Water quality data from estuarine variable hydrologic flow regimes during frequent drought

The present article provides water quality data collected from three South Texas Estuaries (Guadalupe, Nueces and Lavaca-Colorado Estuaries) during frequent drought from 2011 to 2014. The data described here are presented in the research article “The relationship between suspended solids and nutrients with variable hydrologic flow regimes” Paudel et al., 2019. Quarterly (i.e. four times a year) surface water quality data presented here were collected from various stations lie along river-estuary mouth to oceanic salinity gradient. Followings are the water quality data provided from Texas estuaries at different river flow regimes: pH, DO, TSS, salinity, chlorophyll-a, secchi disc reading, and nutrients (dissolved nitrogen, dissolved phosphorus and dissolved silicate). Surface inflow was obtained by adding gauged, modeled and return flow.


Data
Water quality data were provided from three micro-tidal Texas estuaries (Guadalupe, Nueces and Lavaca-Colorado estuaries) during 2011e2013 study (Table 1). Quarterly water quality data were collected along the salinity gradient (from river-estuary mouth towards the ocean inlet) from four stations in the Guadalupe, five stations in the Nueces and nine stations in the Lavaca-Colorado estuaries. Dissolved oxygen, pH, temperature, salinity, conductivity, secchi depth, dissolved inorganic nitrogen (nitrite þ nitrate and ammonia), dissolved silicate, dissolved phosphate, TSS, and chlorophyll-a data were provided for surface (i.e. indicated as 0.1 m depth in Table 1) and bottom (20 cm above sediment bottom) water of the three estuaries. In the attached data file, "Date" column represents the collection date. Collection of water samples and measurements of water quality parameters from river inflow source to the estuary was categorized as "Near e near to the river source" and "Far e far to the river source" stations. Abbreviation of the estuaries' name and water quality parameters are provided in the Table 1.
Total surface inflow from a river basin to an estuarine system was estimated from 2011 to 2013 by summing flows originating in gaged and ungagged watersheds ( Table 2). Gaged flows were obtained from USGS streamflow records. Ungaged flows were the sum of three components: (1) computed streamflow, using a rainfall-runoff simulation model, based on precipitation over the watershed, here termed as "Modelled Flow" (2) flow diverted from streams by municipal, industrial, agricultural, and other users, here termed as "Diversion" and (3) unconsumed flow returned to streams, here termed as "Return Flow". Thus, the inflow rates presented were the modeled inflow data where input to each estuary equals to the sum of gaged flow, modelled flow, and return flow, whereas output or amount of water exiting the system would be diversion plus evaporation (Table 2; https://waterdatafortexas.org/ coastal/hydrology). Specifications table   Subject area  Environmental Science  More specific subject area Environmental Chemistry and Estuarine water quality  Type of data  Table, excel file, and SAS code in word docs. How data was acquired Using YSI hydro sonde (YSI Model 556 MPS) for water quality parameters; using Turner design trilogy fluorometer (Model#7200) for chlorophyll-a, and using OIA segmented flow auto-analyzer (Xylem Brand) for inorganic nutrients.

Data format Raw and analyzed Experimental factors
For chlorophyll-a analysis: Water samples were filtered on site and store frozen. For TSS: Samples were filtered in the laboratory and dried weights were obtained.
For Nutrients: Water samples were filtered on site by 0.45 mm polycarbonate filter paper and kept frozen until analysis. Experimental features Data were collected from four stations in Guadalupe, five stations in Nueces, and nine stations in Lavaca-Colorado estuaries that are along river-estuary mouth to oceanic salinity gradient. Water samples were collected for chlorophyll-a, TSS and nutrients analysis. Data source location Water quality data were collected from three estuaries i.e. Guadalupe, Nueces, and Lavaca-Colorado in South Texas. Inflow rate data were obtained from https://waterdatafortexas.org/coastal/hydrology. Data accessibility The data is with this file. Value of the data Data allow investigation of spatial and temporal changes in water quality parameters. Water quality data allow investigation of changes in parameters during occurrence of drought. Salinity data in the Nueces estuary during drought were higher near river-estuary mouth than in oceanic side, and can be compared with the estuarine data in dry regions. Salinity data in the Nueces estuary is the evidence of "Reverse Estuary" condition, therefore data may be of interest to managers and scientists.
The water quality data collected from the three estuaries was used to calculated difference between near and far stations in journal paper, i.e. reference 1 in the list. A weighted average value was calculated prior to running statistical analyses. SAS code used to calculate weighted average is provided here, MS word file names as "SAS code".      Dist ¼ Distance, this is classified into "near" and "far" from the river inflow to primary and secondary estuary. Abbreviation for water quality parameters. Temp ¼ Temperature in degree C. DO ¼ Dissolved oxygen in mg/L. Sal ¼ Salinty Cond ¼ Conductivity in ms/cm. Chl ¼ Chlorophyll-a in mg/L.
TSS ¼ total suspended solids in mg/L.
PO4 ¼ dissolved phosphate in mmol/L. SiO4 ¼ dissolved phosphate in mmol/L. NH4 ¼ dissolved ammonia in mmol/L. NOx ¼ dissolved nitrite þ nitrate in mmol/L. concentration using a methanol extract method [7]. Analysis was performed within 12e16 h of methanol addition.
Nutrient samples were filtered on site using 0.45 mm polycarbonate filter paper and kept on ice until stored frozen, and were processed for analysis within two weeks. Inorganic nutrients data were obtained using an OIA segmented flow auto-analyzer (Xylem Brand, Rye Brook, NY, USA that combines both segmented flow analysis and flow injection analysis techniques with computer controlled sample selection and peak processing. Nutrient chemistries were measured as specified by the manufacturer of OIA segmented flow auto-analyzer. The range of method detection limits (MDL) are 0.1e10 mmol/L for ammonium (NH 4 þ ), 0.02e10 mmol/L for orthophosphate (o-PO 4 ), 0.35e35 mmol/L for silica (SiO 2 ), and 0.02e40 mmol/L for nitrite þ nitrate (NO 3 À þ NO 2 À , here also referred as NO x ). Silica in samples reacts with molybdate in acid medium and is detected as silicic acid or silicate. Matrix matching between the carrier, standards and the sample matrix minimizes refractive index effects on absorbance, which are caused in part by salinity. Artificial seawater is adequate for the analysis of both o-PO 4 and SiO 2 , but matrix matching is important for dissolved nitrogen (N) chemistries and requires the use of low nutrient seawater (LNSW) to accurately detect low (mmol) levels of N in samples. The typical lowest concentration minimum  [8]. In the present study LCMRL was used to prepare standard curve for the analyses.