Long-term groundwater level changes and land subsidence in Tianjin,China

Acta Geotechnica - A large volume of groundwater is withdrawn annually in Tianjin Municipality, China, to meet agricultural, industrial, and municipal water uses. Groundwater overdraft in the urban...     

Nitrate contamination in irrigation groundwater,Isfahan, Iran

Groundwater is one of the major sources of water in Isfahan. Efficient management of these resources requires a good understanding of its status. This paper focuses on the hydrochemistry and also it wants to assess the nitrate concentration in irrigation groundwater of Isfahan suburb. All the groundwater samples are grouped into three categories, including Na-Cl + Ca-Cl (63 %), Na-SO₄ + Ca-SO₄ (23 %) and Ca-HCO₃ (14 %). According to the EC and SAR, the most dominant classes are C3S1, C4S2 and C4S3. 55 % of samples indicate very high salinity and medium to very high alkalinity that is not suitable for irrigation. 84 % of the groundwater samples show nitrate contents higher than HAV (13 mg l^?), while more than 25 % exceeded the maximum contamination level (44.27 mg l^?) according to EPA regulations. The horizontal and vertical distribution patterns of nitrate in groundwater samples show a surficial origin for nitrate contamination. The high nitrate content can be attributed to the agricultural activities along with domestic sewage and industrial wastewaters in populated area. Based on results, using high nitrate groundwater for irrigation can minimize the requirement for inorganic fertilizers and reduce the cost of cultivation and nitrate contamination.     

Modelling the response of vegetation restoration to changes in groundwater level,based on ecologically suitable groundwater depth

Groundwater-level fluctuations at a large scale have a significant effect on the preservation and restoration of vegetation. This study determined suitable groundwater depth within which natural vegetation grows well, and analysed the effect of groundwater regulation on vegetation restoration in Tianjin City, northern China. Normal and lognormal distributions were used to fit the curve of the relation between vegetation and groundwater depth. The groundwater depth range corresponding to the higher frequency of vegetation distribution was regarded as the ‘suitable water depth’ range for vegetation growth. The suitable groundwater depth for shrub growth was 3–5 m and for grass growth 1–3 m. A groundwater flow model predicted the future changes of groundwater depths in the vegetation distribution area under the condition that the current levels of groundwater extraction are maintained. The results showed that there is potential for the extraction of groundwater in shrubland areas, but for grassland areas the water-table elevation showed a downward trend, meaning that water shortages in some areas may be more severe in the future. Finally, based on the current groundwater extraction regime, two regulation schemes were developed: (1) for shrubland, groundwater extraction was reduced by 10% in the ecological water deficit areas, and extraction was increased by 10% in the ecological water surplus and suitable areas, and (2) for grassland, groundwater recharge was increased by the restoration of the wetland areas. In conclusion, the groundwater depths in most of the area would be more suitable for vegetation growth under the regulation schemes.     

Hydrogeochemical assessment of groundwater in Isfahan province, Iran

Groundwater quality in five catchment areas in Isfahan province of Iran is assessed by measuring physicochemical parameters including major cation and anion compositions, pH, total dissolved solid, electrical conductivity and total hardness. For this purpose, 567 piezometric well samples were collected in October 2007. The abundance of major ions in four of the catchment areas including Gavkhuni, Ardestan, Salt lake and Central Iran desert basins is similar and follows Cl^??>?SO₄ ^2??>?Na⁺?>?HCO₃ ^??>?Ca²⁺?>?Mg²⁺?>?K⁺?>?CO₃ ^2? trend, while in the fifth basin (Karoon), the trend changes into HCO₃ ^??>?Ca²⁺?>?Cl^??>?SO₄ ^2??>?Mg²⁺?>?Na⁺?>?K⁺?>CO₃ ^2?. In general, four water facies are determined and it is shown that alkali elements and strong acids are dominating over alkaline earth and weak acids. Statistical analysis including Mann?CWhitney U test indicate that physicochemical parameters in three of the five investigated basins [Gavkhuni, Ardestan and Central Iran desert (CID)] are similar, while Karoon and salt lake basins display different characteristics. The result indicate that groundwater west of the province is suitable for irrigation, while in the central and eastern parts of the province the groundwater loses its quality for this purpose. It is concluded that mineral dissolution and evapotranspiration are the main processes that determine major ion compositions.     

