John E Mccray

• PhD Hydrology and Water Resources, University of Arizona
• Head of Faculty at Colorado School of Mines

Urban stormwater may contain pollutants from different traffic vehicular sources including brake and tire wear, exhaust emissions, and atmospheric deposition. In this research, we took advantage of COVID-19 restrictions to evaluate the effects of historically low vehicular circulation on stormwater quality (metal concentrations and mass loads) gene...

This study leverages a Random Forest model to predict flood hazard in Arizona, New Mexico, Colorado, and Utah, focusing on enhancing sustainability in flood management. Utilizing the National Flood Hazard Layer (NFHL), an intricate flood map of Arizona was generated, with the Random Forest Classification algorithm assessing flood hazard for each gr...

Though surface water quality has been monitored in southern Peru over the past and current century, it has been implemented by multiple organizations. The data lacks a centralized repository and access requires logistical and temporal hurdles associated with official requests. A substantial portion of the data has not been quality assured and is in...

To better query regional sources of metal(loid) exposure in an under-communicated region, available scientific literature from 50 national universities (undergraduate and graduate theses and dissertations), peer-reviewed journals, and reports published in Spanish and English were synthesized with a focus on metal(loid) bioaccumulation in Peruvian f...

Urban stormwater quality has been sampled and chemically analyzed in the city of Arequipa, southern Peru. Stormwater samples generated from a 0.04 km² drainage area in a downtown location were collected during two rainy seasons (2022 and 2023), including both first flush and peak flow for each storm event, analyzing physical and chemical (metals) v...

Climate change and increases in human activities are threatening water availability in the Arequipa Region (southern Peru). However, to date, there has not been a comprehensive inventory of surface water data or an investigation of current surface water conditions or forecasted future conditions resulting from increased anthropic demand or stresses...

Drinking water can be a major source of poly- and perfluoroalkyl substance (PFAS) exposure for humans. The lack of historic data on PFAS drinking-water concentrations and consumption patterns are a limiting factor for developing estimates of past exposure. Here, in contribution to a community-scale PFAS health effects study near fire training facil...

Biosolids are an important resource for agricultural practice but have recently received increased focus as a potential source of per- and polyfluoroalkyl substances (PFAS) in the environment. Few studies have investigated the transport of PFAS through the unsaturated zone under conditions relevant to biosolids application sites. Herein, the unsatu...

Forest ecosystems play an important role in hydrological processes as surface and subsurface runoff, as well as the storage of water at the catchment scale. Therefore, it is important to have a greater understanding of the effects of forests in the long-term water balance of Mediterranean catchments. In this sense, this study evaluates the effect o...

The arid Coquimbo region of Chile has experienced a significant economic growth in recent decades, fueled in large part by water-intensive activities such as mining and agriculture. Under this context, a monthly and annual trend analysis of precipitation, streamflow, and piezometric levels was carried out. Thus, 43 pluviometric stations, 11 fluviom...

When performing calculations or numerical simulations for the fate and transport of PFAS and other surface-active solutes in the vadose zone, accurately representing the relationship between the area of the air-water interfaces (Aaw) as a function of water saturation (Sw), and changes in that relationship resulting from changes in soil texture, are...

Dry-weather flows in urban channels and streams, often termed “urban drool”, represent an important source of urban surface water impairment, particularly in semi-arid environments. Urban drool is a combination of year-round flows in urban channels, natural streams, and storm-sewer systems (runoff from irrigation return flow, car washes, street cle...

Groundwater professionals require tools to evaluate a variety of technical issues related to per‐ and polyfluoroalkyl substances (PFAS). These include the potential impact of PFAS precursors on groundwater plumes of perfluoroalkyl acids (PFAAs). Numerical modeling results show that, by adjusting the mass loading rate, source zones with or without a...

Green stormwater infrastructure mirrors natural hydrologic processes and is presented as an alternative or complement to traditional gray stormwater infrastructure, which uses concrete channels and pipes to convey flows away from neighborhoods. To encourage green infrastructure installation, practitioners promote co-benefits, also called ancillary...

As we move into an era of increased urbanization, stormwater practitioners are charged with creating multibenefit solutions through the installation of stormwater control measures (SCMs). Two drivers facilitate the accrual of benefits in SCMs: hydrologic or water quality process and vegetation. This study investigated the feasibility of incorporati...

Stormwater quality in three urban watersheds in Denver that have been undergoing rapid infill redevelopment for about a decade was evaluated. Sampling was conducted over 18 months, considering 15 storms. Results: (1) The first-flush effect was observed for nutrients and total suspended solids (TSS) but not for total dissolved solids (TDS), conducti...

