Hydrology and Earth System Sciences www.hydrol-earth-syst-sci.net 1027-5606 1607-7938 10 6 2006 10.5194/hess-10-861-2006 http://www.hydrol-earth-syst-sci.net/10/861/2006/ http://www.hydrol-earth-syst-sci.net/10/861/2006/hess-10-861-2006.html http://www.hydrol-earth-syst-sci.net/10/861/2006/hess-10-861-2006.pdf 861 871 2006-11-16 Simplified stochastic soil-moisture models: a look at infiltration J. R. Rigby jrrigby@duke.edu A. Porporato Department of Civil and Environmental Engineering, Duke University, Durham NC, USA A simplified, vertically-averaged model of soil moisture interpreted at the daily time scale and forced by a stochastic process of instantaneous rainfall events is compared with a vertically-averaged model which uses a non-overlapping rectangular pulse rainfall model and a more physically based description of infiltration. The models are compared with respect to the importance of short time-scale (intra-storm) variable infiltration in determining the probabilistic structure of soil-moisture dynamics at the daily time-scale. Differences in approach to infiltration modelling show only minor effects on the probabilistic structure of soil-moisture dynamics as simulated in the two models. The partitioning of losses during a single rainfall event are examined closely and the conditions under which surface-controlled runoff is significant, as a proportion of total losses, are delineated. Benjamin, J. R. and Cornell, C. A.: Probability, Statistics and Decision for Civil Engineers, New York, McGraw-Hill, 1970. Brooks, R. H. and Corey, A. T.: Properties of porous media affecting fluid flow, Journal of Irrigation and Drainage ASCE, 92(IR2), 61–88, 1966. Cox, D. R. and Miller, H. D.: The Theory of Stochastic Processes, London, Methuen, 1965. Daly, E. and Porporato, A.: Impact of Hydro-Climatic Fluctuations on the Soil Water Balance, Water Resour. Res., 42, W06401, doi:10.1029/2005WR004606, 2006. Eagleson, P.: Climate, Soil and Vegetation 1. Introduction to water balance dynamics, Water Resour. Res., 14, 705–712, 1978. Eagleson, P.: Climate, Soil and Vegetation 2. The distribution of annual precipitation derived from observed storm sequences, Water Resour. Res., 14, 713–721, 1978. Eagleson, P.: Climate, Soil and Vegetation 3. A simplified model of soil moisture movement in the liquid phase, Water Resour. Res., 14, 722–730, 1978. Guswa, A., Celia, M., and Rodriguez-Iturbe, I.: Models of soil moisture dynamics in ecohydrology: A comparative study, Water Resour. Res., 38(9), 1166–1181, 2002. Kim, C., Stricker, J., and Torfs, P.: An analytical framework for the water budget of the unsaturated zone, Water Resour. Res., 32, 3475–3484, 1996. Laio, F., Porporato, A., Ridolfi, L., and Rodriguez-Iturbe, I.: Plants in water-controlled ecosystems: Active role in hydrologie processes and responce to water stress II. Probabilistic soil moisture dynamics, Adv. Water Resour., 24(7), 707–723, 2001. Liu, M. C., Parlange, J. Y., Sivapalan, M., and Brutsaert, W.: A note on the time compression approximation, Water Resour. Res., 34, 3683–3686, 1998. Milly, P. C. D.: An analytic solution of the stochastic storage problem applicable to soil water, Water Resour. Res., 29(11), 3755–3758, 1993. Parlange, J. Y., Lisle, I., Braddock, R. D., and Smith, R. E.: The three parameter infiltration equation, Soil Sci., 133, 337–341, 1982. Philip, J. R.: The Theory of Infiltration 4. Sorptivity, and algebraic infiltration equations, Soil Sci., 84, 257–264, 1957. Porporato, A., Daly, E., and Rodriguez-Iturbe, I.: Soil water balance and ecosystem response to climate change, American Naturalist, 164(5), 625–632, 2004. Rodriguez-Iturbe, I., Porporato, A., Ridolfi, L., Isham, V., and Cox, D.: Probabilistic modelling of water balance at a point: the role of climate, soil and vegetation, Proc. Royal Soc. London A, 455, 3789–3805, 1999. Rodriguez-Iturbe, I. and Porporato, A.: Ecohydrology of water-controlled ecosystems: Soil moisture and Plant Dynamics, Cambridge, New York, 2004. Sherman, L. K.: Comparison of F-curves derived by the methods of Sharp and Holtan and of Sherman and Mayer, Eos Transactions AGU, 24, 465–467, 1943. Smith, R. E. and Parlange, J. Y.: A paremeter-efficient hydrologic infiltration model, Water Resour. Res., 14, 533–538, 1978. Smith, R.: Infiltration Theory for Hydrologic Applications, AGU, Washington, D.C., 2002.