Water Level 



As with river flow, there was also a proportional iacrease in total flow through the Nueces Overflow Channel 

 with an increase in super-elevation of stage. A s imil ar sorting by water levels also occurred when the 

 event-duration data for flow volume in Rincon Bayou was plotted against the event mean super-elevation 

 (Figure 4). In this figure, all 28 events were plotted, not just those events which met the criteria, as was done in 

 Figure 3 Again it was observed that the larger flow volumes were associated with greater depths, independent 

 of the magnitude of the super-elevation. Therefore, a given hydraulic head gradient drives a greater flow if the 

 water is deeper. 



I 

 U 



2500 



c 2000 



(0 



O 



o 



"E 

 a 



> 



O 

 o 



0) 



3 



1500 



1000 



^ 500 



i 



o 



is: 



a> 



> 



(D 



15 

 o 



00 



0.5 



1.0 



1.5 



2.0 



2.5 



3.0 



Event mean super-elevation (ft) 



Figure 4: Flow volume diverted through the Nueces Overflow Channel for all events versus 

 event-mean super-elevation. 



Note: 1 ft = 0.3046 m, 1 acre-ft = 1.2336 10' m' 



Salinity 



Upon examination of the relation between salinity response of Nueces Bay before and after the opening of the 

 Nueces Overflow Channel, all hydrographic events occurring from 1992 through 1999 were considered, rather 

 than just those occurring after the initiation of the demonstration project. The incremental percentage salinity 

 responses (%chg) of each event was plotted against the total event flow volume in the Nueces River (Figure 5). 

 Data for events during which the starting salinity was less than 5 ppt were not included due to "noise" in the 

 salinity measurements themselves. Several inferences immediately followed an inspection of this figure. 



First, for total event flows greater than 12,336 10^ m^ (10,000 acre-ft), there was no obvious difference between 

 the fractional salinity response of events occurring before the opening of the overflow chaimel and those after 

 it. That is, the same general relation of diminishing percent salinity response with increasing event flow in the 



B-10 ♦ Hydrography of the Nueces Delta and Estuary: 1992-1999 



