Scientists are very interested in learning more about the global water cycle and the role soil moisture plays in interactions between the Earth’s surface, the atmosphere and the environment. New computer models and satellites are currently being built to study and explore these important relationships.
You can participate in this effort by helping to collect data that will provide a regional snapshot of the real distribution of soil moisture. We can then compare your data with new computer or satellite data sets. We hope that you and your students are as excited as we are to apply their observations to addressing real world scientific questions.
Soils
supply plants with a place to take root, with water, and with nutrients. As water moves through the soil, it picks up
nutrients from minerals and decaying organic matter. Water can also carry away harmful salts and elements by ‘rinsing’
the soil. The process by which
materials are removed from the soil by water is known as leaching.
Leached materials may be held in lower layers of the soil or may stay in the
water and flow into rivers, lakes, and groundwater.
Water
also helps to form the soil. In cold
climates, water freezing in cracks causes rocks to break apart and moves soil
particles around within the soil profile. This freeze-thaw action is a
primary soil builder in cold climates.
In tropical climates, soil properties change as water dissolves minerals
in the soil. Water promotes the decay
of dead plant and animal matter that becomes part of the soil. Soils found in places with little water,
like deserts, support only certain types of vegetation and animal life. Places
where the soil is so waterlogged that there is virtually no oxygen present,
such as bogs, can preserve plant and animal remains for centuries because of
the slow rate of decomposition. What role does soil moisture play in your
ecosystem?
Soil
acts like an enormous sponge spread across the land surface. Soil absorbs rain
and snowmelt, slows runoff and helps to control flooding. Absorbent soils, like
those found in wetlands, can soak up floodwaters and release them slowly,
rather than allowing large runoffs that may cause damage downstream. If soils
are already saturated with water, there is no space available for
additional water to enter them, so new rainfall must flow across the surface to
low lying areas. Water that is absorbed into the soil is held on
particle
surfaces and in the open spaces between soil particles. Most of the water held in soil is available
for use by plants during times of little precipitation. Some of the water
absorbed by the soil will evaporate back into the air, or drain through the
soil into groundwater. Measuring the amount of water stored in the soil helps
us track the ability of soils to moderate other components of the water cycle.
Soil moisture measurements also help us to estimate the soil water balance,
which is the pattern of how much water is stored in the soil over a year. How
many months each year are your soils saturated or dusty?
Some
of the water stored in the soil evaporates back into the atmosphere. This cools
the soil and increases the relative humidity of the air. Changes in relative
humidity from evaporation of soil moisture can affect the weather. The amount
of water in the soil also affects soil temperature because liquid water heats
up more slowly than either air or soil. Thus, changes in soil moisture affect
local weather and climate, and hence soil moisture data can be used to improve
numerical models of weather prediction. How do you think soil moisture affects
your local weather and water cycle?
The
GLOBE program (www.globe.gov) is an
international collaboration of schools, scientists and educators, involving
students worldwide in hands-on field data collection and analysis. GLOBE data,
collected by students, are archived in a public database on the Internet,
making it accessible for environmental research projects by students, teachers
and scientists. While we recommend that teachers become GLOBE qualified by
participating in a GLOBE sponsored training workshop, it is still possible to
participate in the Soil Moisture Data Campaign by contacting the GLOBE soil
moisture campaign coordinators (below). GLOBE is sponsored by NASA and this
work is funded by the National Science Foundation (NSF).
For
more information, please visit our web site: www.hwr.arizona.edu/globe/sci/SM/SMC/,
The GLOBE program web site: www.globe.gov or contact:
The GLOBE soil moisture
campaign
The University of Arizona
Tucson, AZ 85721-0011,
Martha Whitaker or Jim
Washburne
mplw@hwr.arizona.edu jwash@hwr.arizona.edu jwash@hwr.arizona.edu
(520) 621-3041 or -9715