63% of the capacity held in Wales’s 150 reservoirs supplies England with its water. Between the 1890s and the 1960s, the construction of three reservoirs in Wales – Fyrnwy, Tryweryn, Elan / Claerwen - enabled the continued population growth and industrial development of Merseyside and the English West Midlands. The construction of the reservoirs involved the infamous drowning of Welsh-language communities, which in the case of Tryweryn, lit the touchpaper of the Welsh-language movement, drew attention to the Welsh democratic deficit within the UK, and boosted the cause of Welsh independence. Less well known is that the construction of each reservoir also established enormous watersheds around each lake – areas in which economic and industrial development was severely restricted. For Elan / Claerwen, the area of the watershed equalled the size of Birmingham, the main city in the region that the reservoir supplied. For these three lakes alone, the watersheds constitute 3% of Wales’ land surface. This paper records some of the ways in which the literary record has registered these reservoirs, their watersheds and what they mean for Welsh culture – focusing especially on poems by Ruth Bidgood, R.S. Thomas and Harri Webb.