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8 | 8 | \item With this release, there are now two supported executables for MODFLOW 6. The standard executable has no external dependencies and is straightforward to install and use on common operating systems. The extended executable for MODFLOW, which is called Extended MODFLOW, has additional capabilities beyond the standard executable. These additional capabilities presently include parallel computing and support for NetCDF input and output files. Extended MODFLOW relies on third-party libraries, which must be available for the software to run properly. The MODFLOW 6---Description of Input and Output includes a new section on Extended MODFLOW. This input and output guide was also revised to clearly mark in red those input variables that only work with Extended MODFLOW. |
9 | 9 | \item A new adaptive time stepping (ATS) capability was added to the Advection (ADV) Package of the Groundwater Transport (GWT) Model. A new input option, called ATS\_PERCEL, specifies the fractional cell distance that a particle of water can travel within one time step. When ATS\_PERCEL is specified by the user, and the ATS utility is activated in the TDIS Package, the ADV Package will calculate the largest time step that will meet this fractional cell distance constraint, and will submit this time step to the ATS utility. This option may improve time stepping for solute transport models and for variable-density flow and transport models by allowing step lengths to be calculated as a function of the flow system rather than being specified as input by the user. |
10 | 10 | \item Added the capability to write sorbate concentrations to binary output files. A new SORBATE option is now available in the Mobile Storage and Transfer (MST) Package and the Immobile Storage and Transfer (IST) Package of the GWT Model to provide the name of the binary output file for sorbate concentrations. Sorbate concentrations will be written to the binary output file whenever concentrations for the GWT model are saved, as determined by the GWT Output Control option. |
11 | | - \item Add kinematic-wave routing option for the Streamflow Routing (SFR) Package. Prior to this change, the SFR Package could only simulate unidirectional, steady, uniform flow. With kinematic-wave routing, unidirectional waves can now propagate through the SFR network by explicitly including a storage term in the reach continuity equation. The kinematic-wave routing option is based on the ``TRANSROUTE'' option available in the SFR Package in MODFLOW-NWT. The kinematic-wave routing option is enabled by specifying ``STORAGE'' in the SFR Package OPTIONS block. |
| 11 | + \item Added kinematic-wave routing option for the Streamflow Routing (SFR) Package. Prior to this change, the SFR Package could only simulate unidirectional, steady, uniform flow. With kinematic-wave routing, unidirectional waves can now propagate through the SFR network by explicitly including a storage term in the reach continuity equation. The kinematic-wave routing option is based on the ``TRANSROUTE'' option available in the SFR Package in MODFLOW-NWT. The kinematic-wave routing option is enabled by specifying ``STORAGE'' in the SFR Package OPTIONS block. |
12 | 12 | \item The Freundlich and Langmuir isotherms can now be used to represent sorption in the immobile domain when simulating solute transport using the Groundwater Transport (GWT) Model. Prior to this change, only linear sorption could be used with the Immobile Storage and Transfer (IST) Package for the GWT Model. With this change, the SORPTION keyword specified in the OPTIONS block of the IST Package must be followed by LINEAR, FREUNDLICH, or LANGMUIR. If the FREUNDLICH or LANGMUIR isotherms are specified, then the user must also include the SP2 array in the GRIDDATA block of the IST Package. This change breaks backward compatibility for GWT Models that used the SORPTION option in the IST Package, which previously did not require the type of sorption to be specified after the SORPTION keyword. Details on the implementation of the nonlinear Freundlich and Langmuir sorption isotherms are described in a new chapter in the MODFLOW 6 --- Supplemental Technical Information guide, which is included with the MODFLOW 6 distribution. |
13 | 13 | \end{itemize} |
14 | 14 |
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44 | 44 | \item The PRT model's particle release point (PRP) package previously allowed two particles to be released at the same time from the same point. This could occur if an explicitly specified release time happened to coincide with a release time configured via period block settings. Each release point may now only release one particle at a time. Times falling within a configurable tolerance of one another (defaulting to $\sisetup{input-digits = 0123456789\epsilon} \num{\epsilon e+9}$, where $\epsilon$ is machine precision) are considered coincident and merged into a single release time. |
45 | 45 | \item A new option RELEASE\_TIME\_FREQUENCY was added to the PRT model's particle release point (PRP) package. This option configures release times on a regular interval for the duration of the simulation, with the first release at the simulation start time. The PRP package's release schedule is the union of times configured via RELEASE\_TIME\_FREQUENCY, the RELEASETIMES block, and period block release settings, up to the tolerance mentioned in the previous item. If none of these are provided, a single release time is configured at the beginning of the first stress period's first time step. (A related bug has also been fixed which erroneously activated this default when user-specified release times were configured.) |
46 | 46 | \item The PRT model's particle release point (PRP) package's FRACTION period-block release time setting has been removed. Period-block release settings can now be used only to release particles at the beginning of specified time steps, as is the case for period-block timing settings in the output control (OC) packages for all models. For fine control over release timing, specify times explicitly using the RELEASETIMES block. |
47 | | - \item The Stress Package Concentration (SPC) utility available with the SSM Package is now the referred to as the Stress Package Component utility in the MF6IO guide. Additionally, some relatively minor refactoring of the code facilitates use of the SPC utility with the GWE model type so that TEMPERATURE arrays may be read by the utility. The SPC acronym was maintained to preserve backward compatibility. |
| 47 | + \item The Stress Package Concentration (SPC) utility available with the SSM Package is now referred to as the Stress Package Component utility in the MF6IO guide. Additionally, some relatively minor refactoring of the code facilitates use of the SPC utility with the GWE model type so that TEMPERATURE arrays may be read by the utility. The SPC acronym was maintained to preserve backward compatibility. |
48 | 48 | \item The GWF-GWF Exchange has been fixed to support the configuration of the Mover package (MVR) also in cases where the number of exchanges equals zero (NEXG = 0). In earlier versions this has caused MODFLOW to terminate with an error. |
49 | 49 | \item A PRT bug was fixed in which array-based input read from the RCH (recharge) or EVT (evapotranspiration) packages could fail to be processed correctly by the PRT FMI (flow model interface) package, causing a crash. |
50 | 50 | \item When the SQUARE\_GWET option was invoked in the UZF options block, evapotranspiration from the water table (GWET) was calculated incorrectly. Instead of acting as a sink, the calculated evapotranspiration flux was added as a source of water. The applied fix ensures that groundwater evapotranspiration is removed from the water table and as a result the GWET values are accumulated as outflows in the budget table. |
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