Assessment of deep aquifer groundwater quality in a geographically unique climatic region of Southern Western Ghats,India using water quality indices

Water quality index (WQI) models are generally used in hydrochemical studies to simplify complex data into single values to reflect the overall quality. In this study, deep groundwater quality in the Chittur and Palakkad Taluks of the Bharathapuzha river basin of Kerala, India, was assessed by employing the WQI method developed by the Canadian Council of Ministers of the Environment (CCME). The assessment of overall water quality is indispensable due to the specific characteristics of the study area, such as geography, climate, over-drafting, and prevalent agricultural practices. Forty representative samples were collected from the study area for monsoon (MON) and pre-monsoon (PRM) seasons. The results showed a general increase of contents from MON to PRM. The major cations were spread in the order Ca²⁺>Na+>Mg²⁺>K⁺ and the anions HCO₃⁻>Cl⁻>CO₃²⁻ based on their relative abundance. Among various parameters analysed, alkalinity and bicarbonate levels during MON were comparatively high, which is indicative of carbonate weathering, and 90% of the samples failed to meet the World Health Organization (WHO, 2017)/Bureau of Indian Standards (BIS, 2012) drinking water guidelines. The CCME WQI analysis revealed that nearly 50% of the samples during each season represented good and excellent categories. The samples in the poor category comprised 10% in MON and 15% in PRM. The overall WQI exhibited 15% of poor category samples as well. The spatial depiction of CCME WQI classes helped to expose zones of degraded quality in the centre to eastward parts. The spatial and temporal variations of CCME WQI classes and different physicochemical attributes indicated the influence of common factors attributing to the deep groundwater quality. The study also revealed inland salinity at Kolluparamba and Peruvamba stations, where agricultural activities were rampant with poor surface water irrigation.     

Assessment of the Hydrogeochemistry and Groundwater Quality of the Tarim River Basin in an Extreme Arid Region, NW China

The concentrations of the major and trace elements in the groundwater of the Tarim River Basin (TRB), the largest inland river basin of China, were analyzed before and during rainy seasons to determine the hydrogeochemistry and to assess the groundwater quality for irrigation and drinking purposes. The groundwater within the TRB was slightly alkaline and characterized by high ionic concentrations. The groundwater in the northern sub-basin was fresh water with a Ca²⁺–HCO₃ ^? water type, whereas the groundwater in the southern and central sub-basins was brackish with a Na⁺–Cl^? water type. Evaporite dissolution and carbonate weathering were the primary and secondary sources of solutes in the groundwater within the basin, whereas silicate weathering played a minor role. The sodium adsorption ratio (SAR), water quality index (WQI), and sodium percentage (%Na) indicated that the groundwater in the northern sub-basin was suitable for irrigation and drinking, but that in the southern and central sub-basins was not suitable. The groundwater quality was slightly better in the wet season than in the dry season. The groundwater could be used for drinking after treatment for B³⁺, F^?, and SO₄ ^2? and for irrigation after control of the sodium and salinity hazards. Considering the high corrosivity ratio of the groundwater in this area, noncorrosive pipes should be used for the groundwater supply. For sustainable development, integrated management of the surface water and the groundwater is needed in the future.     

Application of Multivariate Statistical Methods and Water-Quality Index to Evaluation of Water Quality in the Kashkan River

The Kashkan River (KR), located in the west of Iran, is a major source of water supply for residential and agricultural areas as well as livestock. The objective of this study was to assess the spatial and long temporal variations of surface water quality of the KR based on measured chemical ions. The Canadian Council of Ministers of Environment Water Quality Index (CCME WQI) technique was utilized using measurements from 10 sampling stations during a period of 36 years (1974–2009). The measured data included cations (Na⁺, K⁺, Ca²⁺, Mg²⁺), anions (HCO₃ ^?, Cl^?, SO₄ ^2?), pH, and electrical conductivity. Principal component analysis was performed to identify which of the parameters to be included in the CCME WQI calculations were actually correlated and which ones were responsible for most of the variance observed in the water-quality data. In addition, KR water quality was evaluated for its suitability for drinking and irrigation purposes using conventional methods. Last, trend detection in the WQI time series of the KR showed water-quality degradation at all sampling stations, whereas the Jelhool sub-basin more adversely affects the quality of KR water in the watershed. Nonetheless, on average, the water quality of the KR was rated as fair.     

