River Boyne Water Quality Management Plan - EPA

River Boyne Watcr Quslily Msnagrment Plan5.3.1 River Boyne System - Dissolved OxygenDissolved oxygen (D.O.) has been identified as a key parameter, particularly in the context of fishlife. Specifically, the Salmonid regulations require 50% of values to be in excess of 9mgIl 02. TheE.U. directive for salmonid waters sets guideline values of 100% of samples greater then 7mg/l 02.Minimum D.O. levels in the presence of heavy algal or plant growth will tend to occur in earlymornings.The general pattern of D.O. levels and range of values is generally as follows:-River Boyne upstream of Yellow River; this section of the main Boyne chanrjel has sluggishflow and heavy plant growth, including duckweed mats (Lanza minor). Dissolved oxygensurveys since 1990 at low flows showed extremely low night time D.0, levels. well below thesalmoniddirective li~~tits. Levels of less than 20% saturation were recorded in August, 1990.7hese levels could result in fish kills. Recent data since 1994 shows a range from 6.4 -I4.2nig/l at Bollyboggan. Data upstream in Co. Kildure (Clonkeen Bridge and Eder~derryBridgeJslow .rirjiilar tendencies to low D. 0. levels on occusionsFor inspection purposes only.Consent of copyright owner required for any other use.EPA Export 26-07-2013:17:27:01