Understanding the impacts of agriculture on water quality is an extremely important issue. In the Umatilla basin in eastern Oregon, agriculture is a predominant part of the economy, but concerns about the effect of agriculture on water quality and its impact on local salmon populations is creating much concern about best management practices in the area. The proposed project will develop a means for assessing water quality in the basin through the use of macroinvertebrate community structure. Macroinvertebrates are ideal for assessing water quality because they respond to a variety of pollutants and can rapidly respond to increases in water quality. The proposed project will not only develop the methodologies for using macroinvertebrates in water quality assessment but will also use these methods for assessing the effectiveness of riparian conservation easements on water quality. While conservation easements are seen as a major means of improving water quality, their effectiveness is not well understood. If we are to promote good stewardship of agricultural lands, we must understand the utility of best management practices such as riparian conservation easements.
Agriculturists in the Pacific Northwest are faced with numerous policies and restrictions on the use of their land due to the effects of agriculture on riparian ecosystems; the extent of the impact of agriculture on river systems is not yet quantified and is a matter of debate. There is a growing need worldwide to assess the current quality of aquatic habitats adjacent to agriculturally influenced regions, and to monitor restoration attempts over time to evaluate efficacy (Wright, Moss et al. 1984; Clarke, Furse et al. 1996).
The effects of agriculture on riparian ecology are numerous, and have the potential to highly alter aquatic habitat through a variety of interactions, even in areas that are no longer in use for agricultural purposes (Harding, Benfield et al. 1998; Jiongxin 2004; Fiener, Auerswald et al. 2005). These interactions can affect non-target ecosystems and are generally referred to as non-point source interactions. These effects include, but are not limited to, chemical pollution, canopy removal, and habitat alterations, such as channelization of river beds.
Non-point source (NPS) pollution is a critical consequence of agriculture to adjacent riparian systems (NRC 1996). It can be defined as the accumulation of natural and human caused toxins on non-target systems, such as pesticide runoff effects in groundwater, which is ultimately filtered into the nearby river systems. In agro-ecosystems, pesticides are a prominent source of pollution in aquatic systems and can alter the endemic fauna (Mouvet and Bourg 1983; Young, Onstad et al. 1987; Lijklema, Koelmans et al. 1993; Maher, Batley et al. 1999; Blais 2005). The effects of NPS pollution in aquatic systems have yet to be quantitatively defined in many regions due to the complex interactions of toxicants with substrate and vegetation. Riparian areas have been shown to be effective nutrient sinks and to buffer chemical and sedimentation runoff in agro-ecosystems (Lowrance, Todd et al. 1984; Peterjohn and Correll 1984).
Canopy cover, channelization, sedimentation, and a multitude of other factors affect the variability within the habitat, and play an important role in structuring biologic communities and influencing biodiversity (Hutchinson 1959; Menge and Sutherland 1976; Connell 1978). In consideration of the physical properties affecting habitat selection for optimal population success in organismal interactions, no single factor can be attributed. As mentioned above, microhabitat in the substrate and underlying hyporheic zones influence the biotic community structure with variable substrate stability and micro fluctuations in hydraulic properties (Death and Winterbourn 1995; Brooks, Haeusler et al. 2005). Fine balances between food availability, substrate composition, water quality, physical characteristics, vegetation, and interspecific interactions play a role in the designation of habitat niche (Vodopich and Cowell 1984; Palmer, Covich et al. 2000; Nakano and Murakami 2001). The spatial variability of the combination of factors across a landscape, or river bed, can be attributed to higher survivorship and greater diversity within a habitat, by providing patchy refuge for a greater variety of organisms (Lake 2000). Alterations affecting any of the factors mentioned, such as non-point source disturbances, can impact the biotic communities, throwing off the natural balances within the system.