A Gis-Based Assessment of Groundwater Suitability for Irrigation Purposes in Flat Areas of the Wet Pampa Plain, Argentina

The Pampa in Argentina is a large plain with a quite obvious dependence on agriculture, water availability and its quality. It is a sensitive environment due to weather changes and slope variations. Supplementary irrigation is a useful practice for compensating the production in the zone. However, potential negative impacts of this type of irrigation in salinization and sodification of soils are evident. Most conventional methodologies for assessing water irrigation quality have difficulties in their application in the region because they do not adjust to the defined assumptions for them. Consequently, a new GIS-based methodology integrating multiparametric data was proposed for evaluating and delineating groundwater suitability zones for irrigation purposes in flat areas. Hydrogeological surveys including water level measurements, groundwater samples for chemical analysis and electrical conductivity (EC) measurements were performed. The combination of EC, sodium adsorption ratio, residual sodium carbonate, slopes and hydraulic gradient parameters generated an irrigation water index (IWI). With the integration of the IWI 1 to 3 classes (categories of suitable waters for irrigation) and the aquifer thickness the restricted irrigation water index (RIWI) was obtained. The IWI's index application showed that 61.3?% of the area has "Very high" to "Moderate" potential for irrigation, while the 31.4?% of it has unsuitable waters. Approximately, 46?% of the tested area has high suitability for irrigation and moderate groundwater availability. This proposed methodology has advantages over traditional methods because it allows for better discrimination in homogeneous areas.     

Water quality indices appraisal and health risk assessment of nitrate,mercury and lead in water distribution network: A case study of Robat Karim in Tehran,Iran

Groundwater is a basic source of drinking water supply for urban and rural areas. This is especially the case for communities located in arid and semi-arid regions that rely on groundwater for drinking purposes. The present study set out to assess the potential health impacts of water impurities and to investigate the qualitative status of drinking water in Robat Karim rural areas, located in southwest Tehran, Iran. A total of 66 samples were collected from the water distribution network of 11 villages (33 sampling points, on two occasions) during September 2020 and were tested in terms of the most common quality parameters such as pH, mercury (Hg), lead (Pb), copper (Cu), zinc (Zn), chloride (Cl^–), chlorate (ClO₃^–), nitrite (NO₂^–), nitrate (NO₃^–), and flouride (F^–). Multiple methods and indexes including water quality index (WQI), hazard quotient (HQ), and hazard index (HI), were worked out to assess the quality of water and health risk assessment of NO₃^– Pb²⁺ and Hg²⁺. The results revealed that 33% and 90% of sampling sites have significantly high nitrate and total hardness (TH) concentrations, exceeding the maximum permissible limits set by World Health Organization (WHO; 50 and 200 mg/L, respectively). Furthermore, five sampling points exhibited poor WQIs mainly related to NO₃^– and TH. HQ values higher than 1 for nitrate were noticed in most sampling locations. Except for one sampling point, the HQ obtained for Pb²⁺ and Hg²⁺ were below 1 indicating no obvious health hazard. This study represents that children and infants are at higher risk of chronic toxicity by excess NO₃^– intake. The health hazard that is yet imposed on the community by NO₃^– necessitates regular monitoring of drinking water, the use of advanced technologies to purify water or otherwise alternative resources should be proposed.     

Spatial Variability of Groundwater Depth and Quality Parameters in the National Capital Territory of Delhi

The groundwater quantity and quality scenario is of much concern in the National Capital Territory of Delhi, India, which necessitates an investigation to envisage the extent of spatial variability of groundwater depth and pollutant concentration levels in this region. Therefore, in this study, an effort was made to generate the spatial variability map of groundwater depth and quality parameters (viz. chloride, electrical conductivity, fluoride, magnesium, and nitrate). Ordinary kriging was used to analyze the spatial variability of groundwater depth and quality parameters, whereas indicator kriging was used to analyze groundwater quality parameters equal to or greater than the pollution threshold values. It was observed that the semivariogram parameters fitted well in the exponential model for water depth and in the spherical model for water quality parameters. The generated spatial variability maps indicated that in 43% of the study area, groundwater depth was within 20 m. The salinity level was higher than 2.5 dS m⁻¹ in 69% of the study area and the nitrate concentration exceeded 45 mg l⁻¹ in 36% of the area. The probability maps showed that about 24% of the area had the highest probability (0.8–1.0) of exceedence of the threshold electrical conductivity value and an area of 2% exhibited the highest probability of exceedence of the threshold value of nitrate concentration in the groundwater. The generated spatial variability and probability maps will assist water resource managers and policymakers in development of guidelines in judicious management of groundwater resources for agricultural and drinking purposes in the study area.     

