Groundwater Chloride Concentrations Research Articles

Endobenthic Organisms Exposed to Chronically High Chloride from Groundwater Discharging along Freshwater Urban Streams and Lakeshores.

Chloride, especially from road salt, is one of the most ubiquitous contaminants of urban groundwater in temperate climates. The discharge of chloride-laden groundwater to freshwater ecosystems may pose a heightened risk to endobenthic organisms (buried in sediments), which may experience high concentrations prior to dilution from the overlying water. However, available exposure data is limited. Presented here are 22 chloride data sets from 15 urban sites across Canada, encompassing >1300 samples of shallow discharging groundwater collected principally during summer through autumn. Over half of the sites had an average chloride concentration above the long-term aquatic life guideline (120 mg/L), while 14% of each site's samples, on average, surpassed the short-term guideline (640 mg/L). Chloride concentrations frequently varied substantially (even >1000 mg/L) between adjacent locations (mostly <20 m separation), indicating patchy exposure. Chloride/bromide ratios, artificial sweeteners, and other tracers suggest a predominant contribution from road salt, with wastewater and landfill leachate important at some sites. Overall, these concentrations exceed those typically reported for urban wells and streams (even during the snowmelt period) in similar climates. These findings suggest that high chloride concentrations in shallow groundwater, largely from road salt, present a long-term threat to endobenthic organisms of urban surface waters in cold-region countries.

Effect of temperature variations on the travel time of infiltrating water in the Amsterdam Water Supply Dunes (the Netherlands)

Travel time is one of the important criteria in the design of managed aquifer recharge systems for securing good drinking water quality. Traditionally, groundwater travel time has been modelled without considering the effect of temperature. In this study, a cross-sectional heat transport model was constructed for the Amsterdam dune filtration system (in the Netherlands) to analyse the effect of temperature on groundwater travel times. A groundwater flow model, a chloride transport model, and a heat transport model were iteratively calibrated with measured groundwater levels, chloride concentrations, and temperature series in order to improve model calibration and reduce model uncertainty. The coupled flow and heat transport model with temperature-dependent density and viscosity provided more accurate estimation of travel times. The results show that seasonal temperature fluctuations in the source water in the infiltration pond cause temperature variations in the shallow groundwater. Viscosity is more sensitive to temperature changes and has a larger effect on groundwater travel times. Groundwater travel time in the shallow sand aquifer increases from 60 days when computed with the traditional groundwater flow model to 73 days in the winter season and 95 days in the summer season when computed with the coupled model. Longer travel time is beneficial for water quality improvement. Thus, it is important to consider the effect of temperature variations on groundwater travel times for the design and operation of managed aquifer recharge systems.

Impact of Road Salt on Drinking Water Quality and Infrastructure Corrosion in Private Wells.

Increased road salt use and resulting source water contamination has widespread implications for corrosion of drinking water infrastructure, including chloride acceleration of galvanic corrosion and other premature plumbing failures. In this study, we utilized citizen science sampling, bench-scale corrosion studies, and state-level spatial modeling to examine the potential extent of chloride concentrations in groundwater and the resulting impact on private wells in New York. Across the sampled community, chloride levels varied spatially, with the highest levels in private wells downgradient of a road salt storage facility followed by wells within 30 m of a major roadway. Most well users surveyed (70%) had stopped drinking their well water for aesthetic and safety reasons. In the bench-scale experiment, increasing chloride concentration in water increased galvanic corrosion and dezincification of plumbing materials, resulting in increased metal leaching and pipe wall thinning. Our simple spatial analysis suggests that 2% of private wellusers in New York could potentially be impacted by road salt storage facilities and 24% could potentially be impacted by road salt application. Our research underscores the need to include the damage to public and privately owned drinking water infrastructure in future discussion of road salt management.

Quantification of water and sewage leakages from urban infrastructure into a shallow aquifer in East Ukraine

Leaky water supply and sewer mains can become unmanaged sources of urban groundwater recharge and contamination posing environmental and health risks. Stable isotopes of water and hydrochemical tracer were applied to quantify water and sewage leakages in a shallow aquifer of a large Ukrainian city. Binary and ternary mixing models were used based on the d-excess and chloride concentrations of tap water, rural and urban groundwater to estimate fractions of natural recharge, urban seepage, volumes of water supply and sewage leakages in urban springs. Water supply leakages that recharge aquifer were ~ 3% (6.5 Mm3 a− 1) of the total water supply and strongly correlated with failures on the water infrastructure. Sewage leakages (1.4 Mm3 a− 1) to the aquifer were less in amount than water supply leakages, but induced nitrate and associated contaminants pollution risk of urban groundwater. The proposed method is useful for the pilot evaluation of urban groundwater recharge and contamination and can be applied in other regions worldwide to support the decision-making in water management.

