An investigation into the operation and function of floated water meadows

Floating is a form of water meadow management that uses natural or man made slopes to cause a shallow, but continuous sheet of water to flow through a grass sward, in order to increase productivity. This form of water meadow management was widely practised from the 17th Century, until the early 20th Century, since when it has essentially been abandoned. Investigations were carried out at Britford water meadows, S.S.S.I, Salisbury, Wiltshire. A significantly higher soil temperature was identified in floated areas compared with unfloated areas during two winter seasons (1996-97 and 1997-98). The temperature of floated soils was maintained at, or above 5.5oC, the threshold temperature above which grasses will grow. The hydrological characteristics of the meadows were described and the water budget required for effective floating established. Water samples were analysed for nitrogen (total/available), oxygen, phosphorous (total/available) and suspended sediments. Floated water was found highly oxygenated and maintained oxidative soil conditions throughout the floating period. A significant increase in soil nitrate was recorded immediately after the cessation of floating. However, nitrogen inputs from the incoming water roughly equalled losses via the tail drain. Phosphorous was closely associated with the deposition of suspended sediment, which is considerable in the initial stages of floating. Floating significantly increased dry weight productivity. The implication is that floated water meadows significantly decrease the phosphorous levels from the input water. Controlled experiments at the Rural Technology Unit (UEA, Norwich) found general agreement with the results from Britford, particularly in relation to the thermal regime and sward productivity. The main factors causing the increased grass productivity were identified and formed the basis of a model for water meadow operation.