Discussion

When the ODEQ began pesticide monitoring in 1999, the organophosphate insecticides azinphos-methyl and chlorpyrifos were detected in several creeks at concentrations exceeding the State of Oregon’s chronic or acute criteria for the protection of freshwater aquatic life. In 2001, additional sites were added to the stream sampling network and more samples were collected at each site to better characterize the sources and temporal character of organophosphate transport (appendix B). Stream monitoring has continued through 2010. Throughout the monitoring period, sites were dropped and new ones added in an attempt to characterize pesticide occurrence and distribution in the major salmon-bearing streams in the Hood River basin (appendix H).

Coincident with the monitoring program, the ODEQ, Oregon Department of Agriculture, Hood River Soil and Water Conservation District, the Confederated Tribes of Warm Springs, and the Oregon State University agricultural extension service began an outreach and education program to work with farmers to reduce pesticide drift and runoff from land in their stewardship. The early to mid-2000s also marked the beginning of a period of use restrictions and cancellations for many organophosphates, including azinphos-methyl and chlorpyrifos, as the USEPA implemented the Food Quality Protection Act of 1996 and as less-toxic alternatives to organophosphates became available (Grafton-Cardwell and others, 2005; U.S. Environmental Protection Agency, 2006a, 2006c, 2009c). Pesticide use was further restricted in Oregon, Washington, and California in 2004 by a ruling by the U.S. District Court for the Western District of Washington in the case of Washington Toxics Coalition v. EPA (U.S. Environmental Protection Agency, 2004), which restricted the application of 26 pesticides adjacent to streams used by salmon that are listed as threatened or endangered under the Endangered Species Act. Azinphos-methyl, chlorpyrifos, and 10 other organophosphates were among the pesticides affected by this ruling.

Pesticides Detected Since 2007

Since sampling commenced in 1999, the frequency of detecting most pesticides that were monitored for the entire period appears to have declined. An exact measure of the decline is unknown due to changes in reporting limits, sites, the number of samples collected each year, and the time when samples were collected during the year. In the unscreened dataset, neither diazinon nor malathion has been detected since 2005. Phosmet was detected twice from 2006 through 2009 compared with 11 detections from 2002 through 2005. Chlorpyrifos was detected eight times from 2006 through 2009; however, seven of these detections occurred during a 2-week period in April 2008, and there were no detections in 2009. Preliminary ODEQ data from 2010 monitoring show chlorpyrifos detections in four creeks in March 2010, once exceeding the lowest national and State water-quality criteria (Kevin Masterson, Oregon Department of Environmental Quality, written commun., 2010). Azinphos-methyl and simazine continue to be detected, but are primarily limited to Lenz Creek at mouth and Neal Creek at mouth.

Azinphos-methyl

Sixty-nine of the 76 detections of azinphos-methyl in the unscreened dataset occurred at Lenz Creek at mouth and Neal Creek at mouth. Discussion will be limited to these two sites. Azinphos-methyl primarily was detected in Lenz Creek and Neal Creek between late-May and mid-June and from mid-August through at least mid-October. No samples were collected after mid-October, so the occurrence of azinphos-methyl in the streams of Hood River basin is unknown from mid-October until March. Detections in May and June correspond to the primary period of use of the insecticide in the Hood River basin (Eugene Foster, Portland State University, written commun., 2003; Jenkins, 2003). Trends in detected azinphos-methyl and chlorpyrifos concentrations in May and June of 2000 and 2001 reported here were consistent with the findings of another study conducted in the same area during the same period (Jenkins, 2003). The presence of azinphos-methyl in the creeks during this period is likely the result of spray drift and runoff of irrigation water from treated fields, although neither has been directly measured. Jenkins (2003), who hypothesized that runoff following precipitation events is a major contributor of pesticides to streams, measured instream concentrations of azinphos-methyl and chlorpyrifos and did not find a significant relationship with precipitation. However, use of those pesticides on adjacent agricultural land was not measured. Late-summer concentrations of azinphos-methyl in Lenz Creek tended to be higher than concentrations in May and June; concentrations were similar during both periods in Neal Creek. The higher concentrations in August, September, and October in Lenz Creek likely were due to the discharge of wash water by fruit washing and packing facilities that line that creek (table 10). The median concentration of azinphos-methyl in samples of wastewater discharged from these facilities into Lenz Creek in 2004 and 2005 was 0.95 µg/L; concentrations as high as 37 µg/L were measured in wastewater. Lower instream discharge (flow) rates during those months could also contribute to the higher detected concentrations. Although discharge data are not available for Lenz Creek, other streams in the basin have the lowest mean monthly discharge during July to October (U.S. Geological Survey, 2010).

