2.25 



1 r 



10 12 14 16 18 20 22 24 26 28 



30 1 3 

 Nov 



Flow in Rincon Bayou (Rincon gauge) 



Flow in Nueces River (Calallen gauge) 



— o— Water level in Nueces Bay (White Point gauge) 



Figure 3-10: Selected hydrographic data for Events 12, 13 and 14 (October 2 through 

 November 3, 1996). During this period of low flow in the Nueces River, water level in Nueces Bay 

 (not flow in the Nueces River) was the predominant factor in determining the rate and direction of 

 flow through the Nueces Overflow Channel and Rincon Bayou. 



(5 to 10 inches) over central and south-central Texas, 

 including the headwaters of the Nueces and the Frio 

 drainages. A similar pattern, on a larger scale, affected 

 central and south central Texas in December of 1991, 

 causing 30 to 51 cm (12 to 20 inches) of precipitation 

 over much of south Texas. Direct precipitation in the 

 upper delta from the 1997 storm totaled only 4.9 cm 

 (1.94 inches) through June 21-23, -with the only other 

 measurable precipitation being 0.1 cm (0.04 inches) 

 fromjuly20to21. 



These two hydrographic events (16 and 17) 

 exemplified a common resulting flow pattern in the 

 lower Nueces River from precipitation events in the 

 greater watershed: namely, a duel-peak hydrograph in 

 the river at the point of diversion into the delta 



(Figure 3-7). The first principal peak (Event 16) 

 arrived at the upper delta on June 26, and represented 

 runoff primarily in the lower (eastern) watershed. 

 Approximately 20 days later, during which time the 

 Nueces River at Calallen experienced a sustained flow 

 of about 39.6 m'/s (1,400 cfs), the second principal 

 peak (Event 17) arrived on July 15. This peak 

 represented runoff from the same storm but from the 

 upper (western) watershed. As a result of the total 

 river inflow into the bay system, the salinity of Nueces 

 Bay was reduced from 26.8 ppt at the beginning of 

 Event 16, to 3.4 ppt at the end of Event 17. 



Because the average ambient water level in Nueces Bay 

 was so low and the average stage in the river at the 

 point of diversion was so high, the hydraulic head 



3-16 ♦♦♦ Hydrography 



