Environmental change and high status water-bodies

Abstract

High status water-bodies (HSWs), as designated under the European Union (EU) Water Framework Directive (WFD), are rivers, lakes, transitional waters and coastal waters, that are close to natural status, representing conditions that are largely unimpacted by anthropogenic activities. These HSWs are sensitive areas that require special attention. However, in recent years large declines in the number of HSWs in Ireland have been observed, with these declines being attributed to pressures from point source pollution or unintentional discharges, along with low intensity practices potentially resulting from changes in land use and land cover. With this background, this PhD set out to present a review of HSWs and their management strategies in the European Union, and to investigate in three separate studies, the potential for HSW deteriorations to be caused by: 1) land use and land cover change; 2) hydrological (streamflow) modifications; and 3) sediment pressures. For these three studies, HSWs in Ireland were determined to have either: "Lost" their high status (e.g. gone from high to good, moderate, poor or bad); consistently "Maintained" their high status; or "Gained" in status (e.g. from good to high).

The review of HSWs in Europe (Chapter 1) highlighted how it may be counter-productive for countries to focus exclusively on achieving the "good" status objective of the WFD, while ignoring deteriorations to HSWs. Additionally, using case studies from four Member States with relatively large numbers of HSWs (Sweden, Austria, Ireland, and UK (Scotland)), the review assessed variations in strategies employed to manage HSWs. Based on these case studies it was determined that lag times between implementing management strategies and seeing actual benefits make assessing the effectiveness of such measures difficult, but that countries that have developed strategies may benefit from the sharing of knowledge, for example Ireland and Scotland.

The land cover change study (Chapter 2) demonstrated methods for assessing land cover change using CORINE data for three time periods: 2006-2012, 2000-2006 and 2000-2012; and found that anthropogenically influenced changes in land use and land cover types were linked to declines in water body status, with a higher level of natural/semi-natural land occurring in Maintained catchments. For example, in the period 2006-2012, land that changed from Forestry to Heterogeneous Agricultural areas was 17.5 times more likely to result in Lost status, whereas land that remained as Forestry or remained as Inland Wetlands reduced the chance of Lost status occurring by 15% and 4% respectively. However, the similarity of land cover trends between sites that have Lost and Gained status provided further research questions. In the hydrological (streamflow) modifications study (Chapter 3), despite differences being found in Lotic Index for Flow Evaluation (LIFE) scores between the Lost and Maintained status categories, all LIFE scores were generally about 7.25 and reflective of rivers hosting invertebrate communities with a preference for medium/high streamflow rates. While some hydrometric stations in the wider study area did display changing streamflow trends, which may potentially be linked to drainage and/or change in status, the overall conclusion was that for most sites, streamflow alterations are not likely to have been a major factor leading to deteriorations. However, for certain sites, and potentially in combination with other stressors, streamflow alterations may be problematic. The sediment study (Chapter 4) found that, macro-invertebrate taxa occurring in HSWs were pre-dominantly sediment sensitive taxa.

However, for two sediment specific metrics, the Proportion of Sediment-sensitive Index (PSI) and the Empirically-weighted PSI (E-PSI), significant differences were observed between sites that Lost status and those that Maintained status, implying that at some sites, sedimentation is impacting on macro-invertebrates. Again, no difference between Lost and Gained sites was observed, leaving an important caveat. While weak to moderate relationships were observed between the sediment metrics and the physical sediment variables, no difference between status categories for any of the physical sediment variables was observed, although this may be related to the sampling resolution. Chapter 4 also highlighted the potential for multiple-stressors, such as the interaction between sediment, organic pollution and streamflow alterations, to contribute to deteriorations in status. However, nutrient sampling indicated little or no evidence of nutrient enrichment at the majority of sample sites, and it is suggested that nutrient analysis at HSWs may be better served by higher resolution monitoring. Finally, key recommendations were suggested based on the overall findings of the PhD, that included: investigating if measures being implemented in catchments with Gained status may be replicated and possibly used to improve conditions at Lost status sites; and potentially including "impacting on high status water-bodies" as an additional category requiring Environmental Impact Assessments (especially in relation to drainage works).

Date of Award	Jun 2019
Original language	English
Sponsors	Department of Agriculture, Food and the Marine, Ireland
Supervisor	Joerg Arnscheidt (Supervisor), Phil Jordan (Supervisor) & Donnacha Doody (Supervisor)