Trends in Base Flows and Extreme Flows in the Beaver Kill Basin, Catskill Mountains, New York, 1915 – 94 Open-File Report 98 – 65
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Prepared in cooperation with the Town of Rockland Trends in Base Flows and Extreme Flows in the Beaver Kill Basin, Catskill Mountains, New York, 1915 – 94 Open-File Report 98 – 65 U.S. Department of the Interior U.S. Geological Survey Cover Photo: Beaver Kill and elevated Route 17, by Jock Conyngham Trends in Base Flows and Extreme Flows in the Beaver Kill Basin, Catskill Mountains, New York,1915-94 By Barry P. Baldigo U.S. GEOLOGICAL SURVEY Open-File Report 98-65 Prepared in Cooperation with the Town of Rockland science for a changing world Troy, New York 1999 i U.S. DEPARTMENT OF THE INTERIOR BRUCE BABBITT, Secretary U.S. GEOLOGICAL SURVEY Charles G. Groat, Director The use of firm, trade, and brand names in this report is for identification purposes only and does not constitute endorsement by the U.S. Geological Survey For additional information write to: Copies of this report can be purchased from: U.S. Geological Survey U.S. Geological Survey 425 Jordan Road Branch of Information Services Troy, NY 12180-8349 Box 25286 (518) 285-5600 Denver, CO 80225-0286 ii CONTENTS Abstract . 1 Introduction . 2 Purpose and Scope. 2 Acknowledgments . 4 Study Area . 4 Methods . 5 Trends in Base Flows and Extreme Flows. 6 Relation of Stream Stage to Discharge. 6 Discharge-Duration Curves . 7 Peak and Bankfull Discharges . 7 Annual Average Discharge and Base Flow. 11 Monthly Average Discharge and Base Flow. 12 Annual 1-day and High Flow . 12 Monthly 1-day Low and High Flow . 13 Limitations of Analyses . 14 Suggestions for Additional Study . 15 Conclusions . 16 Selected References. 16 FIGURES 1. Maps showing: A. locations of active and inactive USGS streamflow gaging stations and NY 17 in the Beaver Kill Basin and, B. the basin’s location in relation to the Catskill Park in southeastern New York State. .3 2. Graphs showing discharge as a function of stage before and after 1965 at: A. the Cooks Falls site and, B. the Little Beaver Kill site. (Locations are shown in figure 1.) . 7 3. Discharge-duration curves at the Little Beaver Kill site for the 14 years before 1965 and the 14 years after. 8 4. Graphs showing recurrence probabilities of instantaneous peak flows at (a) the Cooks Falls site and (b) the Prattsville site for 30 years before 1965 and the 30 years after. 8 5. Total annual precipitation, average annual discharge and base flow, and the ratio of annual average base flows to annual average flows (annual B/A flow) at the Cooks Falls site, 1914-94. 9 6. Total annual precipitation, average annual discharge and base flow, and the ratio of annual average base flows to annual average flows (annual B/A flow) at the Little Beaver Kill site, 1924-80. 11 7. Total July precipitation, average July discharge and base flow, and the ratio of July average base flows to July average flows (July B/A flow) at the Cooks Falls site, 1914-94. 12 8. Annual 1-day high flows at the Little Beaver Kill and Cooks Falls sites, 1925-94. 13 Contents iii TABLES 1. Drainage area, annual average daily discharge, and average total annual runoff of streams at study sites in the Beaver Kill Basin and at the control site in the Schoharie Creek basin, NY. .. 4 2. Estimated peak flows of 2-, 10-, 25-, and 100-year recurrence intervals for Beaver Kill at Cooks Falls, N.Y., and for three streams in nearby basins before and after 1965. 10 CONVERSION FACTORS Multiply By To Obtain Length foot (ft) 0.3048 meter mile (mi) 1.609 kilometer Area square mile (mi2) 2.590 square kilometer Volume cubic feet (ft3) 0.02832 cubic meter Flow cubic foot per second (ft3/s) 0.02832 cubic meter per second iv Contents Trends in Base Flows and Extreme Flows in the Beaver Kill Basin, Catskill Mountains, New York, 1915-94 By Barry P. Baldigo ABSTRACT after 1965 are not statistically significant, but, changes in flow-duration curves and annual peak flows are Long-term records from five streamflow-gaging evident. Flow-duration curves at this site indicate that stations within and near the 300-square mile Beaver there is a 16 percent increase in average daily flows Kill Basin were analyzed to determine whether after 1965. Annual peak flow data indicate that peak construction and presence of New York State Route 17 flows from storms recurring at 2-year (and longer) (NY 17), which was completed in the late 1960’s, intervals after 1965 are significantly larger than those could have altered hydrologic processes in the basin that recur at the same frequencies before 1965. The and thereby adversely affected the basin’s trout lack of comparable increases in peak flows from populations. The hypothesis investigated is that NY 17 has altered surface-water and shallow ground-water several nearby reference sites after 1965 indicate that flowpaths where it parallels the stream and has the observed increases in peak flows may be unique to increased