Groundwater quality assessment: an improved approach to K-means clustering, principal component analysis and spatial analysis: a case study

"K-means clustering and principal component analysis (PCA) are widely used in water quality analysis and management. Nevertheless, numerous studies have pointed out that K-means with the squared Euclidean distance is not suitable for high-dimensional datasets. We evaluate a methodology (K-means based on PCA) for water quality evaluation. It is based on the PCA method to reduce the dataset from high dimensional to low for the improvement of K-means clustering. For this, a large dataset of 28 hydrogeochemical variables and 582 wells in the coastal aquifer are classified with K-means clustering for high dimensional and K-means clustering based on PCA. The proposed method achieved increased quality cluster cohesion according to the average Silhouette index. It ranged from 0.13 for high dimensional k-means clustering to 5.94 for K-means based on PCA and the practical spatial geographic information systems (GIS) evaluation of clustering indicates more quality results for K-means clustering based on PCA. K-means based on PCA identified three hydrogeochemical classes and their sources. High salinity was attributed to seawater intrusion and the mineralization process, high levels of heavy metals related to domestic-industrial wastewater discharge and low heavy metals concentrations were associated with industrial wastewater punctual discharges. This approach allowed the demarcation of natural and anthropogenic variation sources in the aquifer and provided greater certainty and accuracy to the data classification.

Determinación e interpretación de la calidad del agua y del suelo en el Distrito de Riego 066 Del Valle de Santo Domingo, Baja California Sur.

La calidad del agua y del suelo en un área agrícola son factores principales que repercuten en su sustentabilidad, debido a que una baja calidad en estos recursos reduce los rendimientos y causa toxicidad en los cultivos entre otros efectos adversos, afectando la productividad de la actividad y al ambiente. En el Distrito de Riego 066 del Valle de Santo Domingo se han detectado alteraciones notables en estos recursos, por esta razón este estudio planteó como objetivo evaluar e interpretar la calidad del agua del acuífero y suelo en el DR 066 y su relación con la producción agrícola. Se colectaron muestras de agua en 600 pozos de riego y de suelo en 710 parcelas; en cada muestra se determinó los siguientes parámetros: pH, CE, RAS, cationes, aniones, metales pesados y otros elementos. Estos resultados se interpretaron con base a los estándares nacionales e internacionales y además se formularon índices de calidad de agua y suelo (ICA y ICS respectivamente). En el caso de la calidad del agua, los análisis revelan que todos los pozos exceden los niveles máximos permisibles de estándares nacionales e internacionales de Conductividad eléctrica para uso agrícola y consumo humano; asimismo ningún pozo cumple los niveles permisibles de Cu, Mn, Al, Cr, Ni, Pb, y Co para ambos usos. El ICA calculado mostro que el agua es apta para la mayoría de los cultivos de la región excepto para maíz y frijol y para consumo humano se requieren de algún tratamiento de potabilización. Para el caso de la calidad del suelo, con base en los estándares nacionales e internacionales se determinó que los suelos no presentan problemas de salinidad y que las concentraciones de Cd, Pb y Ni no representan riesgo para los cultivos y la salud humana. Sin embargo de acuerdo al ICS los cultivos de frijol, naranja y maíz podrían disminuir sus rendimientos hasta en un 50%. La calidad del agua y suelo no han representado una limitante significativa en el desarrollo de la actividad agrícola en el Distrito, sin embargo existen evidencias de alteraciones en la calidad de los recursos agua y suelo que han obligado a los productores y gobierno a tomar medidas para enfrentar las complicaciones derivadas de este proceso. _______________ DETERMINATION AND INTERPRETATION OF WATER AND SOIL QUALITY IN THE 066 IRRIGATION DISTRICT OF VALLEY OF SANTO DOMINGO, BAJA CALIFORNIA SUR. ABSTRACT: Water and soil quality in an agricultural area are major factors that affect their sustainability, because lower quality on these resources reduces the yields and may cause toxicity on crops among other adverse effects, affecting the productivity of crops and the environment. In the 066 Irrigation District of Santo Domingo Valley alterations have been detected in these resources, therefore this study had the objective of evaluating and interpreting the aquifer and soil quality in the 066 Irrigation District and its relationship with agricultural production. Water samples were collected in 600 irrigation wells and soil samples in 710 agricultural plots. For each sample the following parameters were analyzed: pH, EC, SAE, cations, anions, heavy metals and other elements. The results were interpreted on the basis of national and international standards. Quality indices of water and soil (WQI and SQI respectively) were also determined. In the case of water quality, the analyzes reveal that all the wells exceed maximum permissible national and international standards levels of electrical conductivity for agriculture and human consumption, furthermore none well fulfills the standards of Cu, Zn, Al, Cr, Ni, Pb, and Co for both uses. The calculated WQI was suitable for most crops in the region except for maize and bean crops and for human consumption, since them require some kind of treatment. Regarding soil quality, based on national and international standards, there are not salinity problems, and Cd, Pb and Ni contents do not imply risk for crops and human health. The IQS indicated that yields of bean, orange and corn crops will decrease by up to 50%. Based on the above mentioned, water and soil quality do not represent a significant constraint for agricultural production in the 066 Irrigation District, but there is evidence of alterations in the quality of water and soil resources that have forced producers and government to take actions to cope those problems.Tesis (Doctorado en Ciencias, especialista en Hidrociencias).- Colegio de Postgraduados, 2012.Consejo Nacional de Ciencia y Tecnología (CONACYT)

