2000-05-04_AgendaPacket - Laserfiche WebLink

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^ The depletion of oxygen below the thermocline (where the lake stratifies) By measuring three water quality indicators and comparing them to user perceptions of lake condition, lakes fall into categories representing norms for metro lakes. These categories, or grades, look like this: '~`~ .'.:: ' .~._ '. P~rCnt~I~.:. Grade. ,; ~~"]CC;~iI'4'~+~ ~tl~tt~11r7tUl~t :.:. <23 <10 >10 <10 A C stal clear, beautiful 23-32 10-20 7-10 10-30 B Little algae, minor problems 32-68 20-48 4-7 30-70 C Definite algae, im aired use 68-152 48-77 2-4 70-90 D High algae, un-enjoyable >152 >77 <2 >90 F Severe algae, enjoyment impossible TP =total phosphorus (parts per billion or ppb); CLA =chlorophyll (ppb); SD =Secchi disk transparency (feet). Percentile is a ranking of metro lakes, like a grading curve. The grades are letter assignments and not meant to indicate `passing' or `failing.' Perceived Conditions are based on user perceptions. The water quality trend in Lake Owasso is that of decreasing nutrient levels, decreasing algae abundance and increasing water clarity. By examining seasonal average condition -the measurement of phosphorus, chlorophyll and Secchi disk averaged between May and September - it is apparent that the water quality of Lake Owasso has undergone significant changes over the past three decades.