Nitrate pollution of groundwater in Toyserkan,western Iran

A total of 95 groundwater samples were collected from Toyserkan, western Iran to assess the chemical composition and nitrate (NO₃ ⁻) status of groundwater. The most prevalent water type is Ca–HCO₃ followed by water types Ca–Mg–HCO₃. In comparison with the World Health Organization (WHO) drinking water guideline of 50 mg l⁻¹ for NO₃ ⁻, a total of nine wells (9.5%) showed higher concentrations. In 36% of samples (34) NO₃ ⁻ concentration was low (<20 mg l⁻¹), and in 53.7% of samples (51), in the range of 20–50 mg l⁻¹. The samples were classified into four groups based on NO₃ ⁻ and chloride (Cl⁻) concentrations. Of the samples, 40% were classified as group 4 and were relatively high in Cl⁻ and NO₃ ⁻ (Cl⁻ > 47 mg l⁻¹, NO₃ ⁻ > 27 mg l⁻¹). The high correlation between NO₃ ⁻ and Cl⁻ (r = 0.86, p < 0.01) is consistent with a manure source, resulting from the practice of adding salt to animal feed. Pollution of groundwaters appeared to be affected by the application of inorganic fertilizer at greater than agronomic rates, Cl-salt inputs, and irrigation practice.     

Patterns in groundwater chemistry resulting from groundwater flow

 Groundwater flow influences hydrochemical patterns because flow reduces mixing by diffusion, carries the chemical imprints of biological and anthropogenic changes in the recharge area, and leaches the aquifer system. Global patterns are mainly dictated by differences in the flux of meteoric water passing through the subsoil. Within individual hydrosomes (water bodies with a specific origin), the following prograde evolution lines (facies sequence) normally develop in the direction of groundwater flow: from strong to no fluctuations in water quality, from polluted to unpolluted, from acidic to basic, from oxic to anoxic–methanogenic, from no to significant base exchange, and from fresh to brackish. This is demonstrated for fresh coastal-dune groundwater in the Netherlands. In this hydrosome, the leaching of calcium carbonate as much as 15 m and of adsorbed marine cations (Na⁺, K⁺, and Mg²⁺) as much as 2500 m in the flow direction is shown to correspond with about 5000 yr of flushing since the beach barrier with dunes developed. Recharge focus areas in the dunes are evidenced by groundwater displaying a lower prograde quality evolution than the surrounding dune groundwater. Artificially recharged Rhine River water in the dunes provides distinct hydrochemical patterns, which display groundwater flow, mixing, and groundwater ages. Received, May 1998 · Revised, August 1998 · Accepted, October 1998     

Groundwater level and chemistry changes resulting from tunnel construction near Matsumoto City, Japan

 Before tunnel construction began, the groundwater chemical compositions and levels around the tunnel were studied to determine if water compositions could predict whether surface water will be influenced by tunnel construction. When the chemical composition of the well and springwater was similar to that of the tunnel seepage water, and the altitude of the well and spring was above the tunnel level, the groundwater level in the well and spring was influenced by draining tunnel seepage water. Therefore, comparing the chemical compositions of surface water and groundwater may be used for predictive purposes. However, the results of this study showed there was no noticeable chemical composition change in springwater prior to changes in groundwater level at a particular site. The changes in the hydrology of the plateau caused by tunnel construction were also studied, using measurements of the changes in groundwater chemistry as well as changes in groundwater levels. Prior to tunnel construction, river discharge was greater. Following tunnel construction, some river discharge decreased because springwater was drained as tunnel seepage water and the spring in the catchment dried up. Tritium concentration indicated that 3 years after tunnel construction, surface water did not reach tunnel levels in spite of groundwater level lowering and remaining unconfined groundwater being drained. Received: 17 January 1996 · Accepted: 10 July 1996     

