Summary

Our study is a report on environmental consequences.

During 1993-1994 a large operation was undertaken in a water-course in our nearest environment: The lower course of the Purmo River in Pedersöre, Finland was dredged. A special section of the river is generally called "Strömmen". We have examined the dredging, its extensive advance preparations and consequences in our study. We have also studied the "Strömmen" water-course itself with its vicinity.

It took ten years before the digging project was started and in 1993 the restoration of "Strömmen" could get under way. The water-course was already then very eutrophicated. The dredging was carried out by the help of an excavator, which carried on excavation on ice in the winter.

On 29.4.1994 our regularly taken water samples from different places in "Strömmen" showed that the pH value for the water was approximately 5.7. This is satisfactory in Finnish conditions. One must besides remember that where an area of Finland such as "Strömmen" is located, the earth is often very acid. We made analyses of the water samples during 28.4 - 13.10. 1994 and compared the results with those measured by the local authorities one year earlier. We could deduct that the water of "Strömmen" had not deteriorated by the dredging.

We have studied the consequences of dredging in several different ways. We have e.g. measured the ammonium content, alkality and phosphorus and nitrogen content in the water. We have also test fished' interviewed local experts as well as studied the flora and fauna by Strömmen. Our conclusion is that the environment is in acceptable condition around the water-course, but the after-care should not be neglected.

Preface

Summary
Preface
Table of contents
Introduction
Land rise leads to eutrophication
Strömmen in Östensö
    Background of dredging
    Handling in different instances
    Dredging 1993-1994
    Studies and attitudes
    Better water in Sandundsfjärden
    Water in Strömmen has low alkality
Study of Strömmen
     pH value
    Alkality
    Work processes and methods
    Excavation was carried out during two winters
    Two studies
Diagram on the pH value of the water
What are the consequences?
    Strömmen before excavations
    Acidity in Strömmen
    Second year setbacks
    Differences in water quality 1993-1994
    Ammonium content
    Alkality
    Phosphorus and nitrogen content
    Fish life
    Flora and fauna
References and assistants

Introduction

The impact of the ice age is still felt around the coast of the Baltic Sea. The last thawing of the ice age begun 15 000 - 10 000 years B.C. During the ice age the land was pressed down by an ice cover of a thickness of several kilometers, which can be compared with the inland ice in Greenland today. Since the ice age was over, the area of land which was previously covered by ice has been rising from the sea. This process is still going on. This rise of land occurs the fastest in the most northern part of the Baltic Sea, which is called the Gulf of Bothnia.

The shores of the Gulf of Bothnia are rising approx. 0.9 cm a year. This means that the land rise during the thousands of years has provided the coastal area of Finland with an abundance of new and fertile farmland. At the same time the land rise has brought problems to the residential areas on the coast. One of the examples of this is the location of towns on the coast. The towns were founded during the times at suitable harbors on the coast. After a couple of centuries the land rise had had the effect that the towns no longer were located on the coast. The towns had to be moved nearer the sea.

Land rise leads to eutrophication

When the land rise has closed up the former bays in the sea, large areas of wet land with little flow to the sea have formed. These marshes became ideal places for birds. The marshes are often flooding over in the spring. This creates a problem for farming, as the farmlands are often near the wet lands. Both fertile earth and manure are flushed with floods out to water and thus accelerate the eutrophication of the water-courses and the marshes. The land rise thus means that the water-course will grow over.

By restoring the natural rivers and waterways from the inland to the sea, success has been reached in minimizing the harmful effects of e.g. the overflow. The valuable birdlife by the watercourses and rivers should not be harmed.
We have in our study examined a typical eutrophicated water-course, which was restored. We have studied the "Strömmen" water-course, which has undergone the process described above. We have also studied how the environment has reacted when "Strömmen" was restored.

Dredging 1993-1994

The work in getting the project included in the government budget started after the approval. 1993 the first subsidy of FIM 500,000 was granted for the excavations, which were started when it was still icy in April 1993. In the winter of 1993-1994 the river dredging was completed.
Strömmen had then been excavated from Purmo river to Sandsundsfjärden (see map). Also Kärringhavet was excavated thoroughly and after the excavations the area was to be examined.