To assess impacts on river systems that have been impacted by non-point source disturbances, environmental indicator species are utilized to predict habitat quality and overall water quality. Indicator species are organisms that have defined tolerances to different disturbance events, and thus can provide an estimation of the conditions in a graded response to these disturbances (Metcalfe 1989; Peck, Lazorchak et al. 2001). There are a wide variety of life history strategies in lotic environments, and many are well documented. Invertebrate sensitivity to pollution levels and changes in the ambient environment make them excellent candidates for bio-assessment models (Merrit, Cummins et al. 2008). Macroinvertebrates in river systems are also known to have evolved survival and exploitation strategies to living in disturbed conditions (Lytle 2002; Lytle and Poff 2004). It has also been documented that invertebrates in riparian systems can show immediate responses to alterations in the habitat, and that the community succession following a disturbance event can indicate the recovery of the system to natural processes (Robinson, Aebischer et al. 2004). Using macroinvertebrates in the reference areas as the foundation of the relative analysis of test sites and easement property sites will yield an index of habitat degradation along the Umatilla River, and be effective in the construction of a multivariate model that will predict overall habitat quality
The factors affecting riparian systems that exist in agriculturally dominant systems are difficult to measure, because of the variety of potential impact on the river system. Developing a standard model for determining impacts on system health and habitat quality utilizing environmental indicators is critical for better understanding the impacts of agricultural land use.
Outreach: A critical aspect of this program involves broadly impacting the communities near the river by opening lines of communication between researchers and the public. For any effort toward sustainability to be successful, it must be conceived with the intention to involve the communities that are supported by the resources provided by the systems. Without effective communication, any positive results in management will be short lived. By attending local watershed council meetings, writing for local publications, and participating in outreach events, we will make the connection to the community. Through collaboration and communication, the needs of both agriculturist and conservation parties can be included in the solution.
Use of the Model: Recovery of the Umatilla River is an important undertaking not only to conservationists, but also to the people of the Confederated Tribes, as they depend on local salmon populations. The community is dedicated to finding a solution to preserve this unique system. Buffer systems have provided a tentative answer, but their efficacy is yet to be determined. If proven to be successful means of recovery for the Umatilla River, similar attempts can be made statewide, perhaps with even further reaching implications.
The proposed project will assist greatly in determining the effectiveness of conservation easements on improving conditions in the Umatilla mainstem. We expect that the data will show degraded invertebrate communities where the river has been most disturbed by agriculture in comparison to the reference sites, and a strong recovery trend in the regions employing property easements. This research will contribute to the base knowledge of current conditions of the Umatilla River and will have general implications on other systems with similar environmental factors. These implications can then assist in policies that govern land use in riparian areas that can benefit both the salmon conservation efforts and the need of agriculturalists by helping to determine whether conservation easements can be considered a best management practice.
Sampling of the Umatilla was based on segmentation of the river in 3 parts, delineated on the basis of macroinvertebrate community assemblage. Within each segment, three different types of sites were identified: reference sites, test sites, and easement sites. Each type of site has 2-3 repetitions of each site type.
Reference sites are identified as sites with the least amount of human impacts for the represented river segment. These sites represent the ideal condition for the river within each segment. These sites are identified based on preliminary sampling of invertebrate assemblages and measurements of habitat characteristics, such as dominant vegetation and distance from human induced disturbance, and by best professional judgment (provided by fisheries biologists with Oregon Department of Fish and Wildlife and the CTUIR) as recommended by the Oregon Department of Environmental Quality (Drake 2004). Habitat characteristics for reference sites include adjacent habitat with natural vegetation, complex habitat with substrate heterogeneity and large woody debris, and the presence of braided channels and natural meanders. Macroinvertebrate assemblages found within the reference sites are pooled and used to generate a multivariate clustering. Similarity of reference sites will be evaluated using the Bray-Curtis measure of similarity (Wright, Moss et al. 1984; Moss, Wright et al. 1987; Marchant, Hirst et al. 1997).
Test sites have been identified in locations that have been heavily influenced by human activity, primarily agriculture, both historically and in the present. Adjacent habitat is strongly altered, with significant removal of natural vegetation. The river in these sites is likely to be highly channelized with little complexity.
Easement sites were identified using CTUIR records and land owner cooperation. Habitats will be characterized by re-growth of natural cottonwood galleries and natural undergrowth, the extent of which depends on the number of years managed. In locations with longer restoration, the channels may be beginning to braid and meander across the adjacent landscape.
