'Diffuse pollution' is pollution in which a variety of agents act collectively to inflict significant damage to freshwater ecosystems. Individually, these substances may not have much effect but, in combination, their impact is more serious. In rural areas for instance, the main sources of water pollution may include run-off from farmland, forests, and open spaces.
Such instances of pollution can be caused or exacerbated by rainfall in combination with various land management practices. Agrochemicals, increased nutrients, fecal deposits, chemicals, and sediment can wash off the land into rivers and watercourses, thereby degrading drinking water supplies. A particular problem is eutrophication, the growth of blue-green algae on lakes and rivers, which can deplete oxygen and release toxins into the water. This is usually caused by excessive increases in nutrients such as nitrogen and phosphorus from farmland runoff. Soil erosion can be a particularly serious issue in areas of torrential rainfall.
Wider environmental factors related to climate change, such as higher temperatures, lower river flows, and more frequent or severe flooding, can exacerbate existing water pollution.
The State of Water in Europe Today
In Europe, water quality standards are regulated by the Water Framework Directive (WFD), which was introduced within the European Union (EU) in 2000. EU member states are obliged by the Directive to publish River Basin Management Plans (RBMPs) that advise on how the requirements of the Directive will be met.
Based on data collected in accordance with RBMPs from 2010 to 2015, the report “European Waters Assessment of Status and Pressures 2018,” was published by the European Environment Agency (EEA). This report identified a clear lack of progress by European water protection organizations to restore water resources to healthy conditions. This is a serious problem given that 75% of all water extracted annually comes from surface water resources such as rivers, lakes, and reservoirs. Around forty percent of that is consumed as drinking water.
Challenges to Effective Action
Point sources of water pollution, where pollution comes directly from a single discrete location, are easier to identify and control. Such incidences are, in general, regulated and under control in Organisation for Economic Co-operation and Development (OECD) member countries. In contrast, diffuse-source pollution remains generally unregulated and is a major problem.
Diffuse pollution can come from a variety of sources, both natural and human-caused. Pollutants may follow several different routes (pathways) to their destination. They may also accumulate steadily over years before attaining detectable or noticeable levels. Difficulties in identifying the sources of pollutants hinder implementation of immediate or short-term solutions.
Major Viable Investments to Deliver Improved Water Quality
According to a 2017 OECD report, utilizing a combination of approaches would be most effective in managing pollution. Strengthening economic measures to make pollution a costly activity is one approach, but the most effective solution to water quality issues could be ‘nature-based solutions’ (NBS) such as planting of cover crops, riparian buffers, forest protection, and reforestation. In their 2020 report, “Resilient European Cities: Nature-Based Solutions for Clean Water,” the Nature Conservancy recommended that European countries prioritize NBS approaches in forthcoming River Basin Management plans for 2022-2027.
The planting of cover crops emerged in the report as the NBS with the strongest potential, primarily because they are very effective at preventing sediment and nutrient runoff. Furthermore, cover crops offer the most cost-effective solution and incur the lowest costs. Riparian buffers, vegetated strips of land located along the borders rivers or streams, are less effective but can still be useful at a local level to prevent runoff from reaching waterways.
Forest protection could also be an effective NBS measure. Forests, wetlands, and grasslands help to prevent water pollution, thereby functioning as an important regulator in the hydrological cycle. Of the 109 cities examined by the report, thirty-eight showed a high potential for reducing sediment pollution through forest protection. Reforestation has moderate or high potential in reducing phosphorous and sediment pollution in a significant number of the cities surveyed.
Promising Case Studies
VIENNA
Vienna has established a forest protection zone in its catchment area, consisting of 700 square km of land set aside for water resource conservation. The city has also implemented specific agricultural and forestry management regulations aimed at conserving soil and water resources, particularly groundwater and spring water.
MANCHESTER
Manchester’s drinking water mostly comes from the Lake District and the River Irwell. However, drinking water provision and protection is the responsibility of UK utility company United Utilities. In 2018, this company, alongside the Environment Agency, helped to fund a tree survey carried out by Greater Manchester’s Community Forest, City of Trees. The aim was to develop a strategic model investigating the potential for green investments (GI) to assist water resource protection. It focused particularly on the River Irwell catchment area but has also been extended to cover the Upper and Lower Mersey catchments. United Utilities has also held auctions in which farmers can bid for funding to grow cover crops over winter in order to help prevent excessive leaching of nitrates into the soil which threatens groundwater.
PARIS
In Paris the city public water service provider, Eau de Paris, serves 3 million consumers. Since 2008, it has:
provided farmers with financial assistance programs aimed at reducing fertilizer and pesticide use.
helped farmers to adopt organic farming practices.
helped farmers to develop market opportunities for their products.
purchased land at risk of contamination, which is then leased to the farmers for one euro.
In early 2020, Eau de Paris managed to acquire authorization from the European Commission (EC) to make direct payments to farmers in return for ecological services. This was not previously allowed by the EC as it was considered to be a form of subsidy. The rule change was a breakthrough moment as it could potentially pave the way for similar approaches in other cities.
LYON
Eau du Grand Lyon provides and distributes water in the metropolitan region of Grand Lyon. It does so under contract with the Lyon municipality and is actively protecting 375 hectares of land in the city center. Conserving natural ecosystems is more cost-effective than building a filtration plant and also delivers important biodiversity benefits.
When tailored to local needs, nature-based solutions can be a valuable tool for protecting freshwater. By working together with nature’s own processes, human communities can make great strides in ultimately securing the future of our greatest resource.
*Robin Whitlock is a freelance journalist based in the South West of England, UK and in particular a correspondent for Renewable Energy Magazine since 2011. He specializes in environmental issues, climate change and renewable energy, with other interests in transport, particularly rail, bus & coach and green motoring.