Water for people.pdf - WHO Thailand Digital Repository

1 3 6 / C H A L L E N G E S T O L I F E A N D W E L L - B E I N GProtecting Ecosystems for People and PlanetFigure 6.2: Biological quality of United Kingdom rivers, 1990–2000Biological quality (% of river length surveyed)35302520151050Hydrological informationHydrological information has also been widely used in determiningthe condition of ecosystems. River flows, water levels in wetlands,extent of flooding, storage capacity of aquifers and recharge rates,lake volumes and rainfall data are hydrological variables that providea useful handle on the existing condition and changes in freshwaterecosystem condition. A long-standing challenge in hydrology, onewhich poses a constraint through its persistence, is thatmeasurements of river flows (or other variables) contain the signalof humanity’s changing impact within long data series. While this isactually of value in detecting climate change impacts, it hinders ourability to quantify the ‘natural condition’ of the hydrological cycle.Much effort is therefore devoted to the ‘naturalization’ of data byoperational hydrological services – adjusting observed but‘unnatural’ river-flow data series (over many years) to a consistentbaseline that is representative of natural conditions. This is aprecursor to many forms of impact assessment.At the global level, there is a large amount of quantitativeinformation on hydrological flows, thanks to initiatives such as theGlobal Runoff Data Centre (GRDC), and on several variables relevantto water quality (e.g. the Global Environment Monitoring SystemsFreshwater Programme [GEMS/WATER]). Highly detailed regional andnational data are available in most areas, albeit within theVery good Good Fairly good Fair Poor BadThe biological water quality indicators here applied to United Kingdom rivers show that there are a far greater number of rivers classified as ‘very good’, and there is a decreasing numberof those classified as ‘poor’ or ‘bad’. The indicators therefore show the general improvement in water quality in the United Kingdom.Source: Adapted from Environment Agency, UK, 2002.199019952000constraints of the purpose for which the monitoring was originallyestablished, which was rarely ecological. Hydrological tools anddatasets for water resources assessment are discussed moregenerally in chapter 4.Biological assessmentAlthough no single direct measure of ecosystem condition ispossible, and it is impractical to routinely assess its variouscomponents (resistance, resilience), biological assessments aregenerally held to be potentially indicative of ecosystem condition.Because organisms have a fundamental and integral role inecosystem processes, tracking change in aspects of communityorganization is likely to be an efficient, if indirect way, to trackcausal changes in a wide range of variables that impact onecosystem integrity. In contrast to physico-chemical indicators, thesechanges will be integrated temporally over a scale related to thelifespan of the organisms assessed. Biological criteria can be usedto set the biological quality goal that is reached by implementingappropriate management of chemical and physical variables.Many types of biological assessment aim to set a baselinecorresponding to natural or relatively unmodified conditions,commonly designated as the target condition (e.g. Brink et al.,1991). The common first step then is to collect data on the