Hydrochemistry

La localité de Vohibory située dans la région du Sud-Ouest de Madagascar sous climat semi-aride est caractérisée par une raréfaction des ressources en eau. Elle dispose par ailleurs une forte potentialité en ressource minière telle que l’or. La présente étude avait pour objectif d’évaluer la qualité physico-chimique des eaux souterraine et de surface et expliquer les phénomènes à l’origine de leur minéralisation. Des campagnes de prélèvements ont été effectuées en 2016 sur 10 points et couvrant les deux saisons (pluie et sèche) qui règnent dans cette zone. Les Vingt (20) paramètres déterminés (pH, conductivité électrique, MES, turbidité, matière organique, Ca2+, Mg2+, K+, Cl-, fer total, SO4 2-, NO3-,NO2- , dureté totale, titre alcalimétrique complet, PO42-, HCO3-) ont fait l’objet de traitement par les méthodes hydrochimique couplée aux analyses statistiques multivariées (Analyse en Composante Principales et Classification Ascendante Hiérarchique).
Les résultats de l’étude montrent que ce sont des eaux sensiblement neutres à basiques (6.86  pH  8.36), faiblement à fortement minéralisées (59  CE 790 μS/cm). La turbidité et les MES varient respectivement entre 0,55-771 NTU et 2-1940 mg/L. Quant à la M.O, elle a des concentrations qui oscillent entre 0.1 et 8.2 mg/L. La dureté des eaux est comprise entre 2,8 °F et 31,8 °F. Deux types de faciès sont identifiés, à savoir le faciès bicarbonaté calcique et magnésien (85%) et bicarbonaté sodi-potassique (5%). Les teneurs en éléments majeurs sont presque inférieures aux normes recommandées par l’OMS pour les eaux destinées à la consommation humaine, à l’exception des nitrates (0.065 mg/L à 79.48 mg/L) et nitrites (1,44 à 25,56 mg/L) dans certains puits, le Fer total (1,5 mg/L) dans certains cours d’eau. L’Analyse en Composantes Principales (ACP) a mis en évidence deux grands phénomènes à l’origine de la minéralisation des eaux. Le principal phénomène est l’altération des roches suivi des apports anthropogéniques (exploitation aurifère et élevage) et éventuellement l’intrusion d’eaux marines.

The paper presents the hydrogeological characteristics of the quarry of the Badenian gypsum at Pisky near Lviv, Ukraine, where – at the bottom of the excavation – there is an outcrop of the recently weathering anhydrites and due to the increase in volume during their hydration, the unique dome-like forms of relief and hydration caves have been formed. In order to identify the chemistry and origin of surface waters that have a major impact on the processes of weathering and hydration, chemical analyzes of 35 water samples collected in 2009-2014 from various environments in the quarry – from rock crevices, caves, ponds and puddles, including ice and snow, were performed. The quality of chemical analyzes of waters was assessed using the anion-cation balance method, and their chemical composition was characterized using selected hydrochemical indicators and graphical methods. The studied waters show a clear temporal and spatial variability in chemical composition and mineralization, as well as a remarkably sulphate-calcium character. The significant dominance of calcium and sulphates over other components confirms that the most important process of creating the composition of water is the dissolution of gypsum-anhydrite rocks. The chemical composition of the water from the hydration caves and crevices in the bottom of the quarry is very similar, which suggests their relationship to the same water circulation system. These waters are characterized by mineralization between 1816 and 2586 mg/l (2318 mg/l in average). The water from ponds and puddles has a clearly greater mineralization (between 2246 and 2967 mg/l, 2646 mg/l in average) and the concentration of individual ions, which is certainly the result of more intensive evaporation. The chemical composition of surface waters from the Pisky quarry is typical for the environment of gypsum-anhydrite rocks and sulphate karst.
У статті представлені гідрогеологічні характеристики баденських гіпсів кар’єру в селі Піски поблизу Львова, на дні якого розкриті ангідрити, які зазнають вивітрювання, і завдяки збільшенню об’єму під час їхньої гідратації утворюються унікальні куполоподібні форми рельєфу та гідратаційні печери. З метою вивчення хімізму та походження поверхневих вод, які мають великий вплив на процеси вивітрювання та гідратації, проведено хімічні аналізи 35 проб води, відібраних у 2009–2014 роках з різних ділянок кар’єру – з тріщин гірських порід, печер, водойм та калюж, включно з льодом та снігом. Якість хімічного аналізу вод оцінювали методом балансу аніонно-катіонної рівноваги, а їхній хімічний склад характеризували вибраними гідрохімічними показниками та графічними методами. Досліджувані води демонструють чітку часову та просторову мінливість хімічного складу та мінералізації і яскраво виражений сульфатно-кальцієвий характер. Значне домінування кальцію та сульфатів над іншими компонентами підтверджує, що найважливішим процесом формування складу вод є розчинення гіпсово-ангідритових нагромаджень. Хімічний склад вод з гідратаційних печер і тріщин на дні кар’єру дуже подібний, що свідчить про їхню приналежність до спільної системи циркуляції води. Ці води характеризуються мінералізацією між 1816 і 2586 мг/л (в середньому 2318 мг/л). Води зі ставків і калюж мають явно більшу мінералізацію (від 2246 до 2967 мг/л, в середньому 2646 мг/л) і концентрацію окремих іонів, що, ймовірно, є результатом інтенсивнішого випаровування. Хімічний склад поверхневих вод кар’єру в Пісках типовий для середовища гіпсово-ангідритових нагромаджень та сульфатного карсту.