Azinphos-methyl was detected in 66 samples from Lenz Creek at mouth and Neal Creek at mouth from 1999 through 2006. From 2007 through 2009, there were 3 detections. The dramatic decrease in the occurrence of azinphos-methyl cannot, with certainty, be ascribed to decreasing instream concentrations. Azinphos-methyl was commonly detected at these sites in June, during the peak application period; however, just one sample was collected in June 2007 and no samples were collected in June 2008. Weekly samples were collected at the two sites in June 2009. Similarly, a shift in the time of sample collection after 2006 resulted in just five samples (two at Lenz Creek at mouth, three at Neal Creek at mouth) being collected during the months of the historically highest instream azinphos-methyl concentrations—August, September, and October.

Azinphos-methyl was not detected at Lenz Creek or Neal Creek in June 2009. The reporting limit for azinphos-methyl was stable during this period and lower than it was in the early to mid-2000s. These data suggest that the causes of azinphos-methyl transport to the creeks during the June application period have been addressed, but sampling frequency was not ideal to make this assertion with certainty. There was one detection of azinphos-methyl in September 2009 in Lenz Creek, suggesting that there may still be reason for concern about effluent from the fruit washing and packing houses. Though rarely detected, concentrations of azinphos-methyl detected since 2007 have all exceeded the chronic Oregon water-quality criteria. Azinphos-methyl is set to be phased out on its last registered uses (alkali bee beds, apples, blueberries, cherries, parsley, and pears) by September 30, 2012 (U.S. Environmental Protection Agency, 2009c).

Simazine

Simazine was detected in the unscreened 2007–2009 data at about the same frequency and concentration at which it was detected in 2005 and 2006. Most detections were at Lenz Creek at mouth and Neal Creek at mouth. Concentrations of simazine detected since 2007 range from 0.0063 to 0.299 µg/L and are within an order of magnitude of those found to cause a reduced olfactory response to a female priming pheromone in adult male Atlantic salmon (Moore and Lower, 2001). Two recent studies using common carp (Cyprinus carpio) have demonstrated histopathological changes in liver and kidney tissues in fish exposed to simazine concentrations as low as 4 µg/L (Velisek and others, 2009) and 42 µg/L (Oropesa and others, 2009). The effect on salmonids has not been documented. Other studies have demonstrated that high concentrations of simazine (greater than 25 µg/L) increase the toxicity of organophosphates to aquatic invertebrates (Schuler and others, 2005; Trimble and Lydy, 2006). The highest simazine concentration measured in any Hood River stream was 1.9 µg/L at Lenz Creek at mouth in 2003. The highest concentration observed in 2009 was 0.299 µg/L, also at Lenz Creek at mouth. These concentrations are within an order of magnitude of documented deleterious effects in fish and aquatic invertebrates. While detected concentrations of simazine are not necessarily cause for concern on their own, simazine use in the basin is common, and it has the potential to compound the toxicity of more deleterious pesticides.

New Pesticides for 2009

In 2009, 14 pesticides were detected in the 8 streams that were sampled. Of these 14 pesticides, 12 were new pesticides added to the suite of analyses in 2009. Pesticides were detected in at least one sample collected from every site except West Fork Hood River at Moving Falls (RM 2.5). Data from 2010 analyzing the same suite of 100 pesticides became available in early 2011, but their analysis is outside the scope of this study. The data are available through the ODEQ’s LASAR database (Oregon Department of Environmental Quality, 2008).

