Characterizing the performance of a new iniltrometer and hydraulic properties of roadside swales

Abstract

A roadside swale is an infiltration practice that removes water during rainfall-runoff, infiltrate water into the soil and filter the soil and associate pollutant from the water. Infiltration rate is an important factor affecting the performance of a swale. Though roadside swales convey and treat road runoff, data on the performance of swales with regards to infiltration is relatively sparse. Therefore, the objective of this study is to, 1) Modify the optimization technique of the new Modified Philip Dunne (MPD) infiltrometer, 2) Verify the results obtained from this MPD infiltrometer for uniform soil, layered soil and uniform soil with macopores by numerical simulation, 3) Utilize the MPD infiltrometer to characterize the field-saturated hydraulic conductivity (Kfs) of five roadside swales located in Twin-Cities, MN and one swale located in Madison, WI and 4) Analyze the derived results obtained from the measurements taken by the MPD infiltrometer. From numerical simulations it was found that MPD Infiltrometer overestimates Kfs value by 10 to 36% for the uniform soil, 12% to 63% for layered soil and 4% to 29% for uniform soil containing macropores. MPD infiltrometer allows collecting multiple infiltration measurements simultaneously to capture the spatial variation of infiltration rate of an infiltration practice. In this study a total of 720 infiltration measurements were collected in swales located in Twin-Cities, MN and in Madison, WI. Statistical analysis was performed on the Kfs values to analyze the effect of initial soil moisture content, season, soil texture class and distance in downstream direction on the geometric mean Kfs value of a swale. Because of high spatial variation of Kfs value in the same swale no effect of initial soil moisture content, season and soil texture class was observed on the geometric mean Kfs value. But the distance in downstream direction may have positive or negative effect on the Kfs value.