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Imhoff Cone Determination of Sediment in Irrigation Runoff
Author(s) -
Sojka R. E.,
Carter D. L.,
Brown M. J.
Publication year - 1992
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/sssaj1992.03615995005600030034x
Subject(s) - sediment , settling , surface runoff , erosion , hydrology (agriculture) , volume (thermodynamics) , soil water , environmental science , soil science , geology , geotechnical engineering , environmental engineering , geomorphology , ecology , physics , quantum mechanics , biology
There is a need to rapidly quantify erosion from irrigated farmland. The prevailing method consists of collecting runoff samples, then filtering, drying, and weighing them to determine sediment concentration. Labor cost and slow data availability prompted development of a faster, less expensive technique. Sediment settling volume in a graduated vessel was expected to correlate well with total mass of suspended sediment. Eight soils varying in texture, mineralogy, and organic‐matter content were sampled, fragmented, and air dried. A series of 1‐L suspensions was prepared with sediment concentrations from 1 to 30 g L −1 . Samples were either hand shaken for 30 s or mechanically blended for 60 s. Suspensions were decanted into graduated Imhoff cones and allowed to settle for 0.5 h (1800 s). The series was repeated three times for each soil. Settling volume was regressed against sediment concentration (total sediment, g L −1 ). Field calibrations for two soils were developed from furrow runoff samples. Laboratory regressions had a mean r 2 of 0.99. Field regressions of two soils had r 2 of 0.94 or higher. Cone design did not permit accurate volume estimates of the first 1 mL, causing slopes and intercepts to very among field regressions for sediment concentrations < 1.0 g L −1 . These samples, however, represent negligible erosion, and therefore have little value. Slope and intercept of field regressions corresponded closely to 30‐s‐shaken laboratory regressions but different statistically at P ≤0.05. The technique provided a rapid, inexpensive, and accurate suspended‐sediment determination in the field for concentrations >1.0 g L −1 . Several settling‐volume predictions based on textural components and organic‐matter content had r 2 >0.60. Laboratory 30‐s hand‐shaken calibrations may be adequate for diagnostic purposes, but individual field calibrations should be performed for research purposes.