest and thought to mention it to me. You know, since I was going there. 

A meromictic lake? In Malaysia? Of course, being a nature nerd, I had to go see it too. 

What is a meromictic lake?

A meromictic lake is a lake which has two layers of water feeding into it, that do not mix. Typically the bottom layer is more saline than the top (otherwise the top would be denser, and there will inevitably be mixing as the top layer sinks down). This phenomenon results in a lake with a sharp halocline, or saline gradient, separating the two parts.

It’s pretty cool. I mean, it’s not like it’s visible to the naked eye, but nonetheless pretty cool.

I suspected that the one in the State Park was probably going to be due to the lake being fed both by incoming sea tide, as well as a freshwater creek. But it surely needed to be fairly smooth, almost laminar flow for those competing streams not to disturb the stratification. Unless the lake was big, but it didn’t seem likely. I mean, Penang is a pretty small island. I don’t remember big lakes mentioned for Penang in geography class. 

Getting to Penang State Park

I took the Hop-On Hop-Off tourist bus to get to Penang State Park (Taman Negara Pulau Pinang, in the local language). It was not a long ride, though it was nearly the last stop on the route.

The entrance had a convincing arch, assuring me of my arrival to the correct place. Around the entrance were stalls and shops with sellers hawking food and other tourist wares.

When I exited the park, this was where I bought my favourite blue-and-magenta pareo, which I nearly lost after glamping in Koh Laoliang (but which was returned to me via many trusty Thai hands). 

The hike to the meromictic lake in Penang

There are a number of jungle trails within the park. I determined that the meromictic lake lay along the route towards Pantai Kerachut. So I registered myself at the ranger station and started on that route. Having just returned from the Blue Mountains, I had recovered a considerable amount of my hiking confidence.

The start of the trail was easy enough. It even had boarded tracks, and well-constructed steps to manage inclines, all of which looked reasonably well-maintained. I was pretty impressed, especially considering the not inconsiderable maintenance challenges posed by equatorial rainforest conditions.

Hiking Penang State Park | path in Penang National Park |
Beginning of the trail…

A bit further, the park authorities have allowed more natural tracks to dominate. The atmosphere inside was – as is typical for the country – very humid and very hot. The sun was blinding white, but the trees close overhead and buffered its intensity.

Occasionally there were some discreetly constructed hiking aids, such as anchored ropes to assist with inclines, or stumps over waterlogged stretches.

Later on though, there were quite a few tough stretches. It was not exactly difficult, but challenging enough that I recalled that my friend claimed he hiked it in sandals. I was impressed with his agility, considering the muddy inclines were slippery enough even with my hiking boots!

Wooden stumps | waterlogged hiking trail | Hiking Penang State Park | Trekking Penang State Park | Taman Negara Pulau Pinang | Pantai Kerachut | meromictic lake | tasik meromiktik | Malaysia
Crossing a waterlogged stretch

The “invisible river”

Along the way the Forestry Department had placed information placards and boards, in an admirable persistence to ambush the hiking public with education.

Unfortunately, I find that I can never remember this sort of information. Not even useful ones of survival importance, despite the best efforts of my mother and various quite excellent jungle guides. I kind of remember what the hanging root looks like that you can cut open for potable water, and the leaf that you can use as soap. But that’s about it.

But I recognise this one, because it is my day job. So I geeked out a bit to see it. :) It is about groundwater. 

Groundwater information board | Penang State Park
Groundwater = the invisible (halimunan) river

The usual term for ‘groundwater’ in Malay is a fairly literal translation, ‘air tanah‘. But here, the powers that be have opted for a more romantic – albeit less accurate – term: ‘sungai halimunan‘. In English, that’s ‘invisible river’.

I sent the photo straight away to a couple of colleagues, who felt it was rather a dashing improvement on the staid technical term.

Hiking safety in tropical forests

There are ranger guide services that you can ask for in Penang State Park, but usually I can manage the smaller of Malaysia’s forest parks with a map of the trails, as I have a sense of what is meant by ‘trail’ in these parts. More like ‘woods’ rather than ‘jungle’, these are also more trafficked by the public.

However, you should definitely have a guide for the proper-sized jungles on the mainland, like Taman Negara or any of the Borneo ones. These are the ones where you can easily get lost, and are big enough to contain very dangerous creatures – large and small. Think of them as ‘trekking peers’ sharing trail knowledge if it makes you feel better.

You see, even though you register before going in, it’s not like the rangers make sure you check back out at the end of the day. So really, if you’re lost in there, there’s not going to be a search until someone misses you and raises the alarm.

Arriving at the meromictic lake in the wrong season

As I emerged out of the jungle into the open banks, and gained upon the lake, I immediately sensed my mistake. The lake looked a bit too shallow. Too shallow to possibly maintain two, unmixing layers of water. 

Meromictic lake | Penang State Park | Tasik meromiktik | Taman Negara Pulau Pinang

And I knew why. I was there early in the year, when the northernmost parts of Malaysia would experience a drier season similar to Thailand. This meant that the freshwater stream flow would reduce, and may not be enough to make a stable upper layer against the incoming and outgoing tidal flows from the sea.

It was a smallish lake. I walked around it to verify my suspicions.

First, I found the place where the sea pushed inland into the lake through a small channel. I didn’t check the tide tables beforehand, so I did not know the tide cycle. Nonetheless, water was visibly flowing from the sea through the channel. It widened and meandered for a short distance to the lake. Apparently this was enough to quiet the flow so that by the time it entered the lake, it became a smooth glide.

