Groundwater Electrical Conductivity Research Articles

Statistical Approach to River–Aquifer Interaction in the Lower Nakdong River Basin, Republic of Korea

AbstractThe construction of river barrages has led to an increase in groundwater (GW) levels (WL_G) near the upstream regions of these barrages, particularly in the wet season. Statistical approaches were applied in this study to examine the relationships between WL_G and river water (RW) level (WL_R), and electrical conductivity of groundwater (EC_G) and electrical conductivity of river water (EC_R) in the Changnyeong–Haman river barrage area located downstream of the Nakdong River for the period June 2011–January 2014. Our finding suggested that the WL_G increased and the concentrations of most chemical constituents in the GW decreased in the study area owing to the construction of the barrage. However, long‐term operation of the barrage is expected to trigger a decrease in the RW–GW interaction resulting from the clogging of the bed and the wall of the river, which would in turn increase GW contamination. Copyright © 2016 John Wiley & Sons, Ltd.

Seasonal changes of spatial variation of some groundwater quality variables in a large irrigated coastal Mediterranean region of Turkey

Soil and groundwater degradations have taken considerable attention, recently. We studied spatial and temporal variations of groundwater table depth and contours, and groundwater pH, electrical conductivity (EC), and nitrate (NO3) content in a large irrigated area in Western Mediterranean region of Turkey. These variables were monitored during 2009 and 2010 in previously constructed 220 monitoring wells. We analyzed the data by geostatistical techniques and GIS. Spatial variation of groundwater table depth (GTD) and groundwater table contours (GTC) remained similar across the four sampling campaigns. The values for groundwater NO3 content, EC, and pH values ranged from 0.01 to 454.1gL−1, 0.06 to 46.0dSm−1 and 6.53–9.91, respectively. Greatest geostatistical range (16,964m) occurred for GTC and minimum (960m) for groundwater EC. Groundwater NO3 concentrations varied both spatially and temporally. Temporal changes in spatial pattern of NO3 indicated that land use and farming practices influenced spatial and temporal variation of groundwater NO3. Several hot spots occurred for groundwater NO3 content and EC. These localities should be monitored more frequently and land management practices should be adjusted to avoid soil and groundwater degradation. The results may have important implications for areas with similar soil, land use, and climate conditions across the Mediterranean region.

Coastal aquifer hydrodynamics and salinity in response to the tide: case study in Lisbon, Portugal

The variability in dynamics and salinity of the coastal alluvial aquifer on which the city of Lisbon is located was evaluated. The evaluation was based on the analysis of level and groundwater electrical conductivity fluctuations depending on the tide in the Tagus River. The results obtained made it possible to recognize three sectors. First, a littoral sector where the variations in level and salinity are larger on the coast and decrease towards the innermost sections of the alluvial fan. Second, a sector close to the docks where there is greater dynamic and salinity variability than in the coastal sectors, as the excavations of the docks favour the tidal propagation towards the aquifer. And third, a sector located towards the apex of the alluvial fan associated with the dynamics of the stormwater channel. In this sector, the largest periodical water table fluctuations in the aquifer occur, since the freshwater that cannot drain towards the river enters the aquifer at high tide, causing a slight decrease in salinity content. On the basis of these results, conceptual models of hydrogeological behaviour were used to describe the spatial and temporal variations in the hydrodynamic and salinity characteristics of groundwater.

Correlation study among water quality parameters of groundwater of Valsad district of south Gujarat(India)

Groundwater samples were collected from five talukas of Valsad district for one year (from August 2008 to July 2009) and were analyzed for their physicochemical characteristics. The present investigation is focused on determination of parameters like pH, Colour, Electrical Conductivity (EC), Total Hardness (TH), Calcium (Ca), Magnesium (Mg), Total Alkalinity (TA), Total Dissolved Solids (TDS), Silica, Chloride, Sulphate, Fluoride, Sodium, Chemical Oxygen Demand (COD) and metals like Copper (Cu) and Manganese (Mn). Correlation coefficients were determined to identify the highly correlated parameters and interrelated water quality parameters. Correlation matrix of Valsad district suggests that EC of groundwater is found to be significantly correlated with eight out of seventeen water quality parameters studied. It may be suggested that the quality of Valsad district can be checked very effectively by controlling EC of water.

