This broad session is open to contributions concerning methods, strategies and applications that combine the strengths of modeling and measuring to improve our understanding of subsurface flow and transport systems. Particular interests lie on the following themes, (1) inverse modeling using parameter estimation, (2) data assimilation, (3) multi-model ensemble modeling, and (4) the use of novel measurement techniques for improved parameterization of groundwater and vadose zone flow and transport processes. We especially encourage submission of abstracts that deal explicitly with distributed calibration and uncertainty estimation problems, and work that aims to improve the description and analysis of measurement and model error.