This book reviews the latest information on the assessment of surface and groundwater resources in Algeria. The authors cover a large diversity of topics, including the status and assessment of water resources, impacts of pesticides, soil droughts, analysis of flood characteristics, hydrogeological investigations and modeling applications, and evapotranspiration. Special attention is given to the impacts of climate changes on water resources. The assessment methods present in this book can be used or adapted to study other regions of North Africa, Middle East and/or in the Mediterranean with similar climate conditions as Algeria.

This book and the companion volume Water Resources in Algeria - Part II: Water Quality, Treatment, Protection and Development will appeal to engineers, researchers, graduate students and policymakers interested in the field of groundwater and surface water assessment.

This paper introduces new insights into the hydrochemical functioning of lowland river systems using fieldbased spectrophotometric and electrode technologies. The streamwater concentrations of nitrogen species and phosphorus fractions were measured at hourly intervals on a continuous basis at two contrasting sites on tributaries of the River Thames -one draining a rural catchment, the River Enborne, and one draining a more urban system, The Cut. The measurements complement those from an existing network of multi-parameter water quality sondes maintained across the Thames catchment and weekly monitoring based on grab samples. The results of the sub-daily monitoring show that streamwater phosphorus concentrations display highly complex dynamics under storm conditions dependent on the antecedent catchment wetness, and that diurnal phosphorus and nitrogen cycles occur under low flow conditions. The diurnal patterns highlight the dominance of sewage inputs in controlling the streamwater phosphorus and nitrogen concentrations at low flows, even at a distance of 7 km from the nearest sewage treatment works in the rural River Enborne. The time of sample collection is important when judging water quality against ecological thresholds or standards. An exhaustion of the supply of phosphorus from diffuse and multiple septic tank sources during storm events was evident and load estimation was not improved by sub-daily monitoring beyond that achieved by daily sampling because of the eventual reduction in the phosphorus mass entering the stream during events. The results highlight the utility of sub-daily water quality measurements and the discussion considers the practicalities and challenges of in situ, sub-daily monitoring.

Studies on river water quality in the Indian Himalayas are limited to a few larger ones; the smaller ones, although vital for a large section of people, mostly remain untouched. Therefore, Munawar Tawi a tributary of Chenab flowing through Rajouri district of Jammu region, Western Himalayas was selected for the study.

Knowledge of the origin and hydrogeochemical composition of
groundwater is very important for the sustainable development of
groundwater resources in the present state of art. It is imperative
to regularly monitor the quality of groundwater and develop
means to protect it. Accordingly, this study was aimed to conduct
a hydrogeochemical analysis and evaluation of the groundwater
in the Lake Haramaya well field. The water samples taken from
the well field were analyzed for six physicochemical parameters
(temperature, conductivity, TDS, total hardness, pH, and turbidity),
major cations and anions, minor anions and trace metals using
standard procedures, and the results were compared with the
national and international standards. The analysis conducted
using the GW-Chart software has also shown that the origin of the
well water in the study area is shallow fresh groundwater with a
major geochemical composition of calcium carbonate, which was
found to be in line with the previously developed geological and
hydrogeological maps of the site. According to the laboratory
results, the levels of calcium ion in most of the samples were found
to be very high. Moreover, the calcium ion concentrations in most of
the wells, especially in the wells nearby the limestone outcropping
area, were found to be by far beyond the maximum contaminant
standards. Therefore, these facts can assure that the origin of the
groundwater in the study area is shallow and calcium carbonate rich
aquifer. Consequently, the groundwater in the area was evaluated
as hard water.

In a semi-arid to arid climate context, dependency on groundwater resources may lead to overexploita- tion and deterioration of water quality. The Continental Intercalaire (CI) aquifer is one such continental- scale aquifer (more than a million of km2), which is mainly confined, poorly recharged but intensely abstracted. To date, the management of this resource relies on hydrogeological modelling and key param- eters such as recharge/discharge rate and groundwater dynamics. We use a combination of residence time indicators (14C, 36Cl, 4He) and stable isotopes of water (2H and 18O) to give greater constraint on the groundwater residence time in the CI. In previous studies, 14C measurements and steady state mod- elling indicate a residence time of less than 100 ka whereas in others, 36Cl measurements and transient scenarios modelling suggest a longer residence time (>500 ka).
In this study, most of the 14C measurements are below the limit of detection, establishing residence times greater than 40 ka and confirming the necessity of strict sampling protocols to exclude all air and AMS measurements when low 14C concentrations are expected.
In the Tunisian recharge area, detectable 14C indicate sporadic recharge episodes (3–7 ka and 29–43 ka), whereas 4He and 36Cl concentrations in central areas suggest very old (<2 Ma) groundwaters. In these central areas, chlorine concentration can reach more than 2 g/l. Since 36Cl concentrations are up to 4 time less than the initial input, we are confident there is no excessive deep 36Cl production.
We characterise five distinct flowpaths reaching the Tunisian discharge area using their isotopic signa- tures. According to our mixing model, the average contribution from the main recharge area, the Algerian Atlas Mountains, is around 88%. This value is close to hydrogeological models. Conversely, the contribu- tion from the Dahar Mountains is lower than in the hydrogeological modelling (2% against 10%) whereas the Tinhert shows a greater contribution (10% against 1%).
Increase of abstraction from the CI can potentially activate the circulation of old brackish groundwaters and dramatically decrease the water quality in the whole system.

