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Hood Infiltrometer—A New Type of Tension Infiltrometer

^a Institute of Soil Science and Site Ecology, Univ. of Technology, Dresden, Germany
^b Umwelt-Geräte-Technik, Müncheberg, Germany

View larger version (16K): [in this window] [in a new window]   Fig. 1. Principal types of hydraulic conductivity functions (redrawn from Renger et al., 1999); h = supply pressure head.

View larger version (20K): [in this window] [in a new window]   Fig. 2. Schematic of the hood infiltrometer (not to scale). The effective pressure head on the soil surface can be determined with a precision of 1 mm from the difference of the height of the water level in the standpipe and the negative pressure head at the U-tube manometer. The zero point of the scale of the standpipe is at the soil surface (US = negative pressure at the U-tube manometer, H = height of the water table in the standpipe, HK = infiltration chamber height, and T = submergence depth of the air pipe).

View larger version (20K): [in this window] [in a new window]   Fig. 3. Schematic of the hood with nylon guard cloth (not to scale).

View larger version (12K): [in this window] [in a new window]   Fig. 4. Measured water content below the hood during Exp. I. Arrows indicate step changes in the infiltrometer supply pressure head.

View larger version (23K): [in this window] [in a new window]   Fig. 5. Final steady-state infiltration rate for an applied pressure head of h0 = 0 cm and the corresponding final water content under the infiltration surface for repeated infiltration experiments at the same place at the agrometeorological station of the Technical University of Berlin in Berlin-Dahlem (Germany). The time interval between the end of one infiltration run and the beginning of the next was at least 24 h.

View larger version (17K): [in this window] [in a new window]   Fig. 6. (a) Measured and calculated cumulative infiltration curves and (b) their differences for the disk infiltrometer, Exp. II. Arrows indicate step changes in the infiltrometer supply pressure head.

View larger version (27K): [in this window] [in a new window]   Fig. 7. Measured and calculated water content below the disk based on unimodal (van Genuchten, 1980) and bimodal (Durner, 1994) soil water retention functions. Arrows indicate step changes in the infiltrometer supply pressure head.

View larger version (26K): [in this window] [in a new window]   Fig. 8. Hydraulic conductivities of the Dahlem soil calculated using Wooding's (1968) solution and using numerical simulation (unimodal soil water retention function); h = supply pressure head.

View larger version (21K): [in this window] [in a new window]   Fig. 9. (a) Unsaturated hydraulic conductivities at each supply pressure head (h) calculated using Wooding's analysis (the values were corrected as regards the soil pressure heads listed in Table 4) and the corresponding optimized hydraulic conductivity functions and (b) soil water retention values of the Dahlem soil from soil cores and optimized bimodal soil water retention curves obtained from three sequential disk infiltrometer experiments. The infiltration experiments were conducted at the same place: the agrometeorological station of the Technical University of Berlin in Berlin-Dahlem (Germany). Additionally, (a) shows unsaturated hydraulic conductivities of the Dahlem soil obtained from laboratory evaporation experiments. Laboratory soil water retention points were incorporated into the optimization processes.