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 did he reply an old email or something when I was already in Penang? Anyhow, I was already in Penang for the 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 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.
A bit further, the park authorities have allowed more natural tracks to dominate. The atmosphere inside was – as is typical – 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’s 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!
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.
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 ones of Malaysia’s forest parks with a map of the trails, because I have a sense of what is meant by ‘trail’ in these parts. This is riskier for hikers who are not used to jungle trekking in general, since you would be less habituated to recognise what could be considered a trail. These are also more trafficked by the public, so the trails are more obvious.
That said, definitely have a guide for 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 ‘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 else 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.
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 it 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 that by the time it entered the lake, it was a smooth glide. So far so good.
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 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.)
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!