ASSESSMENT OF DEWATERING IMPACTS ON STREAM FISHERIES IN THE ARKANSAS AND CIMARRON RIVERS" Frank B. Cross, Randall E. Moss and Joseph T. Collins Museum of Natural History University of Kansas, Lawrence, Ks. Introduction This report concerns the status of fishes in the Arkansas River and streams south of the Arkansas mainstream in Kansas. It is based mainly on visits to 35 sites on the Arkansas River, Cimarron River, and intervening tributaries (Fig. 1) on 16-23 July 1983. Fish collections were made at 23 sites having water; stream beds were dry at 12 sites. Supplementing our collections are other collections made from 1979 through 1983 by O. T. Gorman and D. Wiseman of the University of Kansas, Dr. Robert Clarke of Emporia State University, K. Brunson and other personnel of the Kansas Fish and Game Commission, and Dr. D. A. Distler and students at Wichita State University. Their collections increase the number of localities represented to 46, and provide replicate samples from some of our 35 sites. Our objectives were to locate populations of several species characteristic of the western Plains segment of the Arkansas River basin; to assess the extent to which these fishes are threatened, by comparison of current and historical distributional records; and to examine the relationship between changes in stream flows and changes in the status of each species. The species of "primary concern" are the Arkansas River form of the Speckled chub (Hybopsis aestivalis tetranemus), Flathead chub (Hybopsis gracilis), Emerald shiner (Notropis atherinoides), River shiner (Notropis blennius), Arkansas River shiner (Notropis girardi), Plains minnow (Hybognathus placitus), Plains killifish (Fundulus zebrinus with which F. kansae is considered conspecific), and Arkansas darter (Etheostoma cragini). Additional species that were captured in 1979-83 are discussed briefly. The various collections included a total of 42 species of fishes. Records of fishes cited in this report extend from 1853 to the present. Reports by Cragin (1885) and Gilbert (1885,1886) provide baseline information on fishes in the western part of the basin, especially the Arkansas River at Garden City and the Medicine Lodge drainage in Barber County during the early years 1 Nongame Wildlife Contract No. 46, Kansas Fish and Game Commission and The University of Kansas (KU 5400-0705). Field work was conducted by the authors and Kelly J. Irwin of Topeka, and at some sites by Ken Brunson, Kansas Fish and Game Commission. All photographs in this report are by J. T. Collins. Figure 1. Location of all sites visited during this study (1979-1983). Large solid circles represent sites containing water and which were sampled in 1983. Open circles represent sites without water during this survey in July 1983. Small solid circles repre- sent sites sampled by 0. T. Gorman in 1979. 2 of settlement. Jordan's (1891) list of species from the "Arkansas River at 1 Wichita" affords an interesting but less secure baseline on the fauna in the lower mainstream; those fishes may have come from various streams in the Wichita area rather than the single site reported. Data available from a few collections made in the 1920's and 1940's are cited. Most of the collections useful for comparison with the 1979-83 series were made in the period 1951-67 by personnel of the University of Kansas. Sampling methods were similar in those collections and the 1979-83 series of collections: haul seines of 6-foot to 30-foot length, 1/8 to 3/8-inch mesh, operated by personnel with comparable training. The same persons were involved in many of the collections. Their main objective was to determine species composition at each site. Early collections did not include counts of fishes captured, but the terms "abundant, common, frequent, scarce, and rare" were used in field notes on many of the collections to indicate relative abundance of the species taken. Specimens catalogued into research 1 collections of the Museum of Natural History provide data on minimum numbers captured in several instances critical for determination of changes in the abundance of species within the 30-year period covered by these records. From about 1962 to date, quantitative records accompany most collections (counts of individual fish of each species caught). Results of stream surveys by personnel of the Kansas Fish and Game Com- mission, chiefly in 1974-76, are incorporated into the report where those records seem appropriate. The KFG collections were intensive on short stream segments, involving use of electrofishing gear or toxins as the principal sampling method. Differences in field methods and objectives of those surveys dictate caution in comparing the KFG results with ours. Stream-flow records were obtained from the U. S. Geological Survey, Water Resources Section, through the cooperation of Dr. Paul Jordan of that agency. Our purpose was to explore possible cause-and-effect relationships between historic changes in discharge and changes in the composition of fish faunas throughout the region surveyed. Therefore gaging-station data were selected on the basis of the number of years each station has operated, and its location with respect to sites from which fish collections are available. The results of this project are arranged under the following headings: 1) Hydrologic records; 2) Fish faunas and habitat notes at sites (or stream reaches)for which an historic record is available; 3) Accounts of species of primary concern; 4) Accounts of other species captured in 1979-83; 5) Summary; and 6) Appendix - field notes on collections made in 1983. 