Nature-Based Solutions for Water - Part Two
Nature-Based Solutions for Water Pollution
TITLE: The United Nations World Water Development Report 2018: Nature Based Solutions for Water Pollution
CORPORATE AUTHOR: UNESCO World Water Assessment Programme
COPYRIGHT LICENSE TYPE: CCBY-SA 3.0 IGO. The text was edited for readability.
As the fifth in a series of annual, theme-oriented reports, the 2018 edition of the United Nations World Development Report (WWDR) focuses on opportunities to harness the natural processes that regulate various elements of the water cycle, which have become collectively known as nature-based solutions (NBS) for water. Maximizing nature’s potential can help to achieve the three main water management objectives – enhancing water availability, improving water quality and reducing water-related risks.
Since the 1990s, water pollution has worsened in almost all rivers in Africa, Asia and Latin America. The deterioration of water quality is expected to further escalate over the next decades and this will increase threats to human health, the environment, and sustainable development. Globally, the most prevalent water quality challenge is nutrient loading, which, depending on the region, is often associated with pathogen loading. Hundreds of chemicals are also impacting negatively on water quality. The greatest increases in exposure to pollutants are expected to occur in low-and lower-middle income countries, primarily because of higher population and economic growth and the lack of wastewater management systems.
Non-point (diffuse) source pollution from agriculture, notably nutrients, remains a critical problem worldwide, including in developed countries. It is also the one most amenable to NBS, as these can rehabilitate ecosystem services that enable soils to improve nutrient management, and hence lower fertilizer demand and reduce nutrient runoff and/or infiltration to groundwater.
Source water protection reduces water treatment costs for urban suppliers and also contributes to improved access to safe drinking water in rural communities. Forests, wetlands, and grasslands, as well as soils and crops, when managed properly, play important roles in regulating water quality by reducing sediment loadings, capturing and retaining pollutants, and recycling nutrients. Where water becomes polluted, both constructed and natural ecosystems can help improve water quality.
Urban green infrastructure is increasingly being used to manage and reduce pollution from urban runoff. Examples include green walls, roof gardens and vegetated infiltration or drainage basins to support wastewater treatment and reduce stormwater runoff. Wetlands are also used within urban environments to mitigate the impact of polluted stormwater runoff and wastewater. Both natural and constructed wetlands also biodegrade or immobilize a range of emerging pollutants, including certain pharmaceuticals, and often perform better than grey solutions. For certain chemicals, they may offer the only solution.
There are limits to how NBS can perform. For example, NBS options for industrial wastewater treatment depend on the pollutant type and its loading. For many polluted water sources, grey-infrastructure solutions may continue to be needed. However, industrial applications of NBS, particularly constructed wetlands for industrial wastewater treatment, are growing.