Table 2: Criteria used to define hydrographic events in the data record by response variables. 



Location Defining Criteria of a Hydrographic Event 



RESPONSE 

 PARAMETER 



Flow 



Stage 



Salinity 



Nueces River A 24-hour nnean (daily) flow^ in the Nueces River at Calallen exceeding 



14.2 m^/s (500 cfs). 



Rincon Bayou A 24-hour mean (daily) flow In Rincon Bayou, either positive or negative, 



exceeding 0.28 m^/s (10 cfs). 



Nueces Bay A 24-hour mean (daily) stage in the vtrater elevation of Nueces Bay exceeding 



0.30 m (1.0 ft). [Referenced to the consistent CBI datum from Ward (1997), 

 established by "empirical leveling".] 



Rincon Bayou A 24-hour mean (dally) stage in the w^ater elevation of Rincon Bayou 



exceeding 0.61 m (2.0 ft). [Relative to Rincon gauge datum, which is 422 cm 

 above the consistent datum for CBI gauges.] 



Super-elevation The sum of Rincon Bayou minus Nueces Bay daily stage values exceeding 

 0.15 m (0.5 ft). [Referenced to common datum] 



Nueces Bay Change in salinity concentrations of Nueces Bay exceeding 5 ppt over a five 



day period. 



criterion was satisfied, though often a longer event period was chosen to be sure that the complete response of 

 the bay or delta was included in the analysis. When several hydrographic events overlapped {i.e., when several 

 variables each satisfied criteria separately and simultaneously), the event duration was at least the period fi:om 

 the first occurrence of the criterion threshold for the earliest parameter to at least the last such threshold for the 

 latest parameter. 



The greatest difficulty in separating such events was met when a time series of events occurred in which the 

 response of one parameter overlapped that of the next. For example, a series of river hydrographs might occur, 

 each of which raises Rincon stage or Calallen flow above the threshold defining an event, and a new surge of 

 inflow occurs before the recession of the preceding has subsided. Separating these into individual events was 

 rather arbitrary, and from the estuarine response point of view, such a sequence might acceptably be considered 

 one long event rather than a sequence of separate events. 



The parameters compiled for each event include the following: event number, date, duration, rainfall, flow, 

 stage and salinity. 



Event Parameters 



Event Number 



For purposes of tracking and reference, each discrete event in the record was assigned an event label. Each 

 event occurring from October 1, 1994, through December 31, 1999 (the duration of the demonstration 

 project), was numbered sequentially in time, begirming with 1. Events occurring before the demonstration 

 period were labeled with sequential letters, beginning with A. 



Date and Dutation 



The span of each event was specified by its starting date. In some cases, the ending date of one event was the 

 starting day of the next, which indicates that a subjective separation had been assumed in the record for 

 purposes of analysis. This arbitrary division may or may not have been capable of differentiation in the actual 

 environment, which may have responded as if the two events were a single "merged" event. 



Rainfall 



For the period of October 1, 1994, through May 15, 1996 {i.e., prior to the activation of the Rincon gauge), local 

 daily precipitation obtained fcom Corpus Christi airport, which evidenced a correlation with the USGS gauge 



Appendix B ♦ B-7 



