HYDROLOGY AND GEOCHEMISTRY OF RIVERS DRAINING PEATLANDS IN NORTHWEST IRELAND

Peatlands are wetland ecosystems with high water tables and large accumulations of organic matter. Globally, peatlands store ~30% of soil carbon but are threatened by anthropogenic and climate fueled degradation. In many locations peatlands have been converted for other land uses, but the Republic of Ireland remains covered by ~15% peatland by area. The integrity of the Irish peatlands varies, as many have been subjected to extraction practices and drainage. These physical alterations can affect the chemistry and hydrology by decreased overland flow and increased transport of particulate organic carbon. Our analysis of Irish EPA and Public Works datasets from 2007–2021 investigated the hydrology and geochemistry of streams draining nearly undisturbed peatlands in northwest Ireland. These peatlands overlie crystalline and limestone bedrock, most of Paleozoic age. Historical data of NH₄, Cl, pH, conductivity, dissolved O₂, NO₂, NO₃, and PO₄ were compared from sixteen streams draining peatland in Counties Mayo, Galway, and Sligo. In all catchments, streams showed inverse relationships of discharge with pH, conductivity, and Cl. These historical data will be augmented with samples for geochemistry to be taken at the study sites in September 2023. Hydrologically, the maximum, mean, and median daily annual discharge for 1980–2020 increased or remained constant for all sites. The minimum daily annual discharge remained constant for the sites with the highest percentage of peatland by area. Disturbed sites with less peatland by area showed changing discharge over time. Catchments with greater peatland area are more hydrologically stable than catchments with less peatland. Catchments with more peatland disturbance are seemingly less flashy than nearly undisturbed ones. Human impacts such as land use change and drainage promote hydrologic changes. Our analyses provide a comprehensive understanding of the geochemical and hydrological relationships which can be used as a baseline for any future restoration.