A Water Quality Index Applied to an International Shared River Basin: The Case of the Douro River

A Water Quality Index (WQI) is a numeric expression used to evaluate the quality of a given water body and to be easily understood by managers. In this study, a modified nine-parameter Scottish WQI was used to assess the monthly water quality of the Douro River during a 10-year period (1992–2001), scaled from zero (lowest) to 100% (highest). The 98,000 km² of the Douro River international watershed is the largest in the Iberian Peninsula, split between upstream Spain (80%) and downstream Portugal (20%). Three locations were surveyed: at the Portuguese–Spanish border, 350 km from the river mouth; 180 km from the mouth, where the river becomes exclusively Portuguese; and 21 km from the mouth. The water received by Portugal from Spain showed the poorest quality (WQI 47.3 ± 0.7%); quality increased steadily downstream, up to 61.7 ± 0.7%. In general, the water quality at all three sites was medium to poor. Seasonally, water quality decreased from winter to summer, but no statistical relationship between quality and discharge rate could be established. Depending on the location, different parameters were responsible for the episodic decline of quality: high conductivity and low oxygen content in the uppermost reservoir, and fecal coliform contamination downstream. This study shows the need to enforce the existing international bilateral agreements and to implement the European Water Quality Directive in order to improve the water quantity and quality received by the downstream country of a shared watershed, especially because two million inhabitants use the water from the last river location as their only source of drinking water.     

Variability of soil-water quality due to Tsunami-2004 in the coastal belt of Nagapattinam district, Tamilnadu

In this study, the Tsunami-caused deterioration of soil and groundwater quality in the agricultural fields of coastal Nagapattinam district of Tamilnadu state in India is presented by analyzing their salinity and sodicity parameters. To accomplish this, three sets of soil samples up to a depth of 30cm from the land surface were collected for the first six months of the year 2005 from 28 locations and the ground water samples were monitored from seven existing dug wells and hand pumps covering the study region at intervals of 3 months. The EC and pH values of both the soil and ground water samples were estimated and the spatial and temporal variability mappings of these parameters were performed using the geostatistical analysis module of ArcGIS((R)). It was observed that the spherical semivariogram fitted well with the data set of both EC and pH and the generated kriged maps explained the spatial and temporal variability under different ranges of EC and pH values. Further, the recorded EC and pH data of soil and ground water during pre-Tsunami periods were compared with the collected data and generated variability soil maps of EC and pH of the post-Tsunami period. It was revealed from this analysis that the soil quality six months after the Tsunami was nearing the pre-Tsunami scenario (EC< 1.5dSm(-1); pH<8), whereas the quality of ground water remained highly saline and unfit for irrigation and drinking. These observations were compared with the ground scenarios of the study region and possible causes for such changes and the remedial measures for taking up regular agricultural practices are also discussed.     

Regression models for estimating concentrations of atrazine plus deethylatrazine in shallow groundwater in agricultural areas of the United States

Tobit regression models were developed to predict the summed concentration of atrazine [6-chloro--ethyl--(1-methylethyl)-1,3,5-triazine-2,4-diamine] and its degradate deethylatrazine [6-chloro--(1-methylethyl)-1,3,5,-triazine-2,4-diamine] (DEA) in shallow groundwater underlying agricultural settings across the conterminous United States. The models were developed from atrazine and DEA concentrations in samples from 1298 wells and explanatory variables that represent the source of atrazine and various aspects of the transport and fate of atrazine and DEA in the subsurface. One advantage of these newly developed models over previous national regression models is that they predict concentrations (rather than detection frequency), which can be compared with water quality benchmarks. Model results indicate that variability in the concentration of atrazine residues (atrazine plus DEA) in groundwater underlying agricultural areas is more strongly controlled by the history of atrazine use in relation to the timing of recharge (groundwater age) than by processes that control the dispersion, adsorption, or degradation of these compounds in the saturated zone. Current (1990s) atrazine use was found to be a weak explanatory variable, perhaps because it does not represent the use of atrazine at the time of recharge of the sampled groundwater and because the likelihood that these compounds will reach the water table is affected by other factors operating within the unsaturated zone, such as soil characteristics, artificial drainage, and water movement. Results show that only about 5% of agricultural areas have greater than a 10% probability of exceeding the USEPA maximum contaminant level of 3.0 μg L. These models are not developed for regulatory purposes but rather can be used to (i) identify areas of potential concern, (ii) provide conservative estimates of the concentrations of atrazine residues in deeper potential drinking water supplies, and (iii) set priorities among areas for future groundwater monitoring.     

