Phosphorous loads in the heilsau catchment spatial distribution and temporal variation

• Main Author: Jann, Valentin Elias
• Publication Date: 2024
• Format: Master thesis
• Language: eng
• Source: Repositórios Científicos de Acesso Aberto de Portugal (RCAAP)
• Download full: http://hdl.handle.net/10400.1/27028
• topic: Phosphorous; Mass balance; Source apportionment; C-Q relationship; Eutrophication; Catchment analysis

Eutrophication of aquatic ecosystems is a global environmental issue. Mostly caused by excessive inputs of nutrients such as phosphorous and nitrogen, a catchment-wide understanding of nutrient and sediment pathways and their drivers is necessary. This thesis focuses on the assessment of phosphorus (P) inputs in the Heilsau Catchment, aiming to better understand its impact on eutrophication. Utilising both historical data and own field measurements, this study examines various sources of phosphorus and their contributions to the total phosphorus load in the catchment. The study area was characterised by its hydrological, topographical, and land use features, with an assessment of soil, watercourses, and anthropogenic modifications. Discharge and precipitation data were integrated with instream water quality measurements to track the temporal variation and potential drivers of phosphorus loads. Furthermore, the concentration-discharge (C-Q) relationship was analysed, and a model was built for estimating P concentrations through baseflow and direct runoff contribution. Sampling of tributaries, sewage effluents, and drainage systems provided additional data on the spatial distribution of phosphorus from point and diffuse sources. Results indicate that the majority of phosphorous reaches the waterbodies through erosion, sewage effluents, and drainage. The analysis on a subcatchment level enabled to identify hotspot areas and hence interpret consequences for an improved catchment management. Measures should include the retention of sediments and dissolved phosphorous from erosion-prone areas, and the enhancement of P-removal in sewage treatment. This study contributes to the ongoing efforts of improving the water quality and secure ecosystem services in the Heilsau catchment, offering actionable insights for environmental management.