In Douglas Adams' comedy novel The Hitchhiker's Guide to the Galaxy, a civilization wanted to know the ultimate answer to life, the universe and everything. They built Deep Thought, an enormous computer that, after seven and a half million years of detailed calculations, produced the answer: 42. The scientists then realized that although Deep Thought had given them the ultimate answer, they did not know the ultimate question.For all scientists, asking and answering the correct questions is fundamental to the development and application of knowledge. However, for conservation scientists there is the additional complication of translating the knowledge gained into effective policy and legislative mechanisms. These rely on effective communication and partnership working.The EC Water Framework Directive (WFD; European Commission, 2000) is an ambitious instrument of Europe-wide legislation that aims to set minimum ecological standards for surface water (including coastal waters) and groundwater by providing a unified policy approach. Unlike almost all previous legislation in the UK and elsewhere, standards are derived with respect to ecological quality rather than physico-chemical thresholds. Individual water bodies are graded into one of five quality classes (high, good, moderate, poor or bad). EU member states are required to ensure that all water bodies reach good ecological status by 2015, and that there is no deterioration from the existing ecological status. Where water bodies are degraded by human activities beyond a level that it is reasonable to expect restoration, they can be designated 'heavily modified'. However, even heavily modified water bodies are required to reach 'maximum ecological potential'.The WFD requires that each member state identify a typology for their water bodies. Types are based on fundamental ecological drivers such as altitude and geology, and their ecological quality is then compared with a 'type-specific reference condition'. Different biological, hydromorphological and physico-chemical 'quality elements' may be used, as appropriate for the habitat type being monitored. A series of generic metrics of environmental quality are identified in the Directive, mainly related to taxon richness and abundance. These are then used to grade the ecological quality of each water body by comparing it with a reference condition using an Ecological Quality Ratio (EQR). The EQR is calculated by dividing the observed metric by the reference value for that metric. The range of EQRs is then divided into five classes ranging from high to bad ecological status. Class status is on a 'one-out, all-out' basis, i.e. the quality element with the worst ecological quality is used to determine ecological class } however, in many water bodies only a single biological quality element } that perceived as being 'most sensitive' to the predominant pressure } needs to be monitored. As a control to ensure that the approach is applied evenly across the EU, an intercalibration process takes place to compare standards of i...