ECONet - Soil Moisture

Drought Severity Categories

U.S. Drought Monitor Category	Description	Percentile Range
-	Exceptionally Wet	98.01 to 100.00
-	Extremely Wet	95.01 to 98.00
-	Severely Wet	90.01 to 95.00
-	Moderately Wet	80.01 to 90.00
-	Abnormally Wet	70.01 to 80.00
-	Normal	30.01 to 70.00
D0	Abnormally Dry	20.01 to 30.00
D1	Moderately Dry	10.01 to 20.00
D2	Severely Dry	5.01 to 10.00
D3	Extremely Dry	2.01 to 5.00
D4	Exceptionally Dry	0.00 to 2.00

These categories were based on the drought categories used by the U.S. Drought Monitor (USDM). The "dry" categories are directly taken from the USDM but there is also value in showing when stations are wetter than average. These categories are the opposite of the "dry" categories. While a station may observe a soil moisture value that is wetter than the average, that does not mean the station is not experiencing drought. Lastly, the percentile ranges are specific to each station, calculated from 20 or more years of daily soil moisture data. These ranges represent how dry or wet a station's soil is for a given month based on historical records.

About Soil Textural Groupings and Classes

Soil moisture measured by the ECONet stations is dependent on the soil class at each station. A “dry” value for pure sand is much different than what “dry” means for clay. To help put the measurements into perspective, information about a station's soil class and textural group can also be found on this page. Soil textural class is determined by the soil’s composition of clay, sand, and silt. Using the percentage of each component in a soil sample and the soil textural triangle below, one can determine the soil class of a sample site. For example, a sample consisting of 65% sand, 10% clay, and 25% silt would be classified as sandy loam. Different textural classes can then be grouped based on the dominant component. Coarse-textured soils contain a higher percentage of sand, while fine-textured soils have a larger proportion of clay relative to the other components. Lastly, medium-textured soils are dominated by silt (Peterson et al.).

Soil Texture Triangle — Soil Class Triangle, taken from the University of Nebraska - Lincoln (Peterson et al.)

Soil Textural Groups, adapted from the University of Nebraska - Lincoln (Peterson et al.)

Some work done by Pan 2010, analyzed soil samples from different ECONet sites. This study, along with soil class data from the USGS, has allowed for soil classes to be determined and displayed below the right-hand side plot. Additionally, users will find the respective soil textural group. North Carolina lacks silt-dominated soils, which is why the term “intermediate” is used as a group instead of “medium.” Otherwise, using the soil textural classes and the table below, one can assign each participating ECONet station to a soil textural group. This information is also displayed on the map, where coarse soils are marked by circles, fine soils by squares, and intermediate soils by triangles.

Citations
Pan, W., 2010: Soil moisture characterization with North Carolina Environment and Climate Observing Network. M.S. thesis, North Carolina State University, Raleigh, NC, 140 pp.
Peterson, J. M. (Ed.), A. P. Christiansen, B. S. Dierberger, R. B. Ferguson, K. D. Frank, P. C. Hay, G. W. Hergert, D. T. Lewis, A. J. Jones, D. Knudsen, D. L. McCallister, E. J. Penas, J. M. Peterson, D. H. Sander, C. A. Shapiro, R. C. Sorensen, R. A. Wiese, and G. L. Zoubek, Soils - Part 2: Physical Properties of Soil and Soil Water, University of Nebraska Cooperative Extension, Institute of Agriculture and Natural Resources.