Assessing groundwater recharge in crystalline and karstic aquifers of the Upper Crocodile River Basin, Johannesburg, South Africa

Groundwater recharge and flow conditions were assessed in the Upper Crocodile River Basin, Johannesburg South Africa. This study revealed high elevation recharge from rainfall that is depleted in stable isotopes of water molecule (δ18O and δ2H) occurring prior to extreme evaporation. The effective recharge occurs from rainfall of varying moisture source and humidity conditions. The δ13C (‰) value in groundwater indicates both open and closed system carbon evolution. Open system was observed in shale, andesite and granitic gneiss aquifers indicating that soil CO2 is a dominant source of carbon in bicarbonate. Enriched δ13C observed in Malmani dolomite aquifers deduced the presence of carbonate dissolution, which indicates a closed system carbon evolution. Mixing of water from open and closed systems, or evolution from closed to open system is also observed in groundwater samples that had intermediate δ13C (‰) values, particularly groundwater samples that are positioned at the periphery of the Basement Complex granitic gneiss near the Malmani dolomite aquifers. The integrated mean annual recharge estimates obtained from BFS for the UCRB is 6.7% while the distributed point recharge estimates in the Malmani dolomite obtained from application of WTF on 43 individual boreholes ranged between 2.5% and 39% with an average of 15% as a percentage of MAP. A comparison between estimated recharge and groundwater abstractions conducted for each sub-catchment revealed that there is an excess of groundwater recharge over groundwater use in most sub-catchments. The CMB point recharge estimates obtained from the Albert Farm spring and the Malmani dolomite springs are 2.5% and 27.8% of MAP, respectively. The low CMB recharge estimates in the shale and quartzite has been attributed to possible anthropogenic chloride sources such as leakage of chlorinated potable water in the pipelines of the city of Johannesburg, which elevate chloride concentrations in groundwater.

Large-scale, probabilistic salinity mapping using airborne electromagnetics for groundwater management in Zeeland, the Netherlands

Seawater intrusion has often resulted in scarce fresh groundwater resources in coastal lowlands. Careful management is essential to avoid the overexploitation of these vulnerable fresh groundwater resources, requiring detailed information on their spatial occurrence. Airborne electromagnetics (EM) has proved a valuable tool for efficient mapping of ground conductivity, as a proxy for fresh groundwater resources. Stakeholders are, however, interested in groundwater salinity, necessitating a translation of ground conductivity to groundwater salinity. This paper presents a methodology to construct a high-resolution (50 × 50 × 0.5 m3) 3D voxel model of groundwater chloride concentration probability, based on a large-scale (1800 km2, 9640 flight line kilometres) airborne EM survey in the province of Zeeland, the Netherlands. Groundwater chloride concentration was obtained by combining pedotransfer functions with detailed lithological information. The methodology includes a Monte Carlo based forward uncertainty propagation approach to quantify the inherent uncertainty in the different steps. Validation showed good correspondence both with available groundwater chloride analyses, and with ground-based hydrogeophysical measurements. Our results show the limited occurrence of fresh groundwater in Zeeland, as 75% of the area lacks fresh groundwater within 15 m below ground surface. Fresh groundwater is mainly limited to the dune area and sandy creek ridges. In addition, significant fresh groundwater resources were shown to exist below saline groundwater, where infiltration of seawater during marine transgressions was hindered by the presence of clayey aquitards. The considerable uncertainty in our results highlights the importance of applying uncertainty analysis in airborne EM surveys. Uncertainty in our results mainly originated from the inversion and the 3D interpolation, and was largest at transition zones between fresh and saline groundwater. Reporting groundwater salinity instead of ground conductivity facilitated the rapid uptake of our results by relevant stakeholders, thereby supporting the necessary management of fresh groundwater resources in the region.