Efectos secundarios por el uso del herbicida paraquat en el cultivo de jícama (Pachyrhizus erosus L.) en la localidad de La Trinidad Tepango, Atlixco Puebla

Para el control de arvenses en el agrosistema jícama (Pachyrhizus erosus L.), los productores de La Trinidad Tepango han optado por utilizar el herbicida paraquat, por su bajo costo y efectividad, no obstante su uso intensivo e inadecuado, ha generado efectos secundarios en las arvenses y en la salud de los productores y jornaleros. Por lo anterior se planteó como objetivo analizar los efectos secundarios ecológicos, sociales y económicos provocados por el paraquat, estudiando los diferentes métodos de control; la identificación de especies arvenses que han disminuido o desaparecido, o que han desarrollado resistencia al herbicida y la emergencia de algunas en el agrosistema; la caracterización de la diversidad de arvenses y sus usos; finalmente la identificación de daños en la salud de los productores y jornaleros por su uso. Para lograr cada objetivo, se aplicaron encuestas y entrevistas a los productores y se aplicó la observación directa. Para identificar las arvenses se aplicó el método de cuadrantes. Los resultados indican que las arvenses han desarrollado resistencia al paraquat, esto ha forzado a los productores a desarrollar nuevos métodos para controlarlas. La disminución y la aparición de nuevas especies arvenses fueron otros de los efectos secundarios en el agrosistema local. Respecto a los efectos en la salud de los productores no existen casos bien documentados de intoxicaciones causadas específicamente por usar paraquat, aunque se han registrado casos por intoxicación por plaguicidas en general. Se puede concluir que el agrosistema se ha deteriorado y han disminuido especies de arvenses. En gran parte, esto es resultado de que los agricultores usan métodos a corto plazo para el control de arvenses los cuales son aparentemente más económicos, pero a largo plazo resultan más costosos, dado que estas arvenses son comestibles y medicinales y ayudan a la estabilidad del agrosistema. A pesar de que la mayoría de los agricultores de la localidad usan paraquat y está incrementando, en la comunidad aún existen métodos tradicionales para su control. Esto sugiere que en la comunidad existe potencial para mejorar el control de arvenses mediante el desarrollo e implementación de prácticas agroecológicas.______For controlling weeds in the agrosystem of yam bean (Pachyrhizus erosus L.), most farmers of La Trinidad Tepango have choice to use paraquat herbicide, due to its low cost and effectiveness. However, local farmers and agrosystem have experimented secondary effects, such as deterioration of health’ farmers and loosing of weeds from local agrosystem. This research deal with this issue and raised the followings goal to analyze ecology, social and economic secondary effects due to using paraquat, by studing of the different ways for controlling weeds; identifing which species of weeds in the local agrosystem have decreased, disappear, developed resistance towards paraquat or if new species have appeared, to describe the uses and characteristics of weeds from local agrosystems; to identify damages in farmer’s health that have been caused by using paraquat. For this, interviews, questionnaires, direct observation and quadrant method were applied. We found that the weeds in the locality have developed resistance towards paraquat, it has to force to farmers to develop new methods for controlling them. The decrease and apparition of new species of weeds were other secondary effects in local agrosystems. Respect to effects in health’ farmers there are not well documented cases of diseases of intoxications caused specifically for using paraquat, although some cases have been registered for intoxication by pesticides in general. It can be concluded that the local agrosystem has been deteriorated and have disappeared species of weeds. To a great degree, this is the result that farmers using shorterm methods for controlling weeds which are apparently more economics but in long-term are more costly, given that this weeds are edible and medicinal and they are benefic for the agrosystem. Although the most of farmers uses paraquat in the locality and seems that the use of paraquat is reasing, there are even persist traditional methods for controlling weeds. This findings suggest that there is potential to improve weeds control by developing and implementing of practices agroecologics which must be more friendly with the agrosystem and affordable in the socio-economical context.Tesis (Maestría en Ciencias, especialista en Estrategias para el Desarrollo Agrícola Regional).- Colegio de Postgraduados, 2009.CONACY

