Towards a policy for sustainable use of groundwater by non-governmental organisations in Afghanistan

A 'first pass' groundwater management policy has been developed for use by non-governmental organisations (NGOs) in Afghanistan, designed to prevent derogation of existing traditional water sources, aquifer over-abstraction and chemical deterioration of soil and groundwater quality. Key elements include (1) continuing promotion of groundwater as a drinking water source, (2) a presumption against use of motorised pumps to abstract groundwater for irrigation unless other options (surface water, qanats) are not available, (3) the use of groundwater for irrigation as a temporary alternative to surface water (i.e. a strategy for drought survival) rather than as a long-term development policy, (4) limiting groundwater abstraction to a long-term average of 1 l s^–1 km^–2, (5) siting irrigation wells at least 500 m from other groundwater sources and (6) analysing irrigation groundwater for electrical conductivity, sodium absorption ratio, boron and residual sodium carbonate alkalinity. Analyses of these parameters indicate that groundwater from some areas is of dubious suitability for irrigation. In some villages and towns, groundwater contains elevated nitrate and faecal bacteria concentrations, probably derived from latrines, sewage or animal wastes. Electronic Publication     

The origin of increased salinity in the Cambrian-Vendian aquifer system on the Kopli Peninsula,northern Estonia

Monitoring of the confined Cambrian-Vendian aquifer system utilised for industrial water supply at Kopli Peninsula in Tallinn over 24 years reveals remarkable changes in chemical composition of groundwater. A relatively fast 1.5 to 3.0-fold increase in TDS and in concentrations of major ions in abstracted groundwater is the consequence of heavy pumping. The main sources of dissolved load in Cambrian-Vendian groundwater are the leaching of host rock and the other geochemical processes that occur in the saturated zone. Underlying crystalline basement, which comprises saline groundwater in its upper weathered and fissured portion, and which is hydraulically connected with the overlying Cambrian-Vendian aquifer system, is the second important source of ions. The fractured basement and its clayey weathering crust host the Ca-Cl type groundwater, which is characterised by high TDS values (2–20 g/L). Intensive water abstraction accelerates the exchange of groundwaters and increases the area of influence of pumping. Chemical and isotopic studies of groundwater indicate an increasing contribution of old brackish water from the crystalline basement and rule out the potential implication of an intrusion of seawater into aquifer.

---

Resumen El origen del incremento en salinidad en un sistema de acuíferos Cámbrico-Vendiano en la Península Kopli, norte de EstonieMonitoreo a largo plazo de un sistema de acuíferos confinados, de edad Cámbrico-Vendiano, que se utiliza como fuente de abastecimiento industrial en la Península Kopli, al norte de Estonie, revela cambios notables en la composición química del agua subterránea. Un incremento de 1.5 a 3 veces en TDS y en concentraciones de iones mayores en agua subterránea explotada ha sido ocasionado por bombeo fuerte. Las fuentes principales de carga disuelta en el agua subterránea Cámbrico-Vendiano son la lixiviación de la roca encajonante y los procesos geoquímicos que ocurren en la zona saturada. Basamento cristalino subyacente, que aloja agua subterránea salada en la parte superior intemperizada y fisurada, y está conectado hidráulicamente con el sistema acuífero Cámbrico-Vendiano sobreyacente, es la segunda fuente importante de iones. El basamento fracturado y su corteza de intemperismo arcillosa alojan agua subterránea de tipo Ca-Cl la cual se caracteriza por valores altos de TDS (2–20 g/l). Debido a extracción intensiva se ha acelerado el intercambio de agua subterránea y se ha incrementado el área de influencia del bombeo. Los estudios químicos e isotópicos de agua subterránea indican una contribución creciente por filtración derivada del basamento cristalino. Es evidente una intrusión de agua salada hacia el sistema de acuíferos con implicaciones subsecuentes para la calidad del agua.

