Municipal Groundwater Supplies Research Articles

Efficacy of urban road salt reduction strategies on public supply well quality

Long-term road salt application has increased chloride (Cl−) concentrations in public drinking water wells in many cold climate communities. A range of Best Management Practices (BMPs) have been adopted to mitigate the impact of road deicing compounds on groundwater quality. Chronic increases in chloride levels have been observed in several municipal well fields within the southern Ontario Regional Municipality of Waterloo (RMOW). In response, the RMOW and City of Kitchener implemented a plan to reduce salt application on roads by 25% within the local capture zones of one of the impacted well fields, the Greenbrook Well Field. Here the influence of salt reduction BMPs on subsurface water quality are examined by documenting changes in pore water Cl− concentrations and stored salt mass in vadose zone core samples collected at sites near the well field both before and after the implementation of the BMPs. The data indicate that ~6 years after salt reduction measures were initiated, average pore water Cl− concentration and average cumulative stored chloride mass in the vadose zone had decreased by approximately 60% and 40%, respectively. Groundwater samples collected from shallow monitoring wells installed at each field site showed similar post-BMP reductions in shallow groundwater Cl− concentration (~35%). Long-term (1973–2022) trends in raw water Cl− concentration data from the deeper public drinking water supply wells clearly demonstrate a slow, time-lagged response of the municipal supply wells to the salt reduction BMPs. The combined results suggest that controlled reductions in road salt applications within vulnerable, capture zone regions of public supply wells can reduce the impact of road salt deicing practices on municipal groundwater supplies over time.

Development of an integrated numerical flow model in the Prairie Environment – A case study of the Leech Lake Aquifer system, Saskatchewan, Canada

Study regionLeech Lake Aquifer, City of Yorkton, Saskatchewan, Canadian Prairies. Study focusGroundwater and surface water interactions have been conducted numerically for bringing out a sustainable management of the Leech Lake aquifer in the southern portion of City of Yorkton area within the province of Saskatchewan, Canada. The aquifer is composed of highly conductive sediments over bedrock strata with low hydraulic conductivity. A fully coupled, physically based surface-groundwater flow model using HydroGeoSphere (HGS) is developed for the purpose of simulation. In this numerical model, different withdrawal scenarios and the effects of climate variabilities (precipitation and snowmelt) are being conducted to investigate the impact of water usage on groundwater level. New hydrological insights for the regionGroundwater from several aquifers serves as the main water supply for the city of Yorkton. Aquifer protection and sustainable use of the limited resource is of utmost importance to the municipality and in support of economic development in the region. Insight and understanding of the risks and impact to the municipal groundwater supply is required. To address the sustainability of the aquifers in the area, a numerical model was developed to provide greater comprehension of the surface and groundwater fluxes. Model calibration and validation was completed with existing long term monitoring information from piezometers in the area. In the semi-arid environment of the Prairie Provinces, water withdrawal and precipitation plays a significant role in affecting groundwater level. Different withdrawal scenarios are conducted to investigate the impact of the water usage on the Leech Lake aquifer that will provide a tool to support the development of a sustainable management plan. Precipitation as well as snowmelt have been incorporated into the model to identify the driving recharge factor for groundwater variation. Temporal and spatial variabilities, as well as estimation of magnitude for exchange flow rates at the interfaces are presented. The fully integrated model developed in this study provides the foundation for future groundwater management applications in climate driven changes within the Prairie environment.

Structural investigation and applications of glassy sodium phosphate including the kinetics of dissolution rates and spectral analysis of the prepared samples with a focus on their effects on water treatment

This paper discuss the preparation of the binary system of Phosphate Based Glass (PBG) xP2O5–(100 − x) Na2O mol% and investigates the compositions that form glassy matrix. It is found that x in the range between x = 40–60 mol% and divided in to 5 glass samples (x = 40, 45, 50, 55, 60) and for compositions of 40 > x > 60 no glassy matrix is formed. The intensities of the peak centers of the IR spectra of sodium phosphate glasses and the suggested vibrational modes of structural phosphate chains, terminal groups and tabulated data imply a shift in absorption bands with increasing the Na2O mol% content. The amount of bridging phosphorous, shows a maximum value for the glass containing 60 mol% Na2O due to the depolymerization of the phosphate matrix with increasing Na2O content from 40 to 60 mol% via a breakdown of some terminal bonds (P=O) in the glass network which decreases the bond strength, consequently the peak center is shifted towards lower wave number. Essentially, five compositions of glassy samples were investigated: (x = 40, 45, 50, 55, and 60) mol%. The kinetics of dissolution rate were investigated by two ways: 1—the weight loss data and 2—electrical properties of the solution (pH, Electrical Conductivity) leached by the glass sample in to the deionized water. It is found that with increasing the Na2O% content, the pH values, the dissolution rate and the solubility are increasing. It could be noticed that the ionic levels increased with the immersion time and were directly related to the solubility of the glasses. The highest in solubility (x = 40) is the highest in EC and pH values caused by high Na2O%. By studying the effect of PBG on the real water medium physical characteristics the following results were achieved: Softening of (Treated drinking water, Nile raw water) by removal of hardness (Ca, Mg) by x = 50; 50% P2O5–50% Na2O, Sequestering and agglomerating of (groundwater, wastewater) of some heavy metals as (Fe, Mn) up to 100% removal by x = 60; 60% P2O5–40% Na2O and the electrical properties (pH, EC) were discussed. Results are assuring the possibility of applying PBG for groundwater treatment of high Fe and Mn content. The data show that municipal groundwater supplies become acceptable according to the guidelines of American Chemistry Council for safe drinking water by using of polyphosphates for water treatment.

