How bad is bad water? About the devil being in the details

stan wód

The Water Framework Directive stipulated that all waters in its host countries reach good status by December 22, 2015. (perhaps with a few exceptions specified in a few paragraphs of Article 4). According to the River Basin Management Plans (RMPs), on that day the first water cycle ended and the second RMPs took effect. After updating the data, it turned out that only about half of the surface water bodies (water bodies) had succeeded in achieving the WFD target, while deviations from its rapid achievement were widely planned.

Based on data from the turn of the first two cycles, the European Environment Agency published in 2018. report entitled European waters. Assessment of status and pressures European waters. Assessment of status and pressures. It turned out that in some countries the condition of almost a hundred percent of the waters was rated as bad. In addition to Germany and Luxembourg, where such a result may come as little surprise, the same was indicated by Austria and Sweden. In the latest report on eutrophication, the problem appears to be greatest in Finland (80% of water bodies) and smallest in France (8%).

Who has it better, who has it worse? Comparing the incomparable

It is not uncommon for scientists to prove counterintuitive things with the help of statistical tools, and these are the most interesting and groundbreaking discoveries. In this case, however, the discrepancy between official reports and the sense of experts is too great. It’s really hard to believe that Alpine and Scandinavian rivers are the most polluted, and that agriculture has put ten times more strain on Finland’s waters than in France. It is clear that the data are incomparable for some reason, and the placing of waters in a particular category apparently depends more on the criteria adopted than the facts. It turns out, for example, that in Finland, the presence of agriculture in their catchment area is enough to declare waters at risk of eutrophication.

The explanation for the poor state of Sweden’s waters may be trivial – the country was one of the first to implement monitoring of polybrominated diphenylethers (pBDEs) not only in water, but also in fish tissues. The environmental standard, set at 8 pg/g fresh weight, is exceeded even by fish caught in the Arctic and Antarctic. Other countries took longer to implement pBDE monitoring (in Poland, until 2016), so the results did not affect the assessment of water status. By way of comparison, it is worth mentioning that in Romania, the chemical state of the water was assessed by the expert method for a long time, whatever that may mean.

In the same context, comparisons of water levels should be considered not only between different countries, but also at different times. In the report on the state of the environment (from 2008) in Poland, there is no information at all on the chemical status of waters, and the ecological status of riverine water bodies reached at least good in 2.2% (2007). A year later, the figure was 12.7%. In the case of lake water bodies, it looked better, as 47.1% of the waters reached good condition in this biennium. A subsequent report, published a decade later, presented not only a classification of ecological and chemical status, but also an overall assessment that is a composite of these. They divided according to the “worst decides” principle and differentiated the waters into only two classes – good or bad condition. A total of 7.25% of water bodies (rivers, lakes, coastal and transitional waters) reached good status. In the Synthetic Report on the State of the Waters 2014 – 2019, this fraction dropped to 0.5%, and in the latest statement to 0.4%. So it seems to be getting worse.

Why the deterioration? The devil is in the details

Keeping in mind the considerations of the first paragraphs, such a conclusion should be approached critically. First, monitoring is supposed to tell the state of water at the national and river basin area scale based on a representative sample, but its system is still developing. Between the 2010-2015 and 2016- 2021 cycles, the number of monitored water bodies increased significantly, which was, among other things, the result of a more thorough analysis of pressures in PGW than previously. More water bodies at risk of failing to meet environmental goals were identified and included in operational monitoring. It is very possible that they were already in poor condition, but this has not been demonstrated.

The factor that probably had the greatest impact on the proportion of waters in good and poor condition is the greater completeness of the classified indicators, and in accordance with the “worst decides” principle cited above, the proportion of bad grades increases. For example, in the 2010 – 2015 cycle, the status of ichthyofauna was able to be classified in 29% of the assessed water bodies, while in the next cycle it was already in nearly half. An example of a river whose condition initially took the first class, and was rated worse in the second survey due to the introduction of the classification of ichthyofauna, is the Białka Tatrzanska. This element indicated moderate condition (third class) due to partitions preventing proper fish migration to the sea.

In 2017. monitoring of lakes was expanded to include classification of the status of benthic macroinvertebrates, which affected downgrading in some lake water bodies.

