TY - JOUR

T1 - Characterisation of the field-saturated hydraulic conductivity on a hillslope

T2 - In situ single ring pressure infiltrometer measurements

AU - Jan, Mertens

AU - Jacques, D.

AU - Vanderborght, J.

AU - Feyen, J.

PY - 2002/6

Y1 - 2002/6

N2 - Spatial variability of surface hydraulic properties is an important factor for infiltration and runoff processes in agricultural fields. At 120 locations on a hillslope, steady-state infiltration rates were measured at two applied pressure heads with a single-ring infiltrometer. The solution of two steady-state infiltration equations for each location (the simultaneous-equation approach, SEA) yielded 41 negative α-values, 79 positive α values and 120 positive Kfs-values. The sensitivity of Kfs and α to small measurement errors was estimated using a Monte-Carlo simulation (MC). Results of this MC simulation showed that the uncertainty on α is extremely high while the uncertainty on Kfs is fairly small. Hence, although the pressure infiltrometer technique as applied here is useful to estimate Kfs at each measurement location, it is not suited for the estimation of an α-value at each measurement location. A new procedure is proposed for the simultaneous estimation of one overall 'field α' and the 79 Kfs values of measurement locations having a positively calculated α using SEA. Using this field α, Kfs values for the other locations with a negative α are hence determined. Finally, the spatial correlation of Kfs on the hillslope is examined. Ranges of ln(Kfs) between 2.85 and 3.8 m were observed, respectively, for the omnidirectional case and the y direction along the hillslope μ.

AB - Spatial variability of surface hydraulic properties is an important factor for infiltration and runoff processes in agricultural fields. At 120 locations on a hillslope, steady-state infiltration rates were measured at two applied pressure heads with a single-ring infiltrometer. The solution of two steady-state infiltration equations for each location (the simultaneous-equation approach, SEA) yielded 41 negative α-values, 79 positive α values and 120 positive Kfs-values. The sensitivity of Kfs and α to small measurement errors was estimated using a Monte-Carlo simulation (MC). Results of this MC simulation showed that the uncertainty on α is extremely high while the uncertainty on Kfs is fairly small. Hence, although the pressure infiltrometer technique as applied here is useful to estimate Kfs at each measurement location, it is not suited for the estimation of an α-value at each measurement location. A new procedure is proposed for the simultaneous estimation of one overall 'field α' and the 79 Kfs values of measurement locations having a positively calculated α using SEA. Using this field α, Kfs values for the other locations with a negative α are hence determined. Finally, the spatial correlation of Kfs on the hillslope is examined. Ranges of ln(Kfs) between 2.85 and 3.8 m were observed, respectively, for the omnidirectional case and the y direction along the hillslope μ.

KW - Hillslope

KW - Hydraulic conductivity

KW - Inverse parameter estimation

KW - Sensitivity analysis

KW - Spatial variability

UR - http://www.scopus.com/inward/record.url?scp=0037054656&partnerID=8YFLogxK

U2 - 10.1016/S0022-1694(02)00052-5

DO - 10.1016/S0022-1694(02)00052-5

M3 - Article

AN - SCOPUS:0037054656

SN - 0022-1694

VL - 263

SP - 217

EP - 229

JO - Journal of Hydrology

JF - Journal of Hydrology

IS - 1-4

ER -