Dynamics of Infiltration Rate and Field-Saturated Soil Hydraulic Conductivity in a Wastewater-Irrigated Cropland

Abstract

The maintenance of a soil's infiltration rate (IR) and field-saturated hydraulic conductivity (K fs ) is crucial for the long-term sustainable functioning of wastewater-irrigated lands. However, an effective procedure for reliably measuring in situ soil K fs remains elusive. To address this issue, this study investigated the dualhead infiltrometer (DHI), a novel instrument for automatically determining IR and K fs , and compared it with a traditional double-ring infiltrometer (DRI) under various field conditions. In the initial phase, we optimized the procedure and settings for the DHIs in a cropland that was spray-irrigated with secondary-treated wastewater for decades in central Pennsylvania. Results showed that our optimized procedure, which used a single, long pressure cycle, yielded more robust measurements of IR than the originally recommended sequence of two short pressure cycles. The values of K fs measured by the DHIs with optimized settings were similar to those measured by DRIs under many (but not all) field conditions, due to their differences in infiltration surface areas, operational procedures, length of infiltration time, and soil spatiotemporal variability. Viscosity-corrected K fs on the irrigated cropland was 123.8 ± 94.0 mm·h −1 , higher than that on the adjacent non-irrigated cropland (103.2 ± 94.6 mm·h −1 ), but the difference was not statistically significant, owing to the high degree of soil spatiotemporal variability and our limited number of measurements. Nevertheless, the higher K fs values measured on irrigated cropland reflect observed changes in soil structure (e.g., soil pore characteristics) that resulted from decades of irrigation. Seasonal variations in K fs values existed between winter and summer conditions, but IRs during all seasons remained much higher than the current spray-irrigation rate (4.25 mm·h −1 ), suggesting that the soil is still capable of handling the routine irrigation, even during winter. However, the coefficients of variation exceeded 67.0% across the field sites investigated, and the time periods covered by our measurements were limited. As this specific site is permitted to discharge treated wastewater year-round, caution must still be exercised to ensure that soil K fs remains high enough to prevent runoff generation, especially during winter frozen conditions.

Electrical resistivity imaging for monitoring soil water motion patterns under different drip irrigation scenarios

“…Several authors have related the higher infiltration capacity of irrigated soils to the formation of macro-pores due to roots activity, which can contribute almost 85% of the total infiltration variation (Bronick and Lal 2005;Cameira et al 2003;Wu et al 2017). However, some authors have pointed out some limitations in the in situ K s determination, as the necessity of a high number of measurements in order to accurately characterize and represent the wide K s variability in space and time (Zhang et al 2019). In particular, K s,FH estimates depend on the initial SWC, on the height of the water released in the soil and on the duration of the soil water motion process (Alagna et al 2016).…”

Quantification of red soil macropores affected by slope erosion and sediment using computed tomography

“…The field‐saturated soil hydraulic conductivity ( K fs ) was measured using a DualHead Infiltrometer (Decagon Devices) following an optimized method of Zhang et al. (2019). Before data collection, grass and vegetative litters were carefully removed, and the surface soil temperature and water temperature were measured using ECH2O 5TE sensors (Meter Group).…”

“…All K fs values were viscosity‐corrected to a standard temperature of 25°C before comparison among different sites. This correction prevented the influence of changes in water effluent viscosity at different temperatures according to a previously described method (Zhang et al., 2019).…”

SWAT Model Performance Using Spatially Distributed Saturated Hydraulic Conductivity (Ksat) and Varying-Resolution DEMs

“…The DHI was chosen for its ease of use, rapidity, accuracy, and efficiency in measuring Ksat values [42]. In each infiltration experiment, a 5 or 10 cm deep, 7.5 cm radius insertion ring was gently hammered into the soil to ensure a good seal with the soil with minimal disturbance [4,42]. To guarantee that the ring was leveled in all orthogonal directions, the infiltrometer head was checked periodically to ensure the seal was intact.…”

“…Saturated hydraulic conductivity (Ksat) is an essential hydrologic parameter that quantitatively represents the ability of soil to transmit water through the saturated zone [1,2]. Accurate Ksat values are essential for determining infiltration, runoff generation, groundwater recharge, leaching, and other hydrological processes [3][4][5]. Consequently, Ksat influences the relative magnitude of local water balance components [2,3,6].…”