Deep urban groundwater vulnerability in India revealed through the use of emerging organic contaminants and residence time tracers

Demand for groundwater in urban centres across Asia continues to rise with ever deeper wells being drilled to avoid shallow contamination. The vulnerability of deep alluvial aquifers to contaminant migration is assessed in the ancient city of Varanasi, India, using a novel combination of emerging organic contaminants (EOCs) and groundwater residence time tracers (CFC and SF6). Both shallow and intermediate depth private sources (<100 m) and deep (>100 m) municipal groundwater supplies were found to be contaminated with a range of EOCs including pharmaceuticals (e.g. sulfamethoxazole, 77% detection frequency, range <0.0001–0.034 μg L−1), perfluoroalkyl substances (e.g. PFOS, range <0.0001–0.033 μg L−1) as well as a number of pesticides (e.g. phenoxyacetic acid, range <0.02–0.21 μg L−1). The profile of EOCs found in groundwater mirror those found in surface waters, albeit at lower concentrations, and reflect common waste water sources with attenuation in the subsurface. Mean groundwater residence times were found to be comparable between some deep groundwater and shallow groundwater sources with residence times ranging from >70 to 30 years. Local variations in aquifer geology influence the extent of modern recharge at depth. Both tracers provide compelling evidence of significant inputs of younger groundwater to depth >100 m within the aquifer system.

Geology and Hydrogeology of Faults on Cape Breton Island, Nova Scotia, Canada: an overview

Cape Breton Island provides a hydrogeological view into the roots of an ancient mountain range, now exhumed, glaciated, and tectonically inactive. It exhibits deep crustal faults and magma chambers associated with formation of the Appalachian mountain belt and the Maritimes Basin during the Paleozoic, as well as Mesozoic rifting relating to the opening of the Atlantic Ocean. Cenozoic exhumation brought these features near surface and into the active groundwater flow field where they were impacted by glaciation and fluctuating sea level. The faults have been important from a societal viewpoint in development of municipal groundwater supplies, controlling inflows to excavations, hydrocarbon exploration, quarry development, and geotechnical investigations. Conceptual models presented here outline fault control on groundwater flow based on seven case studies. Future research should focus on basin-bounding faults in support of managing their role in aquifer development and protection, mountain-front recharge, controlling large-magnitude springs, groundwater–stream interaction, and channel morphology. The hydrogeological importance of these faults has historically been underappreciated.

Developing science-based policy for protecting the Waterloo Moraine groundwater resource

The Waterloo Moraine has been used as a municipal water source for more than 100 years. Groundwater currently provides about 80% of the Region of Waterloo’s municipal water needs with much of this water originating from the Waterloo Moraine. Water supply management and land-use controls are both critical in sustaining and maintaining the groundwater resource. In order to manage the water resource one must understand the science of the resource. As the science becomes more refined, primarily through the development of numerical groundwater models, this information is used to increase the understanding of the sustainability of each well field and to develop appropriate land-use policies to protect the groundwater resource from surface threats of contamination. Over the last 40 years, the scientific understanding of the Waterloo Moraine has increased substantially; however, there will always be uncertainty associated with understanding natural systems. During this time, the Region of Waterloo has continued to develop land-use policies and risk management programs to protect municipal water supply wells in the Waterloo Moraine and elsewhere in the Region. The Province of Ontario has also strengthened the protection of water resources through the Clean Water Act. As the understanding of the science continues to evolve through data collection and development of new technologies, the uncertainty associated with the science needs to be reconciled with the certainty expected of protection policy. Although uncertainty cannot be eliminated, it needs to be adequately explained in order to minimize the credibility gap and increase the level of transparency in the process. This paper explores the evolution of the science and policies and the many factors that are considered in translating scientific data into a defensible policy framework to protect municipal groundwater supplies, both in the Region of Waterloo and throughout Ontario.

