discharge_events: Calculate events from discharge record

In USGS-R/Rainmaker: Rainfall event processing

Calculate events from discharge record

Description

Discharge event determination - calculates event start and end times based on discharge record.

Usage

discharge_events(
  df,
  ieHr = 6,
  qthresh,
  discharge = "Value",
  time = "pdate",
  ieHr_check = TRUE
)

Arguments

df	dataframe that contains discharge and timestamps
ieHr	numeric, Interevent period in hours, defaults to 6. The amount of time between discharge measurements above threshold required to be considered a new event.
qthresh	numeric, Discharge threshold value, over which an event is considered to be occuring.
discharge	string, Column name where discharge values are stored. Defaults to "Value".
time	string, column name where dates are stored as POSIXct values, defaults to "pdate".
ieHr_check	logical, whether to check the calculated events data frame for events that are closer together than ieHr. This can happen due to the start and end time corrections for the "tails" of the event. If TRUE, events closer than ieHr apart will be combined. If FALSE, events will be left as-is. See the details section below for more information.

Details

When a discharge measurement is above qthresh, the algorthim decides whether it belongs to a "new" event by looking backwards at the last measurement above qthresh. If the difference in time is greater than ieHr, then a new event begins. The start and end times of each event, however, are adjusted to the previous or next timestamp, respectively, to account for the "tails" of the event. The consequence of adjusting the start and end times, however, is that depending on the frequency of discharge observations, two observations above qthresh that are greater than ieHr apart (and therefore in seperate events) can have start and end times that are closer together than ieHr. If ieHr_check = TRUE (default), the algorithm makes a final pass through the events dataset and checks for any events that are closer in time than ieHr. If so, it will combine those events. If ieHr_check = FALSE, the algorithm will leave the events as-is, and depending on discharge measurement frequency and ieHr, you may see events that are closer together than ieHr. In most use-cases, ieHr_check = TRUE is appropriate. However, if discharge measurements are infrequent, and the adjustment to the start and end times are significant, the user may not want the secondary filter on the events.

Value

dataframe of all discharge events based on ieHr and qthresh criteria. Includes start and end times for each event.

USGS-R/Rainmaker documentation built on Oct. 11, 2022, 6:05 a.m.