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Year of publication:

Yijian Zeng1,*, Zhongbo Su1, Lianyu Yu1

1 Department of Water Resources, ITC Faculty of Geo-Information Science and Earth Observation, University of Twente





STEMMUS (Simultaneous Transfer of Energy, Mass and Momentum in Unsaturated Soil) is a program for simulating coupled liquid water, water vapor, dry air and heat transfer in unsaturated soil.

A traditional conceptual model for water flow in unsaturated soil neglects the flow-of-gas phase, as can be seen in the statement: "Unsaturated flow . . . is nothing but a special case of simultaneous flow of two immiscible fluids, where the nonwetting fluid is assumed to be stagnant. According to this statement, air always remains at atmospheric pressure and is free to escape from or enter into the vadose zone. This assumption is widely used in the traditional coupled moisture and heat flow model, based on the theory by Philip and de Vries, even when water vapor movement is considered. However, the flow in porous media is actually a two-phase flow problem, in need of complicated mathematical analysis of the response of soil to atmospheric forcing, caused by nonlinearities, moisture retention hysteresis, soil heterogeneity, as well as by multiple length and time scales. The usual approach to solving the numerical model of water flow in soil involves the above cited assumption, which is often called the Richards approximation. Although successful application of this assumption has been demonstrated in many cases, there are situations where the air phase can significantly retard or speed up infiltration or evaporation at surface. To properly describe these gas influenced infiltrations and evaporations, the STEMMUS model was developed.

The STEMMUS has been applied over extreme dry environments (e.g. Badain Jaren desert), semi-arid area (with influence of groundwater) and crop field lysimeters. It will be further developed to be applied over permafrost regions, considering freezing/thawing, biogeochemical cycles and interactions with groundwater.



Scientific articles

  1. Yu, L., Zeng, Z. Su, H. Cai and Z. Zheng (2016). “The effect of different evapotranspiration methods on portraying soil water dynamics and ET partitioning in a semi-arid environment in Northwest China.” Hydrol. Earth Syst. Sci. 20(3): 975-990. download
  2. Zeng, Y. and Su, Z. (2013) Reply to comment by Binayak P. Mohanty and Zhenlei Yang on “A simulation analysis of the advective effect on evaporation using a two-phase heat and mass flow model”. Water resources research, 49: 7836-7840. download
  3. Zeng Y., Z. Su, L. Wan and J. Wen, (2011): A simulation analysis of the advective effect on evaporation using a two-phase heat and mass flow model. Water Resources Research, 47(10), W10529, doi: 10.1029/2011WR010701. download
  4. Zeng Y., Z. Su, L. Wan and J. Wen, (2011): Numerical Analysis of Air-Water-Heat Flow in the Unsaturated Soil Is it Necessary to Consider Air Flow in Land Surface Models. Journal of Geophysical Research – Atmosphere, 116(20), D20107, doi: 10.1029/2011JD015835. download
  5. Zeng Y., Su, Z., Wan, L., Yang, Z., Zhang, T., Tian, H., Shi, X., Wang, X., Cao, W. (2009): Diurnal pattern of the drying front in desert and its application for determining the effective infiltration. Hydrol. Earth Syst. Sci (HESS), 13:703-714. download
  6. Zeng Y., Wan, L., Su Z. Saito, H., Huang, K., Wang, X. (2009): Diurnal soil water dynamics in the shallow vadose zone (field site of China University of Geosciences, China), Environmental Geology, 58:11-23. download


Technical information

Operating system(s): Matlab 2009b or newer, Windows XP or newer

Licence: free

Output(s): flexible

Export format(s): flexible

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