The objective of this research is to develop a module for the design of best management practices based on percent pollutant removal. The module is a part of the site-scale integrated decision support tool (i-DSTss) that was developed for stormwater management. The current i-DSTss tool allows for the design of best management practices based on flo...

Surface spills occur frequently during unconventional oil and gas production operations and have the potential to impact groundwater quality. A screening-level analysis using contaminant fate and transport simulations was performed to: (1) evaluate whether hypothetical (yet realistic) spills of aqueous produced fluids pose risks to groundwater qual...

Three‐dimensional, multiphase simulations are used to analyze migration of methane leakage from a hydrocarbon wellbore. The objective is to evaluate the relevance and importance of coupling fast, advective transport of methane through fractures with slower, diffusive transport in the shale matrix below a freshwater aquifer on water quality assuming...

Majes is one of the largest agricultural areas in the Arequipa region (southern Peru). Low seasonal precipitation and increasing water demands for agricultural irrigation, industry, and human consumption have made water supply projections a major concern. Agricultural development is becoming more extensive in this dry, sunny climate where crops can...

Landslides are considered a natural process, with hundreds of events occurring every year in many regions of the world. However, human activities can significantly affect how stable a slope or cliff is, increasing the chances of slope collapses. Moreover, agricultural irrigation has potential to saturate subsurface materials well below ground level...

The HYDRUS unsaturated flow and transport model was modified to simulate the effects of non-linear air-water interfacial (AWI) adsorption, solution surface tension-induced flow, and variable solution viscosity on the unsaturated transport of per- and polyfluoroalkyl substances (PFAS) within the vadose zone. These modifications were made and complet...

Surface tension isotherms and calculated air-water interfacial (AWI) adsorption data are presented for solution mixtures of per- and polyfluoroalkyl substances (PFAS), specifically a series of binary and one ternary mixtures of homologous linear perfluorocarboxylic acids (PFCAs) in a simulated groundwater, and two 8-component mixtures containing bo...

Transport of ten perfluoroalkyl acids (PFAAs) was studied with one-dimensional (1-D) saturated column experiments using four soil types with an organic carbon fraction (foc) range of ~0–0.045. Columns were operated under conditions relevant to aqueous film-forming foam (AFFF)-impacted fire protection training areas to determine the ability of equil...

Green infrastructure is an increasingly popular approach to mitigate widespread degradation of urban waters from stormwater pollution. However, many stormwater best management practices (BMPs) have inconsistent water quality performance and are limited to on-site, land-based deployments. To address basin-wide pollutant loads still reaching urban st...

Urban greening practices are often adopted to mitigate the negative impacts of increasing impervious surfaces in urban areas. In the United States, green approaches are prevalent in the field of stormwater management as some cities are required to install green stormwater infrastructure (GSI) to meet regulatory requirements. While the primary funct...

Rainwater harvesting (RWH) is a renewable water supply option for nonpotable use, most commonly used for landscaping irrigation. Water rights in Colorado prohibit all RWH except residential rain barrels and a pilot project program that allows centralized rainwater harvesting for new development. Development of a natural catchment creates impervious...

A site-scale integrated decision support tool (i-DSTss) is developed for selection and sizing of stormwater Best Management Practices (BMPs). The tool has several component modules—hydrology, BMP selection, BMP sizing, and life-cycle cost analysis (LCCA)—integrated into a single platform. The hydrology module predicts runoff from small catchment on...

Wildfires commonly increase nutrient, carbon, sediment and metal inputs to streams, yet the factors responsible for the type, magnitude and duration of water quality effects are poorly understood. Prior work by the current authors found increased nitrogen, phosphorus and cation exports were common the first 5 post-fire years from a synthesis of 159...

The release and transport of linear perfluorocarboxylic acids (PFCA) within the vadose-zone beneath per- and polyfluoroalkyl substance (PFAS)- and non-aqueous phase liquid (NAPL)-contaminated source areas is influenced by multi-phase interfacial retention phenomena. Conceptually, interfacial adsorption results in retardation of PFCA velocities in s...

The Denver Basin Aquifer System (DBAS) is a critical groundwater resource along the Colorado Front Range. Groundwater depletion has been documented over the past few decades due to the increased water use among users, presenting long‐term sustainability challenges. A spatiotemporal geostatistical analysis is used to estimate potentiometric surfaces...