Assessment of groundwater quality and hydrochemical characteristics in Farashband plain,Iran

Groundwater in Farashband plain, Southern Iran, is the main source of water for domestic and agricultural uses. This study was carried out to assess the overall water quality and identify major variables affecting the groundwater quality in Farashband plain. The hydrochemical study was undertaken by randomly collecting 84 groundwater samples from observation wells located in 13 different stations covering the entire plain in order to assess the quality of the groundwater through analysis of major ions. The water samples were analyzed for various physicochemical attributes. Groundwater is slightly alkaline and largely varies in chemical composition; e.g., electrical conductivity (EC) ranges from 2314 to 12,678 μS/cm. All the samples have total dissolved solid values above the desirable limit and belong to a very hard type. The abundance of the major ions is as follows: Na⁺ > Ca²⁺ > Ma²⁺ > K⁺ and Cl^? > SO₄ ^2– > HCO₃ ^?. Interpretation of analytical data shows three major hydrochemical facies (Ca–Cl, Na–Cl, and mixed Ca–Mg–Cl) in the study area. Salinity, total dissolved solids, total hardness, and sodium percentage (Na%) indicate that most of the groundwater samples are not suitable for irrigation as well as for domestic purposes and far from drinking water standard. A comparison of groundwater quality in relation to drinking water standards showed that most of the water samples are not suitable for drinking purposes. Based on the US salinity diagram, most of samples belong to high salinity and low to very high sodium type.     

Characteristics of groundwater in karstic region in northeastern Vietnam

The groundwater in the karst region of northeastern Vietnam is found in various structural zones such as the Ha Lang, Song Hien, Hon Gai, Song Lo, Song Gam, and Hoang Lien Son Zones, etc. Results from this study show that groundwater in this region is at different depths: ~120 m deep at Quang Ninh, ~100 m at Lang Son, ~80 m at Cao Bang (The most water-abundant depth observed at Cao Bang varies from 40 to 45 m) while it varies from 18–25 to 80 m deep at Quan Ba (Ha Giang), especially at Meo Vac (Ha Giang), where groundwater is observed at 700–800 m deep (equivalent to local base level of the Nho Que River). Overall, groundwater in the region is fresh with total minerals varying from 250 to 400 mg/l; except for the coastal area of Quang Ninh, where groundwater is characterized by much higher total minerals (M = 3–18 g/l) due to the mixing with the saline sea water. The chemistry of water in the region demonstrates that the water is mainly bicarbonate with a [HCO₃ ^?] concentration varying from 150 to 265 mg/l, pH is of 6.5–8.1, and its hardness is of 3.7–6.0 meq/l.     

Surface and groundwater quality in the northeastern region of Buenos Aires Province, Argentina

This work studies the water quality of the Pergamino–Arrecifes River zone in the Rolling Pampa, northeast Buenos Aires Province, Argentina. Temperature, pH, specific conductivity, Na, K, Mg, Ca, , Cl⁻, , , Si, Ag, Al, As, B, Ba, Be, Br, Cd, Co, Cr, Cu, Fe, Hg, Li, Mn, Mo, Ni, P, Pb, Se, Tl, U, V, Zn, and the environmental stable δ¹⁸O and δ²H isotope ratios were determined in 18 sampling stations. Natural and anthropogenic features influence surface and groundwater quality. Point pollution sources (septic wells and other domestic and farming effluents) increase the nitrate concentration. The values of pH, , Al, As, B, Fe, and Mn exceed the respective Argentine reference thresholds in different sampling stations for human drinking water; B, Mo, U, and V for irrigation; and V and Zn for cattle consumption.     

