Abstract. Excess phosphorus (P) loading is a major cause of deterioration in surface water quality. In Ireland, regulation has focussed on control of P losses from agriculture and wastewater treatment plants (WWTPs): the two main sources of excess P. Hindcast modelling for Lough Leane, south-west Ireland, indicated that, while the only municipal (point) source contributed up to 41% of the annual TP loading until the mid 1980s, over 90% of the TP load was from diffuse sources following upgrading of the WWTP. Field data from [2000][2001][2002][2003][2004][2005][2006] confirmed that most of the TP load came from agriculture, with 73% being exported between September and February, generally the wettest months in the region. However, the WWTP contributed up to 60% of daily loads during summer. Short lake residence times (two to four months) between October and February indicated that external loadings during these months were unlikely to make a significant contribution to summer phytoplankton growth in the lake. In contrast, the potential effects of point sources during low flows were maximised by longer residence times between April and September. The results highlight the importance to aquatic pollution impacts of, and therefore the need for regulatory responses to respect, seasonal variations in loading and residence time.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.