# From HEC-2 model runs 



by US Bureau of Reclamation 



300 400 500 600 



Row (cfs) in Rincon channel 



Figure 2: Proportion of combined flow into upper Nueces delta carried by Rincon channel. Source of 

 HEC-2 model run is Bureau of Reclamation (2000). 



INTERTIDAL (day to day) ANALYSIS 



The depiction of hydrographic time history in the Nueces delta on an intertidal time scale is based upon 

 compiling the data sources and computing their integrated values for each day (24-hour period UCT) within the 

 period of record. (The astronomical tidal period is actually 24.8 hrs, but an average over 24 hours eliminates 

 almost all of the variability it contributes.) The term "integrated" means either averaged or accumulated, 

 whichever is more meaningful for the parameter under consideration. The depiction is best presented either 

 graphically or La tabular summary of the hydrographic variables. 



EVENT-DURATION ANALYSIS 



The intertidal (day to day) analysis covered the period of January 1992 through December 1999. After 

 inspection of the entire period of record on both intertidal and intratidal scales, criteria were formulated to 

 identify an "event" based upon the separate hydrographic behaviors of each of the key response parameters. 

 These response variables included stage (in Nueces Bay, in Rincon Bayou and a super-elevation of the two), 

 flow (in the Nueces River and in Rincon Bayou), and salinity (in Nueces Bay) (Table 2). It should be 

 emphasized that these criteria were ultimately arbitrary, but were utilized to ensure an objective selection of 

 candidate events for analysis. 



It is noteworthy that precipitation was not treated as a separate hydrographic variable, though it was certainly an 

 important hydrographic element in imderstanding the response of the delta ecology. The reason for its 

 exclusion as a defining parameter was that it provides no infotmMon per se on the response of the Nueces 

 Estuary or Delta. A similar argument was made for excluding wind as a defining criterion. 



Once these criteria were established, the daily data for the period of study was manually inspected. Individual 

 occiurences within the record which met at least one of the six criteria were identified as an "event". Then, for 

 each event, the 24-hour mean data for all hydrographic variables during the event were separated and 

 transferred for individual analysis. The duration period for each event was at least that for which the defining 



B-6 ♦ Hydrography of the Nueces Delta and Estuary: 1992-1999 



