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Hydrology and surface water chemistry in a small forested catchment : which factors influence surface water acidity?

Jensen, Maja LU (2017) In Student thesis series INES NGEM01 20171
Dept of Physical Geography and Ecosystem Science
Abstract
Water chemistry alterations such as acidification and eutrophication represent major threats to the running waters of the world, and Swedish waters are among the most vulnerable. In this study the small forested catchment Storskogen, part of the SWETHRO monitoring network, was analysed to examine the links between deposition, catchment hydrological properties and surface water chemistry. Storskogen was characterised in terms of physical and chemical hydrology, and compared to the well-studied catchment Gårdsjön. Both catchments were inventoried to document the distribution of wetlands in order to examine to what extent they influence surface water chemistry. The water balance model FyrisQ was used to model discharge from Storskogen and was... (More)
Water chemistry alterations such as acidification and eutrophication represent major threats to the running waters of the world, and Swedish waters are among the most vulnerable. In this study the small forested catchment Storskogen, part of the SWETHRO monitoring network, was analysed to examine the links between deposition, catchment hydrological properties and surface water chemistry. Storskogen was characterised in terms of physical and chemical hydrology, and compared to the well-studied catchment Gårdsjön. Both catchments were inventoried to document the distribution of wetlands in order to examine to what extent they influence surface water chemistry. The water balance model FyrisQ was used to model discharge from Storskogen and was validated using measurement data collected by IVL from 2014 to 2017.
The stream in Storskogen had an observed median discharge of 0.7 l s-1 and responded quickly to precipitation, which could cause a tenfold increase in discharge. For this reason, the model FyrisQ, was found to be inappropriate because it could not adequately recreate the dynamics of the discharge. Surface water was found to be acidic (pH< 5) with significantly lower acid neutralising capacity and pH upstream in Storskogen than downstream. Surface water in Gårdsjön was more acidic than in Storskogen. Even though the surface waters’ acid neutralising capacity was found to be significantly correlated with deposition, none of the examined factors (deposition, mineralogy and wetland extent) could account for the observed differences in acidity between the upper and lower dam in Storskogen, or between Storskogen and Gårdsjön. The pH of both catchments was correlated with deposition of sea salt however, the amounts did not differ significantly between sites. It is likely that the difference in acidity between the upper and lower part of the catchment in Storskogen can be explained by different transit times but to prove this, further monitoring is encouraged. (Less)
Popular Abstract (Swedish)
Försurning och övergödning utgör betydande hot mot världens ytvatten och svenska vatten är bland de mest utsatta. I den här studien har avrinningsområdet Storskogen analyserats för att undersöka sambandet mellan atmosfäriskt nedfall, hydrologi och ytvattenkemi.

Med atmosfäriskt nedfall menas de luftburna föroreningar som landar på avrinningsområdet antingen för att de fångas upp av trädkronorna eller för att de lösts upp i regnet. Storskogen är en undersökningsyta inom kronddroppsnätet som övervakar atmosfäriskt nedfall av framförallt försurande och övergödande svavel- och kväveföreningar på över 60 skogsytor i Sverige. I Storskogen mättes man inte bara nedfall utan även avrinning, alltså det vatten som lämnar avrinningsområdet som... (More)
Försurning och övergödning utgör betydande hot mot världens ytvatten och svenska vatten är bland de mest utsatta. I den här studien har avrinningsområdet Storskogen analyserats för att undersöka sambandet mellan atmosfäriskt nedfall, hydrologi och ytvattenkemi.

