Watershed EUTROphication management through system oriented process modelling of Pressures, Impacts and Abatement actions.
A MILJØ2015 - TVERS project funded by RCN (190028/S30)
Impact assessments of changes in environmental pressures requires improved system and process understanding to reach the knowledge level needed for sustainable water resource management as well as meeting future demands from the EU Water Framework Directive (WFD). Both conventional and WFD resource management require a catchment-oriented approach to integrate processes.
Between ½ and 1 billion NOK is spent over the past 20 years on abatement actions along Morsa watercourse without optaining significantly lower concentrations of phosphorus (P) in the lake Vansjø. The Morsa site is thoroughly studied with long data records.
About the project
Using a DPSIR approach on its eutrophication problem we set out to achieve conceptual geochemical process understanding of fluxes of bio-available nutrient fractions. This is used to adapt, parameterize and optimize existing catchment and lake models to simulate environmental response to changes in pressures. These models are integrated with stakeholders compliment to abatement actions by means of Bayesian network in order conduct an integrated uncertainty analysis and provide a decision-support tool. In concluding, the societal response to how local and provincial government deal with eutrophication is studied using the Bayes model. The project thereby compile research and monitoring projects at Morsa, build on conclusions and identified knowledge gaps, and bring the science another step towards more policy relevant knowledge.
The aims are to:
- Increase our ability to monitor nutrient fractions
enabling us to
- Obtain a better understanding of the catchment processes governing variation in levels and fluxes of nutrient.
Thereby we will achieve
- A more accurate parameterisation of conceptually based impact of and response prediction models.
The subsequent aim is to facilitate development of sustainable management practices by:
- Estimating the integrated uncertainties linked to simulated environmental impacts as well as to societal responses to the implied abatement strategies by means of Bayesian network.
- Achieve a better understanding of societal response to implied abatement strategies.
The project is organized into five integrated work packages
• WP1 Development of sampling and laboratory methods for phosphorus fractions
• WP2 basin processes - influence of agriculture and hydrology on the transport of nutrients into the lake systems
• WP3 Modelling of catchment and lake processes
• WP4 Comprehensive analysis of uncertainty in estimates of the cost effectiveness of mitigation measures by using Bayesian network methodology
• WP5 Community response measures
Some results so far:
Breakthrough in DGT (NIVA): Promising new analytical method for free phosphate (P) and low molecular weight organic phosphate compounds in water. A new adsorbent of TiO is found to have much better properties.
The processes that control P levels in Vansjø are affected by changes in climate and environmental conditions during the past 25 years, including:
• Increase in rainfall and the frequency of heavy precipitation
• 2 º C increase in average winter temperature
Most of the flux of total P in a typical agricultural stream occurs at high flow, and most come during the spring melt and autumn. Years with mild winters (07/08) have significantly higher P flux than the years with cold winters (09/08 & 10/09). High iron content in soils around western Vansjø play likely a central role in transport and fate of P. High flux of P after floods are due to water saturated soils and low P content in sediments is due to rapid loss of P upon reducing conditions.
• Acid rain has been reduced by > 70%
Runoff from forested fields, which account for 80% of the catchment area, contributes a significant amount DNOM and labile inorganic aluminum (Ali). Since the peak of acid rain deposition the concentrations of DNOM is almost doubled, while Ali has declined to a third in fresh water in southern Norway. This has led to an increased P flux to the lake due to:
- Reduced co-precipitation of PO43- with Al3+ leached from upland acid forests soils upon passing through agricultural land around the lake.
- Increased leaching of P bound in dissolved natural organic matter (DNOM)
- Increased pH causing decreased PO4 sorption
- Decreased competition with SO42- for adsorption sites.
- Decreased ionic strength
Levels and composition of P fractions in Vansjø suggest that the importance of particulate P is overvalued. There appears on the other hand to be desorption of P from particles in the lake before sedmentation. Drainage pipes is an important transportation route of particle bound P. This is due to rapid transport of P from the plow layer through macro pores and erosion of the soil around the pipes which are marine clay saturated with P.
Ykalo Hadush Desta & Frøydis Meen Wærsted.