Abstract: Ground water continues to discharge into the Navidad and Lavaca Rivers by seepage out-flow even though large amounts of ground water are pumped for irrigation. Although a reduction in streamflow probably has occurred, a complete loss of the low flow of the streams by infiltration to a lowered water table seems remote. The large ground-water withdrawals will continue to cause land-surface subsidence, which will range from 0.012 foot to more than 0.026 foot per year. A minimum of about 0.013 to 0.015 foot of annual subsidence at the upper ends of the proposed reservoir and a maximum of about 0.019 foot near the dam site can be expected. Structural failures of manmade features have not occurred from the subsidence, but regional changes in the land slope have occurred and will continue . Numerous fault traces have been mapped in the area, but most of the faults are inactive. If movement along the fault planes should occur, the vertical displacement probably will not exceed the total subsidence.

Abstract: The discharge-weighted average concentrations of dissolved solids, chloride, and sulfate for many of the principal streams in Texas are less than 500 mg/1 (milligrams per liter), 250 mg/1, and·250 mg/1, respectively. At 65 of 131 sites on streams that were sampled at least 10 times, the biochemical oxygen demand of at· least half the samples exceeded 3,0 mg/1. At 20 of the sites, the dissolved-oxygen content of at least !half the samples was less than 5.0_ mg/1. The higher concentrations of minor elements usually were detected in waters from urban areas, indicating a relation to man's activities. Small amounts of some pesticides are widely distributed in low concentrations. The higher concentrations usually were detected in waters from urban areas. Small amounts of some of the pesticides studied are widely distributed in surface waters in Texas. Some of the more widely distributed pesticides were 2,4,5-T at 96 sites, diazinon at 80 sites, 2,4-D at 78 sites, dieldrin at 77 sites, Silvex at 47 sites, DDT at 67 sites, lindane at 59 sites, DDD at 51 sites, DDE at SO sites, and chlordane at 38 sites.

From purpose and scope: The purpose of this study is to provide data and hydrologic interpretations for use by the Bureau of Reclamation in evaluating and quantifying natural water losses that are known to occur along some reaches of the Nueces River. Specifically, this report presents data and analyses describing the conveyance characteristics of that reach of the Nueces River from Cotulla to Simmons.

From abstract: A statistical summary of the available continuous and once-daily discharge, specific-conductance, dissolved oxygen, temperature, and pH data collected at NASQAN stations during the 1973-81 water years and documentation of the period of record on which the statistical calculations were based are presented.

Abstract: This report contains lists of stations at which the U.S. Geological Survey collects water data either on a continuous basis or at least on a daily basis. The files contain daily values for streamflow, reservoir levels or contents, water temperatures, specific conductance, sediment discharge plus data for several other quality parameters that are measured by means of monitoring equipment or result from analyses of samples collected on a daily basis. The stations are listed according to station number within each State. The report lists the availanle retrieval options, the machine -readable output options, user charges and how to obtain data.