The biggest change, however, was the new monitoring system for the aforementioned pBDEs. Just as Germany, Austria and Sweden once did, followed shortly by Slovenia, so now Poland (and other countries as well) has ensured that the standards for this element are almost 100 percent exceeded, with a consequent poor overall condition rating. Not surprisingly, one of the proposed changes to the WFD is the adoption of the principle that chemical status can only be classified on the basis of the set of required elements, not just those that have been successfully measured. This will certainly increase the number of unclassified watercourses, but the results of those that manage to be assessed will be more comparable. Arguably, this will not eliminate all problems, as it is likely that in some countries the more costly chemical analyses will be limited to selected watercourses.

The “worst decides” principle is an important tool in water management, because according to this approach, the most sensitive element is to be protected (the precautionary principle). Unfortunately, the more parameters that are tested, the greater the risk that any of them will exceed standards. The more developed the grading system, the greater the chance of getting a bad grade. This can give a misleading impression when comparing with a result obtained in a system based on fewer elements (e.g., in a different country or a different period). After several years of applying the WFD, it was realized that its assumptions were unrealistic. While some pressures are relatively easy to neutralize by improving the condition of related elements (e.g., upgrade the municipal wastewater treatment plant, which will improve parameters such as BOD or nutrient content), some pollutants have proven very difficult to eliminate. There is a group of so-called. uPBT ( ubiquitous, persistent, bioaccumulative and toxic), or ubiquitous, persistent, bioaccumulative and toxic pollutants, is known not to be quickly disposed of.

In this situation, the EEA has adopted the principle of presenting the results in two versions: one that conforms to the “worst decides” principle, where almost all waters that have been successfully assessed are classified as bad, and one that does not conform to this principle, after excluding uPBT. Then the picture is more diverse (cf. illustration taken from PGW for the Rhine). Water managers are frustrated by the fact that even when dozens of parameters manage to improve, it only takes one to remain below standard for the overall condition of the waters to continue to be rated as poor. The “worst decides” rule is thus subject to criticism, but the history of WFD reviews indicates that it is inviolable.

water levels
Chemical status assessment of the Rhine River and its tributaries according to PGW (as of 2015) including the set of chemical indicators (left panel) and excluding uPBT (right panel); source:

Analyzing historical results, it is difficult to draw correct conclusions. Even when the same parameters are monitored, the criteria for their classification have changed. Water quality has been studied systematically since about the middle of the 20th century, but what is considered a desirable state has been changing. Utility criteria used to dominate – suitability for drinking, recreation, aquaculture, industrial uses. Later, attention turned to the ability to absorb and dilute pollutants, and only – with the WFD – deviation from reference conditions, whatever they may be (quite different for a swamp river than for a mountain stream). The entire 21st century has been a period of intensive development of biotic indicators of water quality in Europe and harmonization of physicochemical indicators with them. It is also a period of development of ecotoxicological studies for priority substances. For an official, the adoption of a value ends the matter, but scientists always want a model that better corresponds to ecological relationships and are constantly striving to improve methods. Officials sooner or later give in and change the class limits. As a rule, to more stringent ones. For example, until a few years ago, an electrolytic conductivity of 1,000 µS/cm meant a very good ecological status for all rivers, but now such a value is allowed only in coastal watercourses.

Another problem in the presentation of results is the number of grade levels. The status of biological elements is rated in five classes. It can be assumed that the transition between the two cycles of evaluation from grade five to grade four or grade two to grade one is a significant improvement (although still unsatisfactory in the first case). This may be the result of a positive trend. A change of a few grades can be more surprising, or even alarming if it gets worse.

Biological elements are classified by numerical indicators that can be normalized to a range of 0-1. Meanwhile, the categorization of physicochemical and chemical elements is not limited by any upper value (ignoring the limitations associated with the saturation threshold of the solution). It is also worth noting that below good condition it is not graded further. This means that exceeding the standard, i.e. the boundary between good and worse-than-good status (formally, the name “bad” is not used for the status of chemical and physicochemical elements) by one or a thousand units is treated the same. Consequently, a reduction in pollution from a thousand units to one unit above the standard will not be reflected in the classification – a point on the map or a cell in the table will still be marked in red (denoting, according to the WFD color code, a poor condition).

