Geology topics

Matthew S. Milburn

Publications and source records attributed to Matthew S. Milburn.

3 recordsLinked to original sources

USGS2009

Regression models to estimate real-time concentrations of selected constituents in two tributaries to Lake Houston near Houston, Texas, 2005-07

In December 2005, the U.S. Geological Survey in cooperation with the City of Houston, Texas, began collecting discrete water-quality samples for nutrients, total organic carbon, bacteria (total coliform and Escherichia coli), atrazine, and suspended sediment at two U.S. Geological Survey streamflow-gaging stations upstream from Lake Houston near Houston (08068500 Spring Creek near Spring, Texas, and 08070200 East Fork San Jacinto River near New Caney, Texas). The data from the discrete water-quality samples collected during 2005-07, in conjunction with monitored real-time data already being collected - physical properties (specific conductance, pH, water temperature, turbidity, and dissolved oxygen), streamflow, and rainfall - were used to develop regression models for predicting water-quality constituent concentrations for inflows to Lake Houston. Rainfall data were obtained from a rain gage monitored by Harris County Homeland Security and Emergency Management and colocated with the Spring Creek station. The leaps and bounds algorithm was used to find the best subsets of possible regression models (minimum residual sum of squares for a given number of variables). The potential explanatory or predictive variables included discharge (streamflow), specific conductance, pH, water temperature, turbidity, dissolved oxygen, rainfall, and time (to account for seasonal variations inherent in some water-quality data). The response variables at each site were nitrite plus nitrate nitrogen, total phosphorus, organic carbon, Escherichia coli, atrazine, and suspended sediment. The explanatory variables provide easily measured quantities as a means to estimate concentrations of the various constituents under investigation, with accompanying estimates of measurement uncertainty. Each regression equation can be used to estimate concentrations of a given constituent in real time. In conjunction with estimated concentrations, constituent loads were estimated by multiplying the estimated concentration by the corresponding streamflow and applying the appropriate conversion factor. By computing loads from estimated constituent concentrations, a continuous record of estimated loads can be available for comparison to total maximum daily loads. The regression equations presented in this report are site specific to the Spring Creek and East Fork San Jacinto River streamflow-gaging stations; however, the methods that were developed and documented could be applied to other tributaries to Lake Houston for estimating real-time water-quality data for streams entering Lake Houston.

Scientific Investigations Report↗

USGS2007

Base flow (1966-2005) and streamflow gain and loss (2006) of the Brazos River, McLennan County to Fort Bend County, Texas

During 2006–07, the U.S. Geological Survey (USGS), in cooperation with the Texas Water Development Board, did a study to quantify historical (water years 1966–2005) base flow and streamflow gains and losses from two streamflow-measuring surveys (March and August 2006) in the Brazos River from McLennan County to Fort Bend County, Texas. The Brazos River is hydraulically connected to the Brazos River alluvium aquifer, which in turn is hydraulically connected to several underlying aquifers, the outcrops of which occur in laterally adjacent layers generally parallel to the coast (major aquifers, Carrizo-Wilcox and Gulf Coast, and minor aquifers, Queen City, Sparta, and Yegua-Jackson). Hydrograph separation was done using the USGS computer program Hydrograph Separation and Analysis with historical streamflow from 10 USGS gaging stations, three on the Brazos River and seven on selected tributaries to the Brazos River. Streamflow data for computation of gains and losses were collected in March 2006 from 36 sites on the Brazos River and 19 sites on 19 tributaries to the Brazos River; and in August 2006 from 28 sites on the Brazos River and 16 sites on tributaries. Hydrograph separation and associated analyses indicate an appreciable increase in base flow as a percentage of streamflow in the reach of the Brazos River that crosses the outcrops of the Carrizo-Wilcox, Queen City, Sparta, and Yegua-Jackson aquifers compared to that in the adjacent upstream reach (on average from about 43 percent to about 60 percent). No increase in base flow as a percentage of streamflow in the reach of the Brazos River crossing the Gulf Coast aquifer compared to that in the adjacent upstream reach was indicated. Streamflow gains and losses computed for March 2006 for 35 reaches defined by pairs of sites on the Brazos River indicated that five reaches were verifiably gaining streamflow (computed gain exceeded potential flow measurement error) and none were verifiably losing streamflow. Four of the five gaining reaches are in the outcrop areas of the Carrizo-Wilcox and Yegua-Jackson aquifers. The results of the synoptic gain and loss surveys are consistent with the results of the base-flow analysis of historical streamflow. Appreciable increases in streamflow, apparently the result of increases in base flow, occur in the reach of the Brazos River that crosses the outcrops of the Carrizo-Wilcox, Queen City, Sparta, and Yegua-Jackson aquifers.

