Gilleland Creek

Watershed Integrity Scores


Very Good






Very Bad

No Data


Watershed Scores

Overall ScoreOverall Score involves averaging together all subcomponents.65GoodGilleland Creek ranks better than 22 other watersheds in Austin
Water ChemistryWater quality subcomponents are calculated from chemical analysis of grab samples from all study sites. Analytical parameters for water quality include ammonia nitrogen, specific conductivity, E. coli bacteria, nitrate-nitrogen, orthophosphorus, and total suspended solids.37PoorWater quality is poor, conductivity is high, nitrate is very high, orthophosphorus is high, suspended solids are high
Sediment QualitySediment sampling is conducted at one site in each watershed located near the mouth upstream from any backwater deposition impacts. Laboratory analysis of sediments includes metals, PAHs, PCBs, organochlorine pesticides, and grain size.86Very GoodPAHs are low, herbicides/pesticides are low, metals are low
RecreationThe suitability of a waterbody for contact recreation use is evaluated using E. coli bacteria concentrations, which is an indicator of pathogenic activity. Existing water quality standards are used to develop the score criterion for the EII.47MarginalBacteria levels may be a threat
AestheticsThe parameters included in the non-contact recreation field assessment include water surface appearance, litter, odor, clarity, and percent algae cover.72GoodSome litter is present, slight offensive odors, cloudy
HabitatParameters used to measure the level of habitat quality include bank stability, epifaunal substrate, embeddedness, velocity/depth regimes, channel alteration, sediment deposition, frequency of riffles, channel flow status, bank vegetation protection, and riparian zone width.67GoodSome sediment deposition, buffer is small
Aquatic LifeAquatic life support at all of the EII study sites is evaluated by sampling and analyzing the macroinvertebrate and diatom community structure.79Very GoodThe benthic macroinvertebrate community is excellent, the diatom community is good

*The above table represents a summary of data collected as part of the Environmental Integrity Index (EII)

Watershed Facts

  • Since 1999, portions of Gilleland Creek have been listed on the State 303(d) List of Impaired Waterbodies for elevated bacteria and the State is continuing to assess the impairment through the Total Maximum Daily Load program.
  • Portions of Gilleland Creek are listed on the State Water Quality Inventory as being of concern for ammonia and nitrate/nitrite enrichment.
  • Wastewater effluent discharge and increasing residential development contributing to elevated nutrient, conductivity and solids concentrations.
  • Gilleland has historically been impacted by agricultural activities, but is now experiencing more urban development.
  • Increased nutrients alter biological communities and unnaturally maintain higher benthic macroinvertebrate diversity despite poorer water quality conditions.
  • Bacteria sampling indicates elevated bacteria levels which may originate from both urban wastewater infrastructure and agricultural practices.