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THE NATURAL HISTORY OF THE SMALLER RADNORSHIRE POOLS F. M. SLATER Ponds and pools tend to be the Cinderellas of the aquatic world lacking the assumed beauty and interest of rivers, lakes and reservoirs. However, like Cinderella's ephemeral elegance, some pools, as we shall see, have, similarly, an often ephemeral claim to fame, but one which puts them in the top league of biological interest. The distinction between pools and ponds is not clear cut, as the former can merge upwards in size into lakes or downwards to blur the distinction between them and ponds. There are, however, several distinct types of small water bodies relating to their origins or position. In the river valleys there are a few pools which occur on the alluvial plain and are frequently related to the former course of the river, but rarely in Radnorshire do they occur as classic ox-bows. There are often quite rich pools in chemical terms and are not infrequently flushed out by the rivers when in flood. The best examples lie in the Wye valley downstream of Llyswen. At the other altitudinal extreme there are peaty hilltop pools particularly in the area of Radnorshire to the west of the River Wye, where the water is acid and brown and the substrate is blanket peat. Here the water chemistry is deficient in most elements making it suitable for collection in reservoirs for public water supply as there are insufficient nutrients to allow contaminating algal growth. Along the hilltops fringing the east of the Wye and Ithon valleys are some shallow, often ephemeral, pools with an unusual flora and fauna being most closely related to sites of the New Forest in Hampshire. Here the water chemistry is intermediate between the two preceding types and probably changes markedly with season as the water evaporates and in consequence the dissolved minerals become more concentrated. Before the advent of piped water and troughs, almost every field needed its pond. Several decades of neglect have seen many disappear but grant aid and a reawakening of environmental awareness have flooded many odd comers of Radnorshire to the benefit of wildlife. Farm and field ponds are as varied in their physical and chemical nature as their position, substrate and inflows dictate, with some pure enough for trout ponds and others with a green Euglenoid algal growth over a rich farmyard slurry. A few water bodies do not fit in to the above classification. For although Llandrindod Wells has its "Lake" it is, from a biological point of view, a large and unique pool and deserves special mention. Other infrequent pool types include quarry pools, lowland bog pools in natural hollows and it may be said that collections from swimming pools have advanced our knowledge of newt distribution in the area! Table 1 illustrates the varied chemical nature of pools in central Powys for chemistry is the keystone governing the natural history of ponds.