Cross section of Strömmen before dredging (According to our measurements):

Studies and attitudes

The studies which formed the basis for the project were carried out by researchers from the Uleåborg University and were made just for this project. Karleby Water and Environment District took measures during April-May of 1993. We have compared our own results with these results measured before the dredging. Already at an early stage of the project its consequences to the environment were discussed. The Fishing District deemed the project dangerous for the water quality of Larsmo lake. The District thought also that certain power plant interests were favored by the project. The Herrfors power plant believed that the excavations would be useful. They agreed that the excavated material should be limed to avoid an "acid shock". This was done and will be done.
The area fishermen did not agree about the effect of the project on fishing. Jakobstads Tidning newspaper (JT) gave a factual report on the project and built its articles on facts. JT did not take a stand on the issue, but Vasabladet newspaper took a negative stand right from the beginning.

Strömmen is the water-course connecting Sandsundsfjärden with Purmo river and running through Östensö. Strömmen was cleaned up during the winters of 1993-1994 and is now a canal. Excavations in Östensö were only part of a larger project, but we have in our studies concentrated only on the approx. 2.2 kilometer long Strömmen canal.

Background of the dredging

In the 1960s the lower course of the Purmo river was excavated and in connection with this excavation a plan was made to dredge Strömmen in Östensö. For financial reasons Strömmen was not dredged at that time.

An Östensö resident Stig Björklund took the first initiative for the dredging of Strömmen. This happened in the late summer of 1983 and the same year the Östensö village made a proposal to the Karleby Water District authorities to dredge the water-course running through the village. (The Karleby Water District is now called Karleby Water and Environment District). The same year the Edsevö residents presented a request to dredge a canal in the so-called Kärringhavet, which is located near the Bergö skiing center.
The Water District then wanted to combine these two projects into one large one. You could then get a so-called over-flow protection, large farmland areas could be saved from the annual floods. Another argument for the combination of the projects was that the upper course of the Purmo river had previously been cleaned up and this had led to the lower course of Purmo to be filled with silt. Strömmen was also a part of the lower course of the river and therefore the Water District decided that the project was necessary. The combination of projects was also reasonable from the economical point of view.
In the beginning and the middle of the 1980s large farm areas had been overflown in e.g. Katternö and Östensö during the spring flood. In Edsevö the residential area of Esse river was threatened. These two arguments for the dredging led eventually to the project called "Cleaning up the lower course of Purmo river." With the clean-up you would 1. Achieve an over-flow protection 2. Increase the recreation value of the water-courses 3. Increase the possibilities for fishing (Opposite views at this point. See under studies and attitudes).

Handling in different instances

At first all those who were going to be affected by the project would be heard in the so-called inspections. The concerned were e.g. the Water District, Wisaforest, Pedersöre community and landowners. Inspector engineer Simo Ventonen and a few trustees could then decide on the clean-up, or on the grounding of the whole assignment. The decision was for dredging, the lower course of the Purmo river would thus be cleaned up and the proposal was sent to the western Finland Water Court to consider. The proposal was discussed for a few years and approved.

Better water in Sandsundsfjärden

With the excavations in Östensö an effort was made to excavate the original riverbed in principle, only the sediment would be removed. An effort was made that as far as possible the alum layer would not be touched. With the dredging more water runs from Purmo river to Sandsundsfjärden. Also the water of Sundbäck runs there but its water has not been good in the recent years. Sandsundsfjärden, which has increasingly become overgrown in the recent years, will now probably get better water from the Purmo river after Strömmen has been excavated. From Sandsundsfjärden the water runs out through the Bockholm canal to Larsmo lake.
The flow from Strömmen to Sandsundsfjärden is 20 cm, which is quite much. Sandsundsfjärden is on the same level as Larsmo lake. This leads to that the stream in Strömmen is rather strong, especially in the narrowest part, the river bridge. The water runs through Strömmen out to Larsmo lake for the same reason as the Purmo river water.

