His orchestral piece "Reservoirs" was inspired by a 1968 poem by R. S. Thomas about the drowning of Welsh valleys such as Tryweryn (a few miles from where Puw grew up) and Clywedog to provide water for England. Puw had a particular affinity with the topic as his grandfather lost farmland in the Tryweryn flooding. Nevertheless, he has said that he "decided not to take the poem too literally because as a composer you can be subject to criticism for doing that." It was nominated in 2005 in the Large-Scale Composition category of the Royal Philharmonic Society Music Awards. The music was used in a BBC2 Wales documentary, "Drowning a Village", broadcast on 9 March 2006. A performance by BBC NOW was broadcast on BBC Radio 3 as part of the 2005 Vale of Glamorgan Festival.