Eight of the new pesticides detected in 2009 are of little concern due to (1) their infrequent or irregular occurrence (table 7) and (2) their low concentrations relative to established water-quality standards and potential for deleterious sublethal effects on aquatic organisms 
(figs.11–22). With the exception of the single detection of endrin at Rogers Spring Creek, the maximum concentrations of the 12 newly identified pesticides were at least one order of magnitude lower than established water-quality standards and concentrations that can cause sublethal toxicity to salmonids and aquatic invertebrates. However, the effects of these pesticides at the measured concentrations are unknown when they occur in mixtures. Additional discussion of four pesticides—carbaryl, diuron, endrin, and hexazinone—is warranted due to the relatively high frequency of detection or toxicity.

Carbaryl

Carbaryl was primarily detected in May and June. Seven of the nine detections occurred at Lenz Creek at mouth or Neal Creek at mouth. Although the maximum concentration of carbaryl was 14 times lower than the chronic USEPA criterion for the protection of freshwater invertebrates, the pesticide has been shown to additively increase acetylcholinesterase inhibition in the presence of other carbamates and organophosphate insecticides at low concentrations (Laetz and others, 2009). Acetylcholinesterase (AChE) inhibition is a commonly used biomarker of exposure to organophosphate and carbamate pesticide exposure in fish (Eugene Foster, Portland State University, written commun., 2003; Scholz and others, 2006). Inhibition of the AChE enzyme has been associated with impairment of swimming, predator detection and avoidance, and migration (Jarrard and others, 2004; Sandahl and others, 2005). The low concentrations of carbaryl at these two sites may not be of concern if concentrations of organophosphates in May and June remain less than aquatic life criteria, as they were in 2009.

Diuron

Diuron was detected at all sites except West Fork Hood River at Moving Falls (RM 2.5), at which only a single sample was collected. It was detected throughout the year at Lenz Creek at mouth, Hood River at mouth, Neal Creek at mouth, and Middle Neal Creek at Hwy 35. Concentrations of diuron were always greater than an order of magnitude (10 times) less than the USEPA chronic criteria for the protection of freshwater fish; most concentrations were more than a factor of 100 lower. Thus, the presence of diuron in the sampled streams is unlikely to pose a threat to aquatic organisms unless it occurs in mixtures of pesticides that potentiate the effects of one or more of those pesticides. 3,4-dichloroaniline (DCA) is a degradation product of diuron that was not analyzed for this project. The acute and chronic toxicities of DCA are lower than those for diuron (Crossland, 1990; U.S. Environmental Protection Agency, 2003). Sublethal effects have been observed in fish at concentrations of about 200 µg/L (Crossland, 1990; Munn and others, 2006).

DCA detections have been common in Oregon streams (U.S. Geological Survey, 2010). In 460 surface-water samples collected in Oregon since 1990, DCA was detected in 150. In samples where both DCA and diuron were detected, the concentration of diuron exceeded the concentration of DCA by a factor of 7 to 39, and DCA was never detected without diuron also being detected. Assuming that DCA is present in all samples collected from the Hood River basin in 2009 that contained diuron, and assuming that the ratio of DCA to diuron in Hood River streams is similar to that observed in other streams in Oregon, it is reasonable to conclude that mortality and sublethal effects resulting from the presence of DCA is probably not a concern in the streams sampled in 2009.

Endrin

The single detection of endrin in 2009 at Rogers Spring Creek is unusual, and serves as a reminder of the persistence of many older pesticides in the environment. The USEPA cancelled the last registered agricultural use of endrin in 1985 (U.S. Environmental Protection Agency, 2000); however, the half-life of endrin in soil can be up 14 years (Agency for Toxic Substances and Disease Registry, 1996). Endrin strongly binds to soil and is unlikely to be found in the dissolved phase; the adsorption coefficient (K_oc) is approximately 34,000 (Agency for Toxic Substances and Disease Registry, 1996). The single detection could have been related to runoff from rainfall that occurred on the day prior to sample collection; however, endrin was not detected in other samples collected after other rain events. Alternately, construction, planting, or tilling could have disturbed soil contaminated with endrin, which was then washed into the creek.

