3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 



Daily stage at Calallen (ft) 



Figure 6: Regression analysis of Calallen daily stage values and daily stage at the Point of 

 Diversion. 



Note: 1 ft = 0.3046 m 



There are three primary limitations to correlating Calallen stage to stage at the point of diversion. First, under 



certain conditions, Calallen gauge data does not represent the total river discharge under the IH 37 and past the 



point of diversion. At higher flows, a portion of the Nueces River spills out of the stream channel upstream of 



the gauge, and re-enters the river via Hondo Creek below Calallen Dam but above the point of natural 



diversion. This portion of the river's flow, 



although relatively small, evades detection 



at the Calallen gauge (Figures 3 and 7). 



Second, a variety of tides, storm surges 



and other hydrographic events in Nueces 



and Corpus Christi bays also affect the 



Rincon stage data. Because the Calallen 



gauge is insulated from all but the most 



extreme of these events by Calallen 



Diversion Dam, correlation between the 



two data sets, especially under low-flow 



conditions, was "noisy". Finally, the lack 



of a long-term record at Rincon limits the 



ability to analyze a full range of hydraulic 



conditions in the Nueces River. 



In summary, the first two steps of this 

 methodology produce a daily stage record 



which represents the approximate water ^'^^'^ ^r View of Hondo Creek under flood conditions 



level of the Nueces River at the point of ^""f 26. 1 997. This road crossing is located approximately 



... r ^ J f 2 miles upstream of the creek s confluence With the Nueces 



natural diversion for the penod of ^^^^ ^^^^^ .^ downstream of the Calallen gauge. The flow is 



January 1, 1940, to December 31, 1999. 3 ^^^^^ ^^ ^^^^^ ^^^^ ^^^ ^^^^^ pj^g^ at a point further 



upstream. Ptioto courtesy of the Bureau of Reclamation. 



C- 1 ^ Analysis of the Historic Flow Rtffme of the Nueces River into the Upper Nueces Delta 