Determination of arsenic contents in groundwater of District Rahim Yar Khan Southern Punjab, Pakistan

In southern Punjab, arsenic (As) contents in groundwater is one of the major problems. A preliminary study was conducted to evaluate the extent of As concentration along with pH, electrical conductivity (EC), total dissolved salts (TDS), and heavy metals Cu, Ni, Cd, Fe, and Mn in 121 groundwater samples of the study area. The range values of As were below detection limit (BDL) to 100 ppb, pH (6.4–7.9), EC (0.503–40.8 mS/cm), Cu (BDL—1142 μg/L), Ni (BDL—179.2 μg/L), Fe (1.1–995.4 μg/L), and Mn (0.2–499.2 μg/L) in groundwater. The As concentration in 33.9 % samples was higher than prescribed limit (10 ppb) of WHO for drinking water while TDS in 70.3 %, Cu in 14 %, Ni in 5.7 %, Fe of 15.7 %, and Mn in 28.92 % were observed higher than their respective permissible limits. The correlation coefficient (r) was carried out for seven parameters, indicating positive correlation of As with Fe (0.27). Contamination index (C d) of 44.9 % ground water was observed >3 indicating the extent of contamination. The present study indicated the water samples collected from riverine area had higher concentration of As than the samples from canal irrigated or in vicinity of the desert area.

Spatial distribution of electrical conductivity and stable isotopes in groundwater in large catchments: a geostatistical approach in the Quequén Grande River catchment, Argentina

Stable isotopes and electrical conductivity in groundwater were used as natural tracers to adjust the hydrogeological conceptual model in one of the largest catchments within the inter-mountainous Pampa plain, Argentina. Geostatistical tools were used to define the model that best fitted the spatial distribution of each tracer, and information was obtained in areas where there was a lack of data. The conventional isotopic analysis allowed the identification of three groundwater groups with different isotopic fingerprints. One group containing 56 % of the total groundwater samples suggested a well-mixed system and soil infiltration precipitation as the main recharge source to the aquifer. The other two groups included samples with depleted (25.5 %) and enriched (18.5 %) isotopic compositions, respectively. The combination of δ18O, δ2H and electrical conductivities maps suggested ascending regional flows and water transfer from the Quequén Grande River catchment to the Moro creek. The spatial interpretation of these tracers modified the conceptual hydrogeological model of the Quequén Grande River.

Where do you draw the line? Determining the transition thresholds between estuarine salt marshes and terrestrial vegetation

The aim of this study was to determine if abiotic thresholds are responsible for maintaining the salt marsh–terrestrial vegetation boundary. In eight estuaries along the South African coast, sediment and groundwater characteristics were measured in quadrats spanning the salt marsh, ecotone and terrestrial habitats. The cover of salt marsh vegetation showed no obvious limitation to any of the recorded environmental variables. This supports Purer's hypothesis that the upper boundary of estuaries is limited by competition. In contrast, terrestrial vegetation cover declined with increasing sediment electrical conductivity (threshold ~20–30mS/cm), groundwater electrical conductivity (threshold ~60–80mS/cm), and groundwater salinity (threshold ~20–40ppt) and sediment moisture content (threshold ~20–25%). These variables were strongly correlated, and may be operating synergistically or a subset of these may be responsible for restricting terrestrial vegetation from occurring in the salt marsh. In the absence of landuse changes at the salt marsh–terrestrial boundary, salt marshes are unlikely to be unaffected by rising sea-levels as a landward migration will not be constrained by abiotic factors.

