Inspection of water level measurement data quality by means of a digital elevation model variogram analog

This presentation will describe a graphical technique for examining variance of ground water elevation values from unconfined aquifers and application of this technique to a case study at Fort Leonard Wood, Missouri. In evaluating quality of ground water elevation data for development of a ground water model, it may not be practical to consider every data point, particularly when working with the large datasets for a regional model. The new graphical technique expedites isolation of misrepresentative points in a large dataset, enabling users to examine the variance of ground water elevation values from an unconfined aquifer and to identify points with high variance. In the case study, potential outliers identified by the graphical variogram process, were evaluated by reviewing well borings, well installation records, and time series of water level measurements. Supplemental ground elevation data from a digital elevation model were used to create a threshold on the experimental variogram of ground water elevation data. This process was verified using a developed synthetic ground water dataset. The method facilitates identification of points that are justified for removal upon inspection of the available records, supports recommendations based on common causes of error, and serves as a preprocessing step prior to kriging.