Texas↗

USGS2005

Water-quality assessment of Lake Houston near Houston, Texas, 2000-2004

Lake Houston is a major source of public water supply and recreational resource for the Houston metropolitan area, Texas. Water-quality issues of potential concern for the lake have included nutrient enrichment (orthophosphorus, total phosphorus, nitrite plus nitrate) and aquatic life use (dissolved oxygen). The , in cooperation with the City of Houston, collected water samples from three sites in Lake Houston and from two streams that discharge to the lake during 2000–2004. Nitrogen compounds, phosphorus, suspended sediment, organic carbon, turbidity, chlorophyll-a, and selected pesticide compounds in water were assessed for all sites. Waterquality conditions of the lake and inflow streams were assessed, and loads and yields were computed for selected constituents in the streams. Selected constituents from samples collected in Lake Houston during 1990–2004 were tested for trends. The three sites sampled in Lake Houston characterized water available to the City of Houston pumping station (site AC), water entering the lake from the largely rural eastern subbasin (site EC), and water entering the lake from the more urbanized, western subbasin (site FC). Most constituent concentrations were largest at site FC, smallest at site EC, and intermediate at site AC. Organic nitrogen was the dominant form of nitrogen in samples collected at all sites. Nitrite plus nitrate concentrations were largest at site FC. Total phosphorus concentrations in all samples were larger than that recommended by the U.S. Environmental Protection Agency to limit aquatic growth in reservoirs. There was a wide range in suspended-sediment concentrations and turbidity in the lake. Twelve pesticides were detected. Atrazine and its breakdown product, 2-chloro-4-isopropylamino-6-amino-s-triazine (CIAT), were the most commonly detected pesticides; concentrations of atrazine were larger than the U.S. Environmental Protection Agency maximum contaminant level of 3.0 micrograms per liter in two samples at site FC. The relative contributions to the water quality of Lake Houston from the eastern and western subbasins were examined by collecting water samples in Cypress Creek and East Fork San Jacinto River. Nitrate and pesticide concentrations were larger in Cypress Creek than in East Fork San Jacinto River. In Cypress Creek, nitrate was the primary form of nitrogen at low flows. Atrazine exceeded 3.0 micrograms per liter in three of 17 samples, with the maximum measured concentration of 21.3 micrograms per liter. In East Fork San Jacinto River, organic nitrogen was the primary form of nitrogen. Atrazine was detected in six of 15 samples. The maximum atrazine concentration was 0.233 microgram per liter. Constituent yields allowed direct comparison of loads from Cypress Creek and East Fork San Jacinto River. In Cypress Creek, storm yields of nitrite plus nitrate nitrogen for high flows ranged from 8 to 45 pounds per square mile per day; in East Fork San Jacinto River, the maximum storm yield for high flows was 1.47 pounds per square mile per day. At low flows, the median daily yield of dissolved phosphorus from Cypress Creek was 84 times larger than the median daily yield from East Fork San Jacinto River; at high flows, it was 16 times larger. At high flows, the maximum daily yield of atrazine from Cypress Creek was 460 times larger than the maximum daily yield at high flows from East Fork San Jacinto River. The concentrations of most constituents at Lake Houston sites showed no trend during 1990–2004; however, significant trends overall or for particular seasons, or both, were detected at some sites for nitrite plus nitrate, dissolved phosphorus, dissolved organic carbon, chlorophyll-a, and diazinon (2000–2004 data only for diazinon).

Texas↗