Roaring Fork Observation Network Data Dashboard

In situ measurements refer to observations taken directly at a specific site location. Di-electric probes are a common form of collecting in situ soil moisture data. These sensors measures soil moisture at a specific point using readings of electrical conductivity between prongs. Many soil moisture networks utilize dielectric probes, including: the Roaring Fork Observation Network (iRON), SNOTEL, and the Center for Western Weather and Water Extremes.

• Precise measurements
• Ability to track moisture at specific depths
• Ability to track soil response to wetting & drying events

• Measures a very small area of soil (on a scale of square inches)
• May lose accuracy in very wet or very dry soils
• Limited to period of record and site locations

Cosmic ray neutron sensors are an in situ soil moisture technology that measures average soil moisture across a landscape scale using movement of naturally occurring neutrons. These sensors measure the average water content in the soil over a landscape scape (~200 acres). In winter, they detect the water in the snow. Measuring soil moisture is a relatively new use of this technology and this application is still being tested. The US Geological Survey uses CRNS sensors for data collection in their NGWOS networks, including the stations deployed in the Roaring Fork Watershed.

• Measures conditions across a field-scale area
• Ability to track average soil moisture response to specific wetting & drying events

• Depth of measurement changes based on soil dryness
• Averages soil moisture across multiple depths
• Limited to sites and time periods with sensors present

Modeled soil moisture data estimates soil moisture conditions at a landscape to regional scale by using computer calculations based on a variety of measured parameters, dependent on the model. Examples of inputs might include climate and physical conditions such as temperature, precipitation, evaporative conditions, and more. Because in situ soil moisture networks with long data records are uncommon, modeled data is often used instead for projections, such as of drought or runoff forecasts. Modeled soil moisture data are used by many agencies, including the Colorado River Basin Forecast Center (CBRFC).

• Data are available for large regions
• Data availability is not dependent on presence of soil moisture sensors

• Soil moisture is averaged to provide a single moisture value for areas across soil multiple depths and heterogeneous landscapes
• Values are modeled, not direct measurements

There are multiple different satellite systems currently used to measure soil moisture at the Earth’s surface. Each satellite uses a different approach for measuring soil moisture. For example, NASA’s SMAP satellite calculates average soil moisture across regions using radio waves (SMAP), while GRACE-FO uses measurements of the Earth’s gravity. Satellite measurements of soil moisture typically perform fairly well in flat landscapes, but satellite measurements are less accurate in forested or complex terrain (such as the Roaring Fork), and modeled soil moisture data simplifies the heterogeneity of soil moisture because large, diverse landscapes are represented as homogenous.

• Data are available for most regions across the globe
• Measurements are not dependent on the presence of physical soil moisture or weather sensors

• Satellite measurements have reduced accuracy for forested areas and areas with complex terrain
• Resolution of soil moisture measurements/ averages for soil moisture values are typically on a scale of multiple square miles

Depending on the intended application of the data, one approach to soil moisture data collection may be more useful than another or a mix of approaches may yield the most helpful picture. Modeled soil moisture provides a means of estimating average soil moisture over large area landscapes, whereas in situ soil moisture data allows for precise comparisons of conditions across different soil depths or different years for a point specific location.