Water in Strömmen has low alkality

Water samples have shown that the Strömmen water-course is very sensitive to acidification and to the effluents from e.g. farming. Therefore in Östensö it was agreed that nature nearest Strömmen should be left untouched. This on its part leads to that vegetation takes up the nutrient salts, which otherwise would run directly out of the river. With this simple method some of the nitrogen can be removed.
Because of the project the land by the water-course is not overflowing any more. These floods led earlier to that the water, when it started to recede, took with it e.g. nitrogen from the fields and this led to that eutrophication became more accelerated.
The background facts above are based on an interview on 3.5.1994 with the contact person for the assignment from the Regional History Society: Bjarne Wikström.

In our study of Strömmen we have mainly examined the water quality, but we have also taken photographs to be able to make comparisons of the area later. On two occasions we have carried out test fishing to control if there is fish in Strömmen after the excavations.
We have studied four factors in the water; the pH value, ammonium content, alkality and temperature. Some of the analyses were performed by the Jakobstad food laboratory.

pH value

The pH value shows how acid the water is. The pH is given in a range between 0 and 14. Water is neutral at pH 7. If the pH is over 7 the water is alkaline, under 7 it is acid. The pH scale is logarithmic. This means that when the pH drops one grade (e.g. from 7 to 6) the water becomes ten times more acid! As the water in nature is never absolutely clean, there are different substances in it. These substances can together have the effect that they lower the effect of acidity.

Alkality

Alkality is measured to get an idea of how sensitive a lake is for acidification (buffer capacity). If alkality is near zero, there are no substances to take care of the acid substances and the lake is very sensitive to acidification. If alkality is higher, the pH is not at first affected by the acid substances, alkality will instead decrease.

Work processes and methods

The study of water was made between 28.4. - 13.10 1994. In the first study we took water samples from eight different places in Strömmen at a depth of approx. 40 cm. Two of the water samples were taken of the inflowing water in Strömmen, sample no 3 from a ditch and sample no 6 from the so-called Sundbäcken.
The water was taken in small glass jars. Before measuring the pH value we kept jars in tepid water overnight so that the water did not come in contact with air. The pH measuring itself was done with electronic pH meter, brand name Knicks, which gives the pH value with the accuracy of two decimals.
The ammonium and alkaline tests were done with the school equipment for this purpose, i.e. with the aid of certain special chemicals, which were put in a box (Merck's indicators) for the purpose to determine the ammonium and alkaline contents.
The temperature was measured with an ordinary thermometer, but the temperature did not in this case have much meaning. At the first measurement the temperature in most of the sample spots was around 6 °C, at the second 8 °C and at the third and fourth measurements around 10°C. We did not measure the temperature on 13.10.

The excavation was done during two winters

The excavations were started in the winter of 1993, and approximately 400 meters were excavated from the place where Purmo river and Strömmen meet. In the winter of 1994 the excavations in Strömmen were completed. This means that we were already in the spring of 1994 after the ice had melted able to study the area where the excavations of the first winter had been done with a perspective of one year, and we could draw conclusions also of the consequences of the 1994 excavations.

Two studies

We made two studies. The first is based on the 8 water samples, which we took on 29.4.1994. As already mentioned, this tells what the Strömmen water was like at just this point of time.
In order to get some kind of a picture of the consequences the excavations will have in Strömmen in the long run and immediately, we compared the different studies. Therefore we requested the Karleby Water and Environment District to send us the relatively extensive study made in 1993 of the Larsmo lake. The Water District had then taken water samples on 28.4, 5.5, 12.5 and 25.5 and besides that during the summer and in the middle of October. We have compared the water samples taken in the middle October with the results of those we took, but let the Jakobstad district food laboratory analyze them. We will return to this study later in this report.
A place where the Water District took water samples was the bridge, where the Kållbyvägen crosses Purmo river and another one was at Strömleden. These studies, especially in Strömleden were not affected by the changes, which the excavations of the first winter may eventually have brought concerning the water quality.
We took water samples besides on 29.4. also on 5.5, 12.5, 25.5 and 13.10.1994 at Strömleden and where the bridge there crosses Purmo river. When we then compared these studies with the results of 1993, we discovered certain changes in the environment caused by the excavations. In view of the consequences of the excavations the second study was necessary.

What are the consequences?

