On March 22, every year, the world turns its attention to the global water crisis on the occasion of World Water Day. Water policies around the world need urgent reform. Water–an essential natural resource on which all life depends–has become a global garbage can. You wouldn’t think you could kill a freshwater ecosystem or an ocean, would you? But the biodiversity of freshwater ecosystems has been degraded more than any other ecosystem. And more than 400 dead zones have been identified in the world’s oceans. Pollution is a major driver of such damage. The effects of water pollution imperil not only ecosystems but also human lives and economic growth. At least half the world’s population suffers from polluted water. Millions of people die each year due to water-related diseases. Pollution hotspots occur in all parts of the world, including OECD countries, where current pollution costs exceed billions of dollars each year. The situation is set to worsen. Population growth and climate change are placing increasing pressure on the ability of finite water bodies to process wastewater, nutrients and other pollutants before they lose their life-supporting function. This will, in turn, increase risks to human health, economic development and ecosystems. While we have seen decades of regulation and investment in wastewater treatment plants in OECD countries, with substantial gains for the economy, human health, environment and social values, there are still significant problems stemming from water pollution. Emerging and developing economies are yet to make such progress. Controlling ‘diffuse’ sources of water pollution is particularly challenging The most difficult part of the job remains to be done: addressing invisible and indirect sources of water pollution. Known as “diffuse pollution,” examples include urban storm water runoff into rivers; sulphur dioxide emissions to the air from fossil fuel combustion causing acid rain and acidification of lakes and nutrients and pesticides washing off the land into surface water or through the soil to groundwater. Controlling diffuse sources of water pollution is particularly challenging. The reasons, as the OECD diffuse pollution, degraded water emergency policy solutions puts it: the complexity of controlling multiple pollutants from multiple sources; their high variability in space and time; associated management and regulation costs as well as limited political acceptability of regulatory measures. Valuable policy options are emerging in several countries and these deserve greater attention, adaptation, replication and scaling up. In Korea, the government has set periodic phosphorus and dissolved oxygen reduction targets and assigned pollution load limits using water quality modelling. Denmark and Norway have implemented pesticide taxes to control the toxicity of pesticides used. In the United Kingdom, a novel Government Support Package was developed to attract private financiers and reduce insurance liabilities to deliver Thames Tideway Tunnel project–a major construction project to intercept and treat London’s sewer overflows. The Lake Taupo nitrogen cap and trade scheme in New Zealand is a policy, which gives farmers the ability to buy and sell their established nutrient allocations without going over the overall catchment limit. In Germany, the water provider for Munich has established a voluntary payment scheme with local farmers to encourage the adoption of more sustainable organic low-cost farming practices and avoidance of a high-cost upgrade of drinking water treatment facilities. Diffuse Pollution, Degraded Waters presents a risk-based policy framework that can assist policymakers and stakeholders through the myriad of decisions required to establish new or alter existing water quality management regimes. The central government has a critical role to play in the transition to the more effective management of the risks from diffuse water pollution. This includes strong over-arching regulatory frameworks, stakeholder engagement, and money allocated to initiate experimental projects. In doing so, the government sends the right signals to local authorities, stakeholders and investors, minimising the cost of water quality management for the society as a whole. If we are serious about cutting water pollution, many other sectoral policy frameworks need to be aligned. For example, policies that support agriculture production, fossil fuel use and irrigation can lead to harmful and costly impacts on water quality. Improving water quality is a critical element of the 2030 Sustainable Development Goals; fulfilling an essential role in reducing poverty and disease and promoting sustainable growth. Without significant attention to this invisible and growing threat, the future deterioration of water quality poses a major risk to freshwater ecosystems and the people that depend on them. To pretend otherwise would be to sell the citizens of the world–and the environment–down the river.