UK ECN site. The River Frome is essentially a rural catchment of high amenity and ecological value. The upper part of the catchment lies within the Dorset Area of Outstanding Natural Beauty and is characterised by steep-sided valleys. The only large urban area within the catchment is Dorchester (population 15,104). In the upper reaches the river is dependent on springs and groundwater levels for flows. Many of the steams are Winterbournes and the streams cease to flow in the Summer or are perched where the River goes underground for part of its length. All stretches of river above Holme Bridge fit into the Environment Agency's River Objective classes 1 & 2. These classes describe water of very good, or good quality suitable for all fish species. The majority of the catchment fits into the Environment Agency's Biological Classification class A. Land use in the catchment is typically permanent grassland with dairying or stock rearing, with some cereals and natural wetland habitats. The majority of the upper reaches lies on chalk which produces the high groundwater component of flow. The lower reaches are dominated by sands, gravels and clays. Rainfall in the catchment varies between 850-1100 mm a year. The Q95 is 34% of the mean annual flow reflecting how much of the flow depends on groundwater and how slowly the River responds to rainfall events.