Dogging lay-bys blocked off at Llwyn Onn reservoir
Lay-bys near a beauty spot in the Brecon Beacons have been blocked off to stop people having sex in their cars.
Welsh Water has been prompted to install concrete blocks around the Llwyn Onn reservoir following complaints about people dogging.
Sandra Davies, of Merthyr Valley Ramblers, called it "a bit too much".
Welsh Water said the bollards were a response to "a number of complaints about anti-social behaviour".
The reservoir is just north of Merthyr Tydfil and the parking restrictions have hit those who fish in the area, as well as ramblers.
Ms Davies told Vanessa Feltz, who is hosting Radio 2's Jeremy Vine programme, Welsh Water could have put something else in place like a "sleeping bollard" which would halt night-time visitors but would allow drivers to park during the day.
"I do feel for the residents but these people have taken the enjoyment away from everybody else," she added.
"A lot of people are unaware that these lay-bys are being closed off."
Welsh Water said the lower car park would be open during the day to visitors and there were other parking spots in the area.
A spokesman said: "We're also working to improve access points around the site for those on foot so visitors genuinely using the reservoir and the facilities can continue to do so."
But Ms Davies said doggers would only be pushed into other areas and planned to raise her concerns with the Ramblers' UK head office.