The month of May brought some rain to the basin, but the amounts were, again, still not enough to break the drought. May is usually the wettest month with typical totals of 4-6 inches. But, this month, the upper reaches received around 2 inches mid-month, or near the end of the month, while Austin and Bastrop saw two to three inches. Downstream of Bastrop, Columbus got almost two inches of rain, but at Bay City rain totals dwindled to less than half an inch. Most of the rains were slow and steady, so there was little runoff to add to area creeks and rivers, which means less potential for pollutants, but also little fresh input.
The San Saba, Llano and Pedernales Rivers and the Highland Lakes all received excellent water quality ratings. Dissolved oxygen levels were optimal for this time of year and bacteria and nutrients were low. Unlike last month’s exceptional clarity, this month, the tributaries and lakes in the upper reaches exhibited slightly shallower visibility, but then lake levels continue to go down too. The average water temperature in the upper basin climbed to a nice swimming temperature of 74.8°F.
The Colorado River at Austin had the coolest water temperatures and highest dissolved oxygen and both Austin and Bastrop were rated excellent in May with all water quality parameters within optimal ranges. Smithville and Columbus received good water quality scores and Wharton and Bay City were both rated excellent. No elevated nutrient levels were reported and bacteria levels were also low and not a concern for recreation. The average water temperature in the lower basin was 74.7°F.
For information on a specific lake or river, see a link below:
Austin Rating: Excellent
The Colorado River at Austin received an excellent rating this month. All water quality parameters were optimal for this time of year. Dissolved oxygen was high enough to support a healthy fish community and nutrients were low. The visibility was the clearest in the basin, at 6.9 feet and the water temperature was the coolest at 68.9°F.
The Colorado River at Bastrop was rated excellent this month. All water quality measurements were within optimal ranges for this time of year. Dissolved oxygen was high enough for a healthy fishery. Bacteria levels were not high enough to be a concern for contact recreation and nutrient levels were also low. The water temperature was 78.8°F and transparency was two and 1/2 feet.
The Colorado River at Bay City was rated excellent in May as all parameters were within optimal ranges for this time of year. Dissolved oxygen levels were high enough to maintain a healthy fish community. Nutrient levels were low. The water temperature was 76.1°F. Water clarity was just over one foot again this month.
Columbus Rating: Good
Water quality conditions at Columbus were good in May. Dissolved oxygen was high enough to sustain a healthy fishery and nutrient levels were low. Bacteria levels were also low and not a concern for contact recreation. The water temperature was 78°F and visibility was described as clear.
May brought an excellent rating to the Colorado River at La Grange. Dissolved oxygen was high enough to support a healthy fish community. Nutrient levels were low. Bacteria levels were also low and not a concern for contact recreation. The water temperature was 78.8°F and water transparency was one foot.
Lake Buchanan Rating: Excellent
Lake Buchanan was rated excellent this month as water quality measurements were optimal for this time of year. Dissolved oxygen was high enough to support a healthy fish community. Bacteria levels were low, allowing for safe contact recreation. Nutrient levels were low and the water temperature was 77.7°F. Visibility was 0.8 feet.
Lake LBJ Rating: Excellent
Water quality conditions for Lake LBJ were optimal in May netting it an excellent rating. Dissolved oxygen was high enough to support a healthy fishery and nutrient levels were low. Bacteria levels were low and therefore not a concern for contact recreation. The water temperature was 71.6°F and the visibility at the sampling site was 2.5 feet.
Lake Marble Falls was rated excellent this month with ideal water quality measurements. Dissolved oxygen levels were high enough to maintain a healthy fishery and nutrient levels were low. Bacteria levels were also low. The water temperature was 71.6°F and visibility was 2.5 feet.
Lake Travis was rated excellent this month, with water quality parameters within ideal ranges. Dissolved oxygen was high enough for a healthy fish community. Bacteria levels were low and therefore not a concern for contact recreation. The temperature was 74.3°F. Visibility was a 5.7 feet.
Llano River Rating: Excellent
The month of May brought excellent ratings to the Llano River. All water quality parameters were desirable for this time of year. Dissolved oxygen levels were high enough to maintain a healthy fish community. Nutrient levels were low. Bacteria levels were also low and were not a concern for contact recreation. The water temperature was 77°F and the visibility at the monitoring site was clear to the total depth of the river at one foot.
In May the Pedernales River received an excellent rating as all water quality parameters were optimal for this time of year. Dissolved oxygen levels were high enough to sustain a healthy fishery. Bacteria levels were low and not a concern for contact recreation and nutrient levels were also low. The water temperature was the warmest in the basin at 80°F. Transparency at the site was an average of 0.6 feet.*
San Saba River at Risien Park Rating: Excellent
The San Saba River received an excellent rating in May as all water quality parameters were within an ideal range. Dissolved oxygen levels were high enough to sustain a healthy fish community. Bacteria levels were low and therefore not a concern for contact recreation. Nutrient levels were also low. The water temperature was 71.6°F and water clarity was less than one foot.
Smithville Rating: Good
The Colorado River at Smithville received a good rating in May. All water quality parameters were within expected ranges. Dissolved oxygen levels were slightly depressed but still high enough to support a healthy fish community and nutrient levels were low. Bacteria levels were not a concern for contact recreation and the water temperature was 78.8°F. Water clarity was 0.7 feet.
Wharton Rating: Fair
An excellent water quality rating was warranted at the Colorado River at Wharton this month. Dissolved oxygen levels were high enough to sustain a healthy fishery. Nutrient levels were low as were bacteria levels. The water temperature was the second warmest in the basin at 79.7°F and visibility was 1.8 feet.
LCRA monitors the quality of the lower Colorado River as part of its responsibility as the river's steward. The water quality index is issued monthly utilizing data collected by LCRA staff and Colorado River Watch Network certified volunteers to characterize the general quality of the river, tributaries and Highland Lakes using ratings of “excellent,” “good,” “fair” and “poor.” The index is based on a list of parameters, including dissolved oxygen, fecal coliform or E.coli bacteria, nutrients (phosphorus and/or nitrogen), temperature and total dissolved solids or conductivity.
LCRA's water quality index is intended to give the public a snapshot of overall water quality conditions. But conditions can change quickly. High water quality index ratings do not preclude the existence of bacteria that may cause infections. Swimming in a river, lake or pond, rather than a disinfected swimming pool, carries some risk. So the public needs to take precautions at all times, such as avoiding stagnant water and staying out of the water after rains.
Here's a primer on what the ratings mean:
Excellent: All water quality parameters measured are within optimal ranges. The water quality supports all designated uses and is esthetically pleasing and suitable for swimming.
Good: At least four of six parameters are within the acceptable ranges. The water quality supports most designated uses and is esthetically pleasing and suitable for swimming.
Fair: Half of the parameters are not within acceptable ranges or bacteria levels exceed state standards. Water quality supports noncontact recreational uses but may not be suitable for swimming.
Poor: At least four of the six parameters, including fecal bacteria, are outside acceptable limits. Contact recreation (such as swimming) is not recommended. To date, major flood events have been the primary reason for a poor rating.
Latest bimonthly water quality report for the entire Colorado River basin
