1. GAM in time series of water chemistry
Jens Fölster

2. In 2015 Swedish freshwater monitoring celebrated 50 year anniversary
This year, the Swedish monitoring celebrates it’s 50th anniversery and we are very grateful to the foreseeing precursors who started it.
11th of may there, will be a big celebration. The King will come
The Swedish monitoring of freshwater has been very successful in producing long term, high quality data of water chemistry and biological parameters.
We hope that the experience from the Swedish case can be of inspiration to other countries that are building up their monitoring programs so that we 50 years from now we will have a good understanding of how human impact has changed fresh water quality on a global scale.

3. Mälaren investigation in 1965
The Swedish Natural Science Research Council initiated the investigation
Resulted in proofs for P as the controlling nutrient
Decisions to introduce P stripping in all larger wastewater treatment plants were made in 1969
It started with the great investigation of the lake Mälare with the first samples taken in the autumn of 1964.
The Swedish Natural Science Research Council thought that the scientific community should take it’s responsibility for socity’s problems with increasing poor water quality in one of Swedns largest lakes.
It funded the investigation as a project at the new limnology department at Uppsala University with prof Willem Rofhe as the professor and Torsten Ahl and Torbjörn Wille,
It gave proofs for P as the controlling nutrient for primary production in the lake and resulted in an evidence based decision on introduction of P stripping in all larger wastewater treatment plants

4. The River mouth network started 1965
Financed by the Swedish Natural Science Research Council
In 1967 the river mouth network together with the meaurements in Mälaren along with 3 other large lakes became the core of the fresh water monitoring program as a part of the newly established SEPA
In 1965 the Swedish Natural Science Research Council started the River mouth network with monthly sampling of water chemistry I the larger river mouths.
In 1967 the river mouth network together with the meaurements in Mälaren along with 3 other large lakes, became the core of the fresh water monitoring program as a part of th enewly established SEPA
Helgeån. Photo Lars-Göran Karlsson

5. The Swedish national fresh water monitoring program today
Large lakes (Start 1965)
3 lakes, 16 sites, chemistry and biology
Lake survey (Since 1972 or 1995)
4 800 lakes, 800 sampled each year
Trend lakes (1984)
108 lakes, chemistry and biology
River mouths (1965)
47 sites, 82 % of land area, chemistry
Trend streams (1984)
67 sites, chemistry and biology (n=48)
Integrated Monitoring (1997)
4 sites
Agricultural catchments (1990)
8 sites
When the acidification problem was discovered, the society responded in starting new progtrams in small lakes and streams and today the national program consists of chemical and biological sampling in:
And with time series often of 30 to 50 years performed by the same laboratory and with a few changes in methods throughout the years
All data is free available on the internet.

6. In some cases, the effects were obvious!
Åtgärden gav omeldelbar effekt nedströms reningsverkn. I nedströms sjöar var det en fördröjning.
Exempel på hur MÖ kan användas som underlag för åtgärder och sedna följa upp att det haft effekt
Mälarundersökningen blev starten på ett nationelt MÖ-program i stora sjöar och flodmynningar
Introductiuon of P stripping

7. Time series of water chemistry
Seasonal variation
Nitrate in Råån
AbsF in

8. Time series of water chemistry
Correlation of concentration to flow
Hysteresis effect
Nitrate in Råån
AbsF in
From Evans and Davies 1998)

9. Lij =αj +βijqij +εij, i=1,2,...,n, j=1,2,...,m,
Semiparametric models for flow normalisation of nitrogen load
Lij =αj +βijqij +εij, i=1,2,...,n, j=1,2,...,m,
Stålnacke et al. 1999
Seasonal-Kendall monotonic trend tests on flow normalised monthly loads
Mann-Kendall monotonic trend tests on annual loads
A few declines related to point sources
Several increases in N downstream lakes with earlier P-reductions

10. Effects from measures against nutrient leaching from agricultural soils
20 year trends
Inorganic N
(nitrite+nitrate + ammonium)
Flow-normalised transport

11. Decreased transport to the sea since the reference year 1995
Inorganic N Skagerak
25%
Oorganiskt kväve Östersjön
Inorganic N Öresund
Inorganic N Kattegatt
24%
21%
Totalfosfor Östersjön
11%
Prickar visar uppmätt årstransport
Svarta linjer visar flödesnomerad transport
Grön linje visar trendlinje anpassad till de flödesnormerade transporter.

12. Example: two Swedish west-coast rivers with decreasing trends
Flow-normalised transport of inorganic N
Obs möjlig ökning på slutet.
Naturlig variation eller trendbrott?
Fortsätt mäta.

13. When does a smoothed line have a significant trend?
GAM-model developed by Gavin Simpson in the evaluation of the UK Acid Waters Monitoring Network (Kernan, 2010)
Cubic spline and cyclic cubic spline smothers
CAR for autocorrelation in time
Testing if the derivate of the smoothed line is different from zero.
CAR continous auto regression

15. Simpson’s model applicated on Swedish nutrient data
By Claudia and Kerstin

16. Application in environmental management
Indicator for following up of environmental goal
A selection of agricultural dominated streams with high quality data
Apply GAM model
For each year calculate the fraction of significant increases and decreases in e.g. NO3 and Tot-P