Eroosiota ja sedimentin kulkeutumista kuvaavan INCA-SED mallin sovellus neljälle valuma-alueelle Suomessa

Suomessa. Valumavesien mukana maa-ainekseen kiinnittyneenä kulkeutuu myös ravinteitavastaanottaviin vesistöihin. Suomessa tärkeimmät eroosion mekanismit ovat sadepisaroiden iskutmaan pintaan, sekä erityisesti savimailla hiukkasten diffuusio kiinteästä maasta veteen. Lisäksimaahiukkasten kulkeutumiseen vaikuttavat uomassa tapahtuvat prosessit. Termillä 'sedimentinkulkeutuminen' kuvataan sekä maa-alueilla tapahtuvaa eroosiota että maahiukkasten kulkeutumistauomia pitkin valuma-alueen purkupisteeseen. Matemaattisen sedimentin kulkeutumista kuvaavanINCA-SED (Integrated Nutrients from CAtchment- Sediment) mallin sovellettavuutta jakäytettävyyttä ilmastonmuutoksen ja maankäytön muutosten vaikutusten arviointiin testattiin EU:nrahoittamassa Euro-limpacs projektissa. Mallista tehtiin sovellukset neljälle pienelle valuma-alueelle,joilla on erilaiset maalajit. Peltoprosentti tutkituilla valuma-alueilla vaihteli 12 ja 36 välillä. INCASEDmalli kykeni simuloimaan sekä joen kiintoainekonsentraation oikean tason että kausivaihtelunsekä savimailla että karkeammilla maalajeilla. Lisäksi mallinnettu sedimentin kulkeutuminen erimaankäyttöluokista vastasi Suomessa mitattuja arvoja. Esimerkiksi mallinnettu eroosiomaankäyttöluokassa 'viljakasvit savimaalla' oli 806 kg ha-1 a-1, kun mitattu arvo vaihteli välillä 760-1500 kg ha-1 a-1. Kiintoaineskonsentraation ja virtaaman välinen korrelaatio vaihteli selvästi eri joissa.Tämä ero selittyi INCA-SED mallissa valuma-alueiden maankäytöllä ja jokien erilaisellamorfologialla. Koska joen kiintoainekonsentraation kausivaihtelun oikea tavoittaminen onedellytyksenä ilmastomuutoksen vaikutusten luotettavalle mallintamiselle INCA-SED mallin voisanoa sopivan sekä maankäytön muutosten että ilmastonmuutoksen vaikutusten arviointiin Suomessa

Modeling denitrification in aquatic sediments

Author Posting. © The Author(s), 2008. This is the author's version of the work. It is posted here by permission of Springer for personal use, not for redistribution. The definitive version was published in Biogeochemistry 93 (2009): 159-178, doi:10.1007/s10533-008-9270-z.Sediment denitrification is a major pathway of fixed nitrogen loss from aquatic systems. Due to technical difficulties in measuring this process and its spatial and temporal variability, estimates of local, regional and global denitrification have to rely on a combination of measurements and models. Here we review approaches to describing denitrification in aquatic sediments, ranging from mechanistic diagenetic models to empirical parameterizations of nitrogen fluxes across the sediment-water interface. We also present a compilation of denitrification measurements and ancillary data for different aquatic systems, ranging from freshwater to marine. Based on this data compilation we reevaluate published parameterizations of denitrification. We recommend that future models of denitrification use (1) a combination of mechanistic diagenetic models and measurements where bottom waters are temporally hypoxic or anoxic, and (2) the much simpler correlations between denitrification and sediment oxygen consumption for oxic bottom waters. For our data set, inclusion of bottom water oxygen and nitrate concentrations in a multivariate regression did not improve the statistical fit.Financial support for AEG to work on the manuscript came from NSF NSF-DEB-0423565. KF, DB and DDT acknowledge support from NOAA CHRP grant NA07NOS4780191

Application of catchment scale sediment delivery model INCA-Sed to four small study catchments in Finland