Análisis y modelización de la salinidad del agua subterránea en la Franja de Gaza

The Gaza Strip suffers from an acute problem in the water quality and quantity. Groundwater is used as drinking water, for agricultural uses, and industrial processes. Salinity is increasing in groundwater in the Gaza Strip. Seawater intrusion is the main source of salinity. A chloride ion-selective is used as indicator of salinity for analysis and modelling of salinity of groundwater in the Gaza Strip by 2023. Research depends on three models for prediction of chloride concentration in groundwater: Forecasting, Linear regression and Multiple regression for the year 2023. The result of three models showed water salinity will increase in all areas in the Gaza Strip by the year 2023. Only a small area in the North Governorate will keep less than 250 mg/L of chloride concentration in fresh water, which represents 4.56 % of the total of the Gaza Strip area. The analysis of seawater intrusion within the cross sections is clear along the coastline and outspreads from the Mediterranean Sea to the East part of the Gaza Strip.

CAD-DRASTIC: chloride application density combined with DRASTIC for assessing groundwater vulnerability to road salt application

Road salt is pervasively used throughout Canada and in other cold regions during winter. For cities relying exclusively on groundwater, it is important to plan and minimize the application of salt accordingly to mitigate the adverse effects of high chloride concentrations in water supply aquifers. The use of geospatial data (road network, land use, Quaternary and bedrock geology, average annual recharge, water-table depth, soil distribution, topography) in the DRASTIC methodology provides an efficient way of distinguishing salt-vulnerable areas associated with groundwater supply wells, to aid in the implementation of appropriate management practices for road salt application in urban areas. This research presents a GIS-based methodology to accomplish a vulnerability analysis for 12 municipal water supply wells within the City of Guelph, Ontario, Canada. The chloride application density (CAD) value at each supply well is calculated and related to the measured groundwater chloride concentrations and further combined with soil media and aquifer vadose- and saturated-zone properties used in DRASTIC. This combined approach, CAD-DRASTIC, is more accurate than existing groundwater vulnerability mapping methods and can be used by municipalities and other water managers to further improve groundwater protection related to road salt application.

Transport and fate of chloride from road salt within a mixed urban and agricultural watershed in Illinois (USA): assessing the influence of chloride application rates

In a typical winter season, approximately 471,000 tons of road salt are deposited along roadways in Illinois, USA. An estimated 45% of the deposited road salt will infiltrate through the soils and into shallow aquifers. Transported through shallow aquifers, chloride associated with the road salts has the potential to reside within groundwater for years based on the pathway, the geologic material, and the recharge rate of the aquifer system. Utilizing MODFLOW and MT3D, simulations employing various road-salt application rates were conducted to assess the net accumulation of chloride and the residence times of chloride in an agriculture-dominated watershed that originates in an urban area. A positive-linear relationship was observed between the application rate of chloride and both the maximum chloride concentration and total mass accumulated within the watershed. Simulated annual recharge rates along impacted surfaces ranged from 1,000 to 10,000 mg/L. After 60 years of application, simulated chloride concentrations in groundwater ranged from 197 to 1,900 mg/L. For all application rates, chloride concentrations within the groundwater rose at an annual rate of >3 mg/L. While concentrations increase throughout the system, the majority of chloride accumulation occurs near the roads and the urban areas. Model simulations reveal a positive relationship between application rate and residence time of chloride (1,123–1,288 days based on application rate). The models indicate that continued accumulation of chloride in shallow aquifers can be expected, and methods that apply less chloride effectively need to be examined.

Using Annual Rainfall to Estimate the Surface Runoff and Groundwater Recharge in Lialan Basin (Southeast Kirkuk - North of Iraq)

The present study intends to estimate the surface runoff and groundwaterrecharge in Lialan basin using the soil conservation service method (curve number)and chloride mass balance method (CMB) respectively. Lialan basin is located at thesoutheast part of Kirkuk governorate, between longitudes (44° 21' 00" E - 44° 42'00" E) and latitudes (35° 7' 30" N - 35° 28' 30" N) , which covering an area of about436 km2 and contains many geological formations. In this study, based on theannual rainfall data extending from (1970 - 2016) obtained from the Kirkukmeteorological station, the surface runoff was calculated using the curve numbermethod (CN), and found to be equal to 90.4 mm/year, which represent 26.07 % ofthe total rainfall. While the groundwater recharge was calculated depending on theannual rainfall and chloride concentrations in rainfall and groundwater using thechloride mass balance method (CMB) and found it equals 23.07 mm/year,representing 7.42 % of the total rainfall. Thus the annual recharge amount for thewhole basin is equal to 10.0585 × 106 m3 / year. Generally, the results indicate adirect relationship between the systems of runoff and groundwater recharge inLialan basin with total rainfall .