Temporal Stability and Periodicity of Groundwater Electrical Conductivity in Luohuiqu Irrigation District, China

Soil salinization is currently a constraint on agriculture development in irrigated areas throughout the world. This study was conducted to examine the temporal stability and periodicity of groundwater electrical conductivity (EC) in irrigation districts. To accomplish this, 51 observation wells were selected for analysis of groundwater EC. Relative difference analysis and the non‐parametric Spearman rank correlation test were used to check EC temporal stability, while the Morlet wavelet analysis was applied to measure the periodic variation of groundwater EC and groundwater level of high and low salinity wells. The mean groundwater EC of the 51 wells did not show an increasing trend over the entire measurement period, but demonstrated a moderate spatial variability, with coefficient of variation values ranging from 61 to 72%. The groundwater EC exhibited a strong temporal stability with Spearman correlation coefficients ranging from 0.81 to 0.98. The mean EC representative location in the study area was well 2, showing a good relationship between groundwater EC and groundwater level. Changes in groundwater EC were mainly affected by lateral groundwater recharge sources in small time scales. However, the groundwater EC and groundwater level always showed an obviously inverse phase with a large time scale due to precipitation effects. In conclusion, the groundwater EC, lateral recharge sources, and irrigation time should be fully considered in irrigation to avoid soil salinization.

Effects of human activities and climate variability on water resources in the Saveh plain, Iran.

Quantity and quality distribution of surface water and groundwater are changing under the impacts of both climate variability and human activities. The main goal of this paper is to evaluate the abovementioned impacts on the water resources in the Saveh plain, central Iran. To achieve this aim, spatial and temporal changes of the surface and groundwater quality and quantity have been analyzed, using hydrometric and meteorological data. The nonparametric Mann-Kendall test was used to identify trends and change points in the annual rainfall and runoff for the period of 1946 to 2011. In order to analyze the impacts of the Saveh Dam on runoff, the dam operation year, 1994, was considered as a change point. Mann-Kendall test results show that rainfall time series was divided into two parts, namely, 1966-1989 and 1990-2007, and averages of annual rainfall in five stations increase from 10 to 21 %. Also, runoff time series was divided into two parts, namely, 1946-1995 and 1996-2007 and averages of annual runoff in four stations decrease from 8 to 83 %. Results show that rainfall changes in Shahabasi, Razin, Jalayer, Emamabad, and Ahmadabad stations increased from 9 to 33 % before and after 1994. Nevertheless, runoff decreased from 24 to 81 %. The results indicate that the greatest lack of runoff between stations is at Shahabasi station and one important reason for the severe lack is operation of the Saveh Dam in 1994. Highest groundwater level decline, about 168.67 cm, occurred in 1994 that is the operation year of the Saveh Dam. Trend analysis of surface water quality show that electrical conductivity increased 957.34 μmho/cm before and after 1994. Also, the Wilcox water quality classification method has been reduced from C3-S1 to C4-S2. Average groundwater electrical conductivity (EC) during 1999-2003 and 2004-2009 increased to 89.6 μmho/cm. Also, the groundwater quality indices for agricultural usages are classified in four classes including, C4-S2 16, C4-S1 46, C3-S1 30, and C2-S1 8 % of the total aquifer area. In conclusion, in order to have a sustainable development, the effects of water projects on environment and water resources need to be predicted very carefully.

Spatial analysis of groundwater electrical conductivity using ordinary kriging and artificial intelligence methods (Case study: Tabriz plain, Iran)

Artificial intelligence (AI) systems have opened a new horizon to analyze water engineering and environmental problems in recent decades. In this study performances of ordinary kriging (OK) as a linear geostatistical estimator and two intelligent methods including artificial neural networks (ANN) and adaptive neuro-fuzzy inference system (ANFIS) are investigated. For this purpose, geographical coordinates of 120 observation wells that located in Tabriz plain, north-west of Iran, were defined as inputs and groundwater electrical conductivities (EC) were set as output of models. Eighty percent of data were randomly selected to train and develop mentioned models and twenty percent of data used for testing and validating. Finally, the outputs of models were compared with the corresponding measured values in observation wells. Results indicated that ANFIS model provided the best accuracy among models with the root mean squared error (RMSE) value of 1.69 dS.m and correlation coefficient (R) of 0.84. The RMSE values in ANN and OK were calculated 1.97 and 2.14 dS.m and the R values were determined 0.79 and 0.76, respectively. According to the results, the ANFIS method predicted EC precisely and can be advised for modeling groundwater salinity.

