Monthly Evapotranspiration Coefficients of Large Reed Bed Habitats in the United Kingdom

The UK National Biodiversity Action Plan highlighted reed beds as a habitat of conservation concern and provided targets for the management, restoration and creation of reed beds throughout the UK, ideally in blocks greater than 20 ha in size. Previous water-use rate research by Aston University targeted small and fringe reed bed habitats. Extensive literature reviews carried out in 2000 identified a lack of information with respect to the water-use rates of larger reed beds. A research programme was developed utilising the lysimeter technique for determining evapotranspiration (ET) rates in large reed beds at three research sites. At each site, meteorological monitoring equipment and lysimeters were installed within the reed beds. Monitoring was carried out monthly throughout 2001 and 2002. Phenological data was collected from fixed quadrats within the reed beds and from the lysimeters during each site visit. This data was utilised to determine which of the lysimeters were ‘successful’, i.e. representative of the reed bed into which they where installed. From the ‘successful’ lysimeters, monthly crop coefficients (Kc) were derived using reference crop evapotranspiration (ETo) data provided by the UK Meteorological Office (MORECS Grass data). The results are compared with relevant published data and show that the findings are comparable with other studies.