1. General Model Information

Name: Enhanced Trickle Down (ETD) Model

Acronym: ETD

Main medium: terrestrial + aquatic
Main subject: biogeochemistry, hydrology
Organization level: ecosystem
Type of model: ordinary differential equations
Main application:
Keywords: acidification, cation exchange, chemical weathering, sulphate sorption,sulphate reduction, snowmelt, interflow, overland flow, groundwater flow, frozen ground processes, seepage


Dr. Nikolaos P. Nikolaidis
Dept. of Civil Engineering
University of Connecticut
BOX U-37
Storrs, CT 06269 USA
Phone: +1 203-486-5648
Fax : +1 203-486-2298
email: nikos@engz.uconn.edu



A generalized soft water acidification model has been developed. The enhanced trickle- down (ETD) model is driven by precipitation, evaporation, acidity, sulphate, and chloride loading time series daily input data. The hydrologic component simulates snowmelt, interflow, overland flow, groundwater flow, frozen ground processes, seepage, and evapotranspiration. Physicochemical and biological processes that affect the alkalinity or sulphate balance and are included in the formulation are cation exchange, chemical weathering, sulphate sorption, and sulphate reduction. The system of 20 ordinary differential equations is solved by using a variable timestep fourth-order predictor-corrector numerical scheme. Shown here is calibration of the ETD model for two lakes in the Adirondack Park of New York. ETD is relatively simple and requires limited input data, and yet it accounts for the predominant hydrologic and biochemical processes of the ecosystem.

Model purpose
The Enhanced Trickle- Down model can be used to model the hydrologic and geochemical response of surface water watersheds to freshwater acidification.

Source of the Abstract:
Joergensen S.E., B. Halling-Soerensen and S.N Nielsen (Edts.) 1996: Handbook of Environmental and Ecological Modelling. CRC Press Boca Raton et al. 672 pp.

II. Technical Information

II.1 Executables:

Operating System(s): DOS

II.2 Source-code:

Programming Language(s): FORTRAN

II.3 Manuals:

II.4 Data:

III. Mathematical Information

III.1 Mathematics

III.2 Quantities

III.2.1 Input

III.2.2 Output

IV. References

Nikolaidis, N.P., Hu, H., and Ecsedy, C., 1994. Effects of climatic variability on freshwater watershed: case studies. Aquatic Sciences, Vol. 56, No. 2, pp. 161-178.
Nikolaidis, N.P., Hu, H., Ecsedy, C., and Lin, J.D., 1993. Hydrologic response of freshwater watersheds to climatic variability; model development. Water Resources Research, Vol. 29, No. 10, pp. 3317-3328.
Nikolaidis, N.P., Muller, P.K., Schnoor, J.L., and Hu, H.L., 1991. Modelling the hydrogeochemical response of a stream to acid deposition using the enhanced trickle- down model. Research Journal of Water Pollution Control Federation, Vol. 63, No. 3, pp. 220-227.
Georgakakos, K.P., Valle-Folho, G.M., Nikolaidis, N.P., and Schnoor, J.L., 1989. Lake acidification studies: the role of input uncertainty in long-term predictions. Water Resources Research, Vol. 25, No. 7, pp. 1511-1518.
Nikolaidis, N.P., Schnoor, J.L., and Georgakakos, K.P., 1989. Modelling of Long-Term Lake Alkalinity Responses to Acid Deposition. Journal of Water Pollution Control Federation, Vol. 61, No. 2, pp. 188-199.
Nikolaidis, N.P., Rajaram, H., Schnoor, J.L., and Georgakakos, K.P., 1988. Generalized softwater acidification model. Water Resources Research, Vol. 24, No. 12, pp. 1983-1996.
Nikolaidis, N.P., 1987. Modelling the Direct Versus Delayed response of Surface Waters to Acid Deposition in the Northeastern United States. Ph.D. Thesis, Civil and Environmental Engineering, University of Iowa, pp. 288.
Schnoor, J.L., Georgakakos, K.P., Lee, S., Nikolaidis, N.P., and Rajaram, H., 1990. Lakes Resources at Risk to Acidification in the Northeastern Unites States: Diract-Delayed Response Project. Final Report, Cooperative Agreement CR-812329, U.S., EPA, ERL, Corvallis, Oregon.

V. Further information in the World-Wide-Web

VI. Additional remarks

Last review of this document by: T. Gabele: 10. 10. 1998
Status of the document:
last modified by Tobias Gabele Wed Aug 21 21:44:42 CEST 2002

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