Figure 3-2: View of the Nueces River at Calallen 

 Diversion Dam. The photo was taken on June 26, 1997, 

 for which the mean daily flow rate in the river was 

 63.7 mVs (2,250 cfs). 



Photo courtesy of the Bureau of Reclamation. 



Identification of Hydrographic 

 Events during the Demonstration 

 Period 



In an effort to develop a common summary' of 

 hydrographic events useable in the analyses of changes 

 in water column productivity (Chapter 4), benthic 

 communities (Chapter 5) and vegetation communities 

 (Chapter 6), the compiled hydrographic data record 

 was divided into separate "events" (or event-duration 

 analysis) (Ward 2000). A hydrographic "event" was 

 considered to include one or more of the following 

 response mechanisms: 1) a substantial volume of 

 freshwater flow, 2) an increase in water level (stage) or 

 3) a decrease in salinity. Where and how each of these 

 three broad response mechanisms were characterized 

 depended largely upon the availability' of data. In 

 general, the responses of freshwater inflow and water 

 level were each divided into two components; one for 

 the upper Nueces Bay (and lower delta), and one for 

 Rincon Bayou (and upper delta). The response of 

 salinity was considered for the hydrographic analysis 

 only in upper Nueces Bay, but was examined in each of 

 the subsequent chapters at the various monitoring 

 stations. The initial conceptual model for such an 

 event was a flood hydrograph translating down the 



Three dme scales were considered of pertinence to the 

 evaluation of the compiled hydrographic data for the 

 Nueces Estuary: intratidal, intertidal and event- 

 duration. The intratidal (or intradiumal) time scale 

 represented short-term behavior at an hourly 

 resolution; the intertidal (or interdiumal) time scale 

 represented day-to-day variations of hydrographic 

 parameters averaged over 24 hours; and the event- 

 duration scale extended over the time period 

 encompassing all responses to a specific hydrographic 

 event, and could range from several days to many 

 weeks. Therefore, to facilitate detailed analysis at 

 varying degrees of detail, all available data was 

 compiled in hourly, daily and event-specific formats 

 (Ward 2000). Further discussion of the approach and 

 results of the intratidal, intertidal and event-duration 

 analyses conducted by Ward (2000) has been included 

 as Appendix B of this Concluding Report. 



Figure 3-3: View of the Rincon gauge 

 (Station 08211503). 



Photo courtesy of the Bureau of Reclamation. 



3-4 



Hydrography 