---

Résumé Lorigine de la salinité croissante dans le système aquifère du Cambrien-Vendien dans la péninsule de Kopli, nord de lEstonieLe suivi à long terme du système aquifère captif du Cambrien-Vendien utilisé pour lapprovisionnement deaux industrielles dans la Péninsule de Kopli, nord de lEstonie, révèle de remarquables changements dans la composition chimique des eaux souterraines. Une augmentation de facteur 1.5 à 3 de la TDS et des concentrations en ions majeurs dans leau souterraine est la conséquence de pompages intensifs. Les sources principales des charges dissoutes dans les eaux de laquifère du Cambrien-Vendien sont le lessivage des roches et dautres phénomènes géochimiques ayant lieu dans la zone saturée. Le soubassement rocheux cristallin, qui renferme des eaux souterraines salines dans sa partie supérieure altérée et fissurée, et est hydrauliquement connecté avec laquifère supérieur du Cambrien-Vendien, est la deuxième importante source dions. Le soubassement fracturé et le matériel argileux de laltération, renferme leau souterraine de type Ca-Cl, caractérisée par un haut TDS (2–20 g/l). A cause de la mobilisation intensive de leau les échanges deau souterraine est sont accélérés et la zone dinfluence des pompages augmentent. Les études chimiques et isotopiques indiquent une contribution croissante du drainage des eaux du soubassement cristallin. Lintrusion deaux salées de la mer dans le système aquifère nest pas un phénomène évident.

     

Irrigation expansion and dynamics of desertification in the Circum-Aral region of Central Asia

The aim of this paper is to examine the causes and dynamics of desertification in one of the world's worst disaster areas, the Aral Sea region. During the 1960s, a large-scale irrigation campaign aimed at achieving independence in cotton production was launched in Soviet Central Asia. From 1960, ever-increasing water withdrawal from the two inflowing rivers—the Amudarya and Syrdarya—has resulted in the dramatic decline of the level, area and volume of the sea. Desiccation was accompanied by the development and further acceleration of various desertification processes. The study reveals that, for different reasons, the predominant direction and trends of desertification have been changing during each of the four identified periods from 1961 to 1995. The main desertification processes recorded in the Circum-Aral region (‘Priaraliye’ in Russian) were a decline in the groundwater level, increased mineralization and chemical pollution of watercourses, soil salinization, the spread of xerophytic and halophytic vegetation, and deflation and aeolian accumulation, with the development of salt storms. Recent improvements in the situation are also discussed, along with their causes. Zonation of Priaraliye is carried out and an outlook for the future is given.     

Salinization of groundwater in the North German Basin: results from conjoint investigation of major, trace element and multi-isotope distribution

Conjoint consideration of distribution of major, rare earth elements (REE) and Y (combined to REY) and of H, O, C, S, Sr isotopes reveals that four types of groundwater are distinguishable by their chemical composition presented by spider patterns. REY patterns indicate thermo-saline deep water and two types of shallow saline groundwaters. Presence of connate waters is not detectable. Sr isotope ratios distinguish three sources of Sr: fast and slow weathering of biotite and K-feldspar in Pleistocene sediments, respectively, and dissolution of limestones. δ¹³C(DIC) indicate dissolution of limestone under closed and open system conditions. Numerous samples show δ¹³C(DIC) > 13‰ which is probably caused by incongruent dissolution of calcite and dolomite. The brines from below 1,000 m represent mixtures of pre-Pleistocene seawater or its evaporation brines and infiltrated post-Pleistocene precipitation. The shallow waters represent mixtures of Pleistocene and Recent precipitation salinized by dissolution of evaporites or by mixing with ascending brines. The distribution of water types is independent on geologic units and lithologies. Even the Tertiary Rupelian aquiclude does not prevent salinization of the upper aquifer.     

Assessing the potential for significant and episodic recharge in southwestern Australia using rainfall data

Agricultural practices in semi-arid parts of southwestern Australia have increased recharge and raised groundwater levels. As a result, land salinization has occurred. Managers aim to address the problem by reducing recharge, but it is not known whether all recharge is regular and seasonal or whether a substantial component is episodic (i.e. occurs in irregular pulses). Approaches that reduce regular recharge may not be effective at reducing recharge that is episodic. Water balances were used to assess the potential for recharge to be episodic at 53 sites throughout Western Australia. The results show that, for the conditions modeled, a substantial proportion of the recharge in drier parts of the agricultural areas occurred episodically, and that direct episodic recharge could be as important in some semi-arid areas as in arid regions. Therefore, mean annual rainfall is not a strong predictor of the ratio of episodic to total recharge at a site. The model indicates that in agricultural areas, most significant and episodic recharge events occurred over just a few days in winter months, when rainfall was dominated by frontal systems. However, substantial episodic recharge also resulted from large storms during the months of January, February, and March. The implication is that it will be difficult to reduce recharge substantially, and thus control salinity, as long as agriculture relies heavily on shallow-rooted winter-growing plants. Electronic Publication     

