The stair-step pattern of the maximum and minimum temperature lines are the result of varying degrees of measurement precision. The vertical portions of each line correspond with even degree increments, suggesting that readings were measured to the nearest degree, rather than the half degree accuracy of the the thermometer specified by GLOBE.
	As can be seen by the vertical segments of the maximum and minimum lines, which correspond to whole pH units, many schools appear to use pH paper rather than pH meters.
	GLOBE dissolved oxygen values are often below saturation, though values for each site generally do follow temperature trends. Low dissolved oxygen values may be due to GLOBE's sampling of bodies of water such as ponds and irrigation ditches that may have lower dissolved oxygen values than a flowing stream.
	Almost 20% of the GLOBE sites have reported zero alkalinity. Since the other two data sets do not have a similar distribution; it is unlikely that these represent actual water conditions. Twenty-nine of those 40 schools reporting 0 mg/L alkalinity measured th parameter less than 6 times and may represent instances in which a new protocol was instituted, then abandoned. GLOBE QA problems are being followed up on a case-by-case basis.
	Maximum and minimum electrical conductivity measurements have distributions similar to that of the mean. GLOBE data have a mean of 490 and a standard deviation of 395, versus a mean of 387 and a standard deviation of 369 for USGS data. Colorado Riverwatch does not report electrical conductivity.