Groundwater system S

Illustrative Example 25.1 Darcy s Law in Groundwater Systems S Illustrative Example 25.2 Dispersion and Advection in Groundwater System S... 

Illustrative Example 25.6 Transport of Tetrachloroethene in Groundwater System S... 

Specific Discharge q, Effective Mean Flow Velocity u, and Travel Time fw for Different Flow Regimes in Groundwater System S... 

Aquifers which are closely connected to a river (as for the case of Groundwater System S) may be influenced by abrupt input variations that are driven by the corresponding concentration changes in the river. In order to analyze the resulting concentrations in the aquifer, the solution of the transport equation (Eq. 25-10) will be discussed for different time-dependent input concentrations at x = 0, Cin(t). In the river typical time scales of change are of the order of minutes (in case of an accidental spill) to days, but seasonal variations also exist for some chemicals. In contrast, transport within the aquifer is slower than most riverine concentration variations. The question arises how the river dynamics are transmitted to the groundwater. Three different cases are discussed ... 

In River R a pollution cloud of 2,4-dinitrophenol (see Illustrative Example 25.2) of duration At = 1 h and concentration Cin =50 ng L-1 is passing by Groundwater System S. Calculate the maximum concentration reached at the wells for the three regimes. Compare these values to the maximum concentrations reached 3 m away from the river. 

On April 5, at noon, the 2,4-dinitrophenol concentration in River R at Groundwater System S (GWS, see Illustrative Example 25.1 and 25.2) suddenly increases from 0 to 50 ng L 1 and then remains constant. At what time does the concentration in the wells of the GWS reach 25 ng L-1 and 47.5 ng L 1, respectively Calculate the time for all three flow regimes. When are these concentrations reached 3 m from the river if no water is pumped from the wells (Natural Regime) ... 

Calculate the annual sinusoidal variation of the PCE concentration in the wells of Groundwater System S relative to the variation in River R. Compare this number with the relative variation of a nonsorbing chemical such as 2,4-dinitrophenol (see Illustrative Example 25.5). Determine the time lag of oscillation in the well relative to the variation in the river. Use all three flow regimes of Illustrative Example 25.1. 

Zheng, C. (1990) MT3D A modular three-dimensional transport model for simulation of advection, dispersion and chemical reactions of contaminants in groundwater systems. S. S. Papadopoulos and Associates, Inc. 

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