3 HYDROLOGIC RECORDS Analysis of Discharge Rates at USGS Gaging Stations Records of mean daily discharge, expressed as cubic feet per second (cfs) were examined for the following USGS stream gaging stations: Arkansas River at Syracuse, Hamilton County; Dodge City, Ford County; Great Bend, Barton County; and Wichita, Sedgwick County; Cimarron River at bridge on Highway K-23, Meade County; Crooked Creek near Nye, Meade County; Medicine Lodge River near Kiowa, Barber County; and Ninnescah River near Peck, Sumner County. The records used were summarized in three ways at each station. The first data set indicated the number of days in each water year (ending September 30) in which the mean daily discharge fell within serially arranged classes (discharge ranges). That summary also included flow duration tables giving daily rates of discharge that were exceeded at specified frequencies (10% to 95% of the time), within certain periods of years. The periods selected for comparison were: origin of records through 1942 (or through 1965, if few records existed prior to 1942 at a station); 1943 through 1965; 1966 through 1976; and 1977 through 1982, the last year for which such summaries were available. The second data set consisted of summaries like the first set, organized on a monthly basis rather than annual basis. The third data set listed the peak flows (highest instantaneous discharge rates rather than mean daily rates) recorded in each year together with the dates on which they occurred. Chronological trends at each station are discussed in the following paragraphs. The ranges and seasonal patterns of discharge are described in successive periods of years; then, attention is given to the incidence of high flows, for reasons relating to reproductive requirements of some fishes of primary concern in this report. Syracuse Discharge records at Syracuse are divided into four periods (1904, 1905, and 1923-42 = 22 years; 1943-65 = 23 years; 1966-76 = 11 years; and 1977-82 = 6 years). Figure 2 is a flow duration curve that indicates the percent of time (days) discharge exceeded the values plotted, in each of the four periods. In 1904-42, flows greater than 980 cfs occurred about 10% of the time. At the other extreme, low-flows 4 - 800 1 400 200 100 W 80 • 60 10 8- 0 4 2 1977-82 \ 1966-76 (1) 30 40 50 60 70 80 90 100 Percent Figure 2. Flow duration in the Arkansas River at Syracuse, Hamilton County, Kansas. Rates of discharge that were exceeded 10%, 25%, 50%, 70%, 75%, 90% and 95% of the time are plotted for four successive periods of years. Lines intersecting the x-axis indicate flows less than 1.0 cfs. Data from gaging station records of the U.S. Geological Survey. 5 (those exceeded 90% of the time) were only about 5 cfs; flows less than 3 cfs occurred 5% of the time. The steep incline of this curve reflects the natural variability of discharge rates in the Arkansas River in western Kansas, although the rates recorded may already have been influenced by irrigation diversions, which began more than a century ago Beginning in 1942, John Martin Reservoir in eastern Colorado modified the flow regime by retaining water, chiefly during high flows, for later release to meet irrigation needs. Thus, in the period 1943-65, flows of 10% frequency at Syracuse were significantly reduced -- from 980 to 450 cfs -- but discharge rates of 50% or greater frequency increased (Fig. 2). For example, flows exceeded 75% of the time averaged only 17 cfs prior to impoundment, but increased to 62 cfs for the 23-year period following construction of John Martin Reservoir. The initial effect of the impoundment was to flatten the curve by moderating both extremes (reducing peak flows and increasing minimum flows). In the third period (1966-76) flows of 10% to 90% frequency declined slightly (Fig. 2), but "minimum" flows (95% frequency) dropped from 5.7 cfs to approximately 1 cfs. The most dramatic reduction in discharge rates of the Arkansas at Syracuse occurred in the final period (1977-82; Fig. 2). The incline of the duration curve for 1977-82 nearly parallels that for the original period (1904-42), but the discharge rates at each level of frequency are only one-fourth to one-tenth those in the original period.