River Boyne Water Quality Management Plan - EPA

River Boynr Walcr Quali* Management Plan2.3 W&r Resources - Hydronielric DatnThe island of Ireland is divided into 40 hydrometric areas for the purposes of collecting hydrometric(River Flow) data. For this purpose, the River Boyne catchment is designated as hydrometric area 07.River flow is recorded at locations throughout the catchment by the following agencies:.OBce of Public Works (OP W)Environmental Protection Agency (EPA)E!ecbiciry Supply Board (ESB)Local AuthoritiesRiver flow data is essential for water resource management, flood flow management and pollutioncontrol. Historical flow data over a significant period of record can be used to estimate the followingparameters of river flow:-n>'Floodflows of vario~is rel~rrn periods (likelihood of occur~:$iice)S-,$. -3-Low flows expressed as niiriiniwn LIT wea~herfl@+~@~~), ~isually defined OS the flow belowwhich the river ,110tild not be expecred 10 faq~?%&e than once in 50 years. More ~is~ially, the.\ .S'95 percentile flow is uset1 when se?tingpol@>.@ sta~~dards and assessing co~npliarse. This is.\clejned as the flow at the locatiori in th&-r,@r which is exceeded 95% of the timee Average dai!vflowprovides a nzwswe oj' the tolal rurt-oflffr.or~i the catch~neatt~hich car1 becross-referenced with rai~&N ,@> catchnre~rt characteristics in estirnari,rg lotal waterresourcesFor inspection purposes only.Consent of copyright owner required for any other use.The most accurate method of measuring channel flow is by constructing a specific control structure(weir, sluice, etc.). However, in practice, flow is estimated from measurement of water level (waterdepth) at a site which is converted to flow by reference to a suitable rating curve. The rating curve isdetermined from an appropriate number of actual measurements of river flow for a range of flowdepths at the site. A good gauging station will have a consistent relationship between flow and waterdepth.Hydrometric gauging station sites in the River Boyne catchment are indicated in Map No.1 andcomprise two types of station. Automatic recorder stations provide a continuous record of waterlevel from which a continuous profile of river flow can be derived. Staff gauge stations, however, aremanually read intermittently and are generally used for spot checks on low flows and flood flows.River flows presented in this Report are based on OPW records and EPA records for the LocalAuthority sites. It would be a requirement for systematic water resource management that the numberof sites be significantly increased with automatic recorder facilities, particularly where significantwater abstractions or water discharges require to be assessed.EPA Export 26-07-2013:17:26:59