Hexazinone

With one exception, all detections of hexazinone occurred at three sites along Neal Creek. Concentrations at Upper Neal Creek below agricultural diversion and Middle Neal Creek were similar for most of the year, and with one exception, were always greater than the concentration at Neal Creek at mouth (fig. 32). The decrease in concentration between Middle Neal Creek and Neal Creek at mouth was probably due to dilution by tributary inflows (such as Lenz Creek) and possibly upwelling groundwater along this reach of the creek. A more detailed examination of the drop in concentration is limited by an absence of flow data at these sites.

In the Hood River basin, most, if not all, hexazinone is used on forest land. It is registered for use along rights-of-ways, but there is no record of its use for this purpose in the Hood River basin (Brian Walker, Oregon Department of Transportation, oral commun., 2010; John Buckley, East Fork Irrigation District, oral commun., 2010; Nate Lain, Hood River County Weed and Pest Division, oral commun., 2010). It also can be applied to alfalfa, grass hay, noncrop agricultural areas, and industrial areas, but these represent small areas of the Hood River basin. The land upstream of Upper Neal Creek is 95 percent forest and the land draining to Neal Creek between the Upper Neal Creek site and the Middle Neal Creek site is 66 percent forest and 37 percent agricultural (appendix A). Considering the limited major users of hexazinone and the land use contributing to the sampling sites where it was detected, forestry use is the most probable source of the hexazinone in Neal Creek. Preliminary 2010 data showing frequent detections of imazapyr, another forestry herbicide, at the three Neal Creek sites and only one detection of hexazinone (Kevin Masterson, Oregon Department of Environmental Quality, written commun., 2010) reflect the annual variability in forestry herbicide use in response to changing needs.

Concentrations of hexazinone detected in Neal Creek are 5 to 6 orders of magnitude less than established water-quality benchmarks. Few studies using environmentally relevant concentrations of hexazinone (< 1 mg/L) exist in the literature. Nieves-Puigdoller and others (2007) found concentrations of hexazinone 100 µg/L had no effect on smolt development in Atlantic salmon. Michael and others (1999) found no change in the aquatic invertebrate community after hexazinone application in a forested watershed. Concentrations as high as 473 µg/L were observed. In lab studies using mammalian test subjects, developmental and reproductive toxicity were observed only at concentrations approaching the 50 percent lethal dose (U.S. Environmental Protection Agency, 1994).

Considering the available evidence, hexazinone at concentrations observed in streams of Hood River basin in 2009 is probably not a concern. However, the pesticide was present in prime salmon-rearing habitat during at least 4 months in 2009; additional research to more confidently determine the sublethal effects of hexazinone on Pacific Northwest salmonids using environmentally relevant concentrations would aid in the assessment of risk to these species.

Pesticide Mixtures in 2009

Thirty-four of the 111 samples collected in 2009 contained at least 2 pesticides (table 9). Mixtures of 2 pesticides were the most common (20 samples) followed by mixtures of 3 pesticides (10 samples). Mixtures of more than 3 pesticides were identified in 4 samples. Three herbicides were among the most common pesticides identified in mixture samples: diuron was a component of 28 mixture samples, hexazinone was a component of 15 mixture samples, and simazine was a component of 13 mixture samples. The insecticide carbaryl was a component of 8 mixture samples. The most common mixture in 2009 was of the herbicides diuron and simazine, which were found together in 12 samples.

Mixtures of pesticides are a concern because of the unknown manner in which the chemicals can affect an organism. Dose-addition models are commonly used to predict cumulative toxicity for co-occurring pesticides. These models predict the toxicity of a mixture by adding the toxic potency of each component in the mixture. Some pesticides have been shown to interact synergistically, resulting in greater toxicity than predicted by a simple dose-addition model (Lydy and Austin, 2004; Schuler and others, 2005; Trimble and Lydy, 2006; Laetz and others, 2009). Conversely, some pesticide mixtures may result in lower toxicity than predicted by a dose-addition model (Key and others, 2007; Brander and others, 2009).

