AIM AIM point-scale plot-scale hillslope-scale Measuring lateral saturated soil hydraulic conductivity at different spatial scales AIM AIM S. Di Prima (sdiprima@uniss.it ), R. Marrosu, M. Pirastru, M. Niedda Agricultural Department, University of Sassari, Viale Italia, 39, 07100 Sassari, Italy LOCATION Characterizing the lateral saturated subsurface flow processes in a hillslope at different spatial scales. Identifying the appropriate measurement technique to obtain reliable saturated soil hydraulic conductivity, Ks (L T–1), values. METHODS point-scale plot-scale hillslope-scale RESULTS CONCLUSIONS

Measuring lateral saturated soil hydraulic conductivity at different spatial scales AIM S. Di Prima (sdiprima@uniss.it ), R. Marrosu, M. Pirastru, M. Niedda Agricultural Department, University of Sassari, Viale Italia, 39, 07100 Sassari, Italy LOCATION LOCATION Location 40°41'53.36" N 8°14'4.15" E Elevation: 55 m a.s.l. Slope: 30% Soil: Lithic Haploxerepts Soil depth: 30-40 cm Parent material: very dense altered substratum of Permian sandstone that exhibits very low drainage Mean annual: 15.8°C Temperature Average annual: 600 mm precipitation METHODS RESULTS CONCLUSIONS

Measuring lateral saturated soil hydraulic conductivity at different spatial scales AIM S. Di Prima (sdiprima@uniss.it ), R. Marrosu, M. Pirastru, M. Niedda Agricultural Department, University of Sassari, Viale Italia, 39, 07100 Sassari, Italy LOCATION-zoom LOCATION Location METHODS RESULTS CONCLUSIONS

BEST-steady algorithm Measuring lateral saturated soil hydraulic conductivity at different spatial scales AIM S. Di Prima (sdiprima@uniss.it ), R. Marrosu, M. Pirastru, M. Niedda Agricultural Department, University of Sassari, Viale Italia, 39, 07100 Sassari, Italy LOCATION Beerkan test point-scale Point-scale BEST-steady algorithm (Bagarello et al. 2014) Beerkan test METHODS plot-scale hillslope- scale RESULTS CONCLUSIONS

Measuring lateral saturated soil hydraulic conductivity at different spatial scales AIM S. Di Prima (sdiprima@uniss.it ), R. Marrosu, M. Pirastru, M. Niedda Agricultural Department, University of Sassari, Viale Italia, 39, 07100 Sassari, Italy LOCATION Cube method point-scale Point-scale METHODS Cube method plot-scale hillslope- scale 11 cm wide by 11 cm long by 14 cm deep soil prisms RESULTS Constant-Head laboratory Permeameter (CHP) method (Klute and Dirksen, 1986) CONCLUSIONS

Measuring lateral saturated soil hydraulic conductivity at different spatial scales AIM S. Di Prima (sdiprima@uniss.it ), R. Marrosu, M. Pirastru, M. Niedda Agricultural Department, University of Sassari, Viale Italia, 39, 07100 Sassari, Italy LOCATION In-situ block method point-scale Plot-a METHODS plot-scale hillslope- scale RESULTS CONCLUSIONS

Measuring lateral saturated soil hydraulic conductivity at different spatial scales AIM S. Di Prima (sdiprima@uniss.it ), R. Marrosu, M. Pirastru, M. Niedda Agricultural Department, University of Sassari, Viale Italia, 39, 07100 Sassari, Italy LOCATION In-situ block method point-scale Plot-b METHODS plot-scale hillslope- scale RESULTS CONCLUSIONS

Measuring lateral saturated soil hydraulic conductivity at different spatial scales AIM S. Di Prima (sdiprima@uniss.it ), R. Marrosu, M. Pirastru, M. Niedda Agricultural Department, University of Sassari, Viale Italia, 39, 07100 Sassari, Italy LOCATION point-scale Darcy’s law: METHODS Darcy plot-scale hillslope- scale where q (L2T-1) is water flow per unit width, T (L) is the thickness of the saturated zone measured perpendicular to the bed, Z (L) is the water table elevation from an arbitrary datum and s (L) is the distance measured in a straight line in the direction of the sloping bed. RESULTS CONCLUSIONS

