Science 1.

Use of GLOBE Hydrology Data in Water Quality Assessments

Martha Conklin, Roger Bales & Josh Clemons

Department of Hydrology & Water Resources, University of Arizona

Water quality assessments aim to establish the attributes of one or more water bodies, establish differences between the water bodies samples, and detect changes in those water bodies over time. The main issue in evaluating data to detect change is how to separate natural variability in water quality associated with variable precipitation patterns, temperature changes and seasonal cycles from changes to climate or land use changes. Professional monitoring programs, such as those of the U.G. Geological Survey and other public agencies have well-established quality assurance and quality control programs that result in a known accuracy and precision for their results. These programs are generally more rigorous from those of GLOBE and other volunteer organizations. The result is that GLOBE and other volunteer data are assigned a lower level of precision as compared to data from professional monitoring programs. However, volunteer data can still make valuable contributions to environmental assessments, as they cover a different population of water bodies than do the professional programs. By comparing the means and seasonal patterns of GLOBE data with that from professional programs we can establish that over periods of months to years, most GLOBE data are sufficiently accurate for assessments. By comparing the variance of GLOBE from a population of schools with similar data from professional monitoring over the same time periods we can estimate the relative precision of GLOBE data. We illustrate with an example water quality assessment.