Assessment of Hydraulic Conductivity Upscaling Techniques and Associated Uncertainty

The use of numerical models for studying subsurface flow and transport has become common practice in hydrology over the last three decades. However, hydraulic parameters introduced to these models are still of a major concern. Data are usually collected at a scale much smaller than that used in numerical models but by using geostatistical techniques, available measurements can be used to stochastically populate the entire domain of the studied area. Models built based on these geostatistical techniques should be on the same scale as the supporting measurements which lead to models with very large number of cells. Dealing with these numerical models stochastically is beyond the capabilities of current computational resources. Upscaling is the process of transforming the detailed description of hydraulic parameters in a grid constructed at measurement scale (fine grid) to a coarser grid with less detailed description (coarse grid) for the purpose of numerical subsurface modeling. The fact that the coarse grid hydraulic conductivity should have a value between the harmonic mean and arithmetic mean of the fine grid conductivities inside this coarse grid cell led researchers to use the power average technique for the upscaling process with exponent varying from -1.0 to 1.0. The objective of this study is to develop a technique for assessing the uncertainty in upscaling flow and transport parameters and the impact of this uncertainty on prediction uncertainty of models relying on upscaled parameter values. This technique is tested using log-normal distribution of hydraulic conductivity with small variance and exponential covariance, results were found to match with analytical solution.Presenters: name: Hassan, Ahmed affiliation: Desert Research Institute-USA and Cairo University- Egyp