Using GIS to estimate the volume of snow and water in a drainage basin Todd Rayne and Dave Tewksbury Hamilton College Clinton, New York

Goals of the exercise: Relationship between linear and volume measurements Spatial variability of snow depth Snow depth and water content Representative sampling Error analysis and GIS experience, naturally! Used as a lab exercise in a spring semester 200-level hydrogeology course with no GIS prerequisite. Students have completed two introductory GIS exercises on their own.

Field area is athletic fields and adjacent golf course Field materials: GPS unit, meter stick, clipboard Time allotted to measure snow depths: ~90 minutes

Example of good sampling distribution

Example of uneven sampling distribution. Note the linear pattern that shows their route.

1. Extract ground elevations at sampling points from DEM and add snow depths in attribute table to create snow elevations. 2. Create polyline boundary to limit the surface extent. 3. Contour snow elevations

Volume map of study area. Red is gain of volume; blue is loss of volume. Why are some of the cells blue when the snow cover is continuous?

Same measurement points with deeper (0.3 m) snow.

Snow volume in an area with unevenly distributed sampling locations.

Follow-up (usually the following day or week): Troubleshooting GIS problems Summation of snow volume values in red cells Measurement of snow density Conversion of snow volume to water volume Discussion of why all the cells in the study area are not red Discussion of snow accumulation and hydrology