Using <sup>14</sup>C and <sup>3</sup>H to understand groundwater flow and recharge in an aquifer window

Abstract. Knowledge of groundwater residence times and recharge locations is vital to the sustainable management of groundwater resources. Here we investigate groundwater residence times and patterns of recharge in the Gellibrand Valley, southeast Australia, where outcropping aquifer sediments of the Eastern View Formation form an "aquifer window" that may receive diffuse recharge from rainfall and recharge from the Gellibrand River. To determine recharge patterns and groundwater flow paths, environmental isotopes (3H, 14C, δ13C, δ18O, δ2H) are used in conjunction with groundwater geochemistry and continuous monitoring of groundwater elevation and electrical conductivity. The water table fluctuates by 0.9 to 3.7 m annually, implying recharge rates of 90 and 372 mm yr−1. However, residence times of shallow (11 to 29 m) groundwater determined by 14C are between 100 and 10 000 years, 3H activities are negligible in most of the groundwater, and groundwater electrical conductivity remains constant over the period of study. Deeper groundwater with older 14C ages has lower δ18O values than younger, shallower groundwater, which is consistent with it being derived from greater altitudes. The combined geochemistry data indicate that local recharge from precipitation within the valley occurs through the aquifer window, however much of the groundwater in the Gellibrand Valley predominantly originates from the regional recharge zone, the Barongarook High. The Gellibrand Valley is a regional discharge zone with upward head gradients that limits local recharge to the upper 10 m of the aquifer. Additionally, the groundwater head gradients adjacent to the Gellibrand River are generally upwards, implying that it does not recharge the surrounding groundwater and has limited bank storage. 14C ages and Cl concentrations are well correlated and Cl concentrations may be used to provide a first-order estimate of groundwater residence times. Progressively lower chloride concentrations from 10 000 years BP to the present day are interpreted to indicate an increase in recharge rates on the Barongarook High.

Remote online monitoring of groundwater quality near burial sites for determination of maintenance priority

Many concerns have been voiced concerning the potential for contamination of groundwater in the vicinity of active burial sites for carcasses. The Korean Ministry of Environment has developed a protocol to screen active burial sites based on monitored groundwater data that might lead to the spreading of pathogens and/or chemicals. This methodology is, however, not effective due to the considerable time and cost. In our study, we proposed that electrical conductivity of groundwater can be used as an indicator to continuously monitor groundwater in the vicinity of active burial site and screen for burial sites that are causing contamination. This technique can be adapted for remote monitoring based on interpretation of long-term monitoring data of monitored wells and background concentration in the vicinity of burial sites.

Hydrological and hydrogeological characterization of groundwater and river water in the North Hanoi industrial area, Vietnam

Degradation of groundwater quality by human activities is a widespread environmental problem in Vietnam. Groundwater there is a major source of water for domestic and industrial purposes. This paper reviews, compiles, and comprehensively analyzes spatiotemporal variations of hydrological and hydrogeological characteristics of shallow and deep groundwater aquifers in northern Hanoi industrial zones and in nearby Red River water. Groundwater level, electrical conductivity, and water temperature were measured in six monitoring wells, complemented by anion, cation, and stable isotope analyses of ground and surface water. The results show that the groundwater in both shallow and deep aquifers was fresh, but mainly calcium-bicarbonate type contaminants and human activities affect groundwater and surface water composition. With the goal of devising sustainable water use regulations, more research must be directed toward long-term monitoring of groundwater and surface water quality, as well as toward detailed investigation of the hydraulic characteristics of local aquifers in the study area.

