The water budget of heterogeneous areas : impact of soil and rainfall variability
1995
Kim, C.P.
In this thesis the heterogeneity of the soil water budget components is investigated. Heterogeneity of soil hydraulic properties and rainfall rate are taken into account by using stochastic methods. The importance of lateral groundwater flow in causing heterogeneity of the water budget components has been investigated by considering the governing physical laws. Through comparison of water budget simulations of simple soil reservoir models with numerical simulations of the governing equation for unsaturated water flow that incorporate the effect of soil heterogeneity, the importance of the lower boundary condition is revealed. The effects of the various sources of heterogeneity on the annual or long term average water budget appear to be markedly different. The dynamical behavior of spatial heterogeneity of infiltration and evapotranspiration rates on the event time scale is investigated by deriving their probability distributions and subsequently tracing their time evolution. Accounting for the influence of soil heterogeneity by means of one set of "equivalent" parameters is shown to be valid only under restricted conditions. Because of lateral groundwater flow an internal hillslope " teleconnection" is present that links the water budget of the uphill recharge and downhill discharge zones. This teleconnection. establishes a negative feedback for the overall hillslope evapotranspiration since water lost as recharge uphill may reappear in the discharge zone.
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