macroinvertebrate and physicochemical study of the Yakima River were used to generate a macroinvertebrate community condition index and a non-pesticide ...
Use of Macroinvertebrate and Chemical Indices to Assess Water Quality of an Irrigation Wasteway Steven K. Early Environmental Science and Regional Planning Washington State University Tri-Cities Richland, WA 99352-1671 USA
Robert L. Newell Fluor Federal Services Richland, WA 99352 USA
and Victor F. Medina Department of Civil and Environmental Engineering Washington State University Tri-Cities Richland, WA 99352-1671 USA
Abstract The Amon Wasteway is an engineered drainage waterway for the Kennewick Irrigation District, which receives its water from the lowerYakima River near Prosser, Washington. Reference conditions that were established in a basin-wide macroinvertebrate and physicochemical study of the Yakima River were used to generate a macroinvertebrate community condition index and a non-pesticide agricultural intensity index. These indices were utilized to ascertain the ecological integrity of the wasteway. Despite the negative connotation often associated with such bodies of water, the wasteway compared well against both reference condition indices for the lower basin. The overall water quality of Amon Wasteway, as measured by macroinvertebrate and physicochemical analysis, was found to be better than its source, the Yakima River. The species composition of the wasteway most closely resembled the makeup of the Yakima River. This river is many times the size of the wasteway, but the nearest source in an arid climate to provide immigrants. Introduction Ecological indicators are measures used to assess the quality or condition of the environment and are direct descriptors of habitat quality (Rosenberg and Resh 1993). Many qualitative and quantitative indices have been developed to relate water quality to the condition of biological communities. Benthic macroinvertebrates constitute the most commonly used taxonomic group because they live in close association with the substrate, are comparatively easy to collect and identify, are sedentary in nature, and have widespread distribution (Plotnikoff and Ehinger 1997). In 1990 the U.S. Geological Survey (USGS), as part of its National Water-Quality Assessment Program, collected biological and physicochemical data throughout the Yakima River Basin, located in south-central Washington state (Cuffney et al. 1997). They divided the watershed into four ecoregions (i.e., Cascades, Eastern Cascades, Columbia Basin, and Large River) based on geomorphology, climate, ecology, and elevation. As part of the assessment, an ecoregion-specific multimetric invertebrate community condition index and a non-pesticide agricultural intensity index (NPAI) were developed. The Yakima River Basin is one of the most heavily irrigated agricultural areas in the United States, with over 2.2 x 109 m3 of water per year delivered to nearly 250,000 ha of farm and residential land (Rinella et al. 1992). Approximately 60 percent of the mean yearly in-stream flow in the basin is diverted for irrigation, municipal use, and power generation. In the lower Yakima Basin, agricultural and water-treatment plant return 191 Journal of Freshwater Ecology, Volume 17, Number 2 - June 2002
flows contribute as much as 80 percent of the flow in the main stem during irrigation season (Fuhrer et al. 1996). Extensive irrigation canal systems have been constructed throughout the basin. These systems include wasteways, which are drains that carry excess and return water flows from canals and fields back to the main stem of the river. This study was designed to: 1) determine the ecological integrity of an engineered stream using community indices derived from ecoregion-specific macroinvertebrate and physicochemical data; 2) contrast the macroinvertebrate diversity of the stream with natural streams of similar order within the ecoregion; and, 3) determine trophic feeding group dynamics in the stream and compare them to neighboring streams within the ecoregion. Methods and Materials Study Area Amon Wasteway is a perennial stream engineered by the Kennewick Irrigation District, which serves the region in and around the cities of Richland, Kennewick, and rural Benton County, located in south-central Washington state. Discharge of water into the wasteway during irrigation season varies inversely with the demand put on the system by its customers. Flow rates at the macroinvertebrate sampling point were 1.4 - 2.0 m3/s during the irrigation season and 0.75 m3/s in the off-season. Stream width during irrigation season was approximately 2.5 mat the macroinvertebrate sampling point.
Macroinvertehrate Sampling and Analysis To mirror the investigation by Cuffney et al. ( 1997) as closely as possible, similar collection dates were selected. Three samples were taken within a riffle on two separate dates using a 0.093-m 2 Surber sampler with a 500-µm mesh net. In addition, a composited qualitative multihabitat sample was taken using a D-frame kick net with 200µm mesh, surveying non-riffle and bank habitat. Each sample was stored in 70% ethanol and analyzed separately. Although sampling equipment and protocol varied slightly between our study and the USGS investigation (Cuffney et al. 1997), a personal communication with the principle investigator suggested that the difference was insignificant•. Benthic macroinvertebrates were separated from the detrital and inorganic components and, in most cases, identified to the lowest possible taxonomic level (with the exception of the chironomids in which genus-level identification was not attempted). Taxonomy, trophic feeding group, and tolerance classifications followed Merritt and Cummins ( 1996), Thorp and Co vi ch ( 1991 ), and McCafferty and Provonsha ( 1981 ). Mean abundance was calculated for each taxon based on the six quantitative samples collected. A taxa richness list was generated from all samples taken (Table I). Data were analyzed using procedures of Cuffney et al. ( 1997) for the Yakima River Basin watershed. Reference sites were specific to the ecoregion rather than the entire Yakima River Basin to compensate for variance in the value of metrics that arise from differences in natural factors such as climate and elevation. Community metrics were scored against reference sites and summed to obtain a community multimetric index score, where: Mitest = the value of the test metric 1; M;reference = the value of metric i at the Columbia Basin reference site; and, n = the number of metrics comprising the index. n Community Multimetric Index = L [(M;testill;reference)lO]/n i=l This study did not identify chironomids to genus level: therefore, Cuffney et al. ( 1997) results were modified to exclude chironomid taxanomic feeding group information. 3
Personal communication with T.F. Cuffney, USGS. December 12. 2000, Raleigh, North Carolina.