Historical analysis of a karst aquifer: recharge, water extraction, and consumption dynamics on a tourist island (Cozumel, Mexico)

On Cozumel Island, access to freshwater depends on the extraction of the resource from the aquifer located north of the island (catchment area). Water resource management on the island must be based on updated knowledge of the indicator dynamics related to the recharge of the aquifer, groundwater extraction and the distribution of the resource. In this study, trends, variations and time series of 30 years of monthly data for precipitation, temperature, evapotranspiration, and estimated aquifer recharge were calculated for the catchment area. Additionally, groundwater extraction, water consumption for the main uses over a 13-year period (monthly data), and the 5-year status of wells were considered. The results show decreasing trends in precipitation and estimated recharge volumes in the catchment area, in addition to increasing trends in mean air temperature, evapotranspiration, water extraction volumes and consumption by the commercial sector for the considered time periods. Additionally, an increase in dejected (77%) and reposed (38%) wells within the catchment area was observed. Evidence from this study suggests a dynamic behaviour of the analysed indicators over time that increases pressure on karstic, Caribbean aquifers for which monthly monitoring and data analysis are encouraged as the basis for adequate management.This study provides evidence of the historical dynamic of hydrometeorological and hydrological indicators related to water availability in Cozumel island and emphasizes the need of updated information analysis as part of an adequate water management based upon an integrative approach that can be replicated on islands with a similar geohydrological settings

Identification of the Hydrogeochemical Processes and Assessment of Groundwater Quality, Using Multivariate Statistical Approaches and Water Quality Index in a Wastewater Irrigated Region

Groundwater quality and availability are essential for human consumption and social and economic activities in arid and semiarid regions. Many developing countries use wastewater for irrigation, which has in most cases led to groundwater pollution. The Mezquital Valley, a semiarid region in central Mexico, is the largest agricultural irrigation region in the world, and it has relied on wastewater from Mexico City for over 100 years. Limited research has been conducted on the impact of irrigation practices on groundwater quality on the Mezquital Valley. In this study, 31 drinking water wells were sampled. Groundwater quality was determined using the water quality index (WQI) for drinking purposes. The hydrogeochemical process and the spatial variability of groundwater quality were analyzed using principal component analysis (PCA) and K-means clustering multivariate geostatistical tools. This study highlights the value of combining various approaches, such as multivariate geostatistical methods and WQI, for the identification of hydrogeochemical processes in the evolution of groundwater in a wastewater irrigated region. The PCA results revealed that salinization and pollution (wastewater irrigation and fertilizers) followed by geogenic sources (dissolution of carbonates) have a significant effect on groundwater quality. Groundwater quality evolution was grouped into cluster 1 and cluster 2, which were classified as unsuitable (low quality) and suitable (acceptable quality) for drinking purposes, respectively. Cluster 1 is located in wastewater irrigated zones, urban areas, and the surroundings of the Tula River. Cluster 2 locations are found in recharge zones, rural settlements, and seasonal agricultural fields. The results of this study strongly suggest that water management strategies that include a groundwater monitoring plan, as well as research-based wastewater irrigation regulations, in the Mezquital Valley are warranted