Leaching of pharmaceuticals and personal care products in turfgrass soils during recycled water irrigation

An important beneficial reuse of treated wastewater (recycled water) in arid and semiarid regions is landscape irrigation. However, the environmental fate, especially groundwater contamination potential, of trace contaminants such as pharmaceuticals and personal care products (PPCPs) is a significant concern that can hinder the acceptance and adoption of such reuses. In this study, we irrigated mature turfgrass plots with nonspiked tertiary treated wastewater for over 6 mo at 100 or 130% of the reference evapotranspiration rate (ETo) and collected leachate water at the 90-cm depth on a weekly basis. In the recycled water, all 14 target PPCPs were consistently found, and the mean levels of atenolol, gemfibrozil, meprobamate, carbamazepine, and sulfamethoxazole were above 100 ng L. However, only five compounds were detected in the leachate at trace levels. Trimethoprim and primidone were frequently found, whereas the detection of sulfamethoxazole, meprobamate and carbamazepine was less frequent (<50%). When detected, the overall mean concentration in the leachate was 10.2 ng L for trimethoprim, 7.1 ng L for primidone, and 2.9 to 12.4 ng L for carbamazepine, sulfamethoxazole, and meprobamate. The majority of the target PPCPs were completely removed. Given that the irrigation rates were higher than normal, this study clearly demonstrated the efficacy of turfgrass systems in attenuating PPCPs during recycled water irrigation. However, it is also apparent that some PPCPs are more susceptible to leaching than others, and these PPCPs thus merit further research attention.     

Influence of alkalinity, hardness and dissolved solids on drinking water taste: A case study of consumer satisfaction

Two surveys of consumer satisfaction with drinking water conducted by Taiwan Water Supply Corp. are presented in this study. The study results show that although a lot of money was invested to modify traditional treatment processes, over 60% of local residents still avoided drinking tap water. Over half of the respondents felt that sample TT (from the traditional treatment process) was not a good drinking water, whether in the first or second survey, whereas almost 60% of respondents felt that samples PA, PB, CCL and CT (from advanced treatment processes) were good to drink. For all drinking water samples, respondent satisfaction with a sample primarily depended on it having no unpleasant flavors. Taiwan Environmental Protection Administration plans to revise the drinking water quality standards for TH and TDS in the near future. The new standards require a lower TH concentration (from currently 400mg/L (as CaCO(3)) to 150mg/L (as CaCO(3))), and a lower TDS maximum admissible concentration from the current guideline of 600 to 250mg/L. Therefore, this study also evaluated the impacts on drinking water tastes caused by variations in TH and TDS concentrations, and assessed the need to issue more strict drinking water quality standards for TH and TDS. The research results showed that most respondents could not tell the difference in water taste among water samples with different TDS, TH and alkalinity. Furthermore, hardness was found to be inversely associated with cardiovascular diseases and cancers, and complying with more strict standards would lead most water facilities to invest billions of dollars to upgrade their treatment processes. Consequently, in terms of drinking water tastes alone, this study suggested that Taiwan Environmental Protection Administration should conduct more thorough reviews of the scientific literature that provides the rationale for setting standards and reconsider if it is necessary to revise drinking water quality standards for TH and TDS.     