So far so good. 

Sea channel to Pantai Kerachut meromictic lake | Penang State Park | Tasik meromiktik | Taman Negara Pulau Pinang
The sea channel

The problem was the freshwater side. On the other side, the creek had dwindled to but a trickle. 

There was not enough flow from the creek to balance out the flow from the sea. Even the water at the very surface was brackish to the taste. But yeah, I could see how the setting could form a meromictic lake, given a wetter season. 

How would you ‘see’ a halocline? 

Thus far during the hike, I had entertained fanciful ideas about what I could possibly engineer with just the things I brought on the hike, to detect the salinity change. Since I wouldn’t be able to visually appreciate the halocline, perhaps there was a more indirect way to ‘see’ it, without resorting to actual scientific instruments. 

An experiment, if you will. Just for fun. Nothing viable came to mind, but it was fun to pretend I might’ve thought of something.

But it was all beside the point with the too-shallow lake.


Pantai Kerachut turtle nesting beach

The hiking trail ends at the little beach of Pantai Kerachut. At one end of the beach, there was a turtle sanctuary of sorts. It seems that turtles come to lay eggs on this beach. I learned it was possible to camp here, with permission from the park authorities. 

It’s a charming strip of sand, shaded lightly by stands of casuarina trees.  I could see families enjoying the beach and having picnics. The is reachable by boat, so you don’t need to hike through the park to get there. In fact, I returned to the entrance by boat, with an off-duty ranger and his boatman friend.

(This was, of course, the very boat trip with the Manchester medical students that led me to Barnsley, kickstarting the second phase of my Blue Period odyssey.)

Pantai Kerachut | Penang State Park | Pulau Pinang | Malaysia
Pantai Kerachut

Sustainability tip: bring food and water in reuseable containers. There are no food sellers within the park, including at Kerachut beach, and limited sanitation services. So it is best to minimise the potential for litter. Think of the baby turtles!!


Fancy a hike to Pantai Kerachut via the meromictic lake? Pin for later!

Hiking to the Meromictic Lake in Penang State Park travel article
Meromictic lake | Pantai Kerachut

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22 Responses

  1. Yvette says:

    I’ve never heard of a meromictic lake before! This hike looks awesome, I’ve always wanted to go to Penang…one day soon I hope. Thanks for all the tips

    • Teja says:

      Yeah, you wouldn’t be able to tell by looking that it’s a special lake. This is the sort of thing I enjoy in my travelling – the secret things that have to be understood, and not apparent otherwise. :)

  2. Aarti Kamath says:

    Wow.. something different to read today!.. I think you made everyone google about “Meromictic lake” today. Quite an informative post for me.

  3. yasmin says:

    I had never heard of a Meromictic lake before, so thanks for the introduction :) I’d love to visit one day and take the jungle hike myself :) thanks for the read!

  4. Ana says:

    That beach at the end of the hike is the best reward anybody could ask!

  5. Ketki says:

    I long studies about Meromictic lake when i was studying Geology and i was fascinated by it. You are lucky to have visited this place. Sounds amazing but the water in the lake looks stagnant and bad. Was it giving a stink?

    • Teja says:

      Hi Ketki! Meromictic lakes have to be somewhat stagnant for the layering to form, though, right?

      No, it didn’t smell. It’s just quite shallow at the time because of the dry season. However, you’re right – it is very common for our lakes to have a green tinge since there is a lot of organic content carried by the stream, and with that much sunlight algal growth is a given. But this one wasn’t quite eutrophic (yet).

  6. Lisa N says:

    This is the first time Iv’e heard about a meromictic lake, I suppose you learn something new every day! Sounds like the hike through the jungle is quite an adventure!

  7. Lien | GetLostAbroad says:

    I am just back from another meromictic lake: Lake Challa in Kenya ;-) I love hiking in national parks! It looks like you had the time of your life :)

  8. Maria Angelova says:

    Wow, I never thought such phenomena existed! I’m a big fan of everything odd and quirky so it’s on my list now!

    • Teja says:

      So am I… I mean, I like great views and absorbing culture as much as the next person. But tease me with some kind of strange and quirky phenomena and I’m stolen away!

  9. Iza Abao says:

    I searched more photos of the meromictic lake. They are cool and amazing. I had no idea about this before. The first part of the trail is nice but the other photo is not. Well, it looks more challenging but it would have been better if there is a proper trail.

  10. I didn’t know there WAS such a thing as a Meromictic Lake!! The hike sounds quite challenging – mud and humidity are never my favourite things – but it sounds like the rewards of seeing something unusual make up for it!

  11. neha says:

    Nature definitely has some amazing phenomenas. The meromictic lake like that only. Two layers of water that never mix! I had never heard of something like this. Very interesting.

    • Teja says:

      :) I’m interested in things like that. The meaning behind the things we visit – whether nature or something else.

  12. Sandy N Vyjay says:

    Reading about the Meromictic lake was fascinating. I always am awed by the limitless phenomenon of nature and how less we actually know anout them. Recently on a trip to Africa, I was at a lake which is know as an exploding lake. This is because of the volcanic activity around which effects the waters.

  13. Wow this is cool, never knew about meromictic lakes. Also the hike looks great, and the beach at the end is just lovely!

  14. Penny says:

    The invisible river does sound more romantic. It conjures a more mystical image in my mind. Something that would get incorporated in a fairy tale or a fantasy book. And people ask what’s in a name?