Longitudinal Profiles of the Upper Towy Drainage System

Abstract

The High Plateau of central Wales has been deeply dissected by numerous rivers, some of which, such as the Severn, the Wye and their tributaries, flow eastwards, ultimately reaching the Bristol Channel; others, such as the Rheidol and the Ystwyth, flow westwards across the Coastal Plateau into Cardigan Bay. The Teifi, which reaches that bay much farther south, lies mainly on the Lower Plateau, its course being for some distance almost parallel to the boundary between the Coastal and the High Plateau. The Towy with its main tributaries arises near the summit of the High Plateau, and discharges into Carmarthen Bay. The southward-flowing trunk stream receives in succession the Camddwr and the Doethie-Pysgotwr, which come in from the north-west (Fig. 3.1). South-west of the Pysgotwr the Cothi flows for a few miles towards the Towy, then turns abruptly at right-angles, eventually joining the Towy at Nantgaredig many miles downstream. The portion which may be distinguished as the Upper Cothi formerly continued south-eastwards along the Gwenffrwd valley into the Towy, but has been diverted into its present course by capture. The Camddwr and Doethie-Pysgotwr join the main river above Rhandirmwyn, which is a mining village 7 miles north of Llandovery and about 15 miles from the source of the Towy. In the 25 miles which intervene between this place and Carmarthen, where it becomes tidal, the Towy receives only four tributaries comparable in size with those mentioned above, namely, the Bran at Llandovery, the Sawdde at Llangadock, the Cothi at Nantgaredig and the Gwili at Abergwili.