MEXICO 



Gulf 



of 



Mexico 



Figure 1-3: The Nueces River Basin, including major drainages and reservoirs. 



Source of topographic base map: U.S. Geological Survey 1997. 



of 186,274 10' m' (151,000 acre-ft) of water per year 

 would be provided to the estuaries by a combination 

 of releases and spills from the reservoir system at Lake 

 Corpus Christi Dam and return flows to Nueces 

 Estuary (Texas Water Rights Commission 1976). 

 Although the dam was completed in 1982, flow into 

 the reservoir was minimal for the first several years. 

 However, in June 1987, record rainfall over the Frio 

 River watershed filled the reservoir, and water was 

 released as flood control for the first time. 



During the mid-1980's, several entities initiated regular 

 monitoring programs in the region. Salinity in the 

 Nueces Estuary began to be sampled continuously by 

 several State agencies and universities. Fish, shrimp, 

 crabs and oysters in Nueces Bay were sampled during 

 routine. State-wide coastal inventory surveys. Modest 



research efforts were also undertaken by university 

 researchers to monitor the effect of the water releases 

 on hydrography and benthos in the estuary. 



By the early 1990's, it had become apparent that there 

 had been a notable reduction in the freshwater inflow 

 to the delta and esmary systems. For example, 

 historically Nueces Bay had supported large popula- 

 tions of shrimp and oysters, which generally require 

 salinity concentrations in the range of 10 to 20 parts 

 per thousand (ppt) salt. During the relatively dry 

 period of the late 1980's and early 1990's, the salinity of 

 the bay had increased to hypersaUne conditions 

 (> 36 ppt), and consequendy the shrimp and oyster 

 populations were reduced. For example, from 1984 

 through 1989, shrimp har%'est declined in Nueces 



Chapter One ♦ 1-3 



