There has been a silver lining to the drought that has parched Central Texas for the past 18 months.

Less rain has meant lower water levels in the Texas Colorado River, Highland Lakes and tributaries. It also has meant less runoff and fewer pollutants, such as sediment, bacteria and nutrients, washed into the waterways.

As a result, bacteria levels in the river and its major tributaries rarely exceeded state standards for contact recreation in 2006. Levels of nutrients, which can promote excessive aquatic plant growth, have been low. Water clarity in some places has been the best in years, according to Lower Colorado River Authority scientists who monitor the river and its tributaries.

However, hot, dry weather caused some tributary streams to dry up and caused the levels of life-giving oxygen to drop in the river in some places. Low oxygen levels were temporary and did not cause any long-term adverse impacts, LCRA scientists said.

Healthy water
As in previous years, the river and its tributaries throughout LCRA’s jurisdiction have been fishable, swimmable and suitable for water supplies in 2006.

“Despite continued population growth in the region, the river has been holding up well,” said John Wedig, an LCRA aquatic scientist who tracks the water’s quality. “This is good news. But continued growth also means we need to stay vigilant.”

LCRA scientists report that the river from San Saba to the Gulf Coast, including the Highland Lakes and tributaries, has had generally good to excellent water quality in 2006, based on LCRA’s water quality rating system.

The Highland Lakes, formed by damming the Colorado River above Austin, have had water quality rated as ”excellent” for most of the year. The clarity of the lake water - particularly lakes LBJ and Travis - was the best that LCRA has measured in several years. Fewer nutrients washed into the lakes kept down the growth of algae – tiny plants that can cloud the water. LCRA scientists reported fewer algae blooms in 2006, compared to years of higher rainfall.

Downstream of Austin, water quality was rated mainly as “good.” In a few places bacteria levels spiked briefly following local rains. Also, nutrient levels increase in winter in the lower river when discharges from wastewater plants, particularly in Austin, dominate the river’s flow. Between March and October, nutrient levels are less of an issue because water releases from the Highland Lakes for agricultural irrigation dominate the river flow and dilute the wastewater discharges.