Hillslope subsurface flow measurement Measuring lateral saturated soil hydraulic conductivity at different spatial scales AIM S. Di Prima (sdiprima@uniss.it ), R. Marrosu, M. Pirastru, M. Niedda Agricultural Department, University of Sassari, Viale Italia, 39, 07100 Sassari, Italy LOCATION Hillslope subsurface flow measurement point-scale METHODS Hillslope-scale plot-scale The lateral saturated subsurface flow above the impeding layer was collected by a 8.5 m long French drain. Outflow from the drain was recorded by an automated tipping-bucket (0.5 l/tip), which allows subsurface flow measurements every 5 minutes until 25 L min–1. hillslope- scale RESULTS CONCLUSIONS

Measuring lateral saturated soil hydraulic conductivity at different spatial scales AIM S. Di Prima (sdiprima@uniss.it ), R. Marrosu, M. Pirastru, M. Niedda Agricultural Department, University of Sassari, Viale Italia, 39, 07100 Sassari, Italy LOCATION Ks values estimated with the BEST method (Ks-BEST) decreased progressively with soil depth Results METHODS No anisotropy detected Vertical, Ks,v-MCM, and lateral, Ks,l-MCM, saturated soil hydraulic conductivity values obtained by the Constant-Head laboratory Permeameter (CHP) method (Klute and Dirksen, 1986) on soil cubes. In situ and Laboratory point-scale measurements RESULTS In situ vs lab Point- vs. Hillslope-scale measurements Cumulative empirical frequency distribution of the saturated soil hydraulic conductivity, Ks-BEST, values obtained with the BEST method at 0, 5, 10 and 20 cm depths. Plot- vs. Hillslope-scale measurements CONCLUSIONS

Measuring lateral saturated soil hydraulic conductivity at different spatial scales AIM S. Di Prima (sdiprima@uniss.it ), R. Marrosu, M. Pirastru, M. Niedda Agricultural Department, University of Sassari, Viale Italia, 39, 07100 Sassari, Italy LOCATION CONCEPT The hillslope-scale measurements were between two and three orders of magnitude larger than the point-scale ones Results Small sampled volumes implied less opportunity to include macropores Samples did not adequately represent the macropore network and connectivity METHODS In situ and Laboratory point-scale measurements RESULTS Point vs hillslope Point- vs. Hillslope-scale measurements Plot- vs. Hillslope-scale measurements where h is the depth to the water table from the soil surface, Ds is the depth from the soil surface to the hydraulically restricting layer such that T = Ds – h CONCLUSIONS

Point vs hillslope Concept Measuring lateral saturated soil hydraulic conductivity at different spatial scales AIM S. Di Prima (sdiprima@uniss.it ), R. Marrosu, M. Pirastru, M. Niedda Agricultural Department, University of Sassari, Viale Italia, 39, 07100 Sassari, Italy LOCATION Small sampled volumes implied less opportunity to include macropores Samples did not adequately represent the macropore network and connectivity The hillslope-scale measurements were between two and three orders of magnitude larger than the point-scale ones Small sampled volumes implied less opportunity to include macropores Samples did not adequately represent the macropore network and connectivity CONCEPT METHODS In situ and Laboratory point-scale measurements RESULTS Point vs hillslope Concept Point- vs. Hillslope-scale measurements Plot- vs. Hillslope-scale measurements where h is the depth to the water table from the soil surface, Ds is the depth from the soil surface to the hydraulically restricting layer such that T = Ds – h CONCLUSIONS Branch-node chart (Modified from Perret et al., 1999).

Measuring lateral saturated soil hydraulic conductivity at different spatial scales AIM S. Di Prima (sdiprima@uniss.it ), R. Marrosu, M. Pirastru, M. Niedda Agricultural Department, University of Sassari, Viale Italia, 39, 07100 Sassari, Italy LOCATION Plot experiments METHODS In situ and Laboratory point-scale measurements RESULTS Plot Point- vs. Hillslope-scale measurements Plot- vs. Hillslope-scale measurements CONCLUSIONS