So it’s not so bad? There is, but it’s more complicated

Thanks to the existence of numerical indicators of the status of biological elements (ecological quality ratio, EQR), it is possible to show changes in their status, even if this does not involve a change in class. With physical and chemical indicators, it is more difficult. This is paradoxical, because in their case you don’t need to create any complex indicators, the measurement result itself (such as temperature or concentration of a substance) is enough. However, the same measure cannot be applied to waters of different types. The same pH level in a lobelia lake and a brackish lake can mean a completely different ecological status. Nitrate concentrations, which are considered low in the Vistula in its Mazovian section, would indicate great pollution in the Beskids. Only very similar water bodies or the same body of water at different times can be compared directly. However, assuming that the set of monitored rivers is reasonably representative at the Polish scale, and that the use of the median mitigates the impact of extreme results, it is possible to compare such values between PGW cycles. For total nitrogen, for both the 2010 – 2015 and 2016 – 2021 cycles, the value was the same at 2.6 mg/L. For total phosphorus, there was almost no change either – it dropped from 0.16 mg/l to 0.15 mg/l, while the median conductivity barely increased from 474 µS/cm to 483 µS/cm.

Due to the constant evolution of the system, it is not always easy to even make such comparisons. In Poland, of the water bodies whose ecological status or potential was classified as at least good in the 2010 – 2015 cycle, about 70 river water bodies and almost 50 lake water bodies maintained a similar status, while the classification of more than 400 river water bodies and about 90 lake water bodies deteriorated. Some 40 river and 14 lake water bodies raised their status from below good to at least good. However, it is known that general classification alone, without analyzing its specific indicators, is fraught with risk.

You can also look at specific water bodies. Among those whose biological elements in the 2010 – 2015 cycle were classified in the second class, and in the following cycle as worse, is the Oder River from Osobloga to Mała Panew. In this water body, only phytoplankton (then just classified in the second class) and physicochemical elements were initially studied. In the last cycle, benthic macroinvertebrates and ichthyofauna were also monitored and assigned to Class IV. In addition, the criteria for physical and chemical elements were tightened – in 2014. The average annual electrolytic conductivity was even slightly higher than in 2020. (1483 µS/cm vs. 1230 µS/cm), but according to the criteria of the time, it was within the standard of good condition, while according to contemporary criteria it is no longer. In the same years, the value of total nitrogen was 4 and 5 mg/l, respectively, which, according to the revised criteria, means a transition from good to below good status. The third quality class was determined by the concentration of phosphate phosphorus. This parameter improved from good to very good status, but the classification of final ecological potential did not improve, and in fact deteriorated to poor, due to the inclusion of macrozoobenthos and fish classifications.

When making comparisons, it is also important to keep in mind the variability of parameters. Some waters have a specific state of pollution, such as the Poison Creek. As a result of the location of gold and arsenic mines above it in the past, subsequent studies confirm excessive amounts of arsenic. The limit of the standard for this element was also exceeded in earlier studies in Pawlowka near Legnica, but no longer in the latest ones. It’s hard to say whether this is a permanent improvement or a fluctuation. Sometimes changes occur not only between PGW cycles, but also during them. For example, in 2016. A record high value of total chromium was recorded in the Slowa River, a tributary of the Suprasl, while just three years later the value of this element was within the norm. A similar situation occurred with antimony in the Dunajec River. It happens that it is not just balancing around the limit. In 2017. maximum concentrations of chlorpyrifos were found in the source section of the Pilica River, and isoproturon in the estuary section of the Little Siletz River. Three years later, their levels at the same points had not even reached the limit of laboratory determination. Hence, single findings of pollution, even record-breaking ones, must be taken as a warning of a possible source of the problem (either contemporary or deposition in sediments), but when analyzing and interpreting them, it is worth taking into account the hydrographic situation and temporal variability.

All of the above deductions indicate how nuanced and cautious any interpretation of water assessment results is. I am not trying, contrary to official reports, to convince that the state of Polish waters is good, because it is not. However, it is important to keep in mind the simplifications that go into most aggregate and synthetic summaries. The issue is much more complex.

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