Rates of salinization by free convection in high-permeability sediments: insights from numerical modeling and application to the Dutch coastal area

Numerical modeling and dimensional analysis is used to study the salinization of thick, high-permeability aquifers by free convection from a salt source at the surface. Current understanding of this process mainly concerns the initial stages of salinization only (boundary-layer development, break-up into fingers and initial phase of finger descent). In the modeling, special attention is paid to the role of two processes in the long-term salinization rate: (1) the progressive loss of salt from fingers by lateral diffusion, and (2) the coalescence of fingers during their descent. From the numerical simulations a relationship is derived that describes the development of the horizontally averaged salinity with depth and time as a function of permeability and initial-density contrast for aquifer Rayleigh numbers up to Ra =6,000. This relationship is consistent with and provides an extension to previous generalized relationships of the rate of finger descent. Its applicability to real-world aquifers (Ra >10⁵) that include complexities due to anisotropy, heterogeneity, and mechanical dispersion is discussed. Application to the Pleistocene coastal aquifer of the Netherlands (thickness 200 m, permeability 10^-11 m²) suggests that salinization of the aquifer during historic episodes of inundation by seawater occurred within decades.

---

Resumen Se utiliza modelos numéricos y un análisis dimensional para estudiar la salinización de acuíferos potentes de alta permeabilidad por convección libre a partir de una fuente salina superficial. El conocimiento acutal de este proceso se limita a las fases iniciales de la salinización (desarrollo de la capa de contorno, creación de digitaciones y fase inicial de la progresión de éstas). En la modelación, se presta atención especial al papel desempeñado por dos procesos de salinización a largo plazo: (1) la pérdida progresiva de sal por difusión lateral desde las digitaciones, y (2) la coalescencia de las digitaciones durante su avance. A partir de las simulaciones numéricas, se obtiene una relación que describe el desarrollo de la salinidad con la profundidad y el tiempo, promediada horizontalmente, el cual depende de la permeabilidad y del contraste inicial de densidad para números de Rayleigh inferiores a 6.000. Esta relación es coherente con índices previos generalizados del avance de las digitaciones, y representa una extensión a estos. Se discute su aplicabilidad a acuíferos reales (con números de Rayleigh superiores a 105), que tienen complejidades asociadas a la anisotropía, la heterogeneidad y la dispersión mecánica. La aplicación al acuífero costero Pleistoceno de los Países Bajos (20 m de potencia y 10-11 m2 de permeabilidad) sugiere que la salinización tuvo lugar en décadas, debido a episodios históricos de inundación por aguas marinas.

---

Résumé Une modélisation numérique et une analyse dimensionnelle ont été mises en oeuvre pour étudier la salinisation d'aquifères épais et à forte perméabilité par convection libre d'une source de sel en surface. La compréhension habituelle de ce processus concerne principalement les étapes initiales de la salinisation seule (développement d'une couche limite, partition en digitations et phase initiale de développement des digitation). Dans la modélisation, une attention particulière a été portée au rôle de deux processus du taux de salinisation à long terme: (1) la perte progressive de sel dans les digitations par diffusion latérale et (2) la coalescence des digitations au cours de leur développement. À partir de simulations numériques, une relation a été obtenue qui permet de décrire l'extension de la salinité horizontalement en profondeur et au cours du temps en fonction de la perméabilité et du contraste initial de densité pour des nombres de Rayleigh de l'aquifère jusqu'à Ra =6,000. Cette relation est compatible avec ces résultats et fournit une extension des relations précédemment généralisées du taux de développement des digitations. On discute son applicabilité à des aquifères réels (Ra >105) incluant des complexités liées à l'anisotropie, l'hétérogénéité et la dispersion mécanique. L'application à l'aquifère côtier du Pléistocène des Pays-Bas (épaisseur environ 200 m, perméabilité environ10–11 m²) laisse penser que la salinisation de cet aquifère au cours d'épisodes historiques d'inondation par la mer s'est produit durant des décennies.