The effects of pesticide mixtures are an area of active research among ecotoxicologists, and the USEPA is developing pesticide regulations that address mixtures of pesticides that have a common mode of action. However, the vast number of possible mixtures of chemicals in the environment combined with differing modes of action makes the issue of cumulative pesticide toxicity particularly difficult to address. Among the better studied mixtures are those involving one or more organophosphate insecticides. Synergistic toxicity to salmonids has been shown for mixtures of carbamate and organophosphate insecticides (National Marine Fisheries Service, 2008). Some triazine herbicides have been shown to potentiate the toxicity effects of organophosphate insecticides on aquatic invertebrates that are salmonid prey items, and thus could indirectly affect salmonids (Lydy and Austin, 2004; Trimble and Lydy, 2006). More work is needed to understand the effects of the mixtures of pesticides commonly observed in streams of the Hood River basin.

Trace Elements

Samples for trace elements were collected and analyzed at 53 sites. Most sites were sampled once or twice; most data were collected from 1999 through 2002. The data provide a preliminary screen of potential salmonid toxicity related to trace elements, but a comprehensive analysis of the data are limited by several factors: (1) most sites were sampled only once or twice, (2) samples were not collected at the same time of year at all sites, (3) samples were not collected throughout the year, (4) the data may not reflect current conditions, (5) many toxicity criteria are dependent upon the hardness of the water, which is not available for these samples, and (6) most samples were analyzed for total recoverable trace elements rather than the dissolved fraction.

With the caveats just noted, it is possible to develop some working hypotheses. A preliminary literature review indicated that concentrations are likely not of concern for most of the trace elements analyzed. However, the median concentrations of the following trace elements exceeded or were within an order of magnitude of criteria established by USEPA or the State of Oregon: aluminum (dissolved), cadmium (dissolved and total recoverable), copper (dissolved and total recoverable), iron (total recoverable), nickel (dissolved), selenium (total recoverable), silver (total recoverable), and zinc (dissolved and total recoverable) (tables 12 and 13). The review identified studies that have documented lethal and sublethal effects of trace elements on salmonids and aquatic invertebrates, at concentrations similar to and higher than State and national water-quality standards. Dissolved concentrations of aluminum, cadmium, copper, iron, nickel, and zinc were detected at concentrations exceeding one or more values in this review (tables 12 and 13). Dissolved data are only available for 26 sites and consist of one sample per site collected in October 1999.

This preliminary screen suggests that some trace elements might occur at concentrations of concern for salmonids or their prey. More work is needed to ascertain their duration and spatial extent in creeks of the Hood River basin and to determine sources and transport mechanisms.

Status of Prey Organisms

The ODEQ has conducted annual surveys of benthic invertebrates at five sites in the Hood River basin since 2000. In an analysis of these data through 2007, ODEQ researchers suggested that there is a spring depression in the invertebrate community following periods of pesticide application and that the community recovers later in the season (Shannon Hubler, Oregon Department of Environmental Quality, written commun., 2008). There is larger within-season variability in the observed-over-expected (O/E) scores than there is over the period of record, making it difficult to determine whether the communities have improved over time. Further, based on their data, it is not possible to understand differences in the communities among sites or changes in community structure over time; information on the type of prey insects and their abundance would be useful.

Information Gaps

The Hood River Watershed Group’s Watershed Action Plan identifies projects and strategies “to improve watershed health, water quality, and fish populations in the Hood River Watershed” (Hood River Watershed Group, 2008). To achieve this goal, a comprehensive evaluation of the spatial and temporal occurrence of all potential toxic contaminants and their effects on the instream biota is needed. Data collected by the HRPSP since 1999 represent important surveys; however, significant gaps still exist.

Spatial Distribution of Contaminants

Most streams (or a nearby downstream reach) that have been identified as critical habitat for steelhead and salmon have been sampled for at least 1 year (appendix H). Several, however, have not, including Green Point Creek, Tony Creek, and Emil Creek. Although Odell Creek is not identified as critical habitat, steelhead have been observed recently in that stream (Joe McCanna, the Confederated Tribes of Warm Springs, oral commun., 2010); the ODEQ began sampling this creek in 2010.

The HRPSP monitoring sites have changed over time. Seven of 16 sites have not been monitored for pesticides since 2006 or earlier (appendix H). Some sites were dropped because of redundancy or because better sites were identified; for example, the two sites on upper Neal Creek. However, some sites were dropped because pesticides were infrequently detected or concentrations were consistently near or less than the reporting limit, such as at Baldwin Creek. Budgetary constraints also limited the number of sites sampled each year. The current network of sampling sites does not comprehensively cover all critical habitat streams (StreamNet, 2010).