Developing a Standardized Water Quality Index for Evaluating Surface Water Quality1

Abstract: There is a significant need for a science‐based approach to interpret water‐monitoring data and to facilitate the rapid transfer of information to water resource managers and the general public. The water quality Index (WQI) is defined as a single numeric score that describes the surface water quality condition at a particular time and location. The objective of this paper is to describe the WQI concept and the approach for developing an ecoregion‐specific standardized WQI that meets the needs described above. The premise of the proposed WQI is based on categorizing scientifically documented aquatic life responses to changes in instream water chemistry. The method uses an aggregated procedure that matches the entire range of standardized probable biological responses to standardized narrative water quality evaluation categories and standardized rank score categories. The calculation of WQI and decision‐making process are performed within an Excel spreadsheet software program. The article includes examples of the proposed WQI applications that could enhance effective water resource management and facilitate timely communication of water quality conditions to water resource managers and the general public.     

Veterinary drugs in groundwater in a dairy region of central Argentina and risk assessment for human health

Veterinary drugs used in dairy production are potential contaminants of surface or groundwater sources, being able to affect human and environmental health. It is known that chronic exposure to antibiotics in low concentrations present in water can generate microbial resistance. This study aimed to evaluate the presence of veterinary drugs in 53 groundwater samples used for animal and human consumption, collected in dairy milking parlors, in an important milk-producing area of central Argentina, and to assess the risk to human health when they are used as drinking water. In 75% of the total samples analyzed, at least one veterinary drug was detected. The most frequently found drugs in water samples were the antibiotics tetracycline in 58.5% and oxytetracycline in 56.6%, and an anti-inflammatory, flunixin in 39.6%. In the water samples, the tetracycline and oxytetracycline concentrations were between 0.1 and 5.3 μg/L and flunixin concentrations were between 0.01 and 2.1 μg/L. The frequency of appearance and the concentration levels of the substances found in the water samples were evaluated according to the productivity, size, and production system (confined or pasture) of the dairy farms. Higher concentrations and proportions of water samples containing antibiotics were observed when the number of animals per dairy farm was >182 and when the productivity was high (>25 liters per animal per day). In the case of flunixin, the percentage of detection was similar in all evaluated categories. The risk assessment for children and adults, considering the intake of drinking water containing residues of these drugs, did not indicate a significant health risk. It would be advisable to evaluate other sources of drinking water, both surface and underground, in other regions of the country, to provide data to assess the impact of these substances and the other contaminants on environmental and human health.     

Assessment of Quality for Middle Level and High School Student‐Generated Water Quality Data

Student scientists have analyzed groundwater used for drinking water in rural areas to understand groundwater quality. This was part of a greater effort to understand risks to drinking water. The data produced by middle level and high school students have not been accepted by experts because of concerns about method and student accuracy. We assessed the inherent errors associated with method accuracy, student precision, and sample variability to establish bounds for attainable trueness in water analyses. Analytical test kits and probes were evaluated for the determination of pH, conductivity, chloride, hardness, iron, total soluble metals, and nitrate. In terms of precision, all methods met or exceeded design specifications. Method trueness was variable and in general ranged from good to poor depending on method. A gage reproducibility and repeatability analysis of instrumental methods (pH and conductivity) partitioned the variances into student error (12‐46%), instrumental error (8‐21%), and random error (45‐68%). Overall, student‐generated data met some of the quality objectives consistent with the method limitations. Some methods exhibited a systematic bias and data adjustment may be necessary. Given good management of the student analyst process, it is possible to make precise and accurate measurements consistent with the methods specifications.     

Evaluation of the vulnerability to contamination of drinking water systems for rural regions in Québec,Canada

The aim of this paper is to describe a method for evaluating the vulnerability of drinking water systems to contamination, in particular in rural regions used intensively for agriculture. To do so, various indicators were developed to represent the source to tap multi-barrier approach for drinking water safety. These indicators correspond to four barriers: source susceptibility to contamination; water treatment efficiency; distribution system management; and, overall management of water quality. The indicators were classified, regrouped and weighted within a model based on a multi-criteria analysis. The method was developed and applied to 39 municipal water systems of rural Quebec, Canada. The model obtained can be used for planning purposes to prioritise water systems requiring improvements.     

