Sub-Recent Changes in Annual Average Water Level in the Shannon Estuary, Western Ireland

Abstract

This paper describes results to date on work to reconstruct the pattern of sub-recent water level changes within the Shannon Estuary, western Ireland. The main database for the study covers the period 1949 to 2002, and includes observed tide gauge data and hydrological data. Routine statistical analyses are used to plot the relative position of the water surface through time, and to asses the relative significance of the components of an averaged water level curve that has been developed for Limerick City Dock at the head of the estuary. The findings form part of a larger project that aims to develop a time series of Mean Water Levels, Mean High Water Levels, Mean Low Water Levels and Mean Tidal Range in the context of human modification of the estuary since the mid-19th C, including land reclamation and environmental responses to predicted sea level changes. The newly assembled data presented indicate that average water levels have changed significantly between 1949 and 2002, including a clear overall rise in water surface elevation within the study period and particularly within the last decade. This paper quantifies the degree and rate of change evident from the averaged water level curve and explores the possible causes of the trend.