If pumploc 0 then the cell in which the intake or

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Unformatted text preview: ned effects of the A, B, and C well-loss coefficients expressed in equation 15) between the well and the cell representing the aquifer, CWC. User must define CWC in dataset 2c or 2d. If there are multiple screens within the grid cell or if partial penetration corrections are to be made, then the effective value of CWC for the node may be further adjusted Appendix 1—Data Input Instructions for Multi-Node Well (MNW2) Package 47 automatically by MNW2. PUMPLOC is an integer flag pertaining to the location along the borehole of the pump intake (if any). If PUMPLOC = 0, then either there is no pump or the intake location (or discharge point for an injection well) is assumed to occur above the first active node associated with the multinode well (that is, the node closest to the land surface or to the wellhead). If PUMPLOC > 0, then the cell in which the intake (or outflow) is located will be specified in dataset 2e as a LAY-ROW-COL grid location. For a vertical well only, specifying PUMPLOC < 0, will enable the option to define the vertical position of the pump intake (or outflow) as an elevation in dataset 2e (for the given spatial grid location [ROW-COL] defined for this well in 2d). Qlimit is an integer flag that indicates whether the water level (head) in the well will be used to constrain the pumping rate. If Qlimit = 0, then there are no constraints for this well. If Qlimit > 0, then pumpage will be limited (constrained) by the water level in the well, and relevant parameters are constant in time and defined below in dataset 2f. If Qlimit < 0, then pumpage will be limited (constrained) by the water level in the well, and relevant parameters can vary with time and are defined for every stress period in dataset 4b. PPFLAG is an integer flag that determines whether the calculated head in the well will be corrected for the effect of partial penetration of the well screen in the cell. If PPFLAG = 0, then the head in the well will not be adjusted for the effects of partial penetration. If PPFLAG > 0, then the head in the well will be adjusted for the effects of partial penetration if the section of well containing the well screen is vertical (as indicated by identical row-column locations in the grid). If NNODES < 0 (that is, the open intervals of the well are defined by top and bottom elevations), then the model will automatically calculate the fraction of penetration for each node and the relative vertical position of the well screen. If NNODES > 0, then the fraction of penetration for each node must be defined in dataset 2d (see below) and the well screen will be assumed to be centered vertically within the thickness of the cell (except if the well is located in the uppermost model layer that is under unconfined conditions, in which case the bottom of the well screen will be assumed to be aligned with the bottom boundary of the cell and the assumed length of well screen will be based on the initial head in that cell). PUMPCAP is an integer flag and value that determines whether the discharge of a pumping (withdrawal) well (Q < 0.0) will be adjusted for changes in the lift (or total dynamic head) with time. If PUMPCAP = 0, then the discharge from the well will not be adjusted on the basis of changes in lift. If PUMPCAP > 0 for a withdrawal well, then the discharge from the well will be adjusted on the basis of the lift, as calculated from the most recent water level in the well. In this case, data describing the head-capacity relation for the pump must be listed in datasets 2g and 2h, and the use of that relation can be switched on or off for each stress period using a flag in dataset 4a. The number of entries (lines) in dataset 2h corresponds to the value of PUMPCAP. If PUMPCAP does not equal 0, it must be set to an integer value of between 1 and 25, inclusive. Note 3: Discharge is reduced under PUMPCAP independently from a reduction related to constraints (and Qlimit). If both are applied to the same well, then the most restrictive condition from the two criteria will take precedence. PUMPCAP is only applied for withdrawal wells (that is, if the specified pumping rate (Qdes in dataset 4a) is negative in sign). If LOSSTYPE ≠ NONE: 2c. Data: {Rw Rskin Kskin B C P CWC} Include the appropriate coefficients in 2c, as consistent with the specified LOSSTYPE defined in 2b, as summarized also in table A1–1. • if LOSSTYPE = THIEM, then specify Rw (the radius of the well). • if LOSSTYPE = SKIN, then specify Rw, Rskin (the radius to the outer limit of the skin), and 48 Revised Multi-Node Well (MNW2) Package for MODFLOW Ground-Water Flow Model Kskin (the hydraulic conductivity of the skin). • if LOSSTYPE = GENERAL, then specify Rw, B, C, and P, where the last three parameters are coefficients in the well-loss equation (equation 2). (See notes and suggestions for GENERAL option under 2b above.) • if LOSSTYPE = SPECIFYcwc, then specify CWC (the cell-to-well conductance; see equation 15). Note 4: Any of the parameters in dataset 2c can be assumed to be constant for the entire length of the open interval of the well (in which case appropriate values are simply specified above), or it can be assumed that...
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