vi CONTENTS Page New York district office locations and addresses . iii Preface. iv List of surface-water stations, in downstream order, for which records are published. vii List of ground-water wells, by county, for which records are published . ix List of discontinued surface-water discharge or stage-only stations . x List of discontinued surface-water-quality stations . xiv List of discontinued crest-stage partial-record stations . xv Introduction. 1 Cooperation. 1 Summary of hydrologic conditions. 2 Surface Water . 2 Water Quality. 8 Ground Water . 8 Special networks and programs . 10 Explanation of records . 10 Station identification numbers . 10 Downstream order system. 11 Latitude-longitude system. 11 Records of stage and water discharge. 11 Data collection and computation . 11 Data presentation . 12 Station manuscript . 12 Data table of daily mean values . 13 Statistics of monthly mean data . 13 Summary statistics . 13 Hydrographs . 14 Identifying estimated daily discharge . 14 Accuracy of the records . 14 Other records available . 15 Records of surface-water quality . 15 Classification of records . 15 Arrangement of records . 15 On-site measurements and sample collection. 15 Water temperature. 16 Sediment . 16 Laboratory measurements. 16 Data presentation . 16 Categories of water-quality data . 17 Frequency-of-sampling notation. 17 Dissolved trace-element concentrations . 17 Change in National Trends Network procedures . 17 Remarks codes . 18 Quality-control data . ..