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Table l. Taxa richness at the Amon Wasteway sample site. Phylum Platyhelminthes Class Turbellarian Tricladida Phylum Annelida Class Oligochaeta Lumbriculidae Tubificidae Class Hirudinea Erpobdellidae Mooreobde/la sp. Phylum Nematotoda Mermithidae Phylum Mollusca Class Gastropoda Ancylidae Ferrissia sp. Lymnaeidae Lanx sp. Physidae Physef/a sp. Class Bivalvia Corbiculidae Corbicula fluminea (Muller) Sphaeriidae Sphaerium sp. Phylum Arthropoda Class Arachnida Hydracarina Class Crustacea Order Amphipoda Gammaridae Hyale/la azteca (Saussure)
Order Decapoda Astacidae Pacifastacus /eniuscu/us (Dana) Order lsopoda Asellidae Caecidotea sp. Class lnsecta Order Ephemeroptera Baetidae Acentrella insignificans Acentrella turbida Came/obaetidius sp. Baetis bicaudatus Baetis tricaudatus Plauditus punctiventris Tricorythidae Tricorythodes sp. Order Trichoptera Hydropsychinae Cheumatopsyche sp. Hydropsyche sp. Hydroptilidae Hydroptila sp. Leptoceridae Mystacides sp. Nectopsyche sp. Limnephilidae Discosmoecus sp. Order Odonata Aeshnidae Anax sp.
Coenagrionidae Argia sp. Order lepidoptera Pyralidae Petrophila confusa/is Order Coleptera Elmidae Adult Stene/mis sp. Stene/mis sp. Adult Optioservis sp. Optioservis sp. Hydrophilidae Tropisternus sp. Order Hemiptera Corixidae Graptocorixa sp. Hesperocorixa sp. Order Diptera Chironomidae Species A Species B Species C Simulidae Prosimulium sp. Simulium sp. Tipulidae Antocha sp.
Cuffney et al. ( 1997) set limits of impairment based on comparisons between several disparate indices measured. Strong correlation between two or more indices indicated points at which impairment was likely to occur. Impairment limits for the community metric index in the Columbia Basin ecoregion were set at 100 for severe impairment. These limits were based on correlation with the range of values associated with community condition index scores. The NP AI index is calculated as shown below, where: n =the number of constituents that compose the index; Xi= the value of one of n constituents that compose the index; and, Ximin = the minimum value of constituent xi observed. n
Non-Pesticide Agricultural Intensity Index=
L (X;/Ximin)/n i=l
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Table 2. Means (SD) of water quality parameters of the Amon Wasteway used to calculate the NPAI index. USEPA methods are from Greenberg et al. (1992). Parameter Embeddedness (%) Conductivity ( Siem) Turbidity (NTU) Nitrate (mg/L) Nitrite (mg/L) Ammonia (mg/L) Phosphorus (mg/L)
Method Estimation EPA Method 8160 Hach Turbidimeter EPA Method 8171 EPA Method 8507 EPA Method 8038 EPA Method 8048
Off-irrigation 40 845 (88) 2.3(1.4) 2.29 (0.8) 0.013 (0.003) 0.05 (0.1) 0.32 (0.2)
Irrigation Period 40 279 (56) 9.2 (3.2) 1.0 (0.3) 0.009 (0.006) 0.02 (0.01) 0.39(0.12)
Results and Discussion Benthic Invertebrate Community Characteristics Riffle habitat supported the majority oftaxa encountered, and insects comprised the major portion of the average invertebrate taxa richness and abundance. The most abundant taxa observed were Baetis tricaudatus. Baetis bicaudatus, and Tricorythodes sp., all ephemeropterans. Amon Wasteway (elevation 119 m) is at the lowest point in the Yakima watershed and lies within the Columbia Basin ecoregion. Using the Cuffney et al. ( 1997) reference data, the Amon Wasteway had a multimetric invertebrate community condition index of 7 .1 (Table 3 and Figure 1). Table 3. Amon Wasteway macroinvertebrate community condition index score using the Cuffney et al. (1997) reference streams Umtanum Creek and Satus Creek. To scale the index to 10 and weight each metric evenly, the maximum score for any metric was set at 100% of the reference score.
Community Metrics Total EPT Mavllv Richness Stooelly Ratio to Total
41 15 6 4 0.1 5
Caddisllv
4
Funtional Shredder feeding groups
~:~~c~:r-filterer
Predator Total EPT Mavflv Density Stonelly Ratio to Total Caddisllv Funtional Shredder feeding Scraper groups Predator Ratio of intolereant to total abundance Community Condition index score Percent of Reference Condition
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9 3 7 1471 628 142 57 0.0 429 47 429 81 1
0.5 0.5 0.4 0.3 0.3 0.4 0.4 0.3 0.5 0.4 0.4 0.4 0.3 0.3 0.3 0.4 0.3 0.4 0.4 0.5 8.9 100
42 13 7 0 0.0 6 3 10 4
3 2804 2270 1982 0 0.0 289 63 1679 104 0.22
0.5 0.4 0.5 0.0 0.0 0.5 0.4 0.5 0.5 0.2 0.5 0.5 0.5 0.0 0.0 0.3 0.5 0.5 0.5 0.2 7.1 79
10.0 9.0 8.0 7.0
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