The areas adjacent to the lower Colorado River are the east end of 

 West Matagorda Bay and the west end of East Matagorda Bay. These areas 

 were the primary concern of the project and shall be termed "bay heads. " 



The average depth of these bay heads within 3 miles of the Colorado 

 River is Z^ feet. Due to their shallowness, they are subject to high tempera- 

 ture and salinity during seasons of warm weather. Heavy downpours seem 

 to have little effect on the salinity regime because they are usually too abrupt 

 and of too short a duration. At present, the biota of these bay heads seem to 

 be comparable to that of other coastal bays of East Texas. This is probably 

 due to the present low salinity and temperature levels. During drought years, 

 usually coupled with low river discharge, high salinities can be expected in 

 these bay heads, which might cause a drastic reduction in desirable biota. 

 Although there is little direct evidence that moderately high salinities in them- 

 selves have a detrimental effect on the biota, there may be associated factors 

 that depend largely on salinity or temperature or both to maintain suitable es- 

 tuarine habitat. 



At the present state of our knowledge, indications are that if these 

 bay heads are to maintain a suitable habitat for estuarine biota, it would be 

 advisable to regulate river discharge so that salinities will be maintained 

 between 10%o and 30%o. This is especially important during the two seasons 

 of greatest influx of the immature forms, i. e. , early spring, and late sum- 

 mer through early fall. During the remainder of the year, precipitation and 

 low tennperatures will probably suffice to maintain the habitat if river dis- 

 charge is not either completely shut off or allowed to flow too freely. 



If a water control gate were installed approximately a nnile and a 

 half below the point at which the river intersects the Intracoastal Waterway, 

 and canals were cut through the riverbanks into the adjacent bayous, fresh 

 water could flow directly into the bay heads under controlled conditions. Dur- 

 ing periods of low rainfall and runoff, this would provide maximum use of the 

 fresh-water discharge. This would in no way affect the lower part of the river 

 as far as sport or bait fisheries are concerned, and it would allow easier ac- 

 cess to the bay heads by boat, thus permitting greater utilization of these 

 areas. 



Salinity check stations could be set up in the bays so that riverflow 

 may be regulated with maximum benefit to all interests. The lower Colorado 

 River itself, below its intersection with the Gulf Intracoastal Waterway, fluc- 

 tuates in salinity with the tides and winds, this varying from day to day as 

 much as 20%o. At Station "A" the surface water is sometimes as low as ifoo 

 and as high as 22%o. The bottom salinity is usually high, ranging from l6%o 

 to 29%o. Anything that would reduce this tremendous fluctuation in river sa- 

 linity would be beneficial to the biota. Every effort should be made to main- 

 tain the present status of these bay heads and possibly to reduce the salinity 

 fluctuations in the river itself. 



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