b"HEADLINETECHNICAL TIPSWant the BestWater Quality Data?It's all about location, location, location!KERRY HUBBARD,Outdoor Water Monitoring Specialist YSI, a Xylem brandSite selection is a critical factor in collecting representative water quality datasometimes more so1 2than the sensors used to make the measurements. \x1f \x1f Many factors go into selecting the perfect location to\x1e \x1etake measurements in aquatic environments, whether for spot/grab sampling, continuous monitoring, or profiling a\x1d \x1dwater column. \x1c \x1c Shaken, Not StirreD?\x1b \x1bFirst, it is essential to choose a site that is well-mixed,Well-Mixed Stratied or poorly mixedespecially when working in rivers and streams. Well-mixed means that constituents at a given location areOverhead view: A river with two cross-section examples. Which are similar across the remainder of the body of water.you trying to measurenatural or pointsource discharge?To verify that a river or stream site is well-mixed, YSIWhen collecting grab samples and setting up instruments recommends collecting a series of water quality readingsfor autonomous data collection (either in pipes or in a horizontal cross-section of the water body; and ifsuspended from buoys), it is essential to install the the channel is deep enough, they should be collected atmeasurement device in a similar location in the water various depths as well. column each time. There can be drastic differences in recorded values if a water quality sonde is placed on a Once you confirm a location is well-mixed, recordedstreambed or seafloor versus suspended in the column, changes can be more confidently expected toespecially in areas where the substrate beneath the have occurred across the entire system, leading toinstrument is composed of fine sediment.better analysis of trends based on time, seasonality, precipitation, and so forth. Stratification and poor mixingCross-Section Points:can tell a story about changes in the water body, but for1 2 3 4 5the most accurate water quality study, sampling should be done at a well-mixed location.Temperature12.11 12.12 12.22 12.15 12.14(C)Keep it Consistent! Specific Cond.89 91 92 90 89Maintaining a consistent sampling location is also vital(mS/cm)to collecting the best data. If a sample is collected at apH 7.11 7.10 7.13 7.09 7.12different location every time, there could be differences in data that would significantly impact any analysis. For example, sampling upstream of a wastewater effluentDissolved O 28.68 8.71 8.74 8.72 8.70pipe on one trip to the field and downstream the next can(mg/L)wreak havoc on your data integrity. Turbidity6.3 7.1 5.9 6.2 6.6(FNU)This is an example data set for well-mixed samples.(For illustration only.)Contact the YSI Technical Support Team:info@YSI.com56 MISSION: WATER"