Pesticides and Water Quality - Texas Center for Policy Studies

The 1996 Assessment concluded that data on organics, including pesticides, are very limited within theColorado River basin. In fact, for all 45 segments studied, the data were insufficient to draw anyconclusions. 59 A fish consumption advisory is in effect for Segment 1429 (Town Lake in Austin) due topast applications of chlordane. 60The 1996 Assessment also questioned the “conventional wisdom which holds that agricultural practicesare the biggest single contributor to water quality problems.” 61 To that end, the LCRA conducted studiesof runoff from various agricultural sites below Austin in the lower sub-basin. The key findings of thosestudies were that: 1) two years is insufficient to reach many quantifiable conclusions; 2) total suspendedsolid levels were dramatically higher from row crop production compared to improved pasture land; 3)nitrogen levels were generally elevated during the first runoff event following fertilizer application, butthen reached background levels; and 4) pesticides could only be detected in the runoff for about onemonth after application, indicative of the short half-life of many pesticides currently in use, such asmetolachlor and atrazine. 62 (The Assessments did not mention any studies or water monitoring data thatindicated that indicated the presence of either metolachlor or atrazine in the Colorado River Basin.)The 1996 Summary of the Water Quality Assessments prepared by the TNRCC stated that the “effects ofagricultural/rural non-point source pollution are currently being studied” for the Colorado River basinsegment running from Austin to Bay City. 63Cypress River BasinThe Cypress River Basin includes Caddo Lake, which is at the base of the Cypress Creek Basinwatershed. The 1996 Assessment report for this basin did not mention the collection of data or analysisfor any pesticides.Guadalupe River Basin and the Lavaca/Guadalupe Coastal BasinThe 1994 report concluded that there was insufficient data for a complete assessment, particularly onorganics, though pesticides are used in the basin. The 1996 reports had no conclusive data on pesticides.Lavaca-Navidad River BasinThe 1994 Assessment for this basin concluded that water quality data on metals, toxics and pesticideswere not sufficient to draw any conclusions. For the last five years, the USGS has been sampling forpesticides and other pollutants in Lake Texana and more recently at four tributary sites. For moreinformation, refer to the Section on Special Studies conducted by USGS.Lower Neches River Basin and Trinity Coastal BasinThe 1992 Regional Assessment of the Lower Neches River Basin identified some possible concerns forpesticides. A 1987 Neches River study by the Texas Water Commission showed that dieldrin occurred inexcess of the human health criteria for ambient water. A 1992 Lower Neches Valley Authorityquestionnaire also stated that pesticides could be a problem in Segment 0701 (Taylor Bayou) due to a59 Lower Colorado River Authority, Regional Assessment of Water Quality Colorado River Basin and Colorado/Lavaca CoastalBasin. Technical Report (Austin: LCRA, 1996), 5.60 Ibid., Chapter B, Sub-watershed Issues, Austin-2.61 Lower Colorado River Authority, Regional Assessment of Water Quality Colorado River Basin and Colorado/Lavaca CoastalBasin, Executive Summary (Austin: LCRA, 1996), 3.62 Ibid., 3.63 TNRCC, Texas Water Quality: A Summary of River Basin Assessments (Austin: TNRCC, 1996), 78.25