The number of sites at which trace elements were sampled and analyzed was larger than the number for pesticides. Most streams identified as critical habitat for steelhead and salmon were sampled. Only five samples for trace elements have been collected from those streams since 2002.

Seasonal Distribution of Contaminants

The ODEQ pesticide monitoring during the past decade was scheduled to coincide with peak pesticide use in the basin (March–June and September). Ninety percent of samples were collected during these 5 months (appendix B). However, pesticides also were detected in February, July, August, October, and December. No pesticides have been detected in November, but only five samples were collected during this month among all sites since 1999. No samples have been collected in January. Pesticides are potentially used throughout much of the year in the basin’s major land uses (appendix I), and several salmonid species (winter and summer steelhead, spring Chinook, coho, and bull trout) are present in streams year-round (National Marine Fisheries Service, 2008).

Most sites were sampled only once (in October) for trace elements. Ten other sites were sampled mainly in March–June. It is reasonable to expect seasonal differences in the concentration of some trace elements. For example, concentrations of trace elements associated with automobiles, such as cadmium, copper, cobalt, iron, nickel, lead, and zinc have been observed to increase seasonally in response to increased runoff from roadways (Hallberg and others, 2007).

Pesticides Used in the Hood River Basin

Many pesticides are commonly used in the Hood River basin or are registered for use for the basin’s major land uses, but have not been analyzed for in its surface waters (appendix C and appendix J). Neonicotinoids are a class of insecticides that were developed as replacements for organophosphate, carbamate, and synthetic pyrethroid insecticides. Use of neonicotinoids and other organophosphate replacements has increased in the basin (Steve Castagnoli, Oregon State University Extension Service, oral commun., 2010), yet many are not included in the 2009 suite of analyzed pesticides. Likewise, many pyrethroid insecticides—a class that is in common use in the basin—have not been analyzed.

Hydrophobic Pesticides

Hydrophobic (particle-bound) pesticides bind strongly to sediments and plant matter and are less likely to be found dissolved in the water column. The presence of particle-bound pesticides in Hood River basin streams could be underrepresented in the current dataset, which only includes water samples, particularly in streams with fine-grained or organic-rich sediments. This is especially relevant for pyrethroid insecticides, which are used in the basin and bind more strongly to particles than most current-use pesticides. Pyrethroid insecticides have been associated with sediment toxicity to benthic invertebrates (Weston and others, 2004; Amweg and others, 2005, 2006; Holmes and others, 2008; Domagalski and others, 2010), are highly toxic to salmonids (Marking, 1974; Coats and O’Donnell-Jeffrey, 1979; Kumaraguru and Beamish 1981; Ural and Sağlam, 2005), and have been shown to interfere with reproductive behavior in brown trout (Jaensson and others, 2007).

Organochlorine pesticides are also hydrophobic. Most organochlorine pesticides, such as aldrin, chlordane, DDT, dieldrin, endrin, and lindane, have been banned in the United States due to their persistence and toxicity. However, they are often found in fish and sediment throughout the Columbia Basin. Two of these pesticides, DDT and lindane, were detected in Hood River and Neal Creek sediments in May 1998, when sediments from five sites were sampled for pesticides (Oregon Department of Environmental Quality, 2008). Endrin was identified in a surface-water sample from Rogers Spring Creek in 2009.

Pesticide Mixtures

Many samples contained at least two pesticides in the same sample. The number of pesticides actually present in any sample of water is potentially even larger because the instream presence of many pesticides used in the Hood River basin is unknown (appendix J). Moreover, instantaneous grab samples can fail to detect pesticides that are intermittently present in a stream; Jenkins (2003) found considerable variability in concentrations of organophosphates measured over periods of hours and days in Neal Creek. An assumption of simple dose-additivity provides a mechanism for initially assessing the potential toxic effects of mixtures. However, even a simple model such as this is limited by the lack of experimental research using pesticide mixtures at concentrations that are environmentally realistic for the Hood River basin.

