Effects of Drain Blocking on the Acrotelm of Two Raised Bogs in the Irish Midlands: A Quantitative Assessment

Abstract

The development of the acrotelm on two Irish Midland raised bogs, Raheenmore Bog and Clara Bog East, where drains were blocked in 1995-1997 is described. The acrotelm of both bogs was surveyed in 1991 and 1992 before the blocking and again in late 2002 and early 2003, when effects seemed visually clear. To quantify the effects, both acrotelm depth and transmissivity were measured and compared in Raheenmore Bog and transmissivity in Clara Bog East. Because acrotelm transmissivity depends on the flow rate, a direct comparison was not possible. It was made by comparing field data with theoretical values based on upstream flow path length, surface slope and specific discharge of water from the bog. The results show a significant positive effect on both acrotelm depth and acrotelm transmissivity.