Effects of slope gradient on the soil saturated hydraulic conductivity of sloping land measured by three single-ring infiltrometers
YONG Chenxu, FAN Jun, WANG Sheng
1. School of Natural Resources and Environment, Northwest A & F University, 712100, Yangling, Shaanxi, China;
2. State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, Institute of Soil and Water Conservation, Chinese Academy of Sciences and Ministry of Water Resources, 712100, Yangling, Shaanxi, China
Abstract：[Background] Soil saturated hydraulic conductivity (Ks) of sloping field is a key parameter to predict soil and water losses, but Ks is mostly measured on the flat land. Therefore, directly measuring saturated hydraulic conductivity on slopes is practically important. The objective of this paper is to study the effect of slope gradient on Ks by three single-ring infiltrometer methods in order to select a suitable method for slope land.[Methods] The slope gradients of 0, 5°, 10°, 15° and 20° in sandy soil, Loessial soil and Lou soil were selected and Ks was measured by three single-ring infiltrometer methods (i.e., two-ponding depth, one-ponding depth and BEST methods), which usually were used for flat lands. All measurements were conducted on undisturbed soil.[Results] 1) On flat soil surface, all three methods obeyed the same order for Ks of different soils as sandy soil > Loessial soil > Lou soil. The Ks of three soils by single-ring BEST infiltrometer were 2.9, 2.1 and 4.5 times, which were larger than those by single-ring two-ponding depth infiltrometer. If cutting-ring infiltrometer was taken as standard, single-ring BEST infiltrometer significantly overestimated the Ks of the Loessial and Lou soil, but the results by single-ring two-ponding depth infiltrometer and single-ring one-ponding depth (10 cm) infiltrometer were close to that by cutting-ring infiltrometer. 2) Ks measured by single-ring two-ponding depth infiltrometer increased with the increase of slope gradient and there was a significant linear correlation between them. The Ks of three soils by single-ring BEST infiltrometer decreased with the increase of slope gradients and this method was affected distinctly by slope gradient due to the change of the ponded water area inside the ring. 3) Under flat ground condition, the results of single-ring one-ponding depth (10 cm) infiltrometer were comparable to single-ring two-ponding depth infiltrometer, but the single-ring one-ponding depth (5 cm) infiltrometer overestimated the results. 4) In sandy soil, Loessial soil and Lou soil, there was no significant difference of Ks between slope<10° and flat land by above 3 methods, but significant while slope >10° (P<0.05).[Conclusions] Therefore, single-ring BEST infiltrometer is not suitable for measuring Ks in sloping field. Single-ring two-ponding depth infiltrometer or single-ring one-ponding (10 cm) depth infiltrometer can be used to correctly measure Ks if the slope is <10°. Furthermore, the calculating equations for saturated hydraulic conductivity by these sing-ring methods should be revised for the three soils in the loess regions if the slope gradient is >10°.
雍晨旭1, 樊军1,2, 王胜2. 坡度对3种单环法测量坡地饱和导水率的影响[J]. 中国水土保持科学, 2018, 16(2): 24-30.
YONG Chenxu, FAN Jun, WANG Sheng. Effects of slope gradient on the soil saturated hydraulic conductivity of sloping land measured by three single-ring infiltrometers. SSWC, 2018, 16(2): 24-30.
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2018, Vol. 16 
