Keywords

1 Water Resources and Diffuse Pollution

Four billion people experience severe water scarcity for at least one month each year. And an estimation is that, by 2025, roughly half of the world’s population could be living in areas facing water scarcity [8]. At the same time, water pollution is worrying all around the world. In many countries, even point source pollution is incompletely controlled. The text below is dealing with diffuse pollution, which is the main reason, for example, for eutrophication of many lakes in Finland. Finland is taken as an example because of a new tool called the Watershed Safety Plan (WSSP) approach to fight against diffuse pollution. The WSSP approach is currently piloted in Finland.

1.1 The Need for Diffuse Pollution Control

There are enough water resources in Finland – precipitation is 660 mm/a, and the total amount of water is more than 2000 km3/inhabitant. When talking about water resources, Finland is number one in the European Union [4]. Even so, climate change will bring some challenges to Finland as well. While in many parts of the world severe droughts are worrying, in Nordic Countries, predictions are showing increment in annual precipitation. In Finland, the growing season for vegetation is roughly four months per year only. When the temperature becomes higher, instead of snow cover and frost during winters, the country will face more rain and thus, more diffuse pollution from agricultural areas mainly, but from forests and urban areas as well [10].

So far, the mitigation of diffuse pollution has depended on single actions placed more or less randomly in catchment areas. For example, the agri-environmental programme in Finland has been supporting farmers in implementing sedimentation ponds, wetlands, etc. according to their own interests and naturally on their own farms – without considering the catchments as a whole. This has not been an efficient way of reducing nutrient loads causing eutrophication in waters. Actually, very little or no reduction has been measured [3, 7].

The European Union Water Framework Directive (WFD 2000) has been shown to be the most ambitious piece of EU environmental legislation. Its aim is to restore European waters, but in spite of positive development, not all results have beent reached so far. The main objectives were – and still are – non-deterioration of water status and achievement of good status for all EU waters. It seems that some new tools are needed to fulfil the directive’s targets [11].

Implementation of EU’s Drinking Water Directive is to ensure healthy drinking water for all. One important task in this work is the so-called risk assessment, taking into account the entire water production and distribution system. Thus, water utilities producing drinking water should have risks assessed in the catchments as well [2].

There are many other reasons to be listed in supporting the need for new approaches in water protection. One regional document to be mentioned is the Road Map for Circular Economy in Kanta-Häme. Kanta-Häme is a region of 11 municipalities in Southern Finland. The road map which was published in the beginning of 2022 includes five sub-areas, one being water use and water bodies. An ambitious goal under this sub-area is to reach the diffuse-pollution-free region by 2035. One important tool mentioned for working towards this goal is the Watershed Safety Plan (WSSP) approach. Thus, when implemented, the road map is one route to reach the targets of WFD as well [6].

2 The Difference Between Point Source Pollution and Diffuse Pollution

The word responsibility has quite an interesting and important role when considering The Constitution of Finland (731/1999) [9]. In Section 20 of the constitution, it is written: “Nature and its biodiversity, the environment and national heritage are the responsibility of everyone.” This is underlined in the Environmental Protection Act (86/2000) [1]. In this act, there are several principles that people and organisations should follow in their daily operations. All should be aware about their effects on the environment, risks should be minimised, the best available technology and best available practices should be taken in use, etc.

Now, when considering the word responsibility and the mentioned legislation, one could answer the following: Who is to mitigate, for example, the pollution seen in the Fig. 1?

Fig. 1.
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Diffuse pollution originates quite often from a visible point.

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Actually, when looking at various pollution sources and legislation carefully, one can notice that the only difference is control. Point source pollution is (or it should be) under control. Small but numerous pollution sources which are not controlled are considered under the concept of diffuse pollution. A good example is on-site sanitation (Fig. 2). Finland enacted new legislation for household-level wastewater treatment in the beginning of this century. Thus, on-site sanitation was taken from the category of diffuse pollution into the category of point source pollution.