Plain Language Summary Freshwater is one of the world's most important natural resources. However, data scarcity in many parts of the world is a substantial barrier to understanding and predicting the impact of environmental changes on freshwater ecosystems. Satellites provide data on water resources in data‐poor regions. The “active‐passive surfac...

Groundwater monitoring is fundamental to understanding system dynamics, trends in storage, and the long-term sustainability of an aquifer. Water-level data are the key source of information used to understand the response. However, groundwater-level data are often irregularly sampled, leading to temporal gaps in the record, and are not adequately d...

Many watershed challenges can be associated with the increased impervious cover that accompanies urban development. This study establishes a methodology of evaluating the spatial and temporal distribution of infill re-development on a parcel scale, using publicly available urban planning data. This was achieved through a combination of linear and l...

Prioritizing stormwater infrastructure projects is challenging. In addition to regulating runoff and complying with water quality standards, agencies also consider factors such as life cycle costs, environmental impacts, and cobenefits to the environment and community. This work reviews literature on these decision-making criteria for stormwater pr...

The hyporheic zone (HZ), located at the interface of surface and groundwater, is a natural bioreactor for attenuation of chemical contaminants. Engineered HZs can be incorporated into stream restoration projects to enhance hyporheic exchange, with flowpaths optimized to promote biological habitat, water quantity, and water quality improvements. Des...

Several US programs provide financial incentives for stream restoration to improve degraded water quality. These efforts prioritize hyporheic zone (HZ) restoration to enhance contaminant attenuation, but no stream restoration or stormwater best management practice (BMP) explicitly tailors hyporheic residence times to target specific contaminants of...

Injecting CO2 into depleted oil reservoirs to extract additional crude oil is a common enhanced oil recovery (CO2-EOR) technique. However, little is known about how in situ microbial communities may be impacted by CO2 flooding, or if any permanent microbiological changes occur after flooding has ceased. Formation water was collected from an oil fie...

https://ascelibrary.org/doi/10.1061/JSWBAY.0000863 Growing cities require accurate knowledge of current and future hydrologic conditions to make effective stormwater management decisions. Yet, this information is lacking because cities are undergoing infill development/redevelopment, for which the hydrologic impacts are not adequately quantified....

The objective of this research is to develop of a planning-level, site scale integrated decision support tool (site scale i-DST) for grey and green stormwater infrastructure. The site scale i-DST has several component modules integrated into a single tool. The component modules include runoff estimation module, water quality module, BMP cost module...

Cities in developing countries frequently suffer from poor water quality. Thus, the ability to make informed decisions on the current state of urban water quality, as well as on rehabilitating or implementing new infrastructure, is necessary. Therefore, the authors present a stochastic and dynamic water quality model for cities by integrating exist...

A gas-water equilibrator (GWE) was developed to be applied in field research of CH4 in groundwater and assist with pre-drill and post-drill screening of groundwater wells near natural gas development. The GWE was designed to operate during well purging and provide real-time field measurements of aqueous CH4 by equilibrating a continuous stream of g...

In recent decades, the Rocky Mountains (RM) have undergone significant changes associated with anthropogenic activities and natural disturbances. These changes have the potential to alter primary productivity and biomass carbon storage. In particular, dissolved organic carbon (DOC) in RM streams can affect heterotrophic processes, act as a source f...

Wildfires are increasing in size and severity in forested landscapes across the Western United States. Not only do fires alter land surfaces, but they also affect the surface water quality in downstream systems. Previous studies of individual fires have observed an increase in various forms of nutrients, ions, sediments and metals in stream water f...

Methane leakage due to compromised hydrocarbon well integrity can lead to impaired groundwater quality. Here, we use a three-dimensional, multiphase (vapor and aqueous), multicomponent (methane, water, salt), numerical model (TOUGH2 EOS7C) to investigate hydrogeological conditions that could result in groundwater contamination from natural-gas well...

This research investigates the impacts of infill development (or “redevelopment”) on urban stormwater runoff and explores avenues for re-inventing stormwater management strategies for the City of Denver, Colorado. As a rapidly developing city, Denver is facing a cycle of increasing population and redevelopment in the form of infill (where under-uti...

Geophysical data have proven to be very useful for lithological characterization. However, quantitatively integrating the information gained from acquiring geophysical data generally requires colocated lithological and geophysical data for constructing a rock-physics relationship. In this contribution, the issue of integrating noncolocated geophysi...

