Caught by the River

Cool Oak Diary #7

30th July 2022

July’s heat brings blanket weed, gulls, and a fire crew to Brent Reservoir (Welsh Harp), as Ben Watt and Cool Oak launch a new online initiative to help secure its future.

Parched July. The heatwave has accelerated the decay of late summer at Brent Reservoir (Welsh Harp). Wilting plants, desiccated grasses, paths of baked mud. A listlessness hangs in the air. Lunch-break workers lick dripping ice cream off the cone. Picnic debris sits in the verges.

On the water, floating mats of blanket weed proliferate, energised by the hot sunlight and high nutrient levels. The reason why lies in the inflowing rivers further upstream, where fertiliser washes off fields and lawns, sewage leaks into stream outfalls, the channels fill with clots of rotting leaves and animal dung. It all pushes up the phosphate and nitrate content of the water — and with little done by the Environment Agency to control it in decades, the rivers bring a banquet of destabilising nutrients to the reservoir. The hungry blanket weed simply thrives on it in summer and dominates. Algal blooms too. Oxygen is robbed from the water. Fish, invertebrates and more fragile aquatic plants suffocate. Feeding grounds on the marshes get incrementally worse. And the canoe club does its best to rake in as much of the damn stuff as it can.

July is also the beginning of gull season. Black-headed gulls are returning in bulk. Two hundred of them were stoically staging a sit-in among the plastic flotsam on the east marsh last week. A lone Mediterranean Gull — the birder’s dream find in a flock of black-headed gulls — dropped in on the north marsh. The first sighting of a common gull crops up on the local WhatsApp group. Other birds are starting to pass through again. I spy a dunlin feeding in the shadow of the crumbling breeding rafts. A gang of flighty sandpipers.

The rafts are now due to be replaced. Following our campaign for SSSI improvements, Canal and River Trust secured £70k-worth of funding for new ones last year. They will be ‘predator-proof modular systems’. The old ones were heroically made by local birders in the 1980s out of railway sleepers and insulation foam taken from the walls of a demolished Bejam supermarket nearby. Most of them are now beached on the silt reefs, slowing breaking apart like a stricken armada.

We’ve had to point out that the new rafts will need a temporary location in deeper water off the marsh, until the silt is dealt with. Half a metre needs skimming off at the deltas of the River Brent and Silk Stream for the rafts to float again. It’s a big expensive job fraught with logistical issues. The silt is thick and treacherous. It is also badly contaminated in places from years of urban runoff and chemical pollutants created by the neighbouring industrial estate. The Environment Agency will need to approve its disturbance. Removing it from site entirely would almost certainly be too costly, so it needs to be redeployed. We’ve recommended new reed bed peninsulas on the reservoir made from the deposits, or the creation of a new bund to contain it close to the estate.

The silt build-up is not just an issue affecting breeding wildlife and the shape of the wetlands. It is about the reservoir’s future flood resilience too. Under pressure from our campaign, Canal and River Trust reluctantly accept they will have to confront it in the end.

The issue forms the backbone of our new Future Habitats initiative launched this month — an online document of detailed maps and specific recommendations for the restoration of the reservoir. We have tried to make the maps crystal clear, the tasks managable, the whole thing inspiring. It has already prompted an encouraging response from the CEO of Canal and River Trust, and last night I presented it to a full house of councillors and stakeholders. I could see quiet nods of approval. I came away upbeat about it all.

Perhaps everyone’s highlight of the month though, was the arrival of the London Fire Brigade stationed in Brent to save the newly restored ‘Bomb Crater’ pond. You might remember how it was recently replanted with rare species once notable at the Welsh Harp but long since gone through poor stewardship. And how they’ve all been threatened by the drought. And how the fire brigade tried to help, but couldn’t get their truck through the gate. Well, breathe easy, readers. Under the guise of a training exercise, four strapping fire crew in tight red t-shirts came back and pumped water from the reservoir with their power pump, topping up the water level in a matter of minutes. They even posted a video thread about it on Twitter. 

As if that weren’t enough, veteran conservationist Leo brought down some extra fringed water lilies from his pond in Norfolk. They began life as cuttings from the Welsh Harp years ago.


Ben Watt is a musician and writer, best known as one half of Everything But The Girl. His memoir ‘Romany and Tom’, about his parents, was nominated for the Samuel Johnson (Baillie Gifford) Prize. He runs Buzzin’ Fly Records, and in 2021 founded environmental pressure group Cool Oak.

Ben’s website / Twitter / Instagram

Cool Oak’s website / Twitter / Instagram