Trace Elements

Trace-element concentration data are approximately 10 years old and exist only for limited parts of a few years (October 1999 and March–July 2000–01). The 1999 samples were analyzed for dissolved trace elements, whereas the 2000–01 samples were analyzed for total or total recoverable trace elements. Total and total recoverable analyses include dissolved constituents and trace elements contained in suspended particulate matter; the latter are less biologically available. USEPA water-quality criteria apply to dissolved trace-element concentrations, whereas Oregon criteria apply to total recoverable concentrations. Data from October 1999 indicate that concentrations of some dissolved trace elements with potential to harm salmonids approached or exceeded Oregon and/or USEPA criteria (dissolved aluminum in Wisehart Creek, cadmium in McGuire and Odell Creeks, and zinc in Lenz Creek). The concentration of some trace elements of concern also approached or exceeded values cited in toxicology literature that were shown to elicit olfactory stimulation or avoidance responses in salmonids (dissolved aluminum in Wisehart Creek and copper and zinc in Lenz Creek) (Tierney and others, 2010). However, the duration of the detected concentrations is unknown and could be less than the time periods upon which the criteria or toxicology studies were based.

Groundwater Contamination

Agricultural and urban use of pesticides has been correlated to their presence in groundwater. The presence of hydrophilic pesticides (those likely to be found dissolved in water) in surface waters of the Hood River basin indicates that there is potential for groundwater contamination. However, the presence and distribution of pesticides in Hood River groundwaters is unknown and outside the scope of this report. Nevertheless, discharge of contaminated groundwater can contribute to pesticide loading in streams (Ebbert and Embrey, 2002). Subsurface and surficial contributions of pesticides to streams were not assessed in this report and would require a sampling plan designed to address this question.

Unsampled Contaminants

Although concern about organophosphate insecticides is waning with their decreasing use, concern about the effects of degraded water quality on threatened salmonids in the basin remains. Numerous chemicals currently or historically used in the Hood River basin have not been analyzed in streams and bed sediment; however, nonpesticide chemicals are not within the scope of the HRPSP project. Throughout the lower Columbia River, polychlorinated biphenyl (PCB) compounds, polycyclic aromatic hydrocarbon (PAH) compounds, mercury, and legacy organochlorine pesticides (such as DDT) are commonly found in fish and birds in Western Oregon (Hinck and others, 2004; Johnson and others, 2007; Henny and others, 2008; Sherman and others, 2009). Additionally, laboratory analytical techniques developed in the last decade now enable scientists to examine contaminants such as pharmaceuticals, synthetic estrogens and androgens, and a variety of other potentially toxic compounds that enter streams from wastewater treatment plants, septic systems, and runoff from developed areas. Sampling conducted in the lower Columbia River basin in 2007 identified many of these chemicals in water, fish, and bed sediment (Lower Columbia River Estuary Partnership, 2007; Nilsen and others, 2007). The environmental fate and toxicity to aquatic biota for many of these novel analytes are still being determined. Analysis of samples from the Hood River wastewater treatment plant and samples of stormwater runoff in the city of Hood River collected in 2008–09 is under review by the U.S. Geological Survey. Those data could provide the first information on many of these compounds from a location in the Hood River basin. Results of additional sampling for PCB compounds, PAH compounds, polybrominated biphenyl ethers, organochlorine pesticides, and mercury in the water column and fish tissue during the summer of 2009 from 31 sites along the middle Columbia River and its major tributaries, including Hood River, are scheduled to be available from the ODEQ in 2011 (Kevin Masterson, Oregon Department of Environmental Quality, written commun., 2011).

Invertebrate Data

Collecting macroinvertebrate assemblages is a common, relatively inexpensive method for assessing biological integrity of streams. Foster and others analyzed macroinvertebrate data collected in 2002 in the Hood River basin (Eugene Foster, Portland State University, written commun., 2003). They found differences in macroinvertebrate assemblages among forested and agricultural sites. They also showed differences in assemblages at the same site before and after insecticide spraying in orchards within the catchments draining to the sampling sites. Macroinvertebrate data have been collected during the spring and summer from 2000 through 2008 at seven sites that were also monitored for pesticides. Although beyond the scope of this report, further analysis of these data could be useful in assessing trends in the invertebrate communities where best management practices have occurred.

First posted June 17, 2011