before the recession of the preceding event has 

 subsided. Separating these into individual events was 

 therefore rather arbitrary, and, from the estuarine 

 response point of view, this division may or may not 

 have been differentiated in the actual environment, 

 which may have responded as if adjacent events in the 

 record were a single "merged" event. 



Characterization of Individual Events 



Once individual events were thus delineated in the 

 record, integrated values for each response parameter 

 in each event were computed. The term "integrated" 

 means either averaged or accumulated, whichever was 

 more meaningful for the parameter under considera- 

 tion. The parameters compiled for each event include 

 the following: event number, date, duration, rainfall, 

 flow, stage and salinity. 



Event Number — For purposes of tracking and 

 reference, each identified event occurring from 

 October 1, 1994, through December 31, 1999 (the 

 duration of the monitoring program), was numbered 

 sequentially in time. 



Date and Duration — The span of each event was 

 specified by its starting date and its duration in days. 

 In some cases, the ending date of one event was 

 immediately before the starting day of the next, which 

 indicates that a subjective separation had been assumed 

 in the record for purposes of analysis. 



Rainfall — Local precipitation for each event was 

 determined by summation of daily totals during the 

 event. For the period of October 1, 1994, through 

 May 15, 1996 (i.e., prior to the activation of the Rincon 

 gauge), precipitation was that reported at Corpus 

 Christi Airport, which e\'idenced a correlation with the 

 Rincon gauge of 0.81 for the 3.7 years of coincident 

 data. After May 15, precipitation was that reported by 

 the Rincon gauge. 



Flow — Daily values for both flow variables (Nueces 

 River and Rincon Bayou) were converted to daily 

 volume and then summed to determine the cumulative 

 event volume. For flow in the Nueces River, daily 

 average flow was also computed for each event by 

 dividing the total flow volume by the event duration in 



days. Because flow in Rincon Bayou was frequendy bi- 

 directional, these data were analy2ed somewhat 

 differendy. Total positive volume (pos) was 

 determined by considering only that flow directed from 

 the river into the delta. Total negative volume (neg) 

 was similarly determined but considering only that flow 

 directed from the delta into the river. Total exchange 

 (gross) was defined to be the sum of the absolute 

 values {i.e., ignoring signs) of the positive and negative 

 volumes. Finally, total net exchange (net) was defined 

 to be the algebraic sum {i.e., observing signs) of the 

 positive and negative volumes. 



It is important to note that, during the demonstration 

 period, the Nueces River did not exceed the natural 

 flooding threshold for the delta, which was 1.64 m 

 (5.40 ft) (Bureau of Reclamation 2000), except on four 

 occasions. This means that, except for these events 

 (Events 16, 18, 25 and 36), the only water exchanged 

 between the Nueces River and Rincon Bayou during 

 the study period passed through the Nueces Overflow 

 Channel. During the excepted events, an additional 

 amount of water also entered Rincon Bayou naturally 

 \'ia the low depressions along the bank of the river. 

 Therefore, for all other events, the Rincon Bayou flow 

 volumes reported were those measured through the 

 Nueces Overflow Channel at the Rincon gauge. For 

 Events 16, 18, 25 and 36, an additional volume was 

 added to that gauged through the overflow channel. 

 This additional amount depended upon the daily stage 

 level attained by the river during the event and was 

 estimated using the hydraulic model developed by 

 Reclamation (2000). Accordingly, for Event 16, which 

 attained a peak daily stage of 1.70 m (5.57 ft) msl, an 

 additional 4 10^ m' (3 acre-ft) were added; for Event 

 18, which attained a peak daily stage of 1.72 m (5.65 ft) 

 msl, an additional 5 10^ m' (4 acre-ft) were added; for 

 Event 25, which attained a peak daily stage of 2.22 m 

 (7.28 ft) msl, an additional 1,189 10' m' (964 acre-ft) 

 were added; and for Event 36, which attained a peak 

 daily stage of 1.74 m (5.72 ft) msl, an additional 6 10' 

 m' (5 acre-ft) were added. The remark "natural flow 

 event" identifies these events in Table 3-3. 



Stage — For the water level in Nueces Bay and Rincon 

 Bayou, both the daily average and peak daily stages 

 were utilized, the latter since the average alone might 



3-6 ^* Hydrography 



