This index shows the station number and name, type of data collected, and the office principally responsible for the data collection. A permanent numerical designation for gaging stations has been adopted on a nationwide basis; stations are numbered and listed in downstream order. In the downstream direction along the main stem, all stations on a tributary entering above a main-stem station are listed before that station. A tributary entering between two main-stem stations is listed between them. A similar order is followed in listing stations on first rank, second rank, and other ranks of tributaries. To indicate the rank of any tributary on which a gaging station is situated and the stream to which it is an immediate tributary, each indention in the listing of gaging stations represent one rank. This downstream order and system of indention show which gaging stations are on tributaries between any two stations on a main stem and the rank of the tributary on which each gaging staion is situated.PARTIAL-RECORD STATION. Because the number of streams for which information is desired far exceeds the number of stations feasible to operate for continuous record, the Geological Survey collects limited streamflow data at other stream-gaging sites. When limited streamflow data are collected on a systematic basis over a period of years for use in hydrologic analyses, the site at which the data are collected is called a PARTIAL-RECORD STATION. There are two basic types of partial-record stations: (1) Those operated for the purpose of defining annual maximum discharges and (or) flood hydrographs, crest-stage partial-record stations; and (2) those operated for the purpose of defining annual minimum discharges, low-flow partialrecord stations. Discharge measurements at low-flow partial-record stations are usually made during the periods of base flow when streamflow is primarily from ground-water effluent. In reconnaissance studies of the general quality of streamflow, partial-record stations are operated to cover a range of discharge and the resulting variation in water quality.At each CHEMICAL-QUALITY STATION~ samples are collected for chemical analyses. At most stations, daily samp 1 es are co 11 ected and the water temperature is measured. At dai 1 y stations • where discharge records are available, discharge-weighted average concentrations of selected chemical constituents are computed for each water year.At PERIODICAL BIOLOGICAL STATIONS, densities (colonies per 100 milliliters) of coliforms, fecal coliforms, and fecal streptococci and (or) phytoplankton are determined from 1 to 12 samples per year.At each PERIOD!~ CHEMICAL-QUALITY STATION, a sample for chemical analysis is collected at frequent intervals. An attempt is made to collect samples over as wide a range in discharge as possible. Periodic chemical-quality stations are operated in conjunction with a stream-gaging station or occassionally with a partial-record station.At PERIODIC ORGANIC-QUALITY STATIONS, from 2 to 12 samples per year are collected for analyses. ...

As of January 1, 1989, the surface-water data-collection network in Texas included 373 continuous ^treamflow, 75 continuous or daily reservoir-content, 37 gage height, 15 crest-stage partial-record, 200 data-collection platforms, 7 periodic discharge through range, 27 flood-hydrograph partia 1-record, 27 low-flow partia1-record , 43 daily chemical-quality, 17 continuous-recording water-quality, 87 periodic biological, 11 lake surveys, 159 periodic organic and (or) nutrient, 2 periodic insecticide, 28 periodic pesticide, 19 automatic sampler, 137 periodic minor elements, 126 periodic chemical-quality, 75 periodic physica1-organic, 17 continuous-recording threeor four-parameter water-quality, 36 periodic sediment, 19 continuous-recording temperature, and 29 national stream-quality accounting network stations. Plate 1 shows the location of surface-water streamflow or reservoir-content and chemical-quality or sediment stations in Texas. Plate 2 shows the location of partial-record surface-water stat ions .

Investigations are under the general direction of C.

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