Hydrochemical and isotopic characteristics of groundwater in the northeastern Tennger Desert,northern China

Groundwater is typically the only water source in arid regions, and its circulation processes should be better understood for rational resource exploitation. Stable isotopes and major ions were investigated in the northeastern Tengger Desert, northern China, to gain insights into groundwater recharge and evolution. In the northern mountains, Quaternary unconsolidated sediments, exposed only in valleys between hills, form the main aquifer, which is mainly made of aeolian sand and gravel. Most of the mountain groundwater samples plot along the local meteoric water line (LMWL), with a more depleted signature compared to summer precipitation, suggesting that mountain groundwater was recharged by local precipitation during winter. Most of the groundwater was fresh, with total dissolved solids less than 1 g/L; dominant ions are Na⁺, SO₄ ^2? and Cl^?, and all mineral saturation indices are less than zero. Evaporation, dissolution and cation exchange are the major hydrogeochemical processes. In the southern plains, however, the main aquifers are sandstone. The linear regression line of δD and δ ¹⁸O of groundwater parallels the LMWL but the intercept is lower, indicating that groundwater in the plains has been recharged by ancient precipitation rather than modern. Both calcite and dolomite phases in the plains groundwater are close to saturation, while gypsum and halite can still be dissolved into the groundwater. Different recharge mechanisms occur in the northern mountains and the southern plains, and the hydraulic connection between them is weak. Because of the limited recharge, groundwater exploitation should be limited as much as possible.     

Geochemistry of groundwater from a rhyolite aquifer,Northwest Iran

Chemical data on groundwater composition in rhyolitic hard rock aquifers with limited global occurrence are rarely found. In this research geochemistry of Mahabad Rhyolite Aquifer, NW Iran, was studied considering major ions, silica and trace elements measured in wet and dry seasons. Based on the results, the mean silica content was 18 mg l^?1, less than the average of the rhyolitic waters. However, the relatively higher electrical conductivity (EC) of 418 µS cm^?1 was measured. Based on a PHREEQCI model, the weathering of the silicate minerals and dissolution of carbonated intercalations turns groundwater dominantly into Ca–HCO₃ type, enhancing EC, pH and silica concentration along the flow path. Trace elements of Sr, Ba and Pb were measured at highest concentrations, the later with an average value of 83 ppb exceeds the drinking guidelines. Cluster analysis confirms biotite weathering and barite dissolution as the main sources of the trace elements in the groundwater. The results signify geochemical features of rhyolitic groundwater which can be a useful tracer of mixing in flow systems containing variety of aquifers including rhyolites.     

Geothermometry and circulation depth of groundwater in Semnan thermal springs,Northern Iran

Semnan thermal springs with high TDS and moderate temperature are located northwest of Semnan, the northern part of Iran. The spatial and temporal variations of physicochemical characteristics of the thermal and cold springs were investigated for the recognition of origin and dominant hydrogeochemical processes. Results show that the thermal springs have the same origin, but due to different ascending flow paths and different conductive cooling mechanism, their temperatures vary. The chemical composition of thermal waters is controlled by dolomite, halite and sulfate minerals dissolution and calcite precipitation and bacterial sulfate reduction. The concentration of major and trace elements in the thermal springs does not change in wet and dry seasons notably because they are derived from old groundwater with deep circulation and high temperature. Seasonal change in the concentration of some trace elements is due to the seasonal variation of pH, Eh, temperature and dilution by shallow waters. Decreasing SO₄ and carbonate saturation index and increasing Na/Cl ratios and Ca content in the dry season show dilution effect caused by the previous heavy rainfall events. The temperature of the heating reservoir based on K–Mg, chalcedony, quartz and chemical equilibrium approach was approximately estimated in the range of 60–80 °C. Hydrogeologically, a conceptual model was suggested for the thermal springs. The general groundwater flow direction is probably from the dolomite Lar Formation in Chenaran anticline toward the adjacent syncline in a confined condition, and then a thrust fault acts as a conduit and redirects the thermal water to the emerging springs at the surface.     