Land cover (LC) products, derived primarily from satellite spectral imagery, are essential inputs for environmental studies because LC is a critical driver of processes involved in hydrology, ecology, and climatology, among others. However, existing LC products each have different temporal and spatial resolutions and different LC classes that rarel...

http://onlinelibrary.wiley.com/doi/10.1111/gwmr.12225/full

Won 1st place in student poster competition. Redevelopment, known also as infill development, is the practice of building within existing developed urban areas on vacant or under-utilized parcels of land, typically resulting in an increase in impervious surfaces such as roofs, driveways, and parking lots. One example of redevelopment is replacing...

Invited seminar talk at the Agricultural Engineering School from Concepción University (FIAUDEC)

Land cover (LC) is a critical variable driving many environmental processes, so its assessment , monitoring, and characterization are essential inputs to study these processes. However, existing LC products, derived primarily from satellite imagery, each have different spatiotemporal resolutions and different LC classes. Most effort is focused on e...

El estudio del agua superficial y subterránea en un medio ambiente cambiante requiere primero una caracterización espacial y temporal detallada del medio ambiente. La cobertura de la superficie terrestre (CST) es una variable crítica que determina en gran medida varios procesos hidrológicos. Por ende, el monitoreo, la evaluación, y la caracterizaci...

Meaningful model-based predictions of water quality and quantity are imperative for the designed footprint of MAR installations. A two-dimensional (2D) synthetic managed aquifer recharge system equipped with automated sensors (temperature, water pressure, conductivity, soil moisture, oxidation reduction potential) and embedded water sampling ports...

Land cover (LC) is a critical variable driving many environmental processes, so its assessment, monitoring, and characterization are essential. However, existing LC products, derived primarily from satellite spectral imagery, each have different temporal and spatial resolutions and different LC classes. Most effort is focused on either fusing a pai...

Land cover (LC) is a critical variable driving many environmental processes, so its assessment, monitoring, and characterization are essential inputs to study those processes. However, existing LC products, derived primarily from satellite spectral imagery, each have different temporal and spatial resolutions and different LC classes. Most effort i...

Few urban studies have evaluated the hydrologic impacts of redevelopment – for example, a rapid conversion from single to multi-family homes – known as infill, or re-urbanization. Redevelopment provides unique stormwater challenges as private property owners in many cities are not mandated to undertake stormwater retrofits leading to an overall inc...

Stimulating in situ microbial communities in oil reservoirs to produce natural gas is a potentially viable strategy for recovering additional fossil fuel resources following traditional recovery operations. Little is known about what geochemical parameters drive microbial population dynamics in biodegraded, methanogenic oil reservoirs. We investiga...

Land cover (LC) is a critical variable driving many environmental processes, so its assessment, monitoring, and characterization are essential inputs to study those processes. However, existing LC products, derived primarily from satellite spectral imagery, each have different temporal and spatial resolutions and different LC classes. Most effort i...

Rising atmospheric carbon dioxide (CO2) concentrations are fueling anthropogenic climate change. Geologic sequestration of anthropogenic CO2 in depleted oil reservoirs is one option for reducing CO2 emissions to the atmosphere while enhancing oil recovery. In order to evaluate the feasibility of using enhanced oil recovery (EOR) sites in the United...

Although the shift from rural to urban land cover has been studied extensively, there is a lack of knowledge regarding the specific hydrologic impacts of the redevelopment of previously urbanized areas – for example, a rapid conversion from single family to multi-family homes – known as infill development, or re-urbanization, especially in the face...

Laboratory experiments evaluated two shale caprock formations, the Gothic Shale and Marine Tuscaloosa Formation, at conditions relevant to carbon dioxide (CO 2) sequestration. Both rocks were exposed to CO 2-saturated brines at 160°C and 15 MPa for *45 days. Baseline experiments for both rocks were pressurized with argon to 15 MPa for *35 days. Var...

Carbon capture, utilization, and storage, one proposed method of reducing anthropogenic emissions of CO 2 , relies on low permeability formations, such as shales, above injection formations to prevent upward migration of the injected CO 2. Porosity in caprocks evaluated for sealing capacity before injection can be altered by geochemical reactions i...

In the Western United States (US), the current mountain pine beetle (MPB; Dendroctonus ponderosae) epidemic has affected more than five million hectares since its start in 1996, including headwater catchments that supply water to much of the Western US. There is widespread concern that the hydrologic consequences of the extensive pine tree die-off...

Converting non-producible crude oil to CH4 via methanogenic crude oil biodegradation in oil reservoirs could serve as one way to increase our energy profile. Yet, field data supporting the direct relationship between methanogenesis and crude oil biodegradation are sparse. Indicators of methanogenesis, based on formation water and gas geochemistry (...

