# Using GIS to estimate the volume of snow and water in a drainage basin

Todd Rayne, Hamilton College

### Summary

This activity uses field measurements and GIS to estimate the volume of water in the form of snow in a field site.

## Context

Type and level of course
I use this in a sophomore-level course in which most, but not all, students have had an introduction to GIS

Geoscience background assumed in this assignment
Minimal background in geosciences is needed. An algebra-level math background is expected.

GIS/remote sensing skills/background assumed in this assignment

1. Basics (opening, saving, adding layers, activating extensions, etc.)
2. Shapefiles (editing, using the attribute table, etc.)
3. Using Spatial Analyst extension

Software required for this assignment/activity:
Excel, ArcMap 9.x

Time required for students to complete the assignment:
Two three hour sessions

## Goals

GIS/remote sensing techniques students learn in this assignment
The overall goal is to become more comfortable with using GIS as an analytical tool. More specific goals include importing x-y-z data into GIS, using the field calculator, and to recognizing the sources of potential error in the estimate of snow volume.

Other content/concepts goals for this activity

• recognition of snow as a source of runoff that is stored temporarily in the solid form
• recognition of sources of error, including biased sampling (measurements).

Higher order thinking skills goals for this activity

• comparison of different estimates of snow volume based on different measurement patterns and locations
• recognition of the value of sampling in a grid

## Description of the activity/assignment

This exercise is designed to show the relationship between linear, area, and volume measurements. Students measure the depth of snow in part of a small drainage basin and enter their data into a spreadsheet and then into a GIS. They use GIS to estimate the volume of snow. By combining the snow volume with a water equivalent estimate of the snowpack and a runoff coefficient, they estimate the amount of runoff from snow melt.

## Determining whether students have met the goals

The students have met the goals of the project if they successfully produce a map showing snow volumes and an estimate of the total volume of snow and a calculation of the equivalent water volume and runoff.