Chadwick Lakes picnickers to be steered away from valley bed

Picknickers will be placed in designated areas due to the disturbance caused to the environment by discarding rubbish, trampling within the valley footprint and poaching tadpoles and frogs

Chadwick Lakes: Invasive crayfish to be eradicated
Chadwick Lakes: Invasive crayfish to be eradicated

A long overdue restoration of Chadwick Lakes is being proposed with the aim of protecting ecologically sensitive areas from being trampled upon by picnickers.

Chadwick Lakes is a popular recreational spot during winter months which attracts hundreds of picnickers.

But these are also known to cause disturbance to the environment by discarding rubbish, trampling within the valley footprint and poaching tadpoles and frogs.

The new project by the national Water and Energy Agency, will seek to limit picnickers to designated recreational areas, detached from the valley bed.

Nature enthusiasts and trekkers will still have access to the valley through trekking guided by informative signage on the area’s aquatic, natural and historical heritage. This will guide trekking to established pathways and avoid trespassing in the valley bed.

The project will also result in the removal of intrusive development, like a playground constructed in the 1990s in the centre of the valley bed.

Studies prepared by Environmental consultants ADI, reveal that the valley is presently in a deplorable state.

Lack of maintenance and proper management have led to a number of problems including a reduced surface water retention capacity due to the accumulation of sediment and debris, a proliferation of invasive and non-native plant species, the dilapidation of the rubble and retention walls and illegal dumping.

A number of off-road motorcyclists are also known to frequent the area and use the rural pathways to ‘scramble’ around the valley. This causes harm to the vegetation.

While EU guidelines specify that surface water used for drinking purposes should not have a nitrate level of 50 mg/l, most tests showed more than double or triple that amount at Chadwick Lakes

Moreover, most of the original infrastructure designed by Lord Chadwick in 1884, has been left in a derelict state. In an average rainfall year, the dams are estimated full, two to five times. If the three dams are repaired, cleaned and maintained, 70,000 cb.m of water would be stored.

Samples taken from surface water from five sites along Wied il-Fiddien and Wied il-Qlejgha, in 2017, had been tested by the Water Services Corporation and showed high values of nitrates, probably related to the use of fertilisers in the adjacent fields. Such fertilisers are transported to the valley bed by surface run-off and groundwater seepage.

Groundwater extraction and the resulting use of saline water due to salt water intrusion explains the high chloride content in the water. While EU guidelines specify that surface water used for drinking purposes should not have a nitrate level of 50 mg/l, most tests showed more than double or triple that amount at Chadwick Lakes.

Invasive crayfish eating tadpoles

Studies have also confirmed the pervasive presence of a crayfish native to North-Eastern Mexico and South-Central USA, which may pose a threat to the conservation of indigenous species at Chadwick Lakes.

The crayfish is tolerant of pollution, reaches sexual maturity within a few months and has a high fecundity rate. Unlike most crayfish species, it is also able to tolerate slightly saline water and low dissolved oxygen content. It is able to survive periods of drought, burrowing in mud.

The crayfish alters the pond landscape through its burrowing activity. This has been observed in a pond at Fiddien valley where the banks have been denuded of vegetation through the burrowing activity of the crayfish. The crayfish has also been seen preying on tadpoles at Chadwick Lakes. The omnivorous species may also pose a risk to plants and trees of conservation interest due to the potential presence of microfungal flora species living in its gutwhich harm other vegetation. This alien could also pose a risk to endemic freshwater crabs if it reaches watercourses where these species occur.

The best way to eliminate this species is through intensive trapping. While other countries like Italy have resorted to the use of the European eel to eradicate this crayfish, the introduction of this species known for its voracious appetite is not being recommended as it could end up gobbling other species.

To further ensure that the species does not survive, the ponds will be dredged and cleared of sediment up to a depth of 1.5 metres. The dredged material shall be disposed of in a dry site to ensure that any crayfish buried in it do not survive.

Another alien of significant concern recorded in the area is a semi-aquatic turtle known as Trachemys scripta elegans which has been recorded under the Ta’ Slampa bridge. This species is carnivorous and thus poses a direct threat to the endemic frog population as well as larger insects. Since only two specimens of this species were recorded during surveys, these can be removed manually and transported off site.

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