i want to assess the hydraulic conductivity ( saturated and unsaturated) in the field through diffrent horizon in the vertical and the horizontal direction. how can i proceed to compute an average mean of the hydraulic conductivity of my field ?.
First of all, if your soil is "conventional" with clay, lemon and sand, the assessment of hydraulic conductivity is based on Darcy's law. If your soil is stony or karstic, there are other experimental methods to apply.
In "Darcian soils", the well and piezometers method of Guyon or the auger method are practical to obtain the saturated hydraulic conductivity. If your soil is drained, there is an indirect method for the estimation of the horizontal saturated hydraulic conductivity involving Darcy's law.
The assessment of the unsaturated hydraulic conductivity is more complex because you may include wet and dry stages of the soil. The methodology is rather based on laboratory measurement of the state variables samples: water content, head pressure and unsaturated hydraulic conductivity. Anyway, the Darcy's law application is also the key to assess the unsaturated hydraulic conductivity.
Dear Yacine,
For field measurement of hydraulic conductivity (Ks), you may use the ''air-entry permeameter'' and ''constant head Guelph permeameter'' method. The study of Lee et al. (1985) indicated that the best choice of method was dependent on the required type and accuracy of the Ks measurement, soil type, and various practical constraints.
Reference: Lee, D. M., Reynolds, W. D., Elrick, D. E. Clothier, B. E. 1985. A
comparison of three field methods for measuring saturated hydraulic conductivity.
Can. J. Soil Sci. 65:563-573.
For your easy access, I attach PDF copy of the above article. Hope you find this input interesting and useful for your research.
Hi. You may wish to consider that the average conductivity for a field depends is not the simple arithmetic average. Neither is it normally obtainable from applying the additive conduction equation to randomly sampled field (though this is much better than a simple mean); G = G1 + G2 + G3+ .... because the spatial distribution of G is not normal. You must seek the maximum G in the paddock and incorporate it into your formula. This is easily explained by analogy with a bathtub. Unless one measures the conductivity of the hole, a bathtub is impervious to water (G = 0 !). And even if one does measure the hole, the simple arithmetic average (G/n) is still quite low and misleading.
Apologies if these principles were well-known to you.
Enjoy your studies.
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