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Predicting Soil Moisture in the Southern Appalachians
Author(s) -
Helvey J. D.,
Hewlett J. D.,
Douglass J. E.
Publication year - 1972
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj1972.03615995003600060033x
Subject(s) - water content , environmental science , streamflow , hydrology (agriculture) , precipitation , moisture , field capacity , soil science , soil water , geology , drainage basin , meteorology , geotechnical engineering , geography , cartography
Soil moisture was measured for 3.5 years on forested slopes in the mountains of western North Carolina to develop equations for predicting soil moisture content of watersheds. Predictors used were precipitation and easily measured topographic, seasonal, and soil physical factors; among these, sand content and moisture retention at 1‐bar suction were the best predictors of moisture content. Position on slope (height or distance from the stream channel) appeared to be an important factor only in the lower 25% of the slope. The annual cycle of soil moisture in the top 213 cm approximated a sine wave with a maximum during mid‐April and a minimum during mid‐October. As expected, moisture changes in surface layers were correlated best with rainfall weighted toward days immediately preceding observation; changes in deeper layers were better correlated with rainfall during previous weeks. Seasonal changes in soil moisture content at all depths were greatest upslope and least in the lower slope. Equations developed account for about 88% of the variation in soil moisture (standard error approximately 2–3% by volume) and can be used to predict antecedent moisture distribution for hydrologic and other purposes. Results support the “variable source area” concept of streamflow, but even with the neutron method slope gradients in field moisture were not easy to detect.