Strömmen after clean-up

An effort was made to excavate only the original riverbed. The riverbed is now approximately 1.5 m deep and 10 - 15 m wide.
The Regional History Society Strömfåran has the responsibility to take care of Strömmen after the excavations. The so-called after-care shall by no means be neglected and Strömmen shall as as soon as possible become an area of natural beauty.
It looked rather unkempt in the summer of 1994 around the canal, but the work is going on all the time to lime and level the material. Dug up material, partly clay, is not a pleasant sight, but when it is sown and birch trees are planted on the masses, there is hope that the area will start looking better. It should be mentioned that the after-care was emphasized all the way from the beginning of the 1980s.

Acidity in Strömmen

After the excavations the material dug up was limed. 10 tons of lime per hectare was used. Agricultural lime was used and it was mixed in the surface layer of the material. Liming was necessary because the material was acid. It was started already during the summer of 1994 to plant birch trees in the residue. These will bind the earth so that it will not eventually run back in the riverbed. Birches have besides a positive effect on the acidity in the earth. Erosion should not be forgotten, because the dredging masses are very vulnerable.
The conclusions of our study of the condition of Strömmen on 29.4.1994 are that the water in Strömmen has improved. This depends to a great extent on that the water is now flowing more rapidly, which has great importance for the water quality. It is mainly water from Purmo river running in Strömmen, which makes the Strömmen water dependent on the upper course of the Purmo river. The average pH value in our eight water samples was 5.50. The water can still be described as acid, because fish will perish at pH 5. With the latest careful determination on 13.10.1994, the pH value was 5.5 (Jakobstad food laboratory analysis).

Second year setbacks

Our conclusions concerning the long-term consequences may be incorrect, if the so-called "second year setbacks" happen in Strömmen in 1995. This could mean that the excavated masses would then be leached by rain and ice and an "acid shock" would occur. At that point the pH value would decrease drastically. Other seasonal setbacks occur almost always after this kind of excavations. It becomes especially serious, if the alum layer has been dug up from the ground. Also heavy metals are then set free and end up in the water. In Strömmen the excavation of alum layers was avoided. But it is evident that the excavations were done this deep in some single spots. The original riverbed was however mainly excavated.
 

Differences in water quality 1993-1994

We received from the Karleby Water and Environment District the part of their water study of 1993, concerning Strömleden and the lower course of Purmo river. Our comparisons concerning the water quality in Strömleden (Sandsundsleden) 1993-1994 are shown in the diagrams of this report. The pH average in 1993 was 5.4 and in 1994 this value was 5.7. It is worth noticing that the pH value has not declined in 5 years as it did in 1993! The pH graph for 1994 was besides considerably more even than for 1993. It is somewhat disturbing that the pH value on 13.10.1994 was 0.1 lower than one year before. This means that the water at this point of time was not any better, but it has not deteriorated to any great extent.
The pH average for the year 1994 in Purmo river was 5.8. The corresponding figure for 1993 was 5.6. This kind of a variation in the pH value can be explained by the fluctuations in weather conditions from one year to another.

Ammonium content

We determined the ammonium content in four of our eight water samples from 29.4.1994. It is good for a water course to have a low ammonium content. The results of the samples were rather similar, the ammonium content in Strömmen is low. The ammonium content in samples during the
early summer 1994 was about zero. On 13.10.1994 the ammonium nitrogen content was 0.16 mg/1.
When a water-course comes in contact with the natural effluence from farming, its ammonium content will increase. But it is positive that the water in Strömmen does not contain any larger amounts of ammonium. It is shown by the water analyses made by the Karleby Water and Environment District in 1993 that the ammonium content is higher in the summer than in the spring and autumn. This depends on that the effluent from farming runs out in Strömmen through the ditches in the summer.

Alkality

We determined the alkality by four water samples. One sample was different from the others, this was no 6, which was taken from Sundbäcken (see map). Alkality there was very low-, near 0 mmol/l. The pH value for Sundbäcken was 4.85, i.e. very low. The other samples had alkality of 0.2 or 0.3 mmol/1.
Water in Sundbäcken is thus most sensitive to acidification. At the time of the measuring the creek was already acidified. Sundbäck is surrounded by fields and plantations, therefore it is to be expected that the creek will become even more acidified later, when the farming gets under way. Rain water carries some of the effluent overflowing from the fields directly out in the watercourse. Since Sundbäcken is an inflow creek into Strömmen, the Sundbäcken water can affect Strömmen in a negative way.
Alkality in Strömmen is relatively good. In an inflow ditch (no 3 on the map) even a 0.3 mmol/1 alkality was measured. The pH value of the ditch was the highest we have measured 29.4 in 1994 in Strömmen. It would be good for Strömmen if the alkality were high, then the water would be less sensitive.

