Calibration and Reliability in Groundwater Modelling: Credibility of Modelling

(Proceedings of ModelCARE 2007 Conference, held in Denmark, September 2007). IAHS Publ. 320, 2008, 226-232.

Modelling two-phase transport of ³H/³He

Ate Visser¹, Joris D. Schaap^2,3, tOON lEIJNSE³, Hans Peter Broers² & Marc F. P. Bierkens^1,2

1 Faculty of Geosciences, Utrecht University, Heidelberglaan 2, NL-3584CS, Utrecht, The Netherlands

a.visser@geo.uu.nl

2 TNO – Environment and Geosciences, Utrecht, The Netherlands

3 WUR – Wageningen University and Research, Wageningen, The Netherlands

Abstract Degassing of groundwater by excess denitrification of agricultural pollution complicates the interpretation of ³H/³He data and hinders the estimation of travel times in nitrate pollution studies. In this study we used a two-phase flow and transport model (STOMP) to evaluate the method presented by Visser (2007a) to interpret degassed ³H/³He data using the total dissolved gas pressure to estimate the depth of degassing. We conclude that the method performs well below the depth of degassing.

Key words ³H/³He; total dissolved gas pressure; two-phase flow; numerical simulation