OBS: Observation Utility Pane

The Obs: Observation Utility pane is on the MODFLOW Features tab of the Object Properties dialog box. It is used to specify observations in MODFLOW 6. For all observations, the user must specify an observation name. For each observation type, the user also needs to check the appropriate check boxes on the Observation Utility pane. For observations defined on the Basic, UZF, and CSUB tabs, the user can define the observation using either an object that also defines the related boundary or one that does not. If the object also defines the boundary, the boundary name (derived from the object name) will be used to identify the appropriate cells in the input file for the observation utility. If the object does not also define the boundary, any boundary cells of the appropriate package that are in the same cells as the object that defines the observation will be included in the input for the Observation Utility and the observations will be identified by their cell ID rather than the boundary name.

For observations of the Streamflow Routing (SFR), Multi-Aquifer Well (MAW), and Lake (LAK) packages, only objects that also define a stream, well, or lake in those packages can be used to define observations of streams, wells. or lakes.

For SFR observations, you must specify the whether you want the observation to be of all the reaches combined, the first reach, the last reach or of each reach individually.

For UZF observations of water content, the user must also specify the depth fraction within the cell where the observation content is desired.

For the CSUB observations of interbed delay cells, the user must also specify the specific cell for which an observation is desired.

For detailed descriptions of the various observation types see the file mf6io.pdf distributed with MODFLOW 6.

The Calibration tab will be present if PEST is activated.

The Calibration tab has two parts Direct Observations on the top and Observation comparisons on the bottom. Direct observations are extracted from MODFLOW output files whereas with Observation comparisons, the observation value is the difference between two direct observation values.

The Observation location name (obsnam) is used to help identify simulated values in the Observation Utility output.

Direct Observations

Observation Name (OBSNME) identifies the name of the direct or comparison observations used by PEST.

Observation Series type relates to the package from which the observation derives.

Observation type is the type of data to be extracted from the MODFLOW observation output file for direct observations.

Observation Group (OBGNME} is the name of the PEST observation group to which the observation is assigned. Observation group names are specified in the Pest Properties dialog box. Observation group names can be be assigned later in the Pest Properties dialog box if a suitable observation group has not yet been defined.

Observation Time is the time at which the observation was made.

Observation Value (OBSVAL) is the measured value to which the simulated value should be compared.

Observation Weight (WEIGHT) is the weight assigned to the observation.

Comment is an optional comment about the observation.

Comparison Observations

Observation Name (OBSNME) is the name of the comparison observation.

Observation Group (OBGNME) is the name of the PEST observation group to which the observation is assigned. Observation group names are specified in the Pest Properties dialog box. Observation group names can be be assigned later in the Pest Properties dialog box if a suitable observation group has not yet been defined.

First Observation (OBSNME1) is the name of the first observation that will be compared.

Second Observation (OBSNME2) is the name of the second observation that will be compared.

Observation Value (OBSVAL) (OBSVAL1 - OBSVAL2) is the observed difference in value between the first and second observations. It is computed as value of the first observation minus the value of the second observation.

Observation Weight (WEIGHT) is the weight assigned to the comparison observation.

Comment is an optional comment about the observation.