The novel catchment scale erosion and sediment delivery model INCA-Sed was applied to four small study catchments in Finland. Three of these, the Mustajoki, Haarajoki and Luhdanjoki, are headwater catchments located in central Finland. The associated rivers have differing morphological characteristics varying from a ditch to a small river. Soil textures in the area are derived from moraine deposits and are largely sand and gravel. The Mustajoki and Haarajoki catchments are forested and only 10% of the area is under cultivation. In the Luhdanjoki catchment agricultural fields cover 40% of the area. The fourth study site, the Savijoki catchment, represents an intensively cultivated area in south-western Finland. Cultivated fields cover 40% of the catchment area, and they are located on clay soils along the river. The INCA-Sed model was able to capture both the correct magnitude and seasonal behaviour of suspended sediment concentrations in the rivers, as well as the correct magnitude of the sediment load derived from different land use classes. Small differences in river morphology and soil textures between the catchments have a significant influence on suspended sediment concentration in the rivers. Correct timing of suspended sediment concentration peaks is not, however, captured by the INCA-Sed model, which may be due to the stochastic nature of erosion and delivery processes at the catchment scale which are not taken into account in the parameter values used in the modelling. Parameter values were estimated from previous researches based on average process loads. The INCA-Sed model was, however, generally found to be a suitable tool for evaluating effects of land use change on erosion and sediment delivery in Finland as it correctly reproduces spatial and seasonal variations in sediment delivery, in addition to annual averages with spatial and temporal variations

An assessment of the fine sediment dynamics in an upland river system: INCA-Sed modifications and implications for fisheries

There is a need for better links between hydrology and ecology, specifically between landscapes and riverscapes to understand how processes and factors controlling the transport and storage of environmental pollution have affected or will affect the freshwater biota. Here we show how the INCA modelling framework, specifically INCA-Sed (the Integrated Catchments model for Sediments) can be used to link sediment delivery from the landscape to sediment changes in-stream. INCA-Sed is a dynamic, process-based, daily time step model. The first complete description of the equations used in the INCA-Sed software (version 1.9.11) is presented. This is followed by an application of INCA-Sed made to the River Lugg (1077 km2) in Wales. Excess suspended sediment can negatively affect salmonid health. The Lugg has a large and potentially threatened population of both Atlantic salmon (Salmo salar) and Brown Trout (Salmo trutta). With the exception of the extreme sediment transport processes, the model satisfactorily simulated both the hydrology and the sediment dynamics in the catchment. Model results indicate that diffuse soil loss is the most important sediment generation process in the catchment. In the River Lugg, the mean annual Guideline Standard for suspended sediment concentration, proposed by UKTAG, of 25 mg l− 1 is only slightly exceeded during the simulation period (1995–2000), indicating only minimal effect on the Atlantic salmon population. However, the daily time step simulation of INCA-Sed also allows the investigation of the critical spawning period. It shows that the sediment may have a significant negative effect on the fish population in years with high sediment runoff. It is proposed that the fine settled particles probably do not affect the salmonid egg incubation process, though suspended particles may damage the gills of fish and make the area unfavourable for spawning if the conditions do not improve

How can water quality be improved when the urban waste water directive has been fulfilled? A case study of the Lot river (France)

International audienceThe Lot river, a major tributary of the downstream Garonne river, the largest river on the Northern side of the Pyrenees Mountains, was intensively studied in the 1970s. A pioneering program called “Lot Rivière Claire” provided a diagnosis of water quality at the scale of the whole watershed and proposed an ambitious program to manage nutrient pollution and eutrophication largely caused by urban wastewater releases. Later on, the implementation of European directives from 1991 to 2000 resulted in the nearly complete treatment of point sources of pollution in spite of a doubling of the basin’s population. At the outlet of the Lot river, ammonium and phosphate contamination which respectively peaked to 1 mg N-NH4 L−1 and 0.3 mg P-PO4 L−1 in the 1980s returned to much lower levels in recent years (0.06 mg N-NH4 L−1 and 0.02 mg P-PO4 L−1), a reduction by a factor 15. However, during this time, nitrate contamination has regularly increased since the 1980s, from 0.5 to 1.2 mg N-NO3 L−1 in average, owing to the intensification of agriculture and livestock farming. Application of the Riverstrahler model allowed us to simulate the water quality of the Lot drainage network for the 2002–2014 period. We showed that, with respect to algal requirements, phosphorus and silica are well balanced, but nitrogen remains largely in excess over phosphorus and silica. This imbalance can be problematic for the ecological status of the water bodies. Using the model, for simulating various scenarios of watershed management, we showed that improvement of urban wastewater treatment would not result in any significant change in the river’s water quality. Even though arable land occupies a rather limited fraction of the watershed area, only the adoption of better farming practices or more radical changes in the agro-food system could reverse the trend of increasing nitrate contamination