Public awareness, behaviours and attitudes towards domestic wastewater treatment systems in the Republic of Ireland

Summary Numerous studies have highlighted and quantified the role of domestic wastewater treatment systems (DWWTSs) as significant sources of human-specific aquatic contaminants in both developed and developing regions, particularly with respect to private and municipal groundwater supplies. However, from a socio-hydrological perspective, little work has focused on these systems and the potential environmental and human burden posed. This is of particular relevance in the Republic of Ireland, where approximately one third of the population is serviced by DWWTSs. The objective of the current study was to examine levels of awareness and subsequent behavioural tendencies among owners and users of DWWTSs in the Republic of Ireland, particularly in light of recent and future (national and EU) legislative amendments. Structured questionnaires were completed bi-modally with 1106 Irish respondents. Analysis identified a number of significant knowledge gaps which currently exist among DWWTS users in Ireland. These were associated with environmentally inadvisable behavioural practises, potentially leading to increased contamination vulnerability and subsequently, increased human exposure to waterborne contaminants. Household water supply type was significantly associated with DWWTS threat acknowledgement (p = 0.014), with unregulated private groundwater users exhibited the lowest awareness of DWWTS as a potential source of aquatic contaminants despite being the group at greatest risk. A bi-modal clustering approach was employed, with respondents found to fall into one of three distinct “attitudinal” clusters. Future engagement strategies should strive to provide guidance regarding the role of people and their activities within the hydrological cycle. The current study reinforces this conclusion, while providing evidence-based recommendations regarding provision of demographically focused educational strategies; these will further increase environmental policy compliance, and in so doing, decrease the human health and environmental contamination burden posed by DWWTSs.

Effective porosity of a carbonate aquifer with bacterial contamination: Walkerton, Ontario, Canada

Summary Preferential flow through solutionally enlarged fractures can be a significant influence on travel times and source area definition in carbonate aquifers. However, it has proven challenging to step beyond a conceptual model to implementing, parameterizing and testing an appropriate numerical model of preferential flow. Here both porous medium and preferential flow models are developed with respect to a deadly contamination of the municipal groundwater supply at Walkerton, Ontario, Canada. The preferential flow model is based on simple orthogonal fracture aperture and spacing. The models are parameterized from borehole, gamma, flow and video logs resulting in a two order of magnitude lower effective porosity for the preferential flow model. The observed hydraulic conductivity and effective porosity are used to predict groundwater travel times using a porous medium model. These model predictions are compared to a number of independent estimates of effective porosity, including three forced gradient tracer tests. The results show that the effective porosity and hydraulic conductivity values closely match the preferential flow predictions for an equivalent fracture network of ∼10 m spacing of 1 mm fractures. Three tracer tests resulted in groundwater velocities of hundreds of meters per day, as predicted when an effective porosity of 0.05% was used in the groundwater model. These velocities are consistent with a compilation of 185 tracer test velocities from regional Paleozoic carbonate aquifers. The implication is that carbonate aquifers in southern Ontario are characterized by relatively low-volume dissolutionally-enlarged fracture networks that dominate flow and transport. The porous matrix has large storage capacity, but contributes little to transport. Numerical models based on much higher porosities risk significantly underestimating capture zones in such aquifers. The hydraulic conductivity – effective porosity prediction framework provides a general analytical framework for a preferential flow carbonate aquifer. Not only is the framework readily parameterized from borehole observations, but also it can be implemented in a conventional porous medium model, and critically tested using simple tracer tests.

Hydraulic conductivity of the Portland Basin deep aquifer system

Abstract The Portland Basin is 900 mi 2 in size and includes portions of Oregon and Washington. A deep aquifer system of the Troutdale Formation is used for municipal ground-water supply in both states over an area of approximately 300 mi 2 . Although lateral sedimentary facies variations are evident in the lithologic record, data from multi-well aquifer tests show that the aquifer forms a continuous hydrostratigraphic unit in both states. The aquifer is synclinal and in the center of the basin is well-confined by low-permeability layers. On the eastern and western margins of the basin, the aquifer is in hydraulic continuity with a buried Columbia River paleo-channel. The paleochannel forms a boundary to the aquifer and relative head differences between the aquifer and the river cause ground water to flow up the formation dip and against the Columbia River gradient in the eastern portion of the basin. The paleochannel acts as a discharge sink during low-pumping periods and a recharge source during extended pumping. Municipal use of ground water in the deep aquifers includes: a) continuous use which has increased from approximately 1 to 2 mgd in 1984 to 13 mgd in 1998 and, b) emergency use which has caused total use peaks of 55 mgd. The increased ground-water use has resulted in a modified flow regime causing the aquifer to receive induced recharge through the paleochannel deposits. The induced recharge available from the Columbia River may allow for further efficient development of groundwater supplies on the eastern and western margins of the basin.

