Texas Water Development Board Research Articles

Water Quality and the First-Flush Effect in Roof-Based Rainwater Harvesting, Part II: First Flush

Rainwater runoff samples from a range of roofing materials were temporally collected from 19 small-scale roof structures and two commercial buildings through simulated and actual storm events, and the concentrations of polycyclic aromatic hydrocarbons (PAHs), phosphorus flame retardants (PFLs), and pyrethroid insecticides and other water quality parameters were analyzed. In Part I of this research, the concentrations of these contaminants in roof runoff and soils receiving runoff from a range of roofing materials were evaluated. In Part II, recommendations have been developed for a first-flush exclusion to improve the quality of water harvesting for nonpotable uses. Recommendations focus on a first-flush diversion based on mass removals of total suspended solids (TSS) and PAHs linked to conductivity measurements throughout a storm event. Additionally, an upper-confidence limit (UCL) was constructed to determine the minimum diversion required to obtain 50, 75, 90, and 95% mass removal of TSS and PAH contaminants. The majority of TSS were produced during the initial 1.2 mm of runoff. Likewise, the majority of PAHs were removed during the initial 1.2 mm of runoff, except for the asphalt shingle roofs, where high PAHs were observed after 6 mm of runoff. The Texas Water Development Board (TWDB)-recommended first-flush diversion of one gallon for every 100 square feet of rooftop was not always adequate for removing 50% of TSS and PAHs from the roofs. Rainwater runoff conductivity decreased drastically between 1.2 to 2.4 mm of rainwater runoff. Diverting the first flush based on conductivity has the potential to also divert the majority of TSS and PAHs in roof runoff.

Case Study of Emerging Groundwater Management Issues at the Forefront of Large-scale Production from a Confined Aquifer: The Vista Ridge Project

Continued population growth, increased demands for water and declining water availability are statewide water concerns in Texas. The development and movement of water from where it is to where it is needed brings with it benefits to the receiving area and concerns for the area of origin. The Vista Ridge project serves as an on-point example and case study of such concerns and processes that can mitigate, in part, negative impacts that are informative to other Texans who will soon be facing similar pressures.. Impacts on the water levels in existing wells made the Vista Ridge Project a focus of significant public discussion in 2022, including Texas House and Senate interim session hearings. This paper spotlights groundwater management issues prominent in the Vista Ridge Project that will likely be of concern with other Texas groundwater projects in the near future. These issues involve well mitigation, significant impacts from groundwater production across groundwater conservation district boundaries, meaningful consideration of nine factors in Texas Water Code §36.108(d), the balance between limiting groundwater production, development of fair share doctrines, the role of the Texas Water Development Board in the

Hydrological Transport and Fate of Brackish and Inorganic Contaminants with Anthropogenic Influence

The objective of our study is to estimate the contamination concentrations in the Permian Basin, US. A total of 481 observation samples were chosen within the following study areas: Andrews, Martin, Midland, Ector, Crane, and Upton Counties. The Dockum, Pecos Valley, Edwards-Trinity Plateau, and Ogallala aquifers were evaluated for inorganic contaminants. Level reports for parameters such as Arsenic (As), Nitrate (NO3−), Fluoride (F), Chloride (Cl), total dissolved solids (TDS), and Uranium (U) were provided by the Texas Water Development Board (TWDB) analyzed with other counties. We demonstrated the average level in each county with different time periods: 1992–2005 and 2006–2019. Our results were compared with the Environmental Protection Agency (EPA) standards and concluded the safety of water consumption in the study areas. We concluded that inorganic pollutants resulted mainly from human impacts such as agriculture, fertilizers, and energy developments. This research offers significant information about inorganic pollutants and brackish aquifers in the Permian Basin, US, contributing to our understanding of how groundwater resources respond to contaminations in dry regions. With freshwater becoming scarcer in arid climates such as the Permian Basin, US, it is important to ensure successful water management in these dry and arid locations.

Technical Overview of the TexMesonet—A Network of Networks for Improved Water Management and Prediction in Texas

Abstract Accurate, timely, and accessible meteorological and soil moisture measurements are essential for a number of applications including weather forecasting, agricultural decision-making, and flood and drought prediction. Such data are becoming increasingly available globally, but the large number of networks and various data reporting formats often make utilization of such data difficult. The TexMesonet is a “network of networks” developed within the state of Texas to collect, process, and make public data collected from more than 1700 monitoring stations throughout the state. This paper describes the TexMesonet, with special attention paid to monitoring sites installed and managed by the Texas Water Development Board. It also provides a case study exemplifying how these data may be used and gives recommendations for future data applications.