Land cover (LC) is a critical variable driving many environmental processes, so its assessment, monitoring, and characterization are essential. However, existing LC products, derived primarily from satellite imagery, each have different temporal and spatial resolutions and different LC classes. Most effort is focused on either fusing a pair of LC p...

The dissolved organic matter (DOM) content of the water in the streams of the Rocky Mountains (RM) highly determines its quality and geochemistry because it contains nutrients, enhances metal transport, absorbs sunlight radiation, and can react with disinfectants used in water treatment plants to form carcinogenic byproducts. The recent Mountain Pi...

Current understanding of streamflow composition in mountain watersheds is often limited by inherent uncertainties and collection limitations in field data and assumptions associated with modeling techniques. Additional complexity arises in catchments experiencing land-cover change. Here, a hillslope model with fully integrated processes from the su...

One dimensional column experiments were conducted using saturated porous media containing residual trichloroethylene (TCE) to understand the effects of non-aqueous phase liquids (NAPLs) and chemical oxidation on perfluoroalkyl acid (PFAA) fate and transport. Observed retardation factors and data from supporting batch studies suggested that TCE prov...

Many urban and agricultural activities have impacted the water quality of streams and lead to high levels of nutrients, pesticides, metals, and pathogens. Non-point source pollution caused by these activities is difficult to identify and treat, preventing the rehabilitation of such streams. This research project aims to evaluate the removal of such...

With the rise in unconventional oil and gas development over the past decade, the public is concerned about how these stimulation, extraction, and production activities may impact groundwater resources. Although there are many possible contamination pathways, the most probable leakage pathway is through a surface spill. The purpose of this study is...

Satellite remote sensing is a valuable source of observations of hydrologic variables, especially over large regional scales and in areas with sparse in-situ data. Gravity anomaly measurements from the NASA/German Space Agency’s Gravity Recovery and Climate Experiment (GRACE) have been used to estimate temporal variations in groundwater, surface wa...

The growing need for water among urban users, agriculture, industry, ecosystems, and energy development, presents challenges in water-limited systems. Lack of adequate temporal and spatial groundwater data can limit our ability to fully understand the stresses that different water users place on aquifers. We estimate groundwater storage changes in...

The natural and anthropogenic cover on the surface of the Earth, more commonly referred to as land cover (LC), is a critical variable driving many environmental processes, including biogeochemical cycling, hydrologic processes, soil erosion, and ecosystems productivity. Thus, the assessment, monitoring, and characterization of LC is essential for g...

In the next ten years, the population of the City and County of Denver is expected to grow by more than 100,000 people. Population increase will be accompanied by new development (including infill redevelopment) leading to an increase in impervious cover, and subsequently, a rise in stormwater runoff. An area that is expected to experience increase...

The hyporheic zone (HZ) has the potential to mitigate nonpoint source pollution that threatens urban streams, but limited flows and inefficient interchange typically constrain its water quality improvements. This paper presents coordinated streambed hydraulic conductivity (K) modifications, termed Biohydrochemical Enhancement Structures for Streamw...

Study region: The Upper Colorado River Basin (UCRB), comprised of the Colorado and Gunnison River basins, is the prime water source for much of the western United States. Study focus: Future climate change models were used to drive a hydrologic model of the UCRB to evaluate future water resources and hydropower potential of the basin, using three d...

In situ chemical oxidation (ISCO) is a remediation approach that is often used to remediate soil and groundwater contaminated with fuels and chlorinated solvents. At many aqueous film-forming foam-impacted sites, perfluoroalkyl acids (PFAAs) can also be present at concentrations warranting concern. Laboratory experiments were completed using flow-t...

The distribution of residual dense nonaqueous phase liquid (DNAPL) in the subsurface plays a critical role in the DNAPL dissolution kinetics. However, measuring residual DNAPL at the field scale in fractured bedrock settings is generally impractical. This research uses a three-dimensional (3D), bench-scale, fractured-rock network comprised of low-p...

Recent mountain pine beetle infestation in the Rocky Mountains of North America has killed an unprecedented acreage of pine forest, creating an opportunity to observe an active re-equilibration in response to widespread land cover perturbation. This work investigates metal mobility in beetle-impacted forests using parallel rainwater and acid leache...

Conventional onsite wastewater treatment system design relies on a septic tank and soil treatment unit (STU) for treatment of wastewater and integration of the final effluent into the environment. Organic water contaminants (OWCs), chemicals found in pharmaceutical drugs, detergents, surfactants, and other personal care and cleaning products, have...