---

     

Hydrogeologic controls on groundwater recharge and salinization: a geochemical analysis of the northern Hueco Bolson aquifer, Texas, USA

Identification of hydrogeologic controls on groundwater flowpaths, recharge, and salinization is often critical to the management of limited arid groundwater resources. One approach to identifying these mechanisms is a combined analysis of hydrogeologic and hydrochemical data to develop a comprehensive conceptual model of a groundwater basin. To demonstrate this technique, water samples were collected from 33 discrete vertical zone test holes in the Hueco Bolson aquifer, located within the Trans-Pecos Texas region and the primary water resource for El Paso, Texas, USA and Juárez, Mexico. These samples were analyzed for a suite of geochemical tracers and the data evaluated in light of basin hydrogeology. On the basis of δ²H and δ¹⁸O data, two regional recharge sources were recognized, one originating from western mountain-fronts and one from through-flow of the adjacent Tularosa aquifer. Chloride concentrations were strongly correlated with lithologic formations and both Cl/Br and ³⁶Cl ratios suggested the primary chloride source is halite dissolution within a specific lithologic unit. In contrast, sulfur isotopes indicated that most sulfate originates from Tularosa basin Permian gypsum sources. These results yielded a more comprehensive conceptual model of the basin, which suggested that chloride salinization of wells is the result of upconing of waters from the Fort Hancock formation.     

Modeling the impact of groundwater harvesting on the hydro-salinity of a saline catchment in southeastern Australia

Recharge to a saline, unconfined shallow-water-table aquifer is normally considered as an irrecoverable loss of water, but such thinking could be reviewed empirically. The use of an appropriate groundwater harvesting system does not only provide an opportunity to recover this lost water, but can also help in catchment salinity management and improvement. Agricultural-based land-drainage systems such as those that use serial biological concentration (SBC) of salts, provide examples of such harvesting methods. The impact of groundwater harvesting has been assessed on the hydro-salinity of a saline catchment in southeastern Australia through modeling. For both the below average rainfall and very wet years, the “do nothing” scenario resulted in increasing salinization in the catchment. However, after introducing a SBC system, groundwater salinity showed a decreasing trend while hydraulic heads tended to stabilize around the depth of subsurface collector wells. However, for a successful groundwater harvesting system, proper understanding of the groundwater flows and salt mobilization associated with a catchment is necessary. The outcomes of this modelling study have the potential to address similar issues (salinization) and/or needs (water harvesting) existing elsewhere in the world, particularly in semi-arid regions.

Contribution to the identification of the sea intrusion mechanism of brackish karst springs

A method of identifying the dominant hydrodynamic sea-intrusion mechanism of brackish karst springs is presented. A karst spring becomes brackish when tubes, which bring the freshwater to the spring (freshwater discharge), intersect other tubes that come from the sea and bring saltwater to the freshwater tubes (saltwater discharge) when the saltwater pressure at the intersection is higher than the freshwater pressure. There are two potential seawater intrusion mechanisms. The first one is the difference between the freshwater density and the seawater density, and the second is the venturi effect. Both mechanisms are present but it is a matter of great significance to know which mechanism dominates. In order to find out the dominant mechanism, the seawater discharge versus the freshwater discharge was charted using the MODKARST model, which estimates these discharges. The model determines how the freshwater discharge affects the saltwater discharge estimating thereby the dominant seawater intrusion mechanism. Application was made to the “Almiros” and “Makaria” springs in Greece.

---

Resumen Se presenta un método para identificar el mecanismo hidrodinámico dominante de la intrusión marina en manantiales salobres cársticos. Un manantial cárstico se vuelve salobre cuando los conductos, que suministran agua dulce al manantial (caudal de agua dulce), interceptan a otros conductos provenientes del mar que traen agua salada a este (caudal de agua salada), bajo la condición que la presión del agua salada en la intersección es mayor que la del agua dulce. Hay dos mecanismos potenciales de intrusión salina. El primero es la diferencia de densidades entre agua salada y agua dulce, mientras que el segundo es el efecto venturi. Ambos mecanismos están presentes en cualquier caso, sin embargo es de gran importancia establecer cual de ellos predomina. Con el fin de hallar el mecanismo dominante se tabularon los valores de caudal de agua salada versus el de agua dulce. Lo anterior fue posible mediante el uso del modelo MODKARST, el cual estima estos caudales. A partir de esta tabla se puede examinar como el caudal de agua dulce afecta al de agua salada, estimando como resultado de lo anterior el mecanismo dominante en la intrusión marina. Esto se aplicó a los manantiales “Almiros” y “Makaria” en Grecia.

---

Résumé On présente une méthode pour déterminer le mécanisme hydraulique dominant de l’intrusion de l’eau salée marine dans le cas des émergences karstiques saumatres. Une émergence karstique devienne saumatre á l’intersection des conduites de l’eau douce avec des autres conduits qui apportent l’eau salée de la mer. Ce processus est possible si la pression de l’eau salée dépasse la pression de l’eau douce. Il y a deux mécanismes potentiels de l’intrusion de l’eau salée. A la base du premier mécanisme se trouve la différence entre les densités de l’eau douce et de l’eau salée pendant que dans le deuxième mécanisme il s’agit de phénomène Venturi. Afin de trouver le mécanisme dominant on a cartographié avec le modèle MODKARST le rapport entre les décharges de l’eau douces et respectivement de l’eau salée. A partir de la carte résultée on peut estimer comment la décharge de l’eau douce influence celle de l’eau salée en estimant en même temps le mécanisme dominat de l’eau salée. On a appliqué la méthode dans le cas des émergences d’Almiros et Makaria de la Grèce.

     

Groundwater recharge and salinization in the arid coastal plain aquifer of the Wadi Watir delta,Sinai, Egypt

The Quaternary coastal plain aquifer down gradient of the Wadi Watir catchment is the main source of potable groundwater in the arid region of south Sinai, Egypt. The scarcity of rainfall over the last decade, combined with high groundwater pumping rates, have resulted in water-quality degradation in the main well field and in wells along the coast. Understanding the sources of groundwater salinization and amount of average annual recharge is critical for developing sustainable groundwater management strategies for the long-term prevention of groundwater quality deterioration. A combination of geochemistry, conservative ions (Cl and Br), and isotopic tracers (^87/86Sr, δ⁸¹Br, δ³⁷Cl), in conjunction with groundwater modeling, is an effective method to assess and manage groundwater resources in the Wadi Watir delta aquifers. High groundwater salinity, including high Cl and Br concentrations, is recorded inland in the deep drilled wells located in the main well field and in wells along the coast. The range of Cl/Br ratios for shallow and deep groundwaters in the delta (∼50–97) fall between the end member values of the recharge water that comes from the up gradient watershed, and evaporated seawater of marine origin, which is significantly different than the ratio in modern seawater (228). The ^87/86Sr and δ⁸¹Br isotopic values were higher in the recharge water (0.70,723 < ^87/86Sr < 0.70,894, +0.94 < δ⁸¹Br < +1.28‰), and lower in the deep groundwater (0.70,698 < ^87/86Sr < 0.70,705, +0.22‰ < δ⁸¹Br < +0.41‰). The δ³⁷Cl isotopic values were lower in the recharge water (−0.48 < δ³⁷Cl < −0.06‰) and higher in the deep groundwater (−0.01 < δ³⁷Cl < +0.22‰). The isotopic values of strontium, chloride, and bromide in groundwater from the Wadi Watir delta aquifers indicate that the main groundwater recharge source comes from the up gradient catchment along the main stream channel entering the delta. The solute-weighted mass balance mixing models show that groundwater in the main well field contains 4–10% deep saline groundwater, and groundwater in some wells along the coast contain 2–6% seawater and 18–29% deep saline groundwater.A three-dimensional, variable-density, flow-and-transport SEAWAT model was developed using groundwater isotopes (⁸⁷Sr/⁸⁶Sr, δ³⁷Cl and δ⁸¹Br) and calibrated using historical records of groundwater level and salinity. δ¹⁸O was used to normalize the evaporative effect on shallow groundwater salinity for model calibration. The model shows how groundwater salinity and hydrologic data can be used in SEAWAT to understand recharge mechanisms, estimate groundwater recharge rates, and simulate the upwelling of deep saline groundwater and seawater intrusion. The model indicates that most of the groundwater recharge occurs near the outlet of the main channel. Average annual recharge to delta alluvial aquifers for 1982 to 2009 is estimated to be 2.16 × 10⁶ m³/yr. The main factors that control groundwater salinity are overpumping and recharge availability.