Correlation of lineaments and groundwater quality in Dasht-e-Arjan Fars,SW of Iran

The NE-oriented Dasht-e-Arjan graben is located 65 km west of Shiraz and has resulted from the active Kare-e-Bas fault segmentations. This extensional graben bounded by two fault system east-Arjan and west-Arjan to the Shahneshin and Salamati anticline. In these study using Landsat 7 ETM images with resolution 2.5 m and directional filtering in the four azimuths and semi-automatic technique for linear structure in the study area. Using the obtained data from extracted lineaments, the rose diagrams of the main strike lineaments are well confirm with field measurements of faults with N56° ± 4°E direction. The structural lineaments of the study area show that the Dasht-e-Arjan area is underlain by the limestone, sandstone, and marl. LANDSAT imagery of the area has been analyzed and interpreted in order to determine the lineament and groundwater quality across the area. The fracture is structurally controlled and mostly influences both the groundwater and surface water pollution and flow directions in the Dasht-e-Arjan. Using visual interpretation, determining the lineaments on the satellite image is very difficult and subjective, and it requires an experienced interpreter. In this study, the lineament analysis is undertaken to examine the orientation of the lineament, the relationship between lineaments and tectonic features and groundwater quality. Lineament density maps show that the lineament density is high around areas. Areas having high lineament density represent areas with relatively high groundwater pollution. Field observations agreed with the results from the analysis of the imagery.     

Hydrogeochemistry and arsenic contamination of groundwater in the Rayen area, southeastern Iran

High As contents in groundwater were found in Rayen area and chosen for a detailed hydrogeochemical study. A total of 121 groundwater samples were collected from existing tube wells in the study areas in January 2012 and analyzed. Hydrogeochemical data of samples suggested that the groundwater is mostly Na–Cl type; also nearly 25.62 % of samples have arsenic concentrations above WHO permissible value (10 μg/l) for drinking waters with maximum concentration of aqueous arsenic up to 25,000 μg/l. The reducing conditions prevailing in the area and high arsenic concentration correlated with high bicarbonate and pH. Results show that arsenic is released into groundwater by two major phenomena: (1) through reduction of arsenic-bearing iron oxides/oxyhydroxides and Fe may be precipitated as iron sulfide when anoxic conditions prevail in the aquifer sediments and (2) transferring of As into the water system during water–acidic volcanic rock interactions.     

Source of salinity in the groundwater of Lenjanat Plain,Isfahan, Iran

The present study aimed at identifying the salinity source in the groundwater of Lenjanat Plain. To do so, non-isotopic geochemical methods were employed: groundwater samples were collected seasonally from 33 wells widespread in the area, and physicochemical parameters as well as major and minor elements were measured in the 132 samples. The data collected from the field and laboratory measurements were interpreted through statistical and hydrogeochemical graphs, mass ratios and saturation indexes obtained from modeling. The results revealed that hydrogeochemical properties of the study aquifer were controlled by rock/water interactions including ion exchange, dissolution of evaporation deposits (halite and gypsum) and precipitation/dissolution of carbonates. Based on the values of Cl/Br ratio in Lenjanat groundwater (329–4,492), dissolution of evaporation deposits in aquifer was the main cause for groundwater salinity. Considering the Lenjanat groundwater geochemical properties, the data confirm the reported Cl/Br ratios for groundwater affected by the dissolution of evaporation deposits (Cl/Br > 300) and overlaps with the range of Cl/Br ratios for domestic sewage effluent groundwater. Selecting the best chemical components and their ratios in non-isotopic geochemical methods provides an accurate distinction between sources of groundwater salinity.