Unincorporated and Underserved: Critical Stormwater Infrastructure Challenges in South Texas Colonias

Most strategies for addressing environmental and climate injustices in the United States are predicated on strong local governance tools, oftentimes tied to land use and zoning. There is, however, no right to local governance in the United States—a serious issue considering an estimated one-third of residents live in unincorporated areas. As a result, many unincorporated communities struggle to receive adequate stormwater management, particularly in the face of climate change. In this article, the effects of unincorporated status are examined in relation to (in)equitable access to stormwater management in the Lower Río Grande Valley of South Texas. Within this region, low-income unincorporated communities known as “colonias,” unincorporated neighborhoods along the U.S./Mexico border that historically lack access to basic services and infrastructure, form the primary focus of this case study. Recently, several major rainstorms provoked the Texas Water Development Board to identify the scope and source of colonia flooding through a flooding survey. Evaluating this assessment against interviews and participant observations from 2014 to 2020, the source of flood injustice in rural communities emerges as limited available flood mitigation strategies, consistent “no's” from government agencies at all levels, and complex flooding sources complicating equitably addressing flood risks. From this case study, the article suggests how planners and policymakers can provide a path forward to equitably protect unincorporated low-income communities from risks and hazards. Primarily, the lack of mitigation strategies for unincorporated communities constitutes a major injustice when addressing environmental risks and hazards.

Hydrogeochemical Evaluation of Groundwater Quality Parameters for Ogallala Aquifer in the Southern High Plains Region, USA.

The purposes of this study are to analyze the groundwater quality of the Ogallala Aquifer and evaluate the hydrological characteristics in the southern High Plains region of the Permian Basin, Texas. Levels of chloride, fluoride, nitrate, selenium, pH, and total dissolved solids (TDS) were analyzed for the period 1990–2016. Data concerning a total of 133 wells were collected from the Texas Water Development Board (TWDB), which is an open database provided by the US government. The average levels of contaminants were compared to their respective Maximum Contaminant Levels (MCL) stipulated by the Environmental Protection Agency (EPA). The study area experienced high concentrations of most parameters including chloride, fluoride, nitrate, selenium, and TDS, within the contaminants’ respective MCLs. Borden and Dawson counties experienced the highest overall amounts of groundwater pollutants. Possible sources of each contaminant are discussed, with oil and gas activities, agricultural practices, and other human actions impacting the conditions. This research provides important information about groundwater quality of the Ogallala Aquifer and contributes to understanding the response to development in the Permian Basin, Texas.

New Geochemical Framework and Geographic Information System Methodologies to Assess Element Occurrence, Persistence, and Mobility in Groundwater and Surface Water

This study presents a geochemical framework and geographic information system (GIS) method for assessing the intrinsic potential of surface water and groundwater to mobilize arsenic, molybdenum, selenium, uranium, and vanadium. The method was created using published groundwater and surface water geochemical data from the National Uranium Resource Evaluation database for 2302 groundwater and 915 surface water samples. The method was evaluated using published groundwater geochemical data from the Texas Water Development Board. Geochemical data were analyzed in GIS. Samples were categorized by environmental condition, which was determined by using reduction–oxidation—as indicated by pe—and pH ranges for each sample based on geochemical mobility frameworks developed by Smith (2007) and Perel’man (1986). Reduction–oxidation and pH influence the occurrence, persistence, and mobility of arsenic, molybdenum, selenium, uranium, and vanadium in groundwater and surface water. Reduction–oxidation categories were assigned to water samples using concentrations of redox-active constituents, including dissolved oxygen, iron, manganese, and sulfur. The presence of iron substrates and hydrogen sulfides were considered in relation to mobility mechanisms. Twelve-digit hydrologic unit code (HUC) boundaries were used in GIS as analysis areas to determine the most commonly occurring environmental condition in each HUC. The resulting maps identify the environmental conditions in different areas that can be used to identify where the elements are mobile. This methodology provides a systematic approach to identify areas where elements in groundwater and surface water may occur and persist and may be transferable to other locations.