For each test and reference site type, at least three possible locations have been selected within each segment, and yearly designation of the sites to be sampled will be selected randomly, to simulate as closely as possible the rotating panel design implemented by EPA’s Environmental Monitoring and Assessment Program (EMAP).
Within the identified site, the length of the sampling stretch is measured as 10 times the wetted width, to make this model as compatible as possible with EMAP. Each stretch will contain at least one riffle habitat. Along the length, habitat complexity is assessed, based on the location of all riffles, runs and pools, and the presence of woody debris greater in diameter than 10 cm and at least 1 m long. Projection of the woody debris into the channel is also recorded, as is the adjacent dominant vegetation type and undergrowth.
Using the location measurements, the riffles are plotted on a three by three grid, and assigned a number, 1-9 (figure 2). The grid is 1 m from the bank on each side. Using a random number table, 8 of the blocks are chosen from the grid, and sampled in the approximate center of the block. If more than one riffle exists in the stretch, the number of blocks chosen within each riffle is chosen relative to riffle size, equaling 8 samples total for the stretch. All samples for the stretch are compiled to be the sample set for the site.
Invertebrate communities are sampled in the 8 blocks selected for each reach using a stream bottom sampling net with 500 micron mesh netting. Placing the net on the bottom of the stream, all large rocks (larger than 3 cm in diameter) within a square foot directly in front of the net are manually scrubbed within the water flow to release all clinging invertebrates into the net. Then a sample of the invertebrates in the substrate is taken by agitating the bottom of the one square foot area for 30 seconds, while the net is held directly downstream to collect invertebrates stirred from the substrate. The 8 samples are combined into one large sample that serves as the representative community for the site. Invertebrate samples are preserved in 70% ethanol for transport to lab for processing.
In the lab, samples are randomly sub-sampled in 5% proportions until a minimum of 500 insects have been counted for each site. The majority of the insects are identified to genus using Merrit and Cummins (2008), with exception for the family Chironomidae, which are identified only to sub-family, and the non-insect invertebrates, which are identified only to Order.
To better assess the ecological interactions at each site, the following parameters are also be measured at time of sampling.
At each of the eight sampling locations within a site, depth, velocity, wetted width, slope, and substrate composition are recorded. The depth is measured with a meter stick, and wetted width, a measuring tape. Velocity is measured using a Marsh-McBirney FlowMate 2000. Slope is assessed using a Brunton Sight Master Clinometer. Substrate composition is estimated using a clear glass pan, to view the riverbed, and broken into categories outlined in the Pebble- count method of Water Quality Monitoring Guidebook, Appendix E- Sediment Deposition version 2.0 (1999).
Water quality is assessed at the beginning point of the measured stretch. This will include alkalinity, conductivity, turbulence and average daily and nightly temperature. Alkalinity is tested using a Orbeco-Hellige Series 942 Total Alkalinity Meter in the field, and for conductivity, a YSI Model 30 Conductivity/Salinity Meter. Turbidity is read by a LaMotte 2020 Turbidimeter. Hobo temperature data loggers are set in place at each sample site in the area least likely to be disturbed, and are programmed to record temperature every half hour once set. Temperature loggers will be left in place for several days after the benthic sample is taken to get a more accurate assessment of locality temperature patterns. The data evaluated for average daily and nightly temperatures, and percentage of readings above, below and within critical temperature ranges for salmonid development.
Percent algal cover in the river bed is estimated as each sample is taken at a site, using a clear glass pan to view the stream bottom. Percent canopy cover is measured with a Convex Densiometer by Forest Densiometers at equal intervals along the sampled stretch. Along the length of the stretch, the locations of pools, riffles and runs are recorded with their distance from the GPS-marked 0-meter point as reference, as well as the location and number of large woody debris protruding into the channel.
Adjacent to the river, dominant vegetation is recorded as dominant tree species and dominant undergrowth. Anthropogenic disturbances, such as agricultural crops, within 50m parallel to the river are also noted, and the proximity to the wetted bank recorded.