Fig. 2.
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When legislation and technology are advancing, more diffuse pollution sources will be removed into the category of point source pollution [5].

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How can small pollution sources be tackled effectively with existing limited resources? This is the question to which the WSSP approach tries to bring a practical solution. The approach is nothing complicated, only working systematically and using so-called common sense.

3 Watershed Safety Plan Approach

The WSSP approach is now in its piloting phase in Finland. The idea is based on Water Safety Plans (WSP) [12] and Sanitation Safety Plans (SSP) [13] promoted by WHO. WSP and SSP are meant to secure human health by investigating the whole water service chain to find and mitigate all possible risks. WSSP is to do the same in the catchment areas. The only difference is that WSSP is concentrating not only on the human health aspects but also on all kinds of risks – ecological, environmental and even economical risks. By utilising WSSP, together with WSP and SSP, the whole water circle (not the atmospheric water) becomes secured (Fig. 3).

Fig. 3.
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WSSp approach will complete the safety of water circulation

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3.1 How to Implement WSSP

There is no fixed way to utilise the WSSP approach yet. The first-ever piloting is on-going in Finland in 2021–2022. The pilot is implemented by following the steps of WSP, as shown in Fig. 4.

To ensure that limited human resources are needed as little as possible, all available open data and various GIS-tools are utlised first. After obtaining various maps of the catchment - land use, ditches, networks for wastewater and run-off waters, point source pollution sites, etc. - and researching them one above the other, possible ‘hot spots’ (= points where the probability of diffuse pollution is obvious) can be located. The steps onward depend on the catchment itself. Tools to be utilised are different when working in agricultural areas, forests or in urban catchments. In some cases, the next tool to be considered might be a drone, in some other cases it might be a set of meetings with land owners, and so on. Naturally, when talking about mitigation actions, the variety of tools is really manifold. That is why, instead of WSSP, one should use the concept WSSP toolbox. From the toolbox, the most appropriate tools are to be utilised, and the whole process is tailormade depending on the local circumstances.

Fig. 4.
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In the first piloting of the WSSP approach, the steps in WSP are followed to some extent.

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So far in the pilot case, the catchment, land use and various networks in the area are defined. An example of the land-use map is in Fig. 5. Today, more detailed investigations are ongoing.

Fig. 5.
figure 5

Various land uses in the Kuhalanoja catchment area in Forssa, Finland

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When applying the WSSP approach in another area, one could use much simpler chains of action than given in Fig. 4. There are just a few principles to take into account:

  • First use open data and tools which limit the need for human resources.

  • In most cases, investigations in private estates are needed. Thus, communication is inevitable to avoid conflicts and drawbacks in water protection.

  • Be systematic – it is the only way that all important diffuse pollution sources can be found and sustainable results gained.

3.2 Development of WSSP Approach

It is evident that more of the pollution sources, which today are considered diffuse, are going to be tackled as point source pollution (see the big arrow in Fig. 2). Thus, either the WSSP approach or something similar must be developed. There are several initiatives where the WSSP approach is involved today, and the development work is advancing.

There are many advantages when using the WSSP approach instead of water quality improvements only. For example, flooding in big cities is causing extremely expensive damages, and WSSP could be used in finding the most risky places to cause flooding problems and tools for mitigating those.

4 Conclusions

While there is plenty of work to do to control point source pollution worldwide, in most parts of Europe, the fight against diffuse pollution is at the top of the list. This is seen, for example, from Sect. 1.1. So far, the actions taken have not been very promising. Thus, new, more-efficient tools are required. The WSSP approach is investigating catchments like using a magnifying glass, and even the smallest pollution sources are found and mitigation measures planned, designed, implemented, monitored and reported.

The challenge to create diffuse-pollution-free catchments and regions is really ambitious. The WSSP approach is one of the tools under piloting. More tools are invited to gain experience and make actual progress in water protection work.