Is the minimum pumping rate or fraction of original

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Unformatted text preview: one of the nodes listed for the well, or if the intake location is specified by elevation and the elevation is above the top of the open interval, then the intake location will be 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 Qlimit > 0: 2f. Data: Hlim QCUT {Qfrcmn Qfrcmx} Hlim is the limiting water level (head) in the well, which is a minimum for discharging wells and a maximum for injection wells. For example, in a discharging well, when hWELL falls below hlim, the flow from the well is constrained. QCUT Qfrcmn Qfrcmx is an integer flag that indicates how pumping limits Qfrcmn and Qfrcmx will be specified. If pumping limits are to be specified as a rate (L3/T), then set QCUT > 0; if pumping limits are to be specified as a fraction of the specified pumping rate (Qdes), then set QCUT < 0. If there is not a minimum pumping rate below which the pump becomes inactive, then set QCUT = 0. is the minimum pumping rate or fraction of original pumping rate (a choice that depends on QCUT) that a well must exceed to remain active during a stress period. The absolute value of Qfrcmn must be less than the absolute value of Qfrcmx (defined next). Only specify if QCUT ≠ 0. is the minimum pumping rate or fraction of original pumping rate that must be exceeded to reactivate a well that had been shut off based on Qfrcmn during a stress period. The 50 Revised Multi-Node Well (MNW2) Package for MODFLOW Ground-Water Flow Model absolute value of Qfrcmx must be greater than the absolute value of Qfrcmn. Only specify if QCUT ≠ 0. Note 7: Only specify dataset 2f if the value of Qlimit in dataset 2b is positive. Do not enter fractions as percentages. For example, if QCUT < 0, and the well must exceed 80 percent of the original pumping rate to remain active, then enter a value of “0.8” for Qfrcmn. If QCUT > 0, then the rates specified for Qfrcmn and Qfrcmx follow the sign convention for MODFLOW; that is, for discharging wells the rate should be negative, and for recharging (injection) wells the rate should be positive. If PUMPCAP > 0: 2g. Data: Hlift LIFTq0 LIFTqmax HWtol Hlift is the reference head (or elevation) corresponding to the discharge point for the well. This is typically at or above the land surface, and can be increased to account for additional head loss due to friction in pipes. LIFTq0 is the value of lift (total dynamic head) that exceeds the capacity of the pump. If the calculated lift equals or exceeds this value, then the pump is shut off and discharge from the well ceases. LIFTqmax is the value of lift (total dynamic head) corresponding to the maximum pumping (discharge) rate for the pump. If the calculated lift is less than or equal to LIFTqmax, then the pump will operate at its design capacity, assumed to equal the user-specified value of Qdes (in dataset 4a). LIFTqmax will be associated with the value of Qdes in the first stress period in which Qdes for the well is less than 0.0. HWtol is a minimum absolute value of change in the computed water level in the well allowed between successive iterations; if the value of hWELL changes from one iteration to the next by a value smaller than this tolerance, then the value of discharge computed from the head capacity curves will be locked for the remainder of that time step. It is recommended that HWtol be set equal to a value approximately one or two orders of magnitude larger than the value of HCLOSE, but if the solution fails to converge, then this may have to be adjusted. Note 8: LIFTq0 and LIFTqmax define the two end points of the performance curve (head-capacity curve) for the pump installed in the well. One or more additional intermediate points on the curve must be defined below in dataset 2h. The model will use linear interpolation to estimate values between defined data points. The number of additional data points on the curve (and lines in dataset 2h) must correspond to the value of PUMPCAP for this well (where PUMPCAP ≤ 25). The data entered are typically provided by the pump manufacturer. The performance curves will only be applied for stress periods in which Qdes < 0.0 and CapMult > 0 (see dataset 4a). If PUMPCAP > 0: 2h. Data: LIFTn Qn LIFTn is a value of lift (total dynamic head) that corresponds to a known value of discharge (Qn) for the given pump, specified as the second value in this line. Qn is the value of discharge corresponding to the height of lift (total dynamic head) specified previously on this line. Sign (positive or negative) is ignored. Note 9: Repeat 2h PUMPCAP times. That is, the number of lines (records) in dataset 2h must correspond to the value of PUMPCAP for this well. Enter data in order of decreasing lift (that is, start with the point corresponding to the highest value of total dynamic head) and increasing discharge. The discharge value for the last data point in the sequence must be less than the value of LIFTqmax. The data entered are typically provid...
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This document was uploaded on 01/20/2014.

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