This paper aims to quantitatively assess water losses of Badovc Lake-Kosovo based on both water balance of the lake
and water hydrochemistry. This attempt was strongly prompt by both the importance of this lake for water supply of Prishtina city
and the lack of water. According to lake water balance, a water loss of 3,738,905 m³ and 1,722,552 m³ for the hydrologic year 2014
and the period January-May (2015) was evaluated. These consistent data favour the opinion that a continuous groundwater outflow
from the lake is present and it is conditioned by the intensively developed fracture system in the lake basement formations. This
was also supported by the chemical data (chloride, sulphate, hardness and electric conductivity etc.) of the water. Water from the
leakages on the right side of the dam shows the same chemical signature as the water from the lake. Whereas, water from the
piezometer, monitoring well and the gallery of Hajvalia mine show similar values with those of the water from the lake. The
calculations of the chloride mass balance showed that the fractions of lake and rainfall waters in the water mixture of Hajvalia mine
were 67% and 33% respectively.

This paper presents the hydro-geological and hydro-chemical study of fractured aquifers that form the Serra Geral Aquifer System (SASG) associated with acid volcanic rocks. The study area comprises part of the city of Carlos Barbosa, located in the northeast region of Rio Grande do Sul State. The study was developed based on the inventory and registration of
existing wells in the region, the survey and interpretation of geological and hydro-geological data, in addition to the collection and analysis of samples from wells that are in operation and used by the CORSAN water supply company.

Although the Po river is the most important fluvial
system of Northern Italy, the systematic geochemical and
isotopic investigations of its water are rare and were never
reported for the whole basin. The present contribution aims to
fill this knowledge gap, reporting a comprehensive data set
including oxygen and hydrogen stable isotopes as well as
major and trace element concentration of dissolved species
for 54 Po river water samples, mainly collected in different
hydrological conditions (peak discharge in April, drought in
August) at increasing distance from the source, i.e., from the
upper part of the catchment to the terminal (deltaic) part of the
river at the confluence with the Adriatic Sea. The isotopic
compositions demonstrate that the predominant part of the
runoff derives from the Alpine sector of the catchment
through important tributaries such as the Dora Baltea, Ticino,
Adda, and Tanaro rivers, whereas the contribution from the
Apennines tributaries is less important. The geochemical and
isotopic compositions show that the Po river water attains a
homogeneous composition at ca. 100 km from the source. The
average composition is characterized by δ18O −9.8 ‰, δD
−66.2‰, total dissolved solid (TDS) 268 mg/L, and chloride 17 mg/L and by a general Ca–HCO3 hydrochemical facies,
which is maintained for most of the river stream, only varying
in the terminal part where the river is diverted in a complex
deltaic system affected by more significant evaporation and
mixing with saline water evidenced by higher TDS and chloride
content (up to 8198 and 4197 mg/L, respectively). Geochemical
and isotopic maps have been drawn to visualize
spatial gradients, which reflect the evolution of the river water
composition at progressive distance from the source; more
detailed maps were focused on the deltaic part in order to
visualize the processes occurring in the transitional zone toward the Adriatic Sea. The data also highlight anthropogenic contributions, mainly represented by significant concentrations of nitrate (average 8 mg/L) and possibly arsenic (average 12 μg/L). These data allow the calculation of geochemical fluxes transferred from the river to the sea, and generally, they contribute to the definition of a “hydro-archive” which is useful to highlight ongoing variations in the related ecosystems.

Drinking water is scarce in Djibouti because of the hot desert climate. Moreover, seawater intrusion or fossil saltwater contamination of the limited number of freshwater aquifers due to groundwater overexploitation affect those who live close to the coastline (~ 80% of the population). Despite this, the geothermal potential of the country's plentiful hot springs could resolve the increasing electricity demand. Strontium isotopes (87 Sr/ 86 Sr) are routinely used to determine sources and mixing relationships in geochemical studies. They have proven to be useful in determining weathering processes and quantifying endmember mixing processes. In this study, we summarise and reinterpret the 87 Sr/ 86 Sr ratio and Sr concentration data of the groundwater collected to date in the different regions of the Djibouti country, trying to discriminate between the different water sources, to evaluate the water/rock ratio and to compare the data with those coming from the groundwater in the neighbouring Main Ethiopian Rift and the Red Sea bottom brine. New preliminary data from the groundwater of the Hanlé-Gaggadé plains are also presented.