Minimizing Errors in the Prediction of Water Levels Using Kriging Technique in Residuals of the Groundwater Model

Groundwater monitoring and water level predictions have been a challenging issue due to the complexity of groundwater movement. Simplified numerical simulation models have been used to represent the groundwater system; these models however only provide the conservative approximation of the system and may not always capture the local variations. Several other efforts such as coupling groundwater models with hydrological models and using geostatistical methods are being practiced to accurately predict the groundwater levels. In this study, we present a novel application of a geostatistical tool on residuals of the groundwater model. The kriging method was applied on the residuals of the numerical model (MODFLOW) generated by the TWDB (Texas Water Development Board) for the Edwards–Trinity (Plateau) aquifer. The study was done for the years 1995 through 2000 where 90% of the observation data was used for model simulation followed by cross-validation with the remaining 10% of the observations. The kriging method reduced the average absolute error of approximately 31 m (for MODFLOW simulation) to less than 5 m. Furthermore, the residuals’ average standard error was reduced from 9.7 to 4.7. This implies that the mean value of residuals over the entire period can be a good estimation for each year separately. The use of the kriging technique thus can provide improved monitoring of groundwater levels resulting in more accurate potentiometric surface maps.

Toxicity of silver nanoparticles on the clam Ruditapes decussatus assessed through biomarkers and clearance rate * *(This manuscript represents the views of the authors, and not those of the Texas Water Development Board)

The current bioassay aims the evaluation of the ecotoxicity of the silver nanoparticles (NPs) (100 and 200 μg l−1) on Ruditapes decussatus after 48 h and 7 days of its exposure. The biochemical analyses performed at gills and digestive glands showed a disturbance of the antioxidant system following the exposure of clams to Ag NPs. The catalase activity was induced and varied significantly depending on the concentration of Ag NPs and the exposure time, as well as the organ analysed. Simultaneousely, a decrease in Gluthation S-Transferase activity was observed at all concentrations tested and organs considered. The acetylcholinesterase activity results confirmed that the threshold of Ag NPs able to disrupt the the cholinergic system was less than 100 μg l−1. In overall, silver nanoparticles had a significant caused antagonistic effect on clams in both oxidative- and cholinergic states. Furthermore the findings obtained in this study demonstrated that Ruditapes decussatus can employed as a potential bioindicative species in the assessment of the toxicity of such an emerging material as Ag NPs.

Estimating the Occurrence of Arsenic in Residential Drinking Water and Population with Potential High Arsenic Exposure in Texas

BACKGROUND AND AIM: Exposure to arsenic from drinking water raises a public health issue due to its prevalence and potential health effects. The purpose of this study was to assess the occurrence of arsenic levels in residential drinking water and estimate the population potentially exposed to high arsenic levels from consuming drinking water in Texas. METHODS: Data of arsenic testing in both public water systems (PWS) and domestic wells in 254 Texas counties were obtained from the Texas Commissions of Environmental Quality and the Texas Water Development Board to estimate the average arsenic concentration and number of populations potentially exposed to levels above the maximum contamination level (MCL), 10 µg/L over last 10 years. Additionally, the logistic regression model was fitted to estimate the odds of exceeding an MCL by region, water source, well depth, aquifer type, and social vulnerability index. RESULTS:In PWS, 2% of the sites had arsenic over an MCL with a maximum average level of 83.8 µg/L. The odds of an MCL violation were significantly higher in water systems sourced from groundwater and in rural and socially vulnerable areas. However, in private wells, 9.2% of the wells showed water arsenic levels greater than an MCL with average levels up to 569 µg/L. The wells 50-200 feet in depth, sourced from Ogallala and Gulf Coast Aquifers, and in socially vulnerable areas showed significantly higher detections of arsenic levels greater than the MCL. It was estimated that 323,741 people in 74 counties were potentially exposed to arsenic in residential drinking water over the MCL. CONCLUSIONS:Our results facilitated the evaluation of the current arsenic contamination in drinking water and the identification of areas of potential high arsenic exposure. Broader water screening and biomonitoring to determine the burden of arsenic exposure are required to protect public health in these areas. KEYWORDS: Arsenic, Drinking Water, Water Quality, Environmental Health