Med atmosfäriskt nedfall menas de luftburna föroreningar som landar på avrinningsområdet antingen för att de fångas upp av trädkronorna eller för att de lösts upp i regnet. Storskogen är en undersökningsyta inom kronddroppsnätet som övervakar atmosfäriskt nedfall av framförallt försurande och övergödande svavel- och kväveföreningar på över 60 skogsytor i Sverige. I Storskogen mättes man inte bara nedfall utan även avrinning, alltså det vatten som lämnar avrinningsområdet som ytvatten. Den lilla bäcken i Storskogen hade en låg medianavrinning men avrinningen ökade snabbt och kunde bli tio gånger så stor vid kraftiga regn. Ytvattnet visade sig vara surt (pH <5), och både pH och den syraneutraliserande kapaciteten var lägre uppströms än nedströms. I studien testades dessutom en enkel vattenbalansmodell, FyrisQ, för att modellera avrinning från Storskogen. Modellresultaten validerades med hjälp av mätdata. På grund av avrinningens snabba svar på nederbörd visade sig modellen FyrisQ vara olämplig eftersom den inte på ett tillfredsställande sätt kunde återskapa avrinningens dynamik.

Storskogen jämfördes också med ett annat avrinningsområde, nämligen Gårdsjön. Båda avrinningsområdena besöktes för att dokumentera fördelningen av våtmarker för att i sin tur undersöka i vilken utsträckning de påverkar ytvattenkemi. Ytvattnet i Gårdsjön var surare än i Storskogen.

För att försöka förklara skillnaderna i surhet, dels mellan övre och nedre dammen i Storskogen, och dels mellan Storskogen och Gårdsjön, undersöktes det om det fanns några skillnades i nedfall, våtmarksutbredning och mineraljordens sammansättning men inga av de undersökta faktorerna kunde ensamt förklara de observerade skillnaderna Det är troligt att skillnaden i surhet mellan övre och nedre delen av avloppet i Storskogen kan förklaras av olika transittider, men för att bevisa detta behövs ytterligare studier. (Less)
Please use this url to cite or link to this publication:
author
Jensen, Maja LU
supervisor
organization
course
NGEM01 20171
year
type
H2 - Master's Degree (Two Years)
subject
keywords
Physical geography, ecosystem analysis, hydrology, surface water chemistry, acidification, deposition, water balance modelling
publication/series
Student thesis series INES
report number
431
language
English
id
8918357
date added to LUP
2017-06-26 09:49:47
date last changed
2017-06-26 09:49:47
@misc{8918357,
  abstract     = {Water chemistry alterations such as acidification and eutrophication represent major threats to the running waters of the world, and Swedish waters are among the most vulnerable. In this study the small forested catchment Storskogen, part of the SWETHRO monitoring network, was analysed to examine the links between deposition, catchment hydrological properties and surface water chemistry. Storskogen was characterised in terms of physical and chemical hydrology, and compared to the well-studied catchment Gårdsjön. Both catchments were inventoried to document the distribution of wetlands in order to examine to what extent they influence surface water chemistry. The water balance model FyrisQ was used to model discharge from Storskogen and was validated using measurement data collected by IVL from 2014 to 2017.
The stream in Storskogen had an observed median discharge of 0.7 l s-1 and responded quickly to precipitation, which could cause a tenfold increase in discharge. For this reason, the model FyrisQ, was found to be inappropriate because it could not adequately recreate the dynamics of the discharge. Surface water was found to be acidic (pH< 5) with significantly lower acid neutralising capacity and pH upstream in Storskogen than downstream. Surface water in Gårdsjön was more acidic than in Storskogen. Even though the surface waters’ acid neutralising capacity was found to be significantly correlated with deposition, none of the examined factors (deposition, mineralogy and wetland extent) could account for the observed differences in acidity between the upper and lower dam in Storskogen, or between Storskogen and Gårdsjön. The pH of both catchments was correlated with deposition of sea salt however, the amounts did not differ significantly between sites. It is likely that the difference in acidity between the upper and lower part of the catchment in Storskogen can be explained by different transit times but to prove this, further monitoring is encouraged.},
  author       = {Jensen, Maja},
  keyword      = {Physical geography,ecosystem analysis,hydrology,surface water chemistry,acidification,deposition,water balance modelling},
  language     = {eng},
  note         = {Student Paper},
  series       = {Student thesis series INES},
  title        = {Hydrology and surface water chemistry in a small forested catchment : which factors influence surface water acidity?},
  year         = {2017},
}