Return Flow Of Irrigation Waters Research Articles

Spatiotemporal Changes in the Hydrochemical Characteristics and the Assessment of Groundwater Suitability for Drinking and Irrigation in the Mornag Coastal Region, Northeastern Tunisia

Hydrogeochemical properties and groundwater quality assessment are very important for the effective management of water resources in arid and semiarid regions. The present investigation is a spatiotemporal analysis of groundwater quality using both chemical analysis and water quality indices (WQIs) in the Mornag Basin in northeastern Tunisia. The results exhibit that the Mornag shallow aquifer is dominated by chloride–sodium–potassium water facies, which progress over time toward chloride–sulfate–calcium and magnesium water facies. This may highlight that the mineralization of groundwater, which increases in the direction of groundwater flow, is primarily controlled by a natural process resulting from the dissolution of evaporative minerals and cation exchange with clay minerals relatively abundant in the study area. The anthropogenic activities represented by the return flow of irrigation water, the recharge by wastewater, and climate change also have a key role in groundwater contamination. The temporal evolution in %Na and SAR over the last three years in the Mornag aquifer shows an increasing trend that makes them unsuitable for irrigation. These findings highlight the need for assessing water quality in mapping local water resource vulnerability to pollution and developing sustainable water resources management.

Application of geochemical and isotopic tracers for the evaluation of groundwater quality in the irrigated area of the Sbiba plain (Central West Tunisia)

Hydrochemical and isotopic tracers of groundwater of the Mio-Plio-Quaternary aquifer in the Sbiba plain, central west Tunisia, are used to assess the groundwater quality for drinking and irrigation purposes as well as identifying sources of salinity variation. In this plain, the evaporation and water-rock interactions including dissolution of evaporite and carbonate minerals and cation exchange are the principal hydrochemical processes controlling the groundwater salinization and water types. Moreover, a secondary effect of salinity increase is due to the return flow of irrigation water and mixing between old and recent water within the aquifer. These phenomena are proved by the environmental isotope study. Several water quality parameters for drinking and irrigation purposes were applied. Water Quality Index (WQI) values indicate that 50 % of groundwater samples are suitable for drinking usage with “excellent” and “good” categories. According to Percent Sodium (%Na), Sodium Adsorption Ratio (SAR) and Residual Sodium Carbonate (RSC), all groundwater samples are suitable for agricultural irrigation activities. Based on the electrical conductivity (EC) and Wilcox classification, it appears that only 57 % of water samples are suitable for irrigation use; more than 50 % of these samples are “good” and “permissible”. In general, groundwater in the western and central parts of the Sbiba plain is suitable for drinking and irrigation purposes. However, an attention should be accorded to groundwater salinization processes.

Coastal Aquifer Salinization in Semi-Arid Regions: The Case of Grombalia (Tunisia)

Groundwater resources are facing increasing pressure especially in semi-arid regions where they often represent the main freshwater resource to sustain human needs. Several aquifers in the Mediterranean basin suffer from salinization and quality degradation. This study provides an assessment of Grombalia coastal aquifer (Tunisia) based on multidisciplinary approach that combines chemical and isotopic (δ2H, δ18O, 3H, 14C and δ13C) methods to characterize the relation between groundwater quality variation and aquifer recharge. The results indicate that total dissolved solids exceed 1000 mg/L in the most of samples excepting the recharge area. In addition to water–rock interaction, evaporation and nitrate pollution contributing to groundwater mineralization, the reverse cation exchange process constitute an important mechanism controlling groundwater mineralization with enhancing risk of saltwater intrusion. Environmental isotope tracers reveal that groundwater is evolving within an open system to close system. A significant component of recent water that is recharging Grombalia aquifer system is confirmed by applying correction models based on the δ13C values and 14C activities and tritium contents. However, this recharge, which is mainly associated to the return flow of irrigation water, contributes to the groundwater salinization, especially for the shallow aquifer.

Tracing groundwater salinization processes in an inland aquifer: A hydrogeochemical and isotopic approach in Sminja aquifer (Zaghouan, northeast of Tunisia)

Sminja plain is an inland aquifer in Zaghouan prefecture, northeast of Tunisia. In some parts of the aquifer, salinity exceeds 13 g L−1, which poses serious problems to the safe use of the groundwater in irrigation and drinking purposes.The present work aims to delineate the saline water plumes and to understand their salinization processes. A field survey including surface water and groundwater sampling was conducted. The taken samples were analyzed for major chemical elements (Na+, Ca2+, Mg2+, K+, Cl−, SO42− and NO3−) and stables isotopes composition (18O and 2H). The geochemical data were used to characterize and classify the water samples. Stable isotopes are useful tools to understand recharge processes and to differentiate between salinity origins. Indeed, the saline groundwater zones are concentrated in the center, the north-west (Aziz mountain) and south-west parts of the plain (City Al Fahs). The evolution of the groundwater salinization according to the main flow direction is principally caused by rock-water interaction which is mainly represented by the dissolution/precipitation of minerals dispersed in the saline reservoir formation and ion exchange reaction. Stable isotopes signature indicates that some water samples are originated from the infiltration of modern precipitation. Non-evaporated water is rapidly infiltrated to the saturated zone with relatively lower contents of δ18O and δ2H. Thus, most of the samples are presenting enrichment in heavy isotopes which highlight the occurrence of evaporation process of meteoric water prior to groundwater recharge. Furthermore, anthropogenic phenomenon represented by the return-flow of irrigation water and the use of nitrogen fertilizers were identified as non negligible contamination sources in the northeastern part of the aquifer near the irrigated perimeters. These wide variations in water salinity indicate variability in geochemical process controlling aquifer water mineralization in Sminja plain.

Hydrochemical and stable isotopic investigation of groundwater quality and its sustainability for irrigation in the Hammamet-Nabeul basin, northeastern Tunisia

The major ion hydrochemistry, sodium absorption ratio (SAR), sodium percentage, and isotopic signatures of Hammamet-Nabeul groundwaters were used to identify the processes that control the mineralization, irrigation suitability, and origin of different water bodies. This investigation highlights that groundwater mineralization is mainly influenced by water-rock interaction and pollution by the return flow of irrigation water. The comparison of groundwater quality with irrigation suitability standards proves that most parts of groundwater are unacceptable for irrigation and this long-term practice may result in a significant increase of the salinity and alkalinity in the soils. Based on isotopic signatures, the shallow aquifer groundwater samples were classified into (i) waters with depleted δ18O and δ2H contents, highlighting recharge by modern precipitation, and (ii) waters with enriched stable isotope contents, reflecting the significance of recharge by contaminated water derived from the return flow of evaporated irrigation waters. The deep-aquifer groundwater samples were also classified into (i) waters with relatively enriched isotope contents derived from modern recharge and mixed with shallow-aquifer groundwater and (ii) waters with depleted stable isotope contents reflecting a paleoclimatic origin. Tritium data permit to identify three origins of recharge, i.e., contemporaneous, post-nuclear, and pre-nuclear. Carbon-14 activities demonstrate the existence of old paleoclimatic recharge related to the Holocene and Late Pleistocene humid periods.

Hydrogeochemical characteristics and groundwater contamination in the rapid urban development areas of Coimbatore, India

The Singanallur Sub-basin is one of the major waterways and it supplies water to the Coimbatore city. Currently, it is vulnerable to pollution due to an increase of unplanned urban developments, industrial, and agricultural activities that compromise both the quality and quantity. In the present study three major hydrochemical facies were identified (mixed Ca-Mg-Cl, Ca-Cl, and Ca-HCO3). Irrigation suitability indexes are specifies that the groundwater in the areas has very high salinity hazard and low to medium alkali hazard. The mechanism controlling groundwater chemistry originally regulated by the evaporation process is dominated by reason of arid condition and anthropogenic activities existing throughout the region. The multivariate statistical analysis (Correlation analysis (CA), principal component analysis (PCA) and Hierarchical cluster analysis (HCA)) indicates, most of the variations are elucidated by the anthropogenic pollutant predominantly due to population growth, industrial effluents, and irrigation water return flow. This study demonstrates enhanced information of evolution of groundwater quality by integrating hydrochemical data and multivariate statistical methods are used to understand the factors influencing contamination due to natural and anthropogenic impacts.

Factors affecting the stable isotopes ratios in groundwater impacted by intense agricultural practices: A case study from the Nile Valley of Egypt

The monitoring of stable isotopes (δ18O and δ2H) in water can provide a sensitive indicator of water loss by evaporation. We obtained water samples from surface water and groundwater from both the young and old alluvial plains in the central part of the Nile Valley of Egypt. Groundwater is the only source for irrigation in the old alluvial plains while both surface water (River Nile and irrigation canals) and groundwater are used in the young alluvial plain. Results showed different isotopic compositions between each group of samples and hydrologic connections between shallow groundwater and surface water in the young alluvial plain. The δ18O and δ2H relationship of the samples collected from the desert areas of the old alluvial plains below agricultural lands define an evaporation line with a slope of 4.5 and low deuterium excess of <−14‰. These values can be attributed to return flow of irrigation water that has been subjected to evaporative processes, further amplified by intense agricultural practices. Average evaporative losses were estimated to be between 31% and 36%.

Groundwater salinization survey of the Upper Cretaceous-Miocene Complexe terminal aquifer in the Sabaa Biar area of southwestern Tunisia

An integrated hydrogeological study involving the Schlumberger depth sounding method, geological data and wells data was conducted at the Sabaa Biar area of southern Tunisia to elucidate the problem of increasing groundwater salinity within The “Complexe Terminal”. The “Complexe Terminal” aquifer near Sabaa Biar region is a bi-layered aquifer comprised of fractured limestones of the Cretaceous (Campanian–Maastrichtian) Berda Formation and sandstone of the Miocene Beglia Formation. The aquifer is affected by a main NW–trending fault, which is a chemical barrier that divides the study area into eastern and western blocks delivering freshwater and saline water, respectively. The salinization of groundwater within the limestone (Campanian–Maastrichtian Berda Formation) is linked mainly to the dissolution of outcropping Coniacian–Santonian gypsum along the core of the Jebel Sidi Bouhlel anticline to the east of the study area. Meteoric water dissolves salt from outcropping gypsum, flows through the fractures networks, and recharges the fractured limestone of the upper Berda Formation. The mobilization of salts stored in the salt-rich Quaternary sediment on hillslopes and inchannels contributes also to the salinization of groundwater within the sandstone (Miocene Beglia Formation) by lateral infiltration subsequent to water drainage during the wet season. The over exploitation of water from the Miocene sandstone causes an influx of saline-rich water from the underlying limestone of the Berda Formation into the sandstone of the Beglia Formation. Other sources of salinization of groundwater (such as ascension of hypersaline water from deep aquifer along faults, and the return flow of irrigation waters in the Djerid region) have been documented in this region, but are not discussed in this paper.

The use of hydrochemical and environmental isotopic tracers to understand the functioning of the aquifer system in the Bou Hafna and Haffouz regions, Central Tunisia

Major ions hydrochemistry and isotopic data (18O, 2H, 3H, 14C) have been used to improve the understanding of mineralisation processes, origins, and circulation patterns of groundwaters of the Bou Hafna and Haffouz region in Central Tunisia. Hydrochemical investigation indicates that the salinity in groundwater, which varies greatly from 0.2 to 1.3 g/l, results mainly from the dissolution of evaporates (halite, gypsum and anhydrite), cation exchange and dedolomitization processes. The use of stable isotopes tracers (δ18O, δ2H) has classified groundwaters samples into two groups. The non-evaporated groundwaters are distinguished by relatively depleted isotope contents, highlighting significant recharge at higher altitudes. The evaporated groundwaters are characterized by enriched δ18O and δ2H contents, reflecting the contribution of return flow of irrigation waters to the recharge of the studied aquifer system. Tritium contents, varying from 0.03 to 1.23 UT, provide evidence of the presence of two sources of recharge that correspond to pre-nuclear recharge, and to a mixture between pre-nuclear water and the contemporaneous recharge. The 14C activities, ranging between 7.4 and 78.6 pmc, identify two groundwater groups. The first group is dominated by the direct infiltration of present day meteoric water at higher altitude. The second group is formed by a mixture of recent and palaeoclimatic groundwaters.

Hydrochemical and isotopic assessment of groundwater quality in the Quaternary shallow aquifer, Tazoghrane region, north-eastern Tunisia

The major ion hydrochemistry and environmental isotope composition (18O, 2H) of the Tazoghrane shallow groundwaters were investigated to identify the sources and processes that affect the groundwater composition. The Quaternary shallow aquifer of Tazoghrane represents one of the most important aquifers in the Cap Bon peninsula. Groundwater from this aquifer is classified into two water types: Ca–SO4–Cl and Na–Cl. The groundwater composition is largely controlled by the water–rock interaction, particularly the dissolution of evaporate minerals and the ion exchange process. Elevated content of nitrates indicates that agricultural activities are probably the most significant anthropogenic sources of nitrogen contamination. The stable isotopic signatures reveal two water groups. Non-evaporated waters, which are distinguished by depleted d18O and d2H contents, indicate the significant recharge by modern rainfall from Mediterranean air masses. Evaporated waters that are characterized by relatively enriched d18O and d2H contents indicate an important component of recharge by return flow of irrigation waters.

Hydrochemical and Isotope Evidence of Groundwater Contamination of Cultivated Fields of Semi-Arid Environments in Tunisia

This present study, which uses geochemical and isotope hydrological approaches, attempts to provide appropriate scientific information about the dominant geochemical processes that influence groundwater chemical composition in a semi-arid region of cultivated field. Therefore, particular emphasis has been placed on (1) the evolution of solute concentrations within the hydrological system as well as in the vadose zone, (2) the contribution of anthropogenic processes to the groundwater contamination, and (3) the estimation of groundwater recharge deriving from return flow of irrigation water. It has been demonstrated that the excess of irrigation waters has significantly influenced the rate of groundwater recharge. The annual amount of groundwater recharge related to the irrigation practices is approximately 100 mm. Modification of the geochemical characteristics of the Zeroud aquifer groundwater is caused by water-rock interaction, including both the dissolution of evaporate and the cation exchange process. However, anthropogenic processes related to the return flow of irrigation waters have led to extremely high nitrate concentrations and flushing of solutes, such as chloride, sulfate, sodium, and calcium. The isotopic signature provides evidence of groundwater contamination. Indeed, the relatively enriched stable isotope concentrations and low tritium concentrations highlight the important contribution of irrigation waters to the local groundwater recharge, particularly in the Menzel Mhiri agricultural area.

Groundwater composition and recharge origin in the shallow aquifer of the Djerid oases, southern Tunisia: implications of return flow

Major ions and stable isotopes in groundwaters of the Plio-Quaternary shallow aquifer of the Djerid oases, southern Tunisia, were investigated to elucidate the origin of groundwater recharge and the mineralization processes. It has been demonstrated that the groundwater composition is mainly controlled by the water–rock interaction, the encroachment of brines from the Chotts and the return flow of irrigation waters. The isotopically depleted groundwater samples suggest that the recharge waters derive from an old palaeoclimatic origin. However, the enriched groundwater samples reflect the presence of evaporated recharge water. Furthermore, the large negative deuterium-excess values indicate the effect of secondary evaporation processes, probably related to the return flow of irrigation waters pumped from the underlying aquifer. Editor D. Koutsoyiannis; Associate editor E. Custodio Citation Tarki, M., Dassi, L. and Jedoui, Y., 2012. Groundwater composition and recharge origin in the shallow aquifer of the Djerid oases, southern Tunisia: implications of return flow. Hydrological Sciences Journal, 57 (4), 790–804.

Hydrogeochemical Analysis of Groundwater Pollution in an Irrigated Land in Cap Bon Peninsula, North-Eastern Tunisia

Situated in semi-arid regions of northern Africa, the Nabeul-Hammamet basin, North-eastern Tunisia, is a typical alluvial plain, where rural population relies exclusively on groundwater as a water-supply source. Major ions hydrochemistry was used in conjunction with hydrogeological data to understand the aquifer hydrodynamic functioning and to identify natural and anthropogenic salinisation processes. An attempt has been made to recognize these processes using Principal Components Analysis (PCA) and bivariate diagrams of major element data. The groundwater composition is extensively modified by the water–rock reaction in the subsurface, that is, dissolution of halite, gypsum, and/or anhydrite; and ion-exchange with phyllosilicates. Nevertheless, overall groundwater samples are characterized by relatively high nitrate contents suggesting that the return flow of irrigation waters is a significant source of the groundwater contamination.

Analysis of Return Flow of Irrigation Water at Test Paddy in the Tedori River Alluvial Fan Area

Analysis of Return Flow of Irrigation Water at Test Paddy in the Tedori River Alluvial Fan Area

Geochemical and isotopic investigation of groundwater mineralization process in the Zeroud basin, central Tunisia

The determination of the origin of the salinity in the Zeroud aquifer (central of Tunisia) and the understanding of its hydrogeological and geochemical behaviors related to severe natural and anthropogenic constraints were approached by the combined survey of major element concentrations and stable isotopes (18O, 2H). The hydrogeochemical investigations of the Zeroud aquifer show that groundwaters can be classified into two major water facies: Ca–SO4–Cl and Na–Cl. The main hydrogeochemical processes that typically control the groundwater mineralization are dissolution of evaporates (halite, gypsum and anhydrite), dedolomitization, cation exchange and mixing processes related to the return flow of irrigation waters and the artificial recharge operations. The stable isotope signatures reveal that the first significant recharge origin is related to the direct infiltration of actual meteoric water particularly observed in the foot of hills bordering the basin and in the vicinity of the Zeroud Wady. A main part of groundwater is significantly affected by evaporation, giving evidence of a recharge mostly from the dam water during the artificial recharge operations. Moderated evaporation of waters was observed in the southern part of the basin, especially in the agricultural areas.

The hydrogeochemical characterization of groundwater in Gafsa-Sidi Boubaker region (Southwestern Tunisia)

Gafsa region is one of the most productive artesian basins in Southern Tunisia. It is located in the southwestern part of the country, and its groundwater resources are developed for water supply and irrigation. Proper understanding of the geochemical evolution of groundwater is important for sustainable development of water resources in this region. A hydrogeochemical survey was conducted on the Plio-Quaternary shallow and on the Complex Terminal aquifers system using major (Ca, Mg, Na, SO4, Cl, NO3 and HCO3) and minor (Sr) elements, in order to evaluate the groundwater chemistry patterns and the main mineralization processes occurring in this system. Hydrochemical and isotopic data were used in conjunction with hydrogeological characteristics to investigate the groundwater composition in these aquifers. It has been demonstrated that groundwaters acquire their mineralization principally by water–rock interaction, i.e. dissolution of evaporites (halite/gypsum, pyrite, etc.) and return flow of irrigation waters, and by anthropogenic activities due to the use of nitrogen (N) fertilizers–pesticides in agriculture. The isotopic study of “stable isotopes, radiocarbon and tritium” (Yermani 2002) shows that a paleoclimatic recharge is corroborated by the relatively low carbon-14 activities (5–25.3%) of the referred groundwater group samples, which were interpreted as recharge occurring during the late Pleistocene and the early Holocene periods. The water feedings of these aquifers are mainly provided by infiltration of precipitations, infiltration of irrigation water, lateral feeding from Cretaceous relieves from the South and the North and along recent and fossil drainage networks that constitute major freshwater sources in groundwater tables (Hamed et al., J Environ Protect 1:466–474, 2010a).

Investigation by multivariate analysis of groundwater composition in a multilayer aquifer system from North Africa: A multi-tracer approach

Abstract A multi-tracer approach has been carried out in the Sbeitla multilayer aquifer system, central Tunisia, to investigate the geochemical evolution, the origin of groundwaters and their circulation patterns. It involves statistical data analysis coupled with the definition of the hydrochemical and isotopic features of the different groundwaters. Principal Components Analysis (PCA) of geochemical data used in conjunction with bivariate diagrams of major and trace elements indicate that groundwater mineralization is mainly controlled by water–rock interaction and anthropogenic processes in relation to return flow of irrigation waters. The PCA of isotopic data and bivariate conventional diagrams of stable and radiogenic isotopes i.e. δ18O vs. δ2H and δ18O vs. 14C provide valuable information about the origin and the circulation patterns of the different groundwater groups. They permit classifying groundwaters into three groups. The first group is characterized by low 3H concentrations, low 14C activities and depleted stable isotope contents. It corresponds to an old end-member in relation with palaeoclimatic recharge which occurred during the Late Pleistocene and the Early Holocene humid periods. The second group is distinguished by high to moderate 3H concentrations, high 14C activities and enriched heavy isotope signatures. It corresponds to a modern end-member originating from a mixture of post-nuclear and present-day recharge in relation to return flow of irrigation waters. The third group is characterized by an average composition of stable and radiogenic isotope signatures. It provides evidence for the mixing between the upward moving palaeoclimatic end-member and the downward moving present-day end-member.

Investigation of groundwater mineralization in the Hammamet–Nabeul unconfined aquifer, north-eastern Tunisia: geochemical and isotopic approach

Detailed hydrogeochemical and isotopic data of groundwaters from the Hammamet–Nabeul unconfined aquifer are used to provide a better understanding of the natural and anthropogenic processes that control the groundwater mineralization as well as the sources of different groundwater bodies. It has been demonstrated that groundwaters, which show Na–Cl and Ca–SO4–Cl water facies, are mainly influenced by the dissolution of evaporates, the dedolomitization and the cation-exchange process; and supplementary by anthropogenic process in relation with return flow of irrigation waters. The isotopic signatures permit to classify the studied groundwaters into two different groups. Non-evaporated groundwaters that are characterized by depleted δ 18O and δ 2H contents highlighting the importance of modern recharge at higher altitude. Evaporated groundwaters with enriched contents reflecting the significance infiltration of return flow irrigation waters. Tritium data in the studied groundwaters lend support to the existence of pre-1950 and post-1960 recharge. Carbon-14 activities in shallow wells that provide evidence to the large contamination by organic 14C corroborate the recent origin of the groundwaters in the study area.

Hydrochemical and isotopic investigation of the groundwater composition of an alluvial aquifer, Cap Bon Peninsula, Tunisia

In the Grombalia region, Cap Bon Peninsula, northeastern Tunisia, increasing population and development of agricultural activity during the last few decades have engendered large expansion of groundwater pumping from the shallow, unconfined aquifer. Recently, the water table has displayed some signs of overexploitation such as decline in the water level in boreholes and considerable deterioration of water quality. Hydrochemical and isotopic data were used in conjunction with hydrogeological characteristics to investigate the groundwater composition in this aquifer. It has been demonstrated that groundwaters, recharged mainly in the surrounding foothills, acquire their mineralization principally by water–rock interaction, i.e., dissolution of evaporites and reverse cation exchange, and secondarily by return flow of irrigation waters. The isotopic signature of groundwaters permits identification of two different types. Water with depleted δ18O and δ2H contents is interpreted as recharge by non-evaporated rainfall, originating from a mixture of Atlantic and Mediterranean air masses. However, water with relatively enriched δ18O and δ2H contents is thought to reflect contamination by return flow of irrigation waters. Tritium contents, ranging between 1.2 and 4.5 TU indicate that groundwaters in an unconfined aquifer derive from post-nuclear recharge or contain a significant component of post-1950s water. The recent origin of these groundwaters is confirmed by the high carbon-14 activities, exceeding sometimes 100%, indicating the existence of a significant fraction of organic 14C. This younger source of radiocarbon is, however, highlighted by the depleted δ13C contents, corresponding to a system where CO2 of C4 plants predominates.

Hydrochemical and isotope evidence of groundwater salinization processes on the coastal plain of Hammamet–Nabeul, north-eastern Tunisia

Major elements concentration, stable (δ 18O, δ 2H) and radiogenic ( 3H, 14C) isotopes are known to provide important additional information to more traditional hydrological data and unravel the processes that underpin the large variations in chemical composition within the Hammamet–Nabeul shallow aquifer, north-eastern Tunisia (Cap Bon peninsula). The hydrogeochemical investigations of Hammamet–Nabeul shallow aquifer show that groundwaters can be classified into two major water facies: Ca–SO 4–Cl and Na–Cl. The main hydrogeochemical processes that typically control the groundwater mineralization are dissolution of evaporates (halite, gypsum and anhydrite), cation exchange and mixing processes related to the return flow of irrigation waters. The stable isotope signatures reveal that the main part of groundwater are not significantly affected by evaporation, which give evidence of a recharge mostly from the foot hill zone in the north of the basin. The tritium and carbon-14 data show mixing processes between modern and old water and suggest that groundwaters recharge occurs according to a long flow path. Nevertheless, moderated evaporation of waters was observed in the southern part of the basin, especially in the agricultural areas.