Texas Reimagines the Fight Against Floods

The Texas Water Journal invited former Chairman of the Texas Water Development Board (TWDB) and current Chairman of the Public Utility Commission of Texas, Peter Lake, to share his thoughts on the 2019 state flood assessment and other framework efforts. The opinion expressed in this commentary is the opinion of the individual author and not the opinion of the Texas Water Journal or the Texas Water Resources Institute. In response to the TWDB’s 2019 state flood assessment and other efforts initiated in the wake of Hurricane Harvey, the 86th Texas Legislature developed a visionary new framework to fight future floods. The TWDB was tasked with overseeing and coordinating this new effort in conjunction with fellow state and federal agencies. In accordance with the guiding legislation, the TWDB is using a familiar framework based on key functional areas: science, planning, and financing. In the case of floods, that framework transforms into mapping, planning, and mitigation—the three pillars of fighting floods in Texas. Citation: Lake P. 2021. Texas Reimagines the Fight Against Floods. Texas Water Journal. 12(1):58-67. Available from: https://doi.org/10.21423/twj.v12i1.7133.

Internet of Texas Water Data Update: Use Cases for Flood, Drought, and Surface Water–Groundwater Interactions

Experts representative of Texas’ water sectors identified critical water data needs and described the design of a comprehensive open access data system that facilitates use of public water data in Texas at the April 2018 Connecting Texas Water Data Workshop as reported in the Texas Water Journal. Participants described potential use cases to initiate work on the most critical data hubs for connecting Texas water data. This update describes progress on a flood dashboard by the Texas Water Development Board and development of use cases by stakeholders with expertise in water data for drought and surface water – groundwater interactions. Citation: Rosen RA, Mace RE, Hermitte SM, Wade R. 2020. Internet of Texas water: use cases for flood, drought, and surface water–groundwater interactions. Texas Water Journal. 11(1):133-151. Available from: https://doi.org/10.21423/twj.v11i1.7109.

Hurricane Harvey Caused Unprecedented Freshwater Inflow to Galveston Bay

Hurricane Harvey heavily impacted Texas in August 2017 due to an extreme amount of rainfall, especially in the large metropolitan area in and around Houston. There was an offshore storm surge associated with Harvey, and while it raised the water level in the bay, possibly prolonging flooding in the Houston area by slowing drainage, it was not responsible for flooding, as water flowed continuously out of the bay during peak flooding. Salinity measured near the mouth of the San Jacinto river dropped to 0 from 15 psu in 1.5 days after the start of storm-related outflow from the bay; the whole bay was fully freshened in 3.6 days. Depth-averaged outflow from the entrance channel reached 2 m/s. Using publicly available oceanographic data within Galveston Bay, we estimate the amount of freshwater that flowed into the bay from this rainfall to be 17 ± 5 km3 (14 million acre feet), or about 5 times the volume of Galveston Bay itself. This is less than, but close to, the freshwater input source: 20 km3 of rain that was estimated from Doppler radar to have accumulated in the drainage basins contributing to the bay. By comparison, the freshwater inflow estimates by the Texas Water Development Board (TWDB) predicts 13 km3 (11.5 million acre feet) of inflow to Galveston Bay during Hurricane Harvey.

A process-based statistical seasonal prediction of May–July rainfall anomalies over Texas and the Southern Great Plains of the United States

With the aim of providing actionable drought early warning information that water managers and reservoir operators in Texas could use to implement drought contingency triggers on water supply sources, we have developed a statistical seasonal prediction system using a canonical correlation analysis prediction model to predict rainfall from May through July (MJJ), the main rainfall season over much of Texas and the Southern Great Plains. The statistical model is trained with data between 1982 and 2005 using standardized anomalous geopotential height at 500 hPa, convective inhibition energy, and soil moisture content in April as the predictors to generate tercile categorical forecasts of MJJ rainfall. Based on commonly used forecast skill metrics, this statistical prediction system provides 20–60% higher skill than that obtained from dynamical seasonal forecasts, and the exceeds skill due to the persistence of MJJ rainfall anomalies over Texas, western Louisiana, Oklahoma and the Southern Kansas. 2011 hindcast shows that below-normal MJJ rainfall anomalies comparable to those observed over most of the region. The forecasts for 2014 captured the above-normal MJJ rainfall anomalies as observed in that year. The forecasts since 2014 have shown acceptable prediction skills at one-to-three months’ lead-time. We have also extended the lead-time to generate probabilistic MJJ rainfall forecasts from January through March using a hybrid dynamical-statistical forecast scheme. The predictions have been used by the Texas Water Development Board to inform the Texas State Drought Preparedness Council and to support the implementation of drought contingency triggers for water supply sources by stakeholders, such as river authorities.