Potential health hazard of drinking water in restaurants and tea stalls

Potable and equitable drinking water (DW) is a fundamental human right and essential for human health. This study is conducted to assess the groundwater and jar water quality of the roadside restaurants and tea stalls used for drinking by the local people around the Gazipur City area in Bangladesh. Water samples from 173 restaurants and tea stalls are collected. The physico-chemical and biological parameters are analyzed according to the guidelines and standards. The results illustrate that the color, EC, and Mn of 41%, 80%, and 62% of the samples, respectively, exceed the WHO and Environmental Conservation Rules (ECR) standards. In addition, E. coli and total coliform exceeding the threshold standards are found in 47% and 64% of the water samples, respectively. The contamination of DW by fecal coliforms is confirmed and supported by prior studies, which indicates that the DW supplied in restaurants and tea stalls are unsafe because of the possible presence of pathogens. These may cause potential health hazards to consumers from various water-borne diseases. Poor sanitation, unhygienic practices, and improper disposal of wastewater are responsible for the microbial contamination of DW. So, the authorities in charge of these places should take the right regulatory steps, such as regular sanitation inspections, DW quality monitoring, hand-washing practices, and better sanitation in these places.     

Community‐based water supplies in Cikarang,Indonesia: are they sustainable?

Community‐based water supply (CBWS) is an example of how a community manages common pool resources (CPR). This results in an alternative approach to solve water supply problems in developing countries by enhancing community participation in managing water supply. This research evaluates the sustainability of five CBWS projects in Cikarang, Indonesia by using Ostrom's design principles, with additional sustainability factors found in the Sustainable Development Goal (SDG) on drinking water and groundwater sustainability. Quinn et al. (2007) criteria were used in the analysis, and the results show that the management of four CBWS institutions were absent and one CBWS institution was weak. With regards to the SDG's drinking water target, the CBWS institutions were unable to comply with safe water standards, and in terms of groundwater sustainability, efforts to monitor and sustain groundwater tables were absent. Results from this research suggest that more focus must be placed on water quality and groundwater sustainability for CBWS projects.     

基于MODFLOW数值模拟法的地下水饮用水源保护区划分

我国城乡居民饮用水安全现状不容乐观,饮用水源污染已经成为较突出的社会问题,其中地下水饮用水源污染更为突出.饮用水源保护区划分是保证水质安全的重要措施,饮用水源保护区划分方法较多,其中数值模拟法能客观并详细地描述含水层结构与水文地质条件,适用于各种背景的地下水水源研究.本文以崇州市城区饮用水源为例,采用MODFLOW软件建立地下水渗流场,应用MODPATH对水源地抽水井进行粒子逆向示踪模拟,根据不同的时间标准确定一、二级保护区范围,并结合区域水文地质条件和地标、地界特点确定各级保护区的界线.     

四川某小区人工湿地中水回用技术

中水回用是提高生活用水重复利用率的主要形式。提高水的重复利用率,是实现城市污水资源化是解决水资源短缺的根本途径。人工湿地既具有景观价值,又有污水处理功能。可以为市政绿化、农田灌溉景观提供水资源。经人工湿地处理的中水水质,出水水质符合我国的城市杂用水水质标准(GB/T18920-2002)、景观环境用水水质标准(GB/T18920-2002)和农田灌溉水质标准(GB5084-2005)。     

The Effects of Irrigation and Climate on the High Plains Aquifer: A County‐Level Econometric Analysis

The High Plains Aquifer (HPA) underlies parts of eight states and 208 counties in the central area of the United States (U.S.). This region produces more than 9% of U.S. crops sales and relies on the aquifer for irrigation. However, these withdrawals have diminished the stock of water in the aquifer. In this paper, we investigate the aggregate county‐level effect on the HPA of groundwater withdrawal for irrigation, of climate variables, and of energy price changes. We merge economic theory and hydrological characteristics to jointly estimate equations describing irrigation behavior and a generalized water balance equation for the HPA. Our simple water balance model predicts, at average values for irrigation and precipitation, an HPA‐wide average decrease in the groundwater table of 0.47 feet per year, compared to 0.48 feet per year observed on average across the HPA during this 1985–2005 period. The observed distribution and predicted change across counties is in the (?3.22, 1.59) and (?2.24, 0.60) feet per year range, respectively. The estimated impact of irrigation is to decrease the water table by an average of 1.24 feet per year, whereas rainfall recharges the level by an average of 0.76 feet per year. Relative to the past several decades, if groundwater use is unconstrained, groundwater depletion would increase 50% in a scenario where precipitation falls by 25% and the number of degree days above 36°C doubles. Editor’s note : This paper is part of the featured series on Optimizing Ogallala Aquifer Water Use to Sustain Food Systems. See the February 2019 issue for the introduction and background to the series.