Environmental Statement volume 4 - Chiltern Evergreen3

and structured approach to local water resources management, encouraging abalance to be found between the needs of abstractors and the needs of theaquatic environment.G1.2 ENVIRONMENTAL QUALITY STANDARDS, RIVER QUALITY OBJECTIVES, TARGETSAND THE GENERAL QUALITY ASSESSMENTRiver quality is one of the 68 indicators identified by the UK government’ssustainable development strategy: Securing the Future, launched in 2005, and isalso one of the 20 indicators outlined within One Future – Different Paths: theUK’s Shared Framework for Sustainable Development, also released in 2005.The quality of watercourses in England is currently classified by theEnvironment Agency under the General Quality Assessment (GQA) scheme.Under this scheme, each watercourse is assessed separately upon its chemical,ecological (biological), aesthetic qualities and nutrient status. Additionaldetails regarding these assessments are provided below.Chemical Quality: based upon dissolved oxygen, biochemical oxygendemand (BOD) and ammonia concentrations, the watercourse is assignedone of six grades: A (very good) to F (bad). These parameters areconsidered to be the best indicators of the extent to which waters areaffected by wastewater discharge and rural land runoff.Biological Quality: based upon macro-invertebrate studies (an indicatorof overall ecological health), one of the six grades A to F is assigned, as perChemical Quality.Aesthetic Quality: gives an indication of our perception of river qualitythrough the assessment of various factors including the presence of litter,foam, oil, fungus, odour and colour. The grading system ranges from1 (good) to 4 (bad).Nutrient Status: based upon phosphate and nitrate concentrations, whichare most likely to be influenced by human activity. A grade of 1 (verylow) to 6 (phosphates: excessively high, nitrates: very high) is assigned.In addition to the GQA, Environmental Quality Standards (EQSs) establishconcentrations of specified substances and are either informal or statutory.Statutory EQSs are generally informed by the Dangerous Substances Directiveand the Surface Waters (Dangerous Substances) (Classification) Regulations, 1997and 1998 (see below for further information).After the GQA has been conducted, and in light of EQSs, River QualityObjectives (RQOs) are generally introduced. RQOs set targets to aid in theprotection and improvement of river quality, based upon the River Ecosystem(RE) Classification. The RE classification specifies the uses a particularwatercourse should ideally be able to provide, in terms, for example, of beingsuitable for supporting fish. The classification is based upon qualityparameters defined within the Freshwater Fish Directive and consists of fiveENVIRONMENTAL RESOURCES MANAGEMENTG1-3CHILTERN RAILWAYS