Pesticides and Water Quality - Texas Center for Policy Studies

Red River BasinThere has been no systematic monitoring for non-point source pollution in this basin. Potential sourcesfor non-point source pollution are cities, industries, agriculture, silviculture and on-site wastewater. The1994 Assessment Report recommended that non-point source pollution and attendant monitoring remain ahigh priority for the basin. 71The 1996 Assessment states: “There has been …limited monitoring of herbicides, pesticides and PCB’s inthe Red River Basin over the past 30 years. Although cultivation of food and fiber crops occurs in manyparts of the basin, there are insufficient water quality data available in the TNRCC records on chemicalsused in crop production to make an assessment using the screening criteria.” 72Rio Grande River BasinFor the purposes of this report, the authors paid special attention to the 1996 Regional Assessment ofWater Quality in the Rio Grande River Basin. This 1996 Assessment stated that little information existson toxic substances, particularly pesticides and heavy metals. The study further stated that informationabout types of land use, pesticide use, population growth, soil conditions, climate and other factors thatinfluence water quality must also be compiled. 73 The Rio Grande Basin study pointed out that in theArroyo Colorado upstream of the Port of Harlingen, the Texas Department of Health has advised peoplenot to consume any fish from the waters. The Health Department is concerned with the presence of thepesticides DDE, toxaphene and chlordane. Use of all three of these pesticides have been banned in theU.S., but persist in the environment. 74 In addition to the analysis of fish tissue, biological methods wereused to assess toxicity levels in the river system. According to the study, “the occurrence of pesticides ismore widespread. Seven different pesticides (out of 50 tested) exceeded criteria at about a third of thesites. [DDT, lindane, dieldrin, DDE, chlordane, chlorpyrifos, diazinon]. The most frequent occurrenceswere in the Lower Rio Grande Valley, an intensively farmed area, and in the Laredo/Nuevo Laredo area.Three of these pesticides are (or were) used for home and garden use, suggesting urban as well asagricultural sources." 75Sabine River BasinThe 1994 Assessment for the Sabine River Basin found a possible pesticide concern (for malathion) inone segment out of 14 total segments. However, the Report stated that “this should not be taken to meanthat there are no problems with organics in the Sabine Basin, it is simply a reflection of the fact that welack sufficient data to assess the situation.” 76 In the 1996 Assessment, preliminary results indicatedambient toxicity in one segment, and pesticides were identified as a possible cause. One of therecommendations of the Assessment report was that the Sabine River Authority sub-watershed inventoryshould continue collecting additional information on land use and other activities which can influencewater quality. 7771 Red River Authority, Red River Basin Water Quality Assessment (Wichita Falls: Red River Authority, 1994), 3-40.72 Red River Authority, Red River Authority of Texas Regional Assessment (Wichita Falls: RRA, 1996), 85.73 Texas Natural Resource Conservation Commission, 1996 Regional Assessment of Water Quality in the Rio Grande Basin(Austin: TNRCC, 1996), 6.74 Ibid., 30.75 Ibid., 41.76 Sabine River Authority, Sabine River Basin Assessment of Water Quality (Orange: Sabine River Authority, 1994), 41.77 Sabine River Authority, Sabine River Basin Assessment of Water Quality (Orange: SRA, 1996), 7.27