Phosphorus and nitrogen content

We have discussed farming earlier in connection with the future of Strömmen. We asked the Jakobstad Regional Food Laboratory to test a water sample for 13.10.1994. The results showed that the water in Strömmen is good. It has not deteriorated so far because of the excavations. (See "Second year setbacks").
The total nitrogen content was 0.90 mg/1, which is a good value according to chemist Bertil Hällis of the food laboratory. The totål phosphorus content was typical for a farm village, 0.069 mg/l. The ammonium nitrogen content was 0.16 mg/1. It is a low figure and can not at all be claimed to be alarming. At the same point of time the nitrate nitrogen content was 0.06 mg/1, which is also a positive figure for Strömmen, stated Hällis.

Fishlife
Before the clean-up of Strömmen the future of the fish stock was disagreed on. In the stretch of Strömmen, which was cleaned in April 1993 you can now see what the excavations have brought with them with a perspective of one year. There is now an abundance of fish in this section. In one trap you can now get up to seven perches a night. Also pikes are common catches. In the summer of 1993 a lot of bream was caught in the traps, but in 1994 not as many breams have landed in the traps. Roaches are rather scarce in the traps.
On 5.5.1994 a half dead roach was found in Strömmen, more specifically in Fladan. This can be due to that the roach is very sensitive to a low pH value. The water in Strömmen one week before finding the dead roach was relatively acid.
During the test fishing we succeeded to catch ides in Strömmen. Usually there are no ides in Strömmen, so at this point it seems that the water has improved.
There is also fish in the part of Strömmen which was cleaned in 1993-1994. In Strömleden it is uncertain how much fish exist, but there will probably be fish there as soon as nature has recovered.
The interest in fishing in Strömmen is great. Many residents of Östensö have traps in the water-course and even nets are there. The village youngsters and even adults angled more than ever during the summer 1994 and with fine catches as the result.

Flora and fauna.

If the pH value in Strömmen is kept relatively good, the flora and fauna will not be harrned either. The muskrat has since the past, according to a local expert, strongly decreased in numbers after the excavations, but not become extinct. It should however be pointed out that the population of muskrats varies a lot from year to year. The Östensö Hunting Association reported in 1994 70 shot or trapped muskrats. At the annual meeting of the association in March 1995, it was concluded that the waterfowl yield in Östensö had been very small. This can almost totally be blamed on the dredging.
At the end of the 1980 Canada geese started to breed by Strömmen. Since then Canada geese have become more and more common visitors in the spring. After the excavations Canada geese have been observed but they did not breed in the summer in Strömmen. This can be thought to be due to that there is a lack of the necessary bottom vegetation. When we took a water sample on 12.5.1994 we noticed a cowslip (flower) on the bank where the excavating residue was. Nature had started to recover fast in this case!
It seems that there are not as many birds by Sandundsfjärden as normally before. The reasons are unknown, but the excavations of Strömmen seem at least have decreased the bird population in their vicinity.
The excavations were after all a big intervention in nature, but in the long-term view we think that birds, plants and animals will be comfortable, provided that the after-care is well taken care of and Strömmen is given the time to recover.

References:

Sursik Naturklubb water studies
IF Brahe's orienteering map 1987
Karleby Water and Environment District water studies 1993
Archives of the Regional Historical Society
Jakobstads Tidning newspaper
Österbottningen newspaper
Keskipohjanmaa newspaper
Vasabladet newspaper
Lagmansgården brochure

Those responsible for this work:

Research: Jonas Wikström, Kim Sundkvist
Water samples and analysis: Jonas Wikström, Kim Sundkvist, the Jakobstad regional food laboratory
Cameraman: Jonas Wikström
Layout and ADP services: Kim Sundkvist
Supervisor: Trygve Forssten

This is the fourth revised edition, which was the basic material for a competition participation in the Tutki-Kokeile-Kehitä competition 1995.