The Effects of Development of a Tidal Barrage Upon the Water and Sediment Quality of the Mersey Estuary (U.K.) and its Biota

Abstract

The prime constraint upon the development of a tidal power generating barrage is the use of the Mersey estuary as a waste disposal facility. Historical disposal of persistent wastes continues to cause environmnetal problems, even though modern practices have resulted in a reduced pollution load. Mercury and lead have the greatest environmental significance, although with reference to barrage operation the nutrient status and increased transmission of light through less turbid water will be of equal or greater importance. A constraint upon the recreational use of the impounded water body will be the unacceptable numbers of faecal bacteria. A criterion for the design of the barrage should be the maximisation of the volume of water entering on each tidal cycle to disperse nutrients and pollutants and import as much oxygen as possible. This will minimise the increase of retention time and reduce the probability of methylation of mercury within the sediment. Additionally it will have implications for the feeding behaviour of the internationally important wildfowl populations.