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INCA-N INCA-P New Papers

Tradeoffs for agri-environmental measure effectiveness

Katri Rankinen and colleagues have published a study of the effectiveness of agri-environmental measures to reduce nitrogen (N) and phosphorus (P) loads to receiving waters in Finland.

In areas with intensive agriculture, excessive nutrient loading causes deterioration of receiving surface waters. A number of measures are used to reduce nutrient loads but there can be tradeoffs. While nitrate and particulate phosphorus load can be efficiently controlled by reducing tillage frequency and increasing vegetation cover, this often leads to increased loading of bioavailable phosphorus. In the latest phase of the EU Rural Programme, measures with the highest potential to reduce the nutrient loading to receiving waters were setting limits for fertilization of arable crops and retaining plant cover on fields with, e.g., no-till methods and uncultivated areas. Due to the latter two measures, the area of vegetation cover Finland has increased since 1995, suggesting clear effects on nutrient loading in the catchment scale as well.

In the new paper, Katri Rankinen and colleagues modeled the effectiveness of agri-environmental measures to reduce N and P loads to receiving waters. They showed that INCA-P was able to simulate both fast (immediate) and slow (non-immediate) processes that influence P loading from catchments. It was also evident that no-till methods had increased bioavailable P load to receiving waters, even though total P and total N loading were reduced.

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New Papers

The Dominant Source Layer

José Ledesma’s paper on shifts in the Dominant Source Layer (DSL) under a future climate is now published in Journal of Hydrology.

The DSL is the riparian zone (RZ) depth layer that contributes most of the water and solute fluxes to streams. Specifically, the DSL concept can be used to explain timing and amount of terrestrial solutes transferred from RZs to headwater streams. Understanding the behavior of the DSL is key to predicting water quality responses to a changing climate. José and colleagues investigated the potential impact of future climate changes on the long-term position of the DSL in a subhumid Mediterranean headwater catchment. They used PERSiST to simulate reference (1981–2000) and future (2081–2100) stream runoff. Possible future conditions were simulated using synthetic temperature, precipitation, and inter-event length scenarios to project possible effects of changes in temperature, rainfall amount, and rainfall event frequency and intensity. Simulated stream runoff was then used to estimate RZ groundwater levels and DSL position. Their simulations suggested that future changes in temperature and precipitation will have similar effects on long-term DSL position. Nearly all scenarios projected drier conditions with less runoff and a deeper DSL. Shallow organic-rich layers in the RZ will likely only be hydrologically activated during sporadic, large rainfall episodes predicted for the most extreme inter-event length scenarios. In the future, terrestrial organic matter inputs to streams will decrease, likely reducing catchment organic matter exports and stream dissolved organic carbon concentrations.