排水沟蓄水条件下农田与排水沟水盐监测研究

PDF HTML阅读 XML下载 导出引用 引用提醒 排水沟蓄水条件下农田与排水沟水盐监测 DOI: 10.5846/stxb201307261948 作者: 作者单位: 西安理工大学教育部西北水资源与环境生态重点实验室,西安理工大学教育部西北水资源与环境生态重点实验室,西安理工大学教育部西北水资源与环境生态重点实验室 作者简介: 通讯作者: 中图分类号: S276.7 基金项目: 国家自然科学基金资助项目（51079122，51279159） Monitoring salt and water dynamics in farmland and drainage ditch in a saline environment under reduced drainage intensity Author: Affiliation: Northwest Key Laboratory of Water Resource and Environment Ecology,Ministry of Education Xi’an University of Technology,Xi’an;China,Northwest Key Laboratory of Water Resource and Environment Ecology,Ministry of Education Xi’an University of Technology,Xi’an;China,Northwest Key Laboratory of Water Resource and Environment Ecology,Ministry of Education Xi’an University of Technology,Xi’an;China Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:为了查明盐碱地排水沟蓄水条件下农田与排水沟之间的水盐交换，基于两年现场观测试验数据，分析了农田与排水沟的水位响应以及电导率变化规律。结果发现：研究区排水沟蓄水条件下，相邻排水沟水位与农田地下水位变化基本一致，作物生长期较为强烈的蒸发蒸腾作用进一步降低了田间地下水位；排水沟水位变化可以直接或间接地影响周围农田的地下水位和水质状况，在无外界来水干扰的情况下，农田地下水和排水沟水样的电导率变化趋势一致，当排水沟受到外来淡水补给时，沟内浓缩的盐分得到稀释，电导率明显低于农田地下水。研究结果可为类似地区盐碱地治理和生态环境保护提供参考依据。 Abstract:The fast population growth and rapid urban development in China have made it necessary to develop marginal lands for agricultural use. One approach to meet such land requirement is to reclaim the existing salinized wasteland through engineering measures through artificial drainage. As salt content in soils poses potential threat to crop growth, understanding the relationships of salt and water exchange between farmland and drainage ditches is of great importance for salinity control in the saline agricultural environment. In this paper, we present a 2 year monitoring study on salt and water dynamics in a reclaimed salt affected farmland area in Shaanxi, China. In 2 strip fields of 100×400m, we observed water table depth and measured electrical conductivity (EC) of water samples taken from monitoring wells, those wells were installed at 1, 2 and 3 m in depth in a cluster in each field; in the mean time, we measured the depth to water level in drainage ditches along the strip fields and sampled the ditch water for their salinity levels. Weather data analysis showed that the rainfall during the monitoring period was close to the long term average values. Rainfall pattern in the study area is generally in accordance with the potential evapotranspiration, making irrigation only necessary when prolonged dry period appears during the growing season. The monitoring data showed that the drainage ditches have effectively controlled the water table in the crop fields: the depth to water table varied between 1.69 to 2.27 in field A and between 1.24 and 2.18 in field B, while the depth to water level in drainage ditches varied between 1.84 and 2.05 by the field A and between 1.16 and 2.0 by the field B. The salinity of the groundwater in the fields, however, was less variable than that in the drainage ditches: the EC in groundwater varied between 4.72 and 7.51ms/cm in field A and between 6.58 and 11.4 in field B, while the EC in drainage ditches varied between 4.86 and 8.69 by the field A and between 1.9 and 14.75 by the field B. The greater variability of EC in the drainage ditches was caused by the dilution effect of freshwater recharge in the end of the irrigation season, when a large amount of irrigation return flow from an upstream irrigation district was discharged to the study area due to its lower elevation. The elevated water level in the drainage ditches had no significant impact on field water table depth due to the short duration. When no additional freshwater recharge is available, salinity in the drainage ditches increased with time due to evaporation concentration.Findings from this research may provide technical guidance for salinity management in the similar salt affected agricultural regions. 参考文献 相似文献 引证文献

