Water Cycle Protocol Bundle

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I. Overview

Water—the main reason for life on Earth—continuously circulates through one of Earth’s most powerful systems: the water cycle. Water flows endlessly between the ocean, atmosphere, and land. Earth’s water is a finite, fixed amount, meaning that the amount of water in, on, and above our planet does not increase or decrease.

NASA studies water in a variety of ways, using satellites, airborne campaigns, and ground-based measurements to collect data. These data are used for many real world applications to answer vital questions that are essential to our survival on this amazing “water planet”. The data that GLOBE scientists, teachers, and students collect are also vital and help us to become better informed and engaged stewards for the water in our environment.


II. List of the GLOBE Protocols included in the bundle




            Relative Humidity

            Surface Temperature



            Water Temperature



            Soil Moisture

            SMAP Soil Moisture


III. Science of the Water Cycle

Diagram of the water cycle


Precipitation is a vital component of how water moves through Earth’s water cycle, connecting the ocean, land, and atmosphere. Knowing where it rains, how much it rains and the character of the falling rain, snow or hail allows scientists to better understand precipitation’s impact on streams, rivers, surface runoff and groundwater. Frequent and detailed measurements help scientists make models of and determine changes in Earth’s water cycle.

The water cycle describes how water evaporates from the surface of Earth, rises into the atmosphere, cools and condenses into rain or snow in clouds, and falls again to the surface as precipitation. The water falling on land collects in rivers and lakes, soil, and porous layers of rock, and much of it flows back into the oceans, where it will once more evaporate. The cycling of water in and out of the atmosphere is a significant aspect of the weather patterns on Earth.


IV. Discussion of each GLOBE Protocol included in the bundle 


  • Precipitation Protocol: How much precipitation falls in a region, when it falls within the year, whether it falls as rain or snow, and the amount that falls in individual events helps define the climate of that region. Materials: Installed rain gauge, snowboard, clean containers for pH samples 100-mL or larger, two or three containers for snow samples, Carpenter’s level, meter stick, pH paper OR meter and pH buffers, salt and salt card or tweezers, sampling jar with lid, 300-mL beakers or cups, stirring rods or spoon, latex gloves
  • Relative Humidity Protocol: Water vapor in the atmosphere is an important part of the hydrologic cycle, and taking relative humidity measurements helps us to understand how rapidly water is moving from Earth’s surface to the atmosphere and back again. Materials: Digital hydrometer or sling psychrometer, instrument shelter, thermometer, calibration thermometer, watch, distilled water
  • Surface Temperature Protocol: The temperature of your surrounding environment is ever changing, and thermal energy is constantly being transferred among all the components of the environment. Surface temperature affects the rate of evaporation. Materials: Hand-held infrared thermometer, thermal glove, meter stick, watch, pencil



  • Water Temperature Protocol: Water temperature influences the rate of evaporation. Materials: Thermometer, watch, string, rubber band, latex gloves.


Pedosphere (Soil)

  • Soil Moisture Protocol: soil moisture may be sampled in several ways.


  • Depth Profile Soil Moisture Protocol

The Depth Profile involves taking a  sample of the top 5 cm and the use of an auger to take soil samples at depths of 10 cm, 30 cm, 60 cm, and 90 cm. Using an auger takes a bit of extra time, but this effort gathers valuable data and complements the Soil Characterization Protocol and the Optional Automated Air and Soil Temperature Monitoring Protocol.


  • Star Pattern Soil Moisture Protocol

The Star Pattern involves collecting  soil samples from 12 different locations  at twelve different time periods in a 2 m x 2 m star-shaped area. For each of the 12 locations, three spots are chosen within 25 cm of each other. Samples from the top 5 cm and from 10 cm deep are collected at each of the three spots, for a total of 6 samples at each location on the star.

This sampling method can be easily coordinated with the Soil Temperature Protocol, whereby students collect their soil temperature measurements at the same depths and locations as the soil moisture measurements.


  • Transect Soil Moisture Protocol

The Transect Pattern requires an open space of at least 50 m length. Thirteen samples are collected from the top 5 cm of soil. This pattern allows students to see spatial variations in surface soil moisture measurements. It is also useful for comparison with soil moisture data collected remotely from satellites or aircraft. These remote measurement techniques sense moisture contained in the top 5 cm of soil and their measurements are averaged over areas of 100’s of square meters or more.


  • SMAP Soil Moisture Protocol: Soil moisture determines how much water is in the soil at a given location. Materials: 500-mL graduated cylinder, balance or scale, sealable plastic bags, 4 sampling cans, plastic wrap, soil-drying oven


IV. Conclusion

The Water Cycle is a key part of the Earth system. The fluxes and reservoirs that comprise it vary over time and space. The data you collect can help characterize the cycle in your area.



Acknowledgements: Special thanks to members of the GLOBE Science Working Group and Brian Campbell for improving the quality of the work.

Compiled by: Claudia Caro and Olawale Oluwafemi (Femi)

Edited by: Dr. Dixon and Prof. Cartalis