Changes

|'''Guelph Permeameter with Tension Disk''' (constant head)  

|'''Guelph Permeameter with Tension Disk''' (constant head)  

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*The Guelph permeameter is another test device for measuring saturated hydraulic conductivity of a soil surface when used with a tension disc attachment. The method is similar to a Tension infiltrometer, but with water being directed to the tension disc from an inner or outer Mariotte reservoir, giving it the capacity to test low and high permeability soils (Soil Moisture Equipment Corp. 1986). Infiltration rates are calculated from monitoring the water level drop in the reservoir until a steady state is approached.

*The Guelph permeameter (See photo example - Source: Hoskin Scientific Ltd., 2022<ref>Hoskin Scientific Ltd. 2022. Guelph Permeameter Kit. https://www.hoskin.ca/catalog/index.php?main_page=product_info&cPath=1_59_67_3677&products_id=5082</ref>)is another test device for measuring saturated hydraulic conductivity of a soil surface when used with a tension disc attachment. The method is similar to a Tension infiltrometer, but with water being directed to the tension disc from an inner or outer Mariotte reservoir, giving it the capacity to test low and high permeability soils (Soil Moisture Equipment Corp. 1986). Infiltration rates are calculated from monitoring the water level drop in the reservoir until a steady state is approached.

*Like the Tension infiltrometer method, tests are run with two applied tensions. Steady state infiltration rates from the two applied tensions are used to calculate a value for saturated hydraulic conductivity. Potentially requires large volume of water and significant length of time for each measurement to reach steady state.  

*Like the Tension infiltrometer method below, tests are run with two applied tensions. Steady state infiltration rates from the two applied tensions are used to calculate a value for saturated hydraulic conductivity. Potentially requires large volume of water and significant length of time for each measurement to reach steady state.  

|[[File:Guelph permeameter hoskins.PNG|350px]]

|[[File:Guelph permeameter hoskins.PNG|350px]]

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|'''Tension Infiltrometer''' (constant or falling head)  

|'''Tension Infiltrometer''' (constant or falling head)  

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*This test involves a porous disc of 10 or 20 cm diameter that is connected to a Marriotte bottle (water reservoir) and a bubbling tower where a negative pressure or tension is set (Figure 8.19). The porous disc must be placed in contact with the soil surface which usually requires removal of any vegetation and debris. In many cases it is necessary to place a thin layer of fine sand onto the soil surface to provide good contact between the disc and the soil. <br>

*This test involves a porous disc of 10 or 20 cm diameter that is connected to a Marriotte bottle (water reservoir) and a bubbling tower where a negative pressure or tension is set (See photo example - Source: ICT International, n.d.<ref>ICT International. n.d. Determination of Soil Unsaturated Hydraulic Conductivity. https://www.ictinternational.com/casestudies/determination-of-soil-unsaturated-hydraulic-conductivity/</ref>). The porous disc must be placed in contact with the soil surface which usually requires removal of any vegetation and debris. In many cases it is necessary to place a thin layer of fine sand onto the soil surface to provide good contact between the disc and the soil. <br>

*Infiltration rates are measured based on the water level drop in the water reservoir. The steady state infiltration rate into the soil is measured for two applied water pressures. To estimate saturated hydraulic conductivity the pressures need to be slightly negative (i.e., tensions) and it is recommended that successive pressures of -5 cm and -1 cm be used (Erickson et al., 2013). The measured steady state infiltration rates are used in equations derived by Reynolds and Elrick (1991) to calculate a value for saturated hydraulic conductivity. <br>

*Infiltration rates are measured based on the water level drop in the water reservoir. The steady state infiltration rate into the soil is measured for two applied water pressures. To estimate saturated hydraulic conductivity the pressures need to be slightly negative (i.e., tensions) and it is recommended that successive pressures of -5 cm and -1 cm be used (Erickson et al., 2013). The measured steady state infiltration rates are used in equations derived by Reynolds and Elrick (1991) to calculate a value for saturated hydraulic conductivity. <br>