地下への海水浸入へ水田灌漑用排水が与える影響に関する考察-東日本大震災前後の地下水電気伝導率実態調査結果-

地下への海水浸入へ水田灌漑用排水が与える影響に関する考察-東日本大震災前後の地下水電気伝導率実態調査結果-

Evaluation of ANFIS, ANN, and geostatistical models to spatial distribution of groundwater quality (case study: Mashhad plain in Iran)

Groundwater is one of the major sources of exploitation in arid and semiarid regions. Spatial and temporal quality distribution is an important factor in groundwater management. Thus for protecting groundwater quality, data on spatial and temporal distribution are important. Geostatistical models are the most advanced techniques for interpolation and spatial prediction of groundwater parameters. Determining the best and the most suitable model is also very essential which is the main aim in this study. In this research, inverse distance weighted (IDW), kriging, and cokriging methods in geostatistical and artificial neural network (ANN) and adaptive network-based fuzzy inference system (ANFIS) models were used for predicting the spatial distribution of groundwater electrical conductivity (EC) and those were compared together. EC and chloride (Cl−) are two important indicators for water quality assessment. Data were related to 120 wells in Mashhad plain (Iran). Groundwater resources have an important role in this region due to surface water deficit. After normalization of data, to geostatistical models, variograme was drawn; for selecting a suitable model for fitness on experimental variograme, less RSS value was used. Then using cross-validation and root mean square error (RMSE), the best method for interpolation was selected. To compare these three models, we used 25 % of observation data and determined the R2, RMSE, and MAE parameters. Different ANFIS structures were examined. Also in ANFIS method, different types of membership function, such as Gaussian, bell shape, and trapezoid for inputs of model, were used. Results showed that for interpolation of groundwater quality, cokriging method is superior to kriging method in geostatistical model. In cokriging method, Cl parameter was selected as auxiliary variable which had the highest correlation with EC. Results showed that ANN model had the best accuracy (R2 = 0.932, RMSE = 367.9, MAE = 265.78 μmos/cm) than ANFIS and geostatistical models.

Identification of surface water-groundwater interaction by hydrogeochemical indicators and assessing its suitability for drinking and irrigational purposes in Chennai, Southern India

Large cities face water quality and quantity problems due to increasing population and improper disposal of solid and liquid wastes. It is essential to monitor the water quality to take corrective measures. This study was carried out in one of the densely populated metropolitan cities in India to ascertain the suitability of groundwater for drinking and irrigation activity, identify the processes controlling the geochemistry of groundwater and the impact of Adyar River on the groundwater quality. Magnesium and pH concentration in groundwater of this area were within the maximum permissible limits of WHO standards. Sodium and potassium concentration of groundwater were greater than the permissible limit in 30.8 % and in 50 % of the samples, respectively. About 35 % of the groundwater samples were not permissible for drinking based on the electrical conductivity (EC). The EC of groundwater was increasing towards the coast. In general, the quality of groundwater for irrigation purpose vary from moderate to good based on Na%, magnesium hazard, residual sodium carbonate, sodium absorption ratio, permeability index, and USDA classification. Na–Cl and Ca–Mg–Cl were the dominant groundwater and surface water type. Increased ionic concentration of groundwater towards the eastern part of the study area is due to the discharge of industrial effluents and domestic sewage into the Adyar River. Seawater intrusion is also one of the reasons for Na–Cl dominant groundwater near the coast. Evaporation and ion exchange were the major processes controlling groundwater chemistry in this area. The groundwater quality of this region is affected by the contaminated surface water.