Irrigation return flows in a mediterranean aquifer inferred from combined chloride and stable isotopes mass balances

The supply of irrigation water often overcomes crop evapotranspiration, and the resulting return flow may infiltrate and significantly contribute to an aquifer water budget. Despite its crucial importance for water resource management, the proportion of irrigation water that contributes to groundwater recharge, namely the return flow coefficient, often remains difficult to assess. Here, a chloride mass balance is combined with an isotopic mixing model (δ18O and δD) to quantify return flow coefficients, in the Crau alluvial-type aquifer (Southern France), characterized by a long-term traditional practice of flood irrigation. Local groundwater compositions are interpreted in terms of average recharge along different flow paths. The high isotopic contrast between irrigation water and regional precipitation allows the partitioning of recharge between rainfall infiltration and irrigation return flows. Isotopic mixing proportions are then used to decipher the chloride concentration of groundwater purely recharged by return flow. This allows an original application of the chloride mass balance approach to estimate return flow coefficients, which doesn't rely on any atmospheric chloride survey. Values around 0.53 ± 0.16 were found for well defined stream lines averaging the functioning of the upstream aquifer, which leads to a return flow rate of 1190 ± 140 mm yr−1. These results are consistent with a local daily time series of recharge fluxes derived from the water-table fluctuation method over the 2003-2009 period, and in line with the spatial average previously quantified over the whole aquifer. This study confirms the ability of geochemical tracers to provide recharge rates fully independent from flux measurements. They can be further used to assess the irrigation efficiency in other similar systems, or to monitor the variations of irrigation return flow, which will result from the future modifications of land use, irrigation practices and climate.

Study of Groundwater Salinity in Few Districts Adjoining River Ganga in Uttar Pradesh - A Case Study

Central Pollution Control Board has focused on impact assessment of sewerage system and groundwater studies on River Ganga particularly in Uttar Pradesh state. Variation of total dissolved solid values in groundwater in some of the locations reveal that the water has become ‘Saline’ and ‘Brackish’ which could be due to over-extraction, besides contamination from anthropogenic sources. The chloride concentration in groundwater in the study shows that 10 locations are beyond the desirable limit as specified by BIS. There is a direct relationship between total dissolved solid and sodium, indicating of contamination. Nitrate content in groundwater in only one location, i.e., Dinapur, exceeded more than 7 times from the Indian Drinking Water Quality Criteria. The higher value of fluoride in groundwater was observed at various locations of Uttar Pradesh and appeared an inverse relationship between calcium concentrations indicating the cause as anthropogenic sources. Similarly, sulphate in 16 locations and phosphate in various locations of Saharanpur and Unnao districts exceeded the maximum permissible limit of BIS specified. Total coliform and faecal coliform counts was found in 27 locations above the permissible limits of BIS specified.

Exploration of groundwater flowpaths and effective recharge in the Amargosa Desert, Nevada, using multivariate statistical analysis and elevation-dependent chloride mass-balance method

Estimation of groundwater flowpaths and effective recharge was performed in the vicinity of Amargosa Desert, Nevada, USA, using multivariate statistical methods (MSMs) and a simple elevation-dependent chloride mass-balance method modified by estimating a minimum effective recharge elevation (MERE). MSMs were applied to major ion data to explain the relationships among different groundwater chemical species, define hydrochemical facies needed to determine groundwater flowpaths and evolution, and identify the influence of surface and geologic features on groundwater. For each defined watershed, an average groundwater chloride concentration is used and the chloride deposition rate is assessed in the subject watersheds over all land elevations above the estimated MERE by assuming two constant spatial and temporal concentrations of chloride in precipitation which is a function of elevation. The MERE for the Amargosa Desert was appraised as 1200 m above mean sea level (m-amsl), based upon the elevation of the orifice of Cane Spring (1237 m-amsl), one of the lowest elevation, permanent springs, on the Nevada National Security Site. This minimum elevation is the cutoff altitude for our calculations at which precipitation is considered to make a significant contribution to recharge. Elevation-dependent precipitation was evaluated relating elevation data from the online mapping software ACME Labs Mapper 2.1 and precipitation data from the PRISM Climate Group’s PRISM. These analyses provide further insight into the hydrology of the region and demonstrate the strong impact surface and geologic features can have on surface water infiltration and groundwater in arid regions. Specifically, evidence is presented of past focused recharge around the ephemeral Fortymile Wash and interaction between geologic faults and groundwater infiltration and flowpaths. In addition, groundwater flow, based upon water chemistry, appears to be segmented by major faults. Groundwater recharge in the vicinity of the Amargosa Desert has been estimated around 15,280 acre-ft/year.

