Precipitation Runoff Modeling System (PRMS) Summary Modules

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Detailed Description

Presents descriptions of the USGS Precipitation Runoff Modeling System (PRMS) Summary modules.
 

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Image Dimensions: 480 x 360

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Length: 00:14:37

Location Taken: Denver Federal Center, CO, US

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Hello, this is Steve Regan of the Modeling of Watershed Systems project. This presentation describes summary output modules in PRMS-IV.

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There are four summary modules, the basin_sum module, which is always active and three optional modules—map_results, nhru_summary, and subbasin.

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The basin_sum module writes a set of basin HRU area-weighted average values to the model output file. Three parameters, specified in the Parameter File; print_freq, print_type and outlet_sta, control the types of output of the basin_sum module. Parameter print_freq is used to select the summary time frequency, which can be the full simulation time period, yearly, monthly, daily, or combinations. Parameter print_type is used to select the type of output, which can be measured and simulated flows, water balance table, or detailed report. Parameter outlet_sta specifies the time-series of measured flow in the Data File that is the basin outlet. If there are multiple outlets in the model domain comparing measured and simulated flows is not meaningful as the simulated flow is the total basin outflow.

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The map_results module provides a means to select one or more computed variables and write time series of values to separate files. The values for each variable can be output at the same or different spatial and temporal resolutions and units from those as computed in the PRMS simulation. These files could be used to loosely couple PRMS with other simulation models. For example, these files have been used as input to the USGS groundwater flow model MODFLOW.

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Two additional dimensions are required: ngwcell—the number of spatial units in the target map and nhrucell—the number of unique intersections between the HRU map and target map.

The parameter ncol specifies the number of columns of output values per row. This provides a means to output the values in a grid format that is required for some models, such as MODFLOW. The temporal resolution of the output can be monthly, yearly, total simulation-period, daily, or combinations depending on the value of parameter mapvars_freq.

The parameter prms_warmup is used to specify the number of years to compute as a warm-up time period to establish model states that are in equilibrium with the dynamic climate. For PRMS simulations one to three years of warm-up is typically adequate. The values computed during the warm-up period are not used to compute values in Map Results Files.

Values for each selected variable are output as area‑weighted‑averages between the HRU map and a target map. The spatial resolution of the output is specified by three aggregating or disaggregating mapping transformation parameters, gvr_cell_id, gvr_hru_id, and gvr_hru_pct. If the HRU map and target map are the same, then the mapping parameters are not required and the dimensions ngwcell and nhrucell are specified equal to nhru.

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Three parameters are specified in the Control File; mapOutON_OFF, mapOutVar_names, and nmapOutVars.

mapOutVar_names specifies the names of the output variables.

nmapOutVars specifies the number of output variables.

mapOutON_OFF specifies whether the map_results module is "on" or "off". If mapOutON_OFF is specified equal to 0, the values of mapOutVar_names and nmapOutVars are ignored.

A separate file will be generated for each variable and time frequency. The available variables that can be output must have the dimension nhru, nssr, or ngw.

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This slide provides example input as required to use the map_results module. The first column is parameters specified in the Control File. The map_results module is specified to be active, 3 variables are to be output; those variables are potential ET, recharge, and soil moisture. The second column is dimensions and parameters specified in the Parameter File. Their values specify that the target map has 30 spatial units using dimension ngwcell. The values of nhrucell and ngwcell are different, which means the HRU map and target map are different and have 60 intersections. Parameter ncol specifies that 6 rows of values are output as a monthly time series. Parameter mapvars_units specifies that the output values are converted from units of inches to meters. The warmup period is specified as 3 years using prms_warmup. Thus, the first three years of the simulation are computed but not output. This is 3 years from the simulation start date as specified by required control parameter start_time, which is not shown.

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The format of the output file is a set of 4 types of lines for each time frequency step. The first line is the simulation timestep on which the values are written, type of output, and mean value for the basin. The basin mean value is the area-weighted mean of computed values for the active HRUs. The next line type is the mapped values output as ncol number of values per row. The last line will have the remainder of nhrucell divided by ncol. Thus, the number of rows is nhrucell divided by ncol rounded up to the next whole number. The last two line types are the line with 22 “#” characters and a blank line. For this example ncol equals 6 and nhrucell equals 24, and the output values are monthly mean values with a spatial resolution equal to the target map. The values are ordered from the first to the last spatial unit of the target map as determined based on the mapping parameters gvr_cell_id, gvr_hru_id, and gvr_hru_pct.

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The nhru_summary module writes daily time-series of selected variables in a Comma Separated Variables format. This module is similar to the map_results module when the target map is the same as the HRU map. The primary differences are the format of the output files, the names of parameters, and there is not an option to convert the units of variables or specify the number of columns per line in the output file. Output files are written in the native units for each variable and there are 10 values written per row. The primary use of this module is to write CSV files that can be used as input to visualization and analysis software such as Excel, R, and Matlab.

Three parameters are specified in the Control File; nhruOutON_OFF, nhruOutVar_names, and nhruOutBaseFileName.

nhruOutVar_names specifies the names of the output variables.

nhruOutBaseFileName specifies the path for the prefix for the name of the output files. Each output file name is the base filename plus the output variable name.

nhruOutON_OFF specifies whether the nhru_summary module is "on" or "off". If nhruOutON_OFF is specified equal to 0, the values of nhruOutVar_names and nhruOutBaseFileName are ignored.

The parameter prms_warmup is identical to that used in the map_results module.

A separate file will be generated for each variable. The selected variables must be dimensioned by nhru, nssr, or ngw.

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This slide provides example input as required to use the nhru_summary module. The first column is parameters specified in the Control File. For this example, the nhru_summary module is specified to be active, 1 variable, recharge, is to be output. The files are written to the directory model_out contained within the current working directory with the filename prefix “PRMSIV_”. The output CSV file is named ./model_out/PRMSIV_recharge. The second column is the parameter specified in the Parameter File. The warmup period is specified as 3 years using parameter prms_warmup. Thus, the first three years of the simulation are computed but not output. This is 3 years from the simulation start date as specified by required control parameter start_time, which is not shown.

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The format of the output files is shown in this slide. All values are separated by a comma. The first line defines the label for each column of CSV values. The first label is always Date. The next labels are the HRU identification numbers from 1 to the dimension nhru. In this example, nhru equals 6. The next lines are the time series of values preceded by the timestep date.

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The subbasin module is used to summarize computed results by groups of HRUs. Values are computed for individual subbasins and totals for all subbasins specified to flow into a subbasin. The outflow of a subbasin equals any streamflow into a subbasin and the sum of the components for flow of all HRUs within the subbasin.

The parameter subbasin_flag is specified in the Control File and is used to turn “on” or “off” the subbasin module. The dimension nsub must be specified greater than 1 in the Parameter File to use the subbasin module. Parameter hru_subbasin that is specified in the Parameter File is used to associate HRUs with each subbasin. Parameter subbasin_down that is specified in the Parameter File is used to specify how subbasins are connected, that is, specify the order of computations for the subbasins and how each subbasin flows to another subbasin or outlet. A value of zero specifies that a subbasin flows to an outlet.

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The subbasin module computes several flow, climate, and storage variables as the area-weighted average value for all HRUs grouped in a subbasin, “subinc” variables, and for each subbasin plus any subbasins upslope, “sub” variables.

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These variables include actual and potential evapotranspiration, components of flow, snow pack states, precipitation, short-wave radiation, and air temperatures.

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This slide provides example input as required to use the subbasin module. The first column is the parameter specified in the Control File. For this example, the subbasin module is specified to be active. The second column is the dimension and parameters specified in the Parameter File. For this example, 4 subbasins are specified. Subbasins 1, 2, and 3 are upslope of subbasin 4, which is an outlet. There are 8 HRUs with 2 HRUs assigned to each subbasin, as specified by parameter hru_subbasin. HRUs 1 and 2 are assigned to subbasin 1, 3 and 4 to subbasin 2, 5 and 6 to subbasin 3, and 7 and 8 to subbasin 4.

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See the PRMS-IV manual for a more detailed explanation of the summary modules, which can be downloaded from this webpage. Be sure to download the Changes in the specification of user inputs document, which provides updated tables. Table 2 contains descriptions of available modules. Table 1-2 contains descriptions to all parameters that can be specified in the Control File. Table 1-3 contains descriptions of all parameters that can be specified in the Parameter File. Table 1-5 contains descriptions of all variables that can be output to the various output files. The FAQ tab can be very helpful as it provides common questions with answers that users have submitted to the MoWS group over the years. If you have questions about the summary modules or need help for other issues related to PRMS you can click on the Help tab and fill out the contact form.