runoff rates and thereby (1) increased the the Beaver Kill Basin. range in stream discharge (prolonged the base flows, Flow-duration curves and many base-flow and decreased the low flows, and increased the high flows), high-flow statistics for the small tributary paralleled by and (2) altered stream-channel morphology through NY 17 in the in the upper reaches of the basin (Little increased volume and velocity of stormflows. Beaver Kill at Livingston Manor) appear to be Analyses of base flows, discharge-duration curves, considerably altered since NY 17 was constructed. stage-to-discharge relations, peak and bankfull Flow-duration curves at this site indicate that there is discharges, and flow extremes at a downstream about a 54 percent increase in average daily flows after (Beaver Kill at Cooks Falls) and a small tributary 1965. Increases in the ratio of average annual base (Little Beaver Kill at Livingston Manor) site provide flow to average annual flow until 1965 then only limited evidence that NY 17 affected hydrologic subsequent decreases suggest an extreme affect of NY processes within the basin. These effects are best 17 on hydrology of the subbasin. The effect of NY 17 indicated by significant increases in the magnitude and on hydrology of the Little Beaver Kill subbasin cannot (or) the frequency of moderate to large discharges be defined with certainty, however, because the flow (exceedence probabilities) on an instantaneous basis at record after 1965 is too short; discharge monitoring the Beaver Kill at Cooks Falls site after 1965. was discontinued in 1981. Increases in stormflows can not be attributed solely to The increases in peak stormflows in the lower NY 17, however, because the trend was evident long Beaver Kill basin through the period of record may before NY 17 was constructed. Changes in land use in have increased the rates of bed-sediment erosion parts of the watershed may have contributed to gradual (degradation) and deposition and accelerated changes and continuous increases in stormflows throughout the in stream-channel morphology, however, these entire 80 (plus) years of record. possible effects were not examined. Suggestions for Changes in most base-flow and low-flow statistics further investigation of the effects of NY 17 and of for the downstream (Beaver Kill at Cooks Falls) site other factors on hydrology, channel morphology, fish Abstract 1 habitat, and fish populations in the Beaver Kill Basin drainage-culvert system that directs runoff from NY include (1) addition of streamflow gages or a crest- 17, were also built during the period (J. Conyngham, stage gage network at critical locations, (2) a review of oral commun., 1996). Features and structures such as engineering records and other aerial photographs for these have been shown to alter shallow ground-water indications of changes in channel morphology, (3) flow paths and flow rates, channel storage and compilation of temperature data and modeling spatial recharge, and base flow of nearby streams, and these extent and magnitude of stressful summer changes, in turn, can alter the elevation and slope of temperatures (to selected trout species), and (4) the water table and diminish the ground-water confirming the extent and severity of toxic thermal contribution to streams, thereby decreasing base flows episodes using in-situ fish toxicity tests. and increasing the range of discharge fluctuations (reducing flow stability) (Blackport and others, 1995). Decreased channel sinuosity and roughness, and INTRODUCTION increased channel gradient (through channel truncation and armoring), can increase the velocity, Trout fishing in the Beaver Kill, in the southwestern power, and magnitude of stormflows and thereby alter Catskill Mountains of New York (fig. 1), has long been streambed morphology and decrease the overall area a major source of income to the region (Francis, 1983). and stability of stream-channel habitat available to Concern has increased recently over the hydrologic and resident fish (Binns, 1979; Fausch and others, 1988). thermal effects that recent development and a four-lane If changes in habitat are extensive, rates of fish State highway (NY 17), may have had on fish habitat survival and reproduction can decline, and the density and trout productivity in the Beaver Kill since its of their populations may decrease (Simonson and construction in the 1960’s (J. Conyngham, Trout others, 1993). Unlimited, oral commun., 1996). Potential hydrologic changes within the basin that could be associated with NY 17, such as decreased base flow (dry-weather flow) Purpose and Scope and increased and prolonged extremes in low- and high-flow conditions, are suspected to have altered the In 1996, the U.S. Geological Survey (USGS), in aerial extent (quantity) and stability of physical habitat cooperation with the Town of Rockland in Sullivan within the Beaver Kill and, thereby, adversely affected County, began a study to determine whether resident fish populations.