Estimation of spatial distribution of groundwater recharge from stream baseflow and groundwater chloride

In this study groundwater chloride concentration and baseflow are used to estimate the spatial variability of recharge. Total recharge over the entire watershed is estimated using the baseflow method, and then the spatial variability of recharge is approximated using groundwater chloride concentration. The efficacy of the method is demonstrated using data from a rural watershed in Alberta, Canada. By using the combination of two well established methods of estimating recharge, baseflow and chloride mass balance, there is no need to estimate wet and dry deposition rate of chloride. The presented method is tested by using a steady-state groundwater flow model. The groundwater model showed higher agreement between modeled vs observed heads when spatially variable recharge forced the upper boundary of the model (root mean square error reduced from 13.5m to 8m). In addition, we demonstrate a unique method for parameterizing hydraulic conductivity of a fluvial aquifer using a sand fraction transfer function. This new method reduces the dimensionality of the parameter estimation problem and provides a consistency check on the spatially varying recharge estimates.

Infiltration Rate of Groundwater in Vadose Zone of Uplifted Carbonate Island

Solute contents in the vadose zone of limestone strata on Miyako Island of the Ryukyu Archipelago in Japan were measured by means of electrical conductivities (EC) of the extracted solutions of limestone core samples. A vertically nonuniform distribution of solute content was observed, which should lead to temporal variations of solute concentration in the groundwater under the water table. On the other hand, the data of chloride concentration in groundwater from 13 wells on the island was analyzed to see their long time variations. Both of these two approaches resulted in recharge rates of around 10^-7 m s^-1 for the vadose zone in the limestone strata of this typical uplifted carbonate island of the western Pacific Ocean.

The smoothing methods used in assessing the influence of pollution sources on groundwater quality – a case study of metallurgical landfill in Lipówka (southern Poland)

Abstract Several methods have been used to determine trends in hydrogeochemical elements. This study is concerned with the ordinary 3-period moving averages, the 3-period moving median and the exponential smoothing method. It has taken into account the chloride concentration in groundwater from the region of the landfill of the Katowice Ironworks (southern Poland). The data from two piezometers were used: T1 screened in the Triassic and Q1 screened in the Quaternary aquifers. The main aim of this article was to compare statistical methods and to choose the most appropriate method for an assessment of the impact of pollution sources on groundwater quality and determining any trends. The choice of chlorides as the analyzed indicator is connected with their chemical conservative character. They are also indicators of negative impact on groundwater of e.g. municipal, metallurgical landfill sites on groundwater. Results showed that the moving median is less sensitive to outliers than the moving average. The running median preserves sharp discontinuities in the signal but the biggest smoothing was observed in the case of exponential smoothing. All of these methods filter out the noise and transform the data into a smooth curve, which is unbiased by outliers. Application of the smoothing method allowed the generalization of the monitoring data which clearly showed trends. In the absence of reliable data for short periods, these statistical methods made it possible to fill in missing values. These methods are easier to calculate than regression models even if they ignore complex relationships in the data. Moreover, they can also be used as a component in many other indicators such as the Moving Average Convergence Divergence.

A Standardized Index for Assessing Seawater Intrusion in Coastal Aquifers: The SITE Index

A large number of coastal aquifers worldwide are impacted by seawater intrusion. A major aim of European Directives 2000/60/EC and 2006/118/EC is to achieve good ecological status in groundwater bodies, including coastal aquifers. To this goal, information is needed about the current state of, and changes over time in, individual aquifers. This information can be obtained by applying methods that determine the status of aquifers in an uncomplicated manner. Methods for this type of assessment must comply with three essential criteria. First, calculation of the index must be straightforward and should be based on easy-to-obtain or commonly available data. Next, the index should be able to highlight important characteristics in understandable terms. Finally, the results should be objective and should be expressed in such a way that different time periods and different aquifers can be compared. In this paper we describe the development of a method to characterize seawater intrusion that meets these criteria and is based on four basic parameters: surface area, intensity, temporality, and evolution. Each parameter is determined by specific calculations derived from the groundwater chloride concentrations. Results are specified as a numerical index and an alphanumeric code. This index, known as SITE, has been applied to four Mediterranean coastal aquifers. The standardized results allowed us to discriminate between, and objectively compare the status of these groundwater bodies. Further, this index will make it possible to prioritize management actions and evaluate the effectiveness of these actions over time.