Geochemistry of groundwater in front of a warm‐based glacier in southeast greenland

Groundwater in front of warm‐based glaciers is likely to become a more integrated part of the future proglacial hydrological system at high latitudes due to global warming. Here, we present the first monitoring results of shallow groundwater chemistry and geochemical fingerprinting of glacier meltwater in front of a warm‐based glacier in outheast reenland (ittivakkat letscher, 65° 41′ , 37° 48′ ). The groundwater temperature, electrical conductivity and pressure head were monitored from ugust 2009 to ugust 2011, and water samples were collected in 2009 and analyzed for major ions and water isotopes (δD, δ18O). The 2-yrs of monitoring revealed that major outbursts of glacier water during the ablation season flushed the proglacial aquifer and determined the groundwater quality for the next 2–8 weeks until stable chemical conditions were reached again. Water isotope composition shows that isotopic fractionation occurs in both groundwater and glacier meltwater, but fractionation due to evaporation from near‐surface soil moisture prior to infiltration has the most significant effect. This study shows that groundwater in ow rctic reenland is likely to possess a combined geochemical and isotopic composition, which is distinguishable from other water sources in the proglacial environment. However, the shallow groundwater composition at a given time is highly dependent on major outbursts of glacier water in the previous months.

Availability of coastal groundwater discharge as an alternative water resource in a large-scale reclaimed land, Korea

This study was conducted to identify the availability of coastal groundwater discharge (CGD), subsurface fluids flowing from inland through the coastal area to sea, as an alternative water resource for a large-scale reclaimed land. The behaviors of stable isotopes indicated that groundwater originated from inland precipitation and traveled as CGD along the coast line. Most of the groundwater samples collected from domestic wells installed along the old coast line were considered to be relatively fresh from the correlation analysis among chemical constituents. The average electrical conductivity (EC) values of the samples were identified as averaging 1,125–1,297 μS cm−1, corresponding to appropriate crop growth. A weathered-rock layer in a small catchment within the reclaimed land was proved to be a main CGD pathway, with electrical resistivity anomalies ranging from 7 to 14 Ω m. Five monitoring wells were placed in this catchment to delineate the occurrence of CGD. Long-term vertical EC profiling results for the monitoring wells indicated that CGD occurs within a depth of 30 m below the ground surface. Annual monitoring data for groundwater level and EC demonstrated that the water quality of CGD was improved by introducing fresh terrestrial groundwater. A remarkable improvement in water quality (EC decrease of 900–1,600 μS cm−1) of CGD was observed during the saline water pumping test that explains how CGD could be an alternative water resource for the reclaimed land.

The role of water use and uptake on two Mediterranean shrubs' interaction in a brackish coastal dune ecosystem

ABSTRACTWater relations are essential in plant–plant interactions, particularly in Mediterranean coastal sand dunes, owing to marked drought periods and the possibility of groundwater (GW) salinization. In this study, seasonal water use dynamics were explored in the interaction between a native–invasive species, Retama monosperma, and the endangered Thymus carnosus, in south‐western Spain. The following variables were measured: xylem water isotopic composition to determine water sources, predawn and midday stem water potential and free leaf proline content as stress indicator. GW electrical conductivity and stable isotopes were also analysed to assess water table salinity. In late summer and spring, the warmest seasons, Thymus beneath Retama displayed significantly lower water potential and higher leaf proline content than isolated Thymus, whereas Retama showed the highest proline content in autumn and winter. Water sources showed different patterns depending on the Thymus situation: Isolated ones always matched the brackish GW, as well as Retama plants, whereas Thymus beneath Retama switched among rainfall, soil and water table, showing a seasonal change in the water‐harvesting strategy. Overall, competition for water sources between both species was discovered, which led to a shift in water use and water uptake strategies of understorey Thymus. The results also demonstrate the importance and potential use of species interaction studies in the development of threatened species management strategies. Copyright © 2013 John Wiley & Sons, Ltd.