Geo Sandbox Water Budget

Jason Cervenec

Byrd Polar and Climate Research Center

This activity was developed for an introductory geosciences class at the high school level. It has also been successfully used at the middle school, advanced high school, and university levels.

Students must be able to measure volumes.

This activity is part of a sequence of activities (second of five activities).

• Matter is made of particles; this includes soil and water.
• Matter is conserved. In other words, matter, and the particles that make it up, can neither be created nor destroyed.
• For convenience, measurements of volume rather than mass are often used by Earth scientists to monitor quantities of water in natural systems. (For this unit, we will ignore volume changes that occur due to changes in temperature.)
• Volumes of water added to a system or removed from a system are calculated by measuring and multiplying the length, width, and depth of water (volume = length x width x depth). A rain gauge provides a measure of depth (of precipitation that falls into the rain gauge), but the length and width of an area must also be measured. In a lake or reservoir, the volume of water can be calculated by the width and length of the water body multiplied by its average depth.
• In a soil and water system, where soil particles are assumed to be fixed, measuring the volume of water added to a system and the volume of water that leaves a system provides a way to estimate the volume of water that remains within a system.
• While water particles are most commonly added to a soil-water system via rain, they can be removed via evaporation, uptake by plants, surface runoff, and subsurface runoff. Water particles can also be stored in the system.
• Humans can alter evaporation, uptake by plants, surface runoff, and subsurface runoff through land use patterns (paving surfaces, re-grading slopes, or changing vegetation cover, for instance).
• Water naturally drains downhill (from a higher elevation to a lower elevation) due to gravity.
• A watershed is a region from which water drains to a common location.

A deliberate effort has been made to use best practices in science education when designing this activity. The activity is based around the 5E Learning Cycle and each investigation is an exercise in guided inquiry. Topics are introduced conceptually in qualitative ways before engaging in extensive quantitative measurements and calculations. While lectures can be used to quickly communicate the information contained in the activity, an explicit goal is to provide ways for major objectives to be "uncovered" and discussed in context of content-rich learning experiences. Hopefully, this will engage students, link content with real-world situations, and support deep understanding and long-term retention of knowledge. This activity is best delivered with a connection to one or two local watersheds. Many online resources referenced in this activity allow teachers to tailor instruction to their local environment and identify local professional who can offer instructional support and serve as guest speakers or site visit coordinators.

During this activity, the instructor introduces a miniature watershed, named a GeoSandbox, to provide a conceptual bridge between the schema created in the soup can water budget activity and the schoolyard watershed activity to follow. Students introduce known quantities of water to the GeoSandbox using spray bottles and measure the resulting surface flow and infiltration. The concepts of topography and land use are also introduced. Additional instructional materials are provided to firmly establish the concept of a watershed for students who need the support.

Byrd Polar and Climate Research Center: Water Cycles and Watersheds

Other Activities in this Series:

• Soup Can Water Budget
• Small Scale Watershed - Schoolyard
• Large Scale Watershed - Battelle Darby Creek
• Land Use Change - Hellbranch Run