Identification of nitrate source using isotopic and geochemical data in the lower reaches of the Yellow River irrigation district (China)

Nitrate contamination in both surface water and groundwater has received considerable attentions in irrigated agricultural areas. Nitrate concentrations, and its nitrogen and oxygen isotopic compositions, as well as oxygen and deuterium isotopic compositions and chloride concentrations of surface water and groundwater from a typical area in the lower reaches of the Yellow River irrigation district were analyzed to ascertain spatial variations of nitrate and its possible sources and transformations. The results of this study showed nitrate in the Yellow River mainly derived from mineralization of organic matter in sediments and nitrification of atmospheric deposition, and nitrate in other important tributaries were greatly affected by agricultural activities, especially synthetic fertilizer. Nitrate in irrigation canals which go through concentrated residential zone mainly originated from domestic effluent and experienced nitrification. Nitrate in groundwater is not only affected by surface nitrate sources, but also closely related to hydraulic conditions which make nitrate source discrimination more complex. In areas belonging to the Yellow River basin with shallow water tables, nitrate is mainly derived from synthetic fertilizer, and denitrification processes controlled nitrate isotopic compositions in extremely shallow groundwater with low hydraulic gradients. While in places belonging to the Haihe River basin with deep water table, groundwater nitrate is largely affected by mixing process of irrigation water. The main sources of nitrate in groundwater are manure and sewage and soil organic matter, while chemical fertilizer and atmospheric deposition in large amount of rainfall are its minor contributors.

Groundwater vulnerability assessment in agricultural areas using a modified DRASTIC model.

Groundwater contamination is a major concern for groundwater resource managers worldwide. We evaluated groundwater pollution potential by producing a vulnerability map of an aquifer using a modified Depth to water, Net recharge, Aquifer media, Soil media, Topography, Impact of vadose zone, and Hydraulic conductivity (DRASTIC) model within a Geographic Information System (GIS) environment. The proposed modification which incorporated the use of statistical techniques optimizes the rating function of the DRASTIC model parameters, to obtain a more accurate vulnerability map. The new rates were computed using the relationships between the parameters and point data chloride concentrations in groundwater. The model was applied on Saveh-Nobaran plain in central Iran, and results showed that the coefficient of determination (R (2)) between the point data and the relevant vulnerability map increased significantly from 0.52 to 0.78 after modification. As compared to the original DRASTIC model, the modified version produced better vulnerability zonation. Additionally, single-parameter and parameter removal sensitivity analyses were performed to evaluate the relative importance of each DRASTIC parameter. The results from both analyses revealed that the vadose zone is the most sensitive parameter influencing the variability of the aquifers' vulnerability index. Based on the results, for non-point source pollution in agricultural areas, using the modified DRASTIC model is efficient compared to the original model. The proposed method can be effective for future groundwater assessment and plain-land management where agricultural activities are dominant.

Salt vulnerability assessment methodology for municipal supply wells

Summary De-icing agents containing chloride ions used for winter road maintenance have the potential to negatively impact groundwater resources for drinking water supplies. A novel methodology using commonly-available geospatial data (land use, well head protection areas) and public accessible data (salt application rates, hydrometric data) to identify salt vulnerable areas (SVAs) for groundwater wells is developed to prioritize implementation of better management practices for road salt applications. The approach uses simple mass‐balance terms to collect chloride input from 3 pathways: surface runoff, shallow interflow and baseflow. A risk score is calculated, which depends on the land use within the respective municipal supply well protection area. Therefore, it is plausible to avoid costly and extensive numerical modeling (which also would bear many assumptions, simplifications and uncertainties). The method is applied to perform a vulnerability assessment on twenty municipal water supply wells in the Grand River watershed, Ontario, Canada. The calculated steady-state groundwater recharge chloride concentration for the supply wells is strongly correlated to the measured transient groundwater chloride concentrations in the case study evaluation, with an R 2 = 0.84. The new method provides a simple, robust, and practical method for municipalities to assess the long-term risk of chloride contamination of municipal supply wells due to road salt application.