Plot- vs. Hillslope-scale measurements Measuring lateral saturated soil hydraulic conductivity at different spatial scales AIM S. Di Prima (sdiprima@uniss.it ), R. Marrosu, M. Pirastru, M. Niedda Agricultural Department, University of Sassari, Viale Italia, 39, 07100 Sassari, Italy LOCATION Plot- vs. Hillslope-scale measurements CONCEPT METHODS For WTD = 5 cm, the Ks,l values determined on the soil monoliths (Ks,l-SM) were similar in magnitude to the hillslope-scale Ks,l values (Ks,l-DRAIN) Ks,l-SM variability increased sharply for higher WTD, i.e., for thinner saturated layer Because the macropore density decreased with depth, the sampled volume should be increased for thinner saturated layer. On the contrary, the increase in WTD from 5 to 15 and finally to 25 cm corresponds to a reduction of the sampled soil volume, which did not allow to estimate consistent Ks,l values with those at a larger scale. In situ and Laboratory point-scale measurements RESULTS Plot vs hillslope Point- vs. Hillslope-scale measurements Plot- vs. Hillslope-scale measurements CONCLUSIONS

Plot vs hillslope Concept 1 Measuring lateral saturated soil hydraulic conductivity at different spatial scales AIM S. Di Prima (sdiprima@uniss.it ), R. Marrosu, M. Pirastru, M. Niedda Agricultural Department, University of Sassari, Viale Italia, 39, 07100 Sassari, Italy Surface LOCATION WTD Plot- vs. Hillslope-scale measurements CONCEPT METHODS For WTD = 5 cm, the Ks,l values determined on the soil monoliths (Ks,l-SM) were similar in magnitude to the hillslope-scale Ks,l values (Ks,l-DRAIN) Ks,l-SM variability increased sharply for higher WTD, i.e., for thinner saturated layer Because the macropore density decreased with depth, the sampled volume should be increased for thinner saturated layer. On the contrary, the increase in WTD from 5 to 15 and finally to 25 cm corresponds to a reduction of the sampled soil volume, which did not allow to estimate consistent Ks,l values with those at a larger scale. In situ and Laboratory point-scale measurements RESULTS Plot vs hillslope Concept 1 Point- vs. Hillslope-scale measurements Plot- vs. Hillslope-scale measurements CONCLUSIONS Branch-node chart (Modified from Perret et al., 1999).

Plot vs hillslope Concept 2 Measuring lateral saturated soil hydraulic conductivity at different spatial scales AIM S. Di Prima (sdiprima@uniss.it ), R. Marrosu, M. Pirastru, M. Niedda Agricultural Department, University of Sassari, Viale Italia, 39, 07100 Sassari, Italy Surface LOCATION Thinner saturated layer corresponds to a reduction of the sampled soil volume. Ks,l values were not consistent with those at a larger scale due to bypass flow. WTD Plot- vs. Hillslope-scale measurements CONCEPT METHODS For WTD = 5 cm, the Ks,l values determined on the soil monoliths (Ks,l-SM) were similar in magnitude to the hillslope-scale Ks,l values (Ks,l-DRAIN) Ks,l-SM variability increased sharply for higher WTD, i.e., for thinner saturated layer Because the macropore density decreased with depth, the sampled volume should be increased for thinner saturated layer. On the contrary, the increase in WTD from 5 to 15 and finally to 25 cm corresponds to a reduction of the sampled soil volume, which did not allow to estimate consistent Ks,l values with those at a larger scale. In situ and Laboratory point-scale measurements RESULTS Plot vs hillslope Concept 2 Point- vs. Hillslope-scale measurements Bypass flow Plot- vs. Hillslope-scale measurements CONCLUSIONS Branch-node chart (Modified from Perret et al., 1999).

Measuring lateral saturated soil hydraulic conductivity at different spatial scales AIM S. Di Prima (sdiprima@uniss.it ), R. Marrosu, M. Pirastru, M. Niedda Agricultural Department, University of Sassari, Viale Italia, 39, 07100 Sassari, Italy Conclusions This investigation was carried out to characterize the lateral saturated subsurface flow processes in a hillslope at different spatial scales, namely point-, plot- and hillslope-scale. Our results, yielded encouraging signs of the applicability of the soil block method (plot-scale), for a plausible estimation of Ks,l by a relatively simple field procedure. The discrepancy between the considered scales, i.e., point vs. plot and point vs. hillslope, were attributed mainly to the impossibility to adequately embody the macropore network and connectivity on small sampled soil volume. LOCATION METHODS RESULTS CONCLUSIONS CONCLUSIONS