UTEP–EPW university–utility partnership: Concentrate enhanced–recovery reverse osmosis process for high water recovery from silica‐saturated desalination concentrates

Since the 1970s, The University of Texas at El Paso and El Paso Water have had a synergistic university-utility partnership, and in 2002, we began a sequence of investigations of enhanced recovery of water from silica-saturated reverse osmosis concentrate: (a) two-pass nanofiltration (NF) and reverse osmosis (RO) treatment, (b) lime softening for silica removal, (c) vibratory shear enhanced processing (VSEP), (d) continuous-flow seawater RO treatment of brackish RO concentrate, and finally (e) high-recovery concentrate enhanced-recovery reverse osmosis (CERRO) process. Studies funded by El Paso Water, Texas Water Development Board, U.S. Bureau of Reclamation, and WateReuse Research Foundation were conducted at the Kay Bailey Hutchison (KBH) Plant in ElPaso and the Brackish Groundwater National Desalination Research Facility in Alamogordo, NM, and showed that as much as 88% of the water could be recovered from silica-saturated KBH concentrate using the CERRO process. Full-scale implementation of the CERRO process at well sites in El Paso has resulted in 70%-75% recovery of RO concentrate with a specific energy consumption of 1.23kWh/m3 (4.6kWh/kgal) and total estimated cost of approximately $0.59/m3 ($2.25/kgal). Cost-effective high-recovery desalination technologies such as CERRO are essential for drought-proof water supply in arid cities such as El Paso. PRACTITIONER POINTS: This two-decade UTEP-EPW research partnership was sustained by a long-term commitment to research and consistent financial support from EPW. Universities can collaborate to leverage utility funding toward larger external grant funding to advance research and development in a win-win partnership. The high-recovery CERRO process was developed through multiple phases of concentrate management research, which would not have been possible without long-term research commitment and risk tolerance from EPW. CERRO systems are being implemented at full scale in El Paso to recover water from silica-saturated RO concentrate at an estimated specific energy consumption of 1.23kWh/m3 (4.6kWh/kgal) and total amortized cost of $0.59/m3 ($2.25/kgal).

Improving probabilistic hydroclimatic projections through high-resolution convection-permitting climate modeling and Markov chain Monte Carlo simulations

Understanding future changes in hydroclimatic variables plays a crucial role in improving resilience and adaptation to extreme weather events such as floods and droughts. In this study, we develop high-resolution climate projections over Texas by using the convection-permitting Weather Research and Forecasting (WRF) model with 4 km horizontal grid spacing, and then produce the Markov chain Monte Carlo (MCMC)-based hydrologic forecasts in the Guadalupe River basin which is the primary concern of the Texas Water Development Board and the Guadalupe-Blanco River Authority. The Parameter-elevation Regressions on Independent Slopes Model (PRISM) dataset is used to verify the WRF climate simulations. The Model Parameter Estimation Experiment (MOPEX) dataset is used to validate probabilistic hydrologic predictions. Projected changes in precipitation, potential evapotranspiration (PET) and streamflow at different temporal scales are examined by dynamically downscaling climate projections derived from 15 Coupled Model Intercomparison Project Phase 5 (CMIP5) general circulation models (GCMs). Our findings reveal that the Upper Coast Climate Division of Texas is projected to experience the most remarkable wetting caused by precipitation and PET changes, whereas the most significant drying is expected to occur for the North Central Texas Climate Division. The dry Guadalupe River basin is projected to become drier with a substantial increase in future drought risks, especially for the summer season. And the extreme precipitation events are projected to increase in frequency and intensity with a reduction in overall precipitation frequency, which may result in more frequent occurrences of flash floods and drought episodes in the Guadalupe River basin.

Evolution of Ground Water Quality and Source Tracking of Nitrate Contamination in the Seymour Aquifer of Texas

Evolution of Ground Water Quality and Source Tracking of Nitrate Contamination in the Seymour Aquifer of Texas

Holistic Water-Energy-Food Nexus for Guiding Water Resources Planning: Matagorda County, Texas Case

Nations, particularly those with well-established infrastructure, have started to look for new, innovative solutions to address the expected, inevitable high demand for primary resources. The WEF (water–energy–food) Nexus approach, which holistically considers the dynamic interlinkages between water, energy, and food resources, has come to the forefront within scientific and practice communities. Supporters assert that sustainable solutions can be revealed though the use of this approach, rather than conventional approaches that often overlook the interlinkages. The authors developed a holistic framework to provide sustainable scenarios that include feasible infrastructure interventions. The framework focuses on water, includes a unique analytic tool for quantifying scenarios, and ultimately produces a sustainability analysis of each scenario. Optimal scenarios are offered that consider site-specific dynamic resource interlinkages. The platform was applied to the case study of Matagorda County, Texas, identified as one of the most water-stressed regions in the state of Texas by the Texas Water Development Board, the state’s executive agency for water resources management. High demands from energy and agriculture sectors in the county and sharp population increase in the upper basins, which include the city of Austin, have put great pressures on the water resources of Matagorda County. Farmers have been forced to change their crops from high to lower water-demand crops, in spite of apparent and relatively abundant local water resources. The findings of the case study present a most sustainable scenario, including infrastructure interventions that will increase the annual income of agriculture sector from $188 million to $239 million. The approach also helps preserve resources while reducing annual water and energy demand by 22 million m3 and 21 million kWh, respectively, and does not sacrifice on-going municipal and industrial water use or energy production in Matagorda, Texas.

Analysis of four governance factors on efforts of water governing agencies to increase water reuse in the San Antonio Region

Securing sources for water reuse and coordinating efforts of water governing agencies to do so are critical to realizing the potential of reused water to provide nearly 24% of the water demand of the San Antonio Region, defined as regions “L” and “K” by the Texas Water Development Board (TWDB). This research identifies key governance factors that contribute to increasing water reuse within the water planning sector and tests four governance-related hypotheses for their impact on efforts to increase water reuse in the Region. Variables tested include: the type and scale of water governance agency, the agency's frequency of communication with the TWDB, and the agency's familiarity with the TWDB water strategy supplies as defined in the Texas State Water Plan of 2017. A questionnaire addressing these variables was sent to water governing agencies in regions L and K; the response rate was 39.5%. Each variable was cross-tabulated with agency efforts to increase water reuse. Seven regression analysis models were calculated among the factors to test for statistical significance and impact on increasing water reuse efforts. Results indicate that nearly 70% of agencies in the regions have efforts to increase water reuse by as much as 10%. Among the tested hypotheses, frequency in communication with the TWDB was statistically significant for increasing agency efforts to reuse water. Results from these hypotheses are expected to help water managers identify key, governance-related factors that contribute to increased water reuse.

Towards bridging the water gap in Texas: A water-energy-food nexus approach

The 2017 Texas Water Development Board's State Water Plan predicts a 41% gap between water demand and existing supply by 2070. This reflects an overall projection, but the challenge will affect various regions of the state differently. Texas has 16 regional water planning zones characterized by distinct populations, water demands, and existing water supplies. Each is expected to face variations of pressures, such as increased agricultural and energy development (particularly hydraulic fracturing) and urban growth that do not necessarily follow the region's water plan. Great variability in resource distribution and competing resource demands across Texas will result in the emergence of distinct hotspots, each with unique characteristics that require multiple, localized, interventions to bridge the statewide water gap. This study explores three such hotspots: 1) water-food competition in Lubbock and the potential of producing 3 billion gallons of treated municipal waste water and encouraging dryland agriculture; 2) implementing Low Impact Developments (LIDs) for agriculture in the City of San Antonio, potentially adding 47 billion gallons of water supply, but carrying a potentially high financial cost; and 3) water-energy interrelations in the Eagle Ford Shale in light of well counts, climate dynamics, and population growth. The growing water gap is a state wide problem that requires holistic assessments that capture the impact on the tightly interconnected water, energy, and food systems. Better understanding the trade-offs associated with each ‘solution’ and enabling informed dialogue between stakeholders, offers a basis for formulating localized policy recommendations specific to each hotspot.