Additionally, this model, with adequate built-in 

 generality, could be applied to other estuary systems 

 with similar characteristics and freshwater allocation 



OPPORTUNITIES FOR 

 INTEGRATION WITH BAY AND 

 ESTUARY RELEASE SCHEDULES 



At present, the City of Corpus Christi is required to 

 make pass-through releases of water from the reservoir 

 system on a monthly basis for bay and estuary needs. 

 Because of the high flooding threshold of north bank 

 of the Nueces River, none of this water direcdy reaches 

 the upper delta. Only with the demonstration project, 

 which allowed for a regular {i.e., daily) exchange of 

 small volumes of water between the river and Rincon 

 Bayou, was released water able to (occasionally) freshen 

 the upper delta. Information gained from the 

 demonstration project indicates that &esh water passing 

 through Rincon Bayou provides a more direct benefit 

 to the estuary ecosystem than water by-passing the 

 Nueces Delta and flowing direcdy into Nueces Bay. 

 Therefore, this finding suggests an opportunity for 

 integrating a permanent diversion project with reservoir 

 operations. 



Demonstration data suggest that the Nueces Estuary 

 would benefit more if freshwater releases could be 

 made in such a way as to trigger positive- flow events 

 into Rincon Bayou and the upper delta. It was 

 observed during the demonstration period that flow 

 events coincident with elevated water levels in Nueces 

 Bay caused a greater proportion of fresh water to be 

 diverted into the upper delta (Ward 2000). Ward 

 (1997) and Chew (1964) have indicated that seasonal 

 secular excursions in the Gulf of Mexico, which are 

 well reflected in water level variations in the upper 

 delta, are Likely during the spring and autumn, although 

 with varying magnitudes and durations. There was also 

 an observed seasonality to the ecology of the Nueces 

 Delta. Animal recruitment and marsh plant growth 

 occurred in spring, and nursery habitat utilization in 

 fall. Therefore, given the combined probability of 

 higher water levels in Nueces Bay and increased 

 ecological benefits to living resources during the spring 



and fall seasons of the year, larger, quarterly (or 

 possibly semi-annual) releases from the reservoir 

 system could be more direcdy beneficial to the delta 

 ecosystem than smaller, monthly releases. 



There are also theoretical reasons why bigger, less 

 frequent inflow events would be more beneficial. An 

 emerging paradigm suggests that large "pulsed," or 

 punctuated, events will favor large phytoplankton that 

 can out-compete small phytoplankton for nutrients 

 when they are present at elevated concentrations (Sutde 

 et al. 1988). Therefore, a pulsed nutrient supply wiU 

 select for larger phytoplankton, which can out-compete 

 smaller phytoplankton (Turpin and Harrison 1980; 

 Sutde et al. 1987). This results in a food-web based on 

 large-size phytoplankton, which is much more efficient 

 in transferring nutrients and energy to higher trophic 

 levels than is a food-web which is based on pico- or 

 nano-plankton. For example, a simple model based on 

 empirical data indicates that distributing nitrogen in 

 pulses rather than at a low homogeneous concentration 

 results ia 1.5 times more carbon in large zooplankton 

 than would occur if the nutrients were present at a low 

 homogeneous concentration (Sutde et al. 1990). The 

 results for phosphate are even more dramatic, where 

 there would be 3.6 times more carbon in large 

 zooplankton under a pulsed delivery regime. These 

 results suggest that releasing water ia large pulses rather 

 than in a continuous manner may deliver more 

 necessary resources to fish and other larger consumers 

 in Nueces Estuary. 



OPPORTUNITIES FOR ADAPTIVE 

 MANAGEMENT 



Incorporating demonstration project features into a 

 permanent diversion project, modifying reservoir 

 operations, and continuiag to smdy resultant biological 

 responses in the Nueces Delta would present a unique 

 opportunity for one of the most comprehensive studies 

 of ecological benefits accrued by adaptive management. 

 Were such an endeavor to be undertaken, four 

 fundamental questions should be addressed: 



8-4 ♦♦♦ Future Opportunities 