Before it can be determined if the restoration practices utilized in the easement sites are effective in returning a degraded site to an ideal condition, there must first be quantifiable differences in the habitat conditions of the degraded test sites versus the ideal, reference sites. The data collected at the sites annually was analyzed in three categories: environmental parameters, temperature, and endemic macroinvertebrate taxa.
The environmental parameters gave indication of either strong or significant evidence in difference of variation between test and reference sites. Conductivity and turbidity were both increased in test sites when compared to the reference sites. This would be expected as increases in runoff would increase the solutes suspended in the water column as well as visible solids.
Canopy cover was higher in test sites when compared to reference sites, though in this case this could be attributed to the increased entrenchment in the agriculturally affected areas of the river. The steep banks and canyon sides can be measured under the unifying metric of “canopy cover” with the densiometer used in this study. Furthermore, the entrenchment has happened over an extended period, and in many cases there are trees and shrubbery growing along the embankment, which can be misleading in this case.
The temperature data reflected significant differences between test site and reference site variation in almost all of the tests conducted, with consistently higher temperatures recorded in reference sites. This happened because the reference sites are generally located at lower elevations than the test sites, below tributary convergences and agricultural withdrawls. It is most likely the elevation at the reference sites that is affecting the variation between the two site types, rather than the land use adjacent to the river.
Bray-Curtis Ordination of the sites based on the endemic taxa show a clustering of test sites away from the reference sites. Unimetric analyses of individual taxa also show significant differences in abundance and diversity between test and reference sites.
Thought not all of the taxonomic and environmental parameter metrics returned significant results separating test and reference sites, there are key parameters setting the two sites types apart. Because the sites exist along the same river continuum, it is not unexpected that the differences will be fewer between site conditions, however, with the differences that have been identified, biomonitoring based on these signals is acceptable.
Conservation Easement Analysis
Utilizing the taxa identified as indicators of the test and reference condition sites in the analysis above, Bray-Curtis ordination and cluster analysis was used to determine the relative relationship for the conservation sites to the test and reference sites. It was found that in the Upper River, the conservation sites associated closely with test sites, indicating that the conservation thus far has not been able to restore the river processes at the level of the benthic macro-invertebrates to the level expected in the ideal conditions. However, the conservation sites were associating with test sites located far upstream from the locations of the conservation easement, indicating that they may be moving from a highly degraded condition to the less severely degraded condition. In the lower river the conservation sites associated more closely with test sites located downstream, and reference sites located even further downstream. This indicates that the conservation easements in this area are having less success returning to a more ideal condition, and are still highly affected by the agricultural use on the adjacent landscape.
Educational & Outreach Activities
This study is part of a doctoral thesis still in progress.
The measurable impacts of this study will be slower in coming, as long-term monitoring of restoration and conservation areas is needed. With continued research support, it is hoped that the longer reaching impacts will lead to changes in policies that will allow growers to get maximum benefits from land while protecting natural resources with wider buffer strips in riparian areas.
In the instance of this study, the land owners of the areas utilized for restoration sites were compensated by the Confederated Tribes. The CTUIR also did maintenance on several of the sites, assisting growers with removal of weeds and fencing. Because if this, the implementation of easement/restoration sites had very little –if any — cost to the growers.
Many of the growers on the Umatilla River participated in this study, having already implemented the conservation easements or by allowing researchers access onto highly affected regions of the river. The easements are supported by the CTUIR, which pays the land owners the amount that a crop planted in the buffer strip would be estimated to supply. This study involved the cooperation of four private land owners and five large-scale cereal crop growers. The growers involved in the conservation easements were given assistance in the restoration projects by the CTUIR in the form of plantings, fences, and management assistance. Overall, the growers were satisfied with the easement areas, as this system is beneficial for both the growers and those concerned with the health of the river habitat.
Areas needing additional study
Long-term monitoring of conservation and restoration sites is critical in understanding the long-term ecological effects of management regimes. Further research into the tolerance thresholds of individual indicator taxa is also needed so that we can better understand the implications of non-point source pollution and agriculture in close proximity to freshwater drainage.