Loe Pool

Understanding our habitat’s past is
the first step in creating thriving environments for the future



Loe Pool is Cornwall’s largest natural lake. The lake is also known as ‘Logh’ from the Cornish, meaning pool. It is a Site of Special Scientific Interest, which means it is an area that’s of particular interest to science due to the rare species of fauna or flora it contains, or because of the important geological or physiological features that lie within its boundaries. It is an area with high conservation value, and needs to be protected.

Loe Pool has been owned and managed by the Natural Trust since 1974. when the Penrose Estate was given to them by Lieutenant Commander Rogers.

The lake’s history so far
Loe Pool used to be brimming with underwater vegetation. However, from the mid-1970s up until 2006, summer algae blooms took over the lake, dominating the water and turning it a murky shade of green, shutting out the light and stripping the water of oxygen. 

Around half of the nutrients leaking into Loe Pool come from sources that are easy to identify such as South West Water’s sewerage treatment works at Helston and Royal Navy Air Station (RNAS) Culdrose, and the rest come from scattered sources such as agriculture, domestic septic tanks and light industry in Helston.

We have made huge progress in reducing the excess of nutrients in the lake, particularly phosphate, with the help of South West Water. Thanks to this, there have been no algae blooms since 2006.

Average total phosphorous concentration across the Cober Catchment
between 1995 and 2019

Loe Pool inputs TP (1)

Source: Environment Agency. Last updated July 2020

farmers 2

Special habitats, wildlife and their management


Important habitats and wildlife in Loe Pool

1 – Willow Carr: The Willow Carr at the Helston end of Loe Pool features a mosaic of reed beds, small shaded pools, large decaying willows, dense carr and open glades. An expanse of Grey Willow also provides an important nectar source for a wide range of insects in spring. In fact, the Cober valley contains the largest community of Grey Willow in West Cornwall

Because the Carr is so exposed, the ground flora has become well-developed, and we have a great diversity of wetland species, such as yellow iris, meadowsweet, and trifid bur-marigold (rare in Cornwall). The southern end of the carr is wetter and covered in common reed.

In 1946 a section of the Cober between Loe Marsh and Helston was turned into canals. While this draining hasn’t affected the plants significantly so far, it could mean that climate warming causes drier summers in the future, which may harm the flora in the wetlands.

2 – Loe Marsh: Loe Marsh is a reedy shoreline which encroaches on the water around the Cober outfall. It rises around 1 metre every 20 years. There has been a gradual spread of reed beds around the edge of the pool over the last 50 years due to grazing being reduced and a  rise in nutrient levels.


Loe Marsh at sunset

You can see some significant bird species such as reed warbler, sedge warbler and reed bunting in the willow carr and reed beds of Loe Pool. Reed bunting, which is on the RSPB Red List has been spotted here – its numbers have halved since 1996.

You’ll also find Cetti’s warbler, which is on the RSPB’s Amber List of species. It was barely present in Cornwall until the late 1970s, and now is only found in the Tamar Valley, Penrose,Gunwalloe and Marazion Marshes in Cornwall.


Otter in Carminowe Creek

3 – Trout and Otters: You can see Loe Trout, which is unique to the area, here. The trout use the river for spawning, but are vulnerable to fishing in the area. The poor water quality and algal blooms of Loe Pool help boost other species, such as rudd and perch. Dredging the river can harm egg development in the gravels, yet, where water quality is good, Loe Trout spawn very successfully. 

You will see otters along the Penrose stretch of the River Cober and around Loe Pool. However, in 1998, work to reduce the effects of flooding damaged their habitat. This work also created an informal path that is regularly used by dog walkers, and this further disturbs the habitat for otters and other wildlife.


Woodlands at Penrose

4 – Woodlands: Woodlands have been important aesthetically and economically at Penrose for centuries. They provide renewable timber, fruit and fuel, and beauty and inspiration for owners and visitors. The woodlands and parkland trees have reflected changes over time and their long lifespan means they still provide glimpses of the past use and management of the land.

woodlands 1

5 thoughts on “Loe Pool

  1. Due to samples taken from pollen below the pool confirmation has been thereby presented that arable land existed there millennia ago, before the sea came up into Helston around 1014 AD. Helston, as we know it, was a port for only a comparatively short period until some time before 1260 AD when the oldest section of St. Johns’ bridge was constructed. During the next 700 years a 25 foot deep belt of silt accumulated along Nansloe Valley upon a seven foot depth of sea sand, upon peat, upon the rock bed. The initial formation of silt began to close off the harbour that was situated in Castle Green car park, with only part of its wall left. That wall extended right up to where the 1833 road is now, enclosing small trees and shrubs by c1800 AD. However, just recently, Roman remains have been detected under the pool; so if Hen Lis ever had a port in Roman times it was not likely to have encroached any further than there.

    • Hi Nathan. I’m afraid the National Trust do not allow any kayaking, watersports, or fishing on Loe Pool. This was at the request of the Rogers family when the estate was donated, to ensure it remained a wildlife haven and place of tranquility for all to enjoy. Thanks.

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