Salt Transport Research Articles

Patterns of salt transport and factors affecting typical shrub in desert-oases transition areas

Soil salinization and water deficits are considered the primary factors limiting economic development and environmental improvement in arid areas. However, there remains limited knowledge of the adaptability of typical shrubs to salinization of desert areas in arid zones. This study was conducted in a desert oasis transition zone (Tarim River, China), aiming to investigate: i) the spatial-temporal changes in soil salinity; ii) the interactions between the pedoenvironment vs typical shrub (Calligonum mongolicum). The van Genuchten soil salinity retention ensemble model (TVGSSREM-3D) was developed to simulate variations in soil water-salt transport in the desert-oasis zