demonstxation period, ranging from over 120 ppt 

 (Station 65) to less than 1 ppt {e.g.. Station 66) 

 (Figure 4-2). The incomplete salinity graphs with 

 missing data mosdy resulted from dry periods when 

 there was no standing water at the stations. The 

 Nueces River site (Station 68) had the lowest salinity at 

 all times except on September 16, 1999. This sampling 

 date was at the conclusion of Event 36 (Chapter 3), 

 when a large volume of water previously diverted into 

 the Rincon Bayou during the event had flowed back 

 into the Nueces River (Figure 3-9) likely transporting 

 acquired salt from the upper delta. 



Measurements of freshwater flow into and out of 

 Rincon Bayou (Chapter 3), and direct precipitation 

 were compared with water column saUruty data 

 (Table 4-1 and Figure 4-3). Because salinity at the 

 water column stations was measured monthly, daily 

 rain and inflow data were summed by water column 

 sampling dates. The variations in average salinity at 

 each site over time clearly showed the liighly variable 

 amounts of precipitation and evaporation over the five 

 year sampling period (Figure 4-3). During the months 

 following high freshwater inflow periods in summer 

 1997 (Events 16 and 17), fall 1998 (Events 23 dirough 



27) and fall 1999 (Events 36 and 37), the upper Rincon 

 Bayou site (Stations 65 and 66) had lower salinity 

 values than those in the central Rincon Bayou site 

 (Stations 61 and 62), and often times lower than the 

 Reference sites (63 and 64). This condition {i.e., salinit)' 

 concentrations lowest in the upper delta) represents a 

 "normal" estuary salinity gradient typically found in 

 unperturbed systems. During dry periods and drought 

 {e.g., the last part of 1995 through the first part of 1996, 

 as well as summer 1998), a "reverse estuary" condition 

 was observed {i.e., the highest salinity concentrations 

 were found in the upper delta), where the upper 

 Rincon Bayou site was predominandy saltier than 

 Reference or central Rincon Bayou sites (Figure 4-3). 

 These observations conformed closely to the project 

 design in that medium to high river flow events 

 circulated tiirough the historical Rincon Bayou 

 channel. 



Nutrients 



Inorganic nutrients are utilized by plants to produce 

 organic matter through the process of photosynthesis. 

 The concentrations of nutrients available and amount 



I I I 

 1996 



I I I I I I I I I I I I I I I I I I I I I I I I I I I 

 1998 1999 



Figure 4-2: Salinity at all water column stations (except Station 62) for each sampling date. Data from Station 

 62 were not plotted because the Tidal Flat site was frequently dry resulting in significant data gaps. 



Chapter Four ♦ 4-5 