Developing and monitoring municipal groundwater supplies in Florida

Developing new municipal groundwater supplies involves comprehensive projections of the effects on other users of the aquifer as well as studies of the terrestrial effects on the area surrounding the wellfield. This article describes the studies undertaken by the West Coast (Fla.) Regional Water Supply Authority to develop a wellfield and to monitor the effects of municipal use on the aquifer in relation to a wet and dry cycle climate.

Modification of the quality of water injected into Louisiana gulf coast sands: Effects of cation exchange

Interest in artificially recharging selected shallow sands in South Louisiana with fresh water has been stimulated by the desire to retard contamination of municipal groundwater supplies by brackish water, to retard ground subsidence and decrease pumping lifts, and to develop emergency subsurface supplies of potable water for communities dependent on surface waters susceptible to contamination. Results of field experiments, laboratory work, and model calculations demonstrate that ion exchange reactions involving clays dispersed in aquifer sands can be expected to modify significantly the composition of waters injected into Gulf Coast sediments. As little as 0.1 weight percent smectite (montmorillonite) can remove, by exchange with absorbed Na, a significant fraction of the dissolved Ca and Mg present in the injected water. The hardness of the water is thus reduced, which may be a desirable modification in water quality. Exchange occurs as fast as the fluids can be pumped into or out of the aquifer, and the water-softening capacity of the aquifer can be restored by allowing sodium-rich native pore waters to sweep back over the dispersed clays. Each acre of an aquifer 50 feet thick and containing 0.1 wt % smectite could soften half a million gallons of injected Mississippi River water. Many individual Gulf Coast aquifers underlie tens of thousands of acres, and their potential softening capacity is thus enormous. Additional exchange processes involving adjacent aquitard shales presumably will operate over long-term periods.

Constraints to Arizona agriculture and possible alternatives

In Arizona, groundwater belongs to the owner of the land overlying the aquifer. To ensure adequate municipal groundwater supplies, the City of Tucson has been purchasing and retiring farmlands. While this is an effective technique, it has a significant impact on the economy of the area. One possible alternative to retiring farmlands and to cultivation of high-water-use crops is the cultivation of arid-adapted vegetation with economic potential. Jojoba (Simmondsia chinensis) is a shrub native to the Sonoran Desert that appears to be an economically-viable arid lands crop. Jojoba oil, extracted from the seed, is a unique, unsaturated oil composed of non-glyceride esters consisting almost entirely of straight-chain acids and alcohols. Such oils are difficult to synthesize in commercial quantities, and the only other known natural source is the sperm whale, an endangered species. Water requirements for jojoba production are approximately 4600 m3 per hectare compared with traditional crops grown in the area with average requirements of 12,315 m3 per hectare or more.

Effects of Uranium Mining and Milling on Ground Water in the Grants Mineral Belt, New Mexico

ABSTRACTGround‐water contamination from uranium mining and milling results from the infiltration of mine, mill, and ion‐exchange plant effluents containing elevated concentrations of radium, selenium, and nitrate. Available data indicate that radium concentrations in the discharge waters of a producing mine tend to increase substantially as the ore body is developed. Whereas natural background radium concentrations are generally about several picocuries/liter (pCi/l), 100 to 150 pCi/l appear in the effluents of operating mines. The discharge of such highly contaminated mine effluents to streams and seepage from tailings ponds, creates a long‐lived source of ground‐water contamination. Seepage of mill tailings at two active mills ranges from 126,000 to 491,000 m3/yr and, to date, has contributed an estimated 2400 Curies of uranium, radium, and thorium to the ground‐water reservoir. The shallow aquifer in use and downgradient from another mill has been grossly contaminated with selenium, attributable to excessive seepage from a nearby tailings pond.Radium, selenium, nitrate and, to a lesser extent, uranium, are of most value as indicators of ground‐water contamination. Gross alpha results are not consistent indicators of radium or uranium in water, although uranium does appear to be the principal contributor of alpha activity. Accurate radium‐s226 analyses yield the most information for radiological evaluation of drinking water.To date, no adverse impacts on municipal groundwater supplies have been observed. However, industry‐sponsored environmental monitoring programs are inadequately designed and implemented, and may not define the full, long‐term impact of mining and milling operations on the ground‐water quality of the study area.

Municipal Ground Water Supplies of Ontario

Journal AWWAVolume 27, Issue 11 p. 1533-1546 Article Municipal Ground Water Supplies of Ontario W. B. Redfern, W. B. Redfern Of James, Proctor & Redfern, Ltd., Consulting Engineers, Toronto, Ont., Can.Search for more papers by this author W. B. Redfern, W. B. Redfern Of James, Proctor & Redfern, Ltd., Consulting Engineers, Toronto, Ont., Can.Search for more papers by this author First published: 01 November 1935 https://doi.org/10.1002/j.1551-8833.1935.tb17076.xAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat Volume27, Issue11November 1935Pages 1533-1546 RelatedInformation