Progress 07/01/02 to 06/30/04
Outputs
The State Water Resources Control Board (SWRCB)/Central Valley Regional Water Quality Control Board (CVRWQCB) contracted with ATL to conduct an investigation of water quality in agricultural drains (IWQAD). The purpose of this investigation was to gain a more complete understanding of the relationship between surface water quality in agricultural drains and irrigation runoff. The focus of IWQAD was on agricultural drains in the lower San Joaquin River and lower Sacramento River watersheds. The objectives IWQAD included: (1) Evaluation of water quality in agricultural drains, (2) Identification of the causes of water quality impacts, and (3) Use of the data and information gained in IWQAD as a basis for recommendations regarding future monitoring and assessment of agriculture-dominated waterways. Acute toxicity testing with two commonly used indicator species was utilized to assess water quality. The two test species were Ceriodaphnia dubia (cladoceran, zooplankton
indicator species) and larval fathead minnows (Pimephales promelas). Over 200 samples were collected and tested in IWQAD. Ten of these samples caused significant mortality to Ceriodaphnia dubia. Seven of 25 sites were characterized by one or more toxic sample. The organophosphorous insecticide, chlorpyrifos, was the cause of mortality in seven of the ten toxic samples. Chlorpyrifos-caused toxicity has been observed frequently in many agriculture-dominated waterways throughout California. ATL's report includes a summary of peer-reviewed, published research on the relationship between agricultural activities and water quality as well as biological condition in aquatic systems. This literature documents that many agricultural activities cause alterations of waterway geomorphology, hydrology, water quality, and instream, as well as riparian habitat that, in turn, degrades biological condition/health. ATL offered 20 recommendations that relate to follow-up on IWQAD, but also for enhancing
monitoring and assessment of aquatic system, including agriculture-dominated waterways.
Impacts
Information obtained from this testing project is highly valuable to the State of California in developing an updated water quality control plan.
Publications
- No publications reported this period
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Progress 01/01/03 to 12/31/03
Outputs
Sampling of 25 sites and toxicity testing were initiated on March 26, 2003. As of September 25th 189 agricultural drain samples have been sampled and tested in Ceriodaphnia dubia and larval Pimephales promelas 96-hour acute (only mortality determined) toxicity tests. Most sites have been sampled on eight to ten occasions. Because of late rains and cool weather in spring, more intense sampling and testing was not initiated until June. Irrigation was extremely limited until July. Information on irrigation volumes from irrigation districts in areas where sites are located would be particularly valuable to data interpretation. Dissolved oxygen (DO), electrical conductivity (EC--indication of salinity), hardness, alkalinity, turbidity, total suspended solids (TSS), dissolved organic carbon (DOC), and total organic carbon (TOC) have been measured in all samples collected. During toxicity testing DO, hardness, alkalinity, DOC, and TOC were within a range unlikely to confound
toxicity testing results. TOC/DOC in agricultural drain samples ranged from 21 to 148 ppm, considered moderate to high. High TSS readings were observed in many samples. The static-renewal toxicity tests conducted in this investigation are not designed to determine the effects of sediment/suspended solids on aquatic biota. Therefore, potential impacts of TSS on aquatic biota will be estimated based on TSS concentrations. TSS in many of the agricultural drainage samples was above 50 mg/L (range 10 to 1203 mg/L). These values are considered high to very high. Turbidity in drain samples ranged from 5 to 261 NTU. Given that many sampling sites are located at or near pumping stations that discharge drain water into the San Joaquin and Sacramento River systems the TSS and DOC/TOC values determined in this investigation may be of concern. The Central Valley Regional Water Quality Control Board has EC water quality criteria for the Sacramento River that range from 230 to 340 mmhos/cm. The
average EC for the Sacramento River is 100 mmhos/cm. Drinking water criteria for EC are generally around 1500 mmhos/cm. EC water quality criteria for the protection of aquatic life need to be established. EC in a majority of agricultural drain samples was above 450 mmhos/cm (range=136 to 1795). EC in agricultural drain waters discharged into the Sacramento and San Joaquin Rivers may, therefore, be of concern to the Central Valley Regional Water Quality Control Board. Many agricultural drain samples were also characterized by high hardness (316 to 596 mg/L as calcium carbonate). In only 11 of 189 samples processed to date has there been an indication of toxicity (mortality) to the indicator test species. In the March 26th Site 7 sample (Lone Tree Creek @ Newcastle Rd.) there was implication of low level, but not statistically significant, toxicity to both test species. There was no follow-up on this consequent to the low level of the signal.
Impacts
Information obtained from this testing project is highly valuable to the State of California in developing an updated water quality control plan.
Publications
- No publications reported this period
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