Type of EarthCache: Fluvial Landscape / Limnology
Mirror Lake, locally known as Tasik Cermin, is a hidden lake enclosed by limestone karst formations of Gunung Rapat. It is a rare gem that cannot be found on any tourist maps and the type of location you typically stumble upon while accidentally reading someone's blog, or via word of mouth.
View over Tasik Cermin, also known as Mirror Lake.
Type of EarthCache: Fluvial landform.
What is an endorheic basin?
Contrary to an exorheic basin, an endorheic basin is a closed drainage basin that retains precipitation and allows no outflow to other bodies of water, such as rivers or oceans, but converges instead into lakes or swamps, permanent or seasonal, that equilibrate through evaporation and/or seepage. Endorheic lakes tend to be sensitive to environmental pollutant inputs, as pollution can be trapped in them and accumulate over time.
How lakes disappear
Some endorheic lakes can disappear seasonally. These are referred to as intermittent, ephemeral, or seasonal lakes and can be found in karstic terrain. Other intermittent lakes are only the result of above-average precipitation in a closed, or endorheic basin, usually filling dry lake beds.
An endorheic basin is always a terminal lake, existing only for as long as the water supplied offsets evaporating and seepage. Should this equilibrium be lost, the lake would dry up completely.
Turbid lakes and lakes with many plant-eating fish tend to disappear more slowly. A lake may also be infilled with deposited sediment and gradually become a wetland such as a swamp or marsh. As such, a disappearing lake typically has extensive plant mats at the water's edge. Water plants will accelerate the closing process significantly as they partially decompose to form peat soils that fill the shallows. These provide a new habitat for other plants and animals. Gradually the lake closes and young peat may form, forming a fen. In the very last stages of succession, trees can grow in, eventually converting the wetland into a forest.
What about Mirror Lake?
Mirror Lake has an overall depth of about 6 metres (20 feet) only, and it is interesting to know that, despite being relatively small and shallow, it has yet to dry up completely.
Worth mentioning is that a cave system hides under its surface. Some claim it to be akin to a cenote, but is likely part of a large underlying aquifer which plays a significant role in the lake's survival. The aquifer spans the entire site known as Gunung Rapat, and thus connects to various other lakes and streams in the area. In layman's terms, the function of the aquifer is best compared to that of a simple water level device; under normal circumstances excess water is slowly absorbed, distributed and expelled through the aquifer, but during the dry season the flow of water might reverse, effectively supplying the lake with groundwater gained from nearby sources.
While significant changes in water level might be observed, the underlying aquifer is able to sustain the lake for a significant amount of time, preventing it from drying up and disappearing completely.
Another possible threat would be the natural closing process. Several decades ago, an iron mine was in operation here. A winch (it's former location still visible) stood here, pulling a huge cable dragging a barge that would take workers directly across to collect the iron deposits. They would fill up the barge, take the iron out through the tunnel, and do it all over again. To accommodate this activity an artificial bank was created, and it is in fact this bank on which the platform for visitors stands today. If it nature would be left to its own devices, this small bank might very well signify the beginning of the end, as it allows for plants to gain a foothold in shallow water, and it would undoubtedly aid and accelerate the closing process as described above.
The good news is that the closing process is a slow one, and Mirror Lake is unlikely to disappear anytime soon because of it! Instead, chances are that uncontrolled development in the surrounding areas might eventually be responsible for the demise of Mirror Lake. Should anything interfere with the workings of the underlying aquifer, things might quickly take a turn for the worst, and the lake might disappear within weeks if not days.
How to claim this EarthCache?
Send me the following;
1. The text "GC7RAGY Mirror Lake - Endorheic Basin" on the first line.
2. The answers to the following questions;
- Is Mirror Lake endorheic or exorheic basin?
- Why does Mirror Lake not overflow?
- Is it possible for Mirror Lake to disappear?
- How do you see Mirror Lake evolve?
3. Provide a photo of yourself or a personal item to prove you have visited the site.*
References
* Effective immediately from 10 June 2019, photo requirements are permitted on EarthCaches. This task is not optional, it is an addition to existing logging tasks! Logs that do not meet all requirements posed will no longer be accepted.
For additional information, visit; Geosociety.org, Geocaching.com Help Center and Geocaching.com Forum.
Finding the answers to an EarthCache can often be challenging, and many people tend to shy away from these caches because of this. However, it is my opinion that geocaching is also meant to be a fun family experience that simply aims to introduce interesting and unique locations such as this one. Flexibility on logging requirements, however, can only be applied if it can be established that you have actually taken the time to visit the site. For this reason, a proper log describing your adventure accompanied by a good number of photos would be much appreciated.
Join us at Geocaching Malaysia