CalcFdcPerf: Computes flow duration curve statistics for WRF-Hydro...

In NCAR/rwrfhydro: R tools for the WRF Hydro Model

Description

CalcFdcPerf calculates flow duration curve statistics for streamflow output.

Usage

CalcFdcPerf(strDf.mod, strDf.obs, strCol.mod = "q_cms",
  strCol.obs = "q_cms", stdate = NULL, enddate = NULL)

Arguments

strDf.mod	The forecast point output dataframe (required). Assumes only one forecast point per file, so if you have multiple forecast points in your output dataframe, use subset to isolate a single forecast point's data. Also assumes model output and observation both contain POSIXct fields (called "POSIXct").
strDf.obs	The observed streamflow dataframe. Assumes only one gage per file, so if you have multiple gages in your dataframe, use subset to isolate a single gage's data. Also assumes model output and observation both contain POSIXct fields (called "POSIXct").
strCol.mod	The column name for the streamflow time series for the MODEL data (default="q_cms")
strCol.obs	The column name for the streamflow time series for the OBSERVED data (default="q_cms")
stdate	Start date for statistics (DEFAULT=NULL, all records will be used). Date MUST be specified in POSIXct format with appropriate timezone (e.g., as.POSIXct("2013-05-01 00:00:00", format="%Y-%m-%d %H:%M:%S", tz="UTC"))
enddate	End date for statistics (DEFAULT=NULL, all records will be used). Date MUST be specified in POSIXct format with appropriate timezone (e.g., as.POSIXct("2013-05-01 00:00:00", format="%Y-%m-%d %H:%M:%S", tz="UTC"))

Details

CalcFdcPerf reads a model forecast point streamflow timeseries (i.e., created using ReadFrxstPts) and a streamflow observation timeseries (i.e., created using ReadUsgsGage) and calculates flow duration curve statistics at various exceedance thresholds (e.g., 10%, 20%, etc.). The tool will subset data to matching time periods (e.g., if the observed data is at 5-min increments and modelled data is at 1-hr increments, the tool will subset the observed data to select only observations on the matching hour break).

Flow Duration Curve Statistics:
(mod = model output, obs = observations)

• p.exceed: exceedance threshold (e.g., 0.2 means a flow value that is exceeded 20% of the time)

• q.mod: MODEL flow value at specified exceedance threshold (in native flow units)

• q.obs: OBSERVED flow value at specified exceedance threshold (in native flow units)

• q.err: difference between model and observed flow values [mod-obs] (in native flow units)

• q.perr: percent error in model flow [(mod-obs)/obs]

Value

A new dataframe containing the flow duration curve statistics.

Examples

## Take forecast point model output for Fourmile Creek (modStrh.mod1.fc) 
## and a corresponding USGS gage observation file (obsStrh.fc), both at an 
## hourly time step, and calculate flow duration curve statistics. The 
## model forecast point data was imported using ReadFrxstPts and the gage
## observation data was imported using ReadUsgsGage.

## Not run: 
CalcFdcPerf(modStr1h.allrt.fc, obsStr5min.fc)

Output:
 p.exceed    q.mod   q.obs
 0.1         3.07    5.25
 0.2         1.35    2.31
 0.3         0.82    1.06
 0.4         0.48    0.65
 0.5         0.29    0.45
 0.6         0.18    0.34
 0.7         0.14    0.25
 0.8         0.11    0.19
 0.9         0.08    0.16

## End(Not run)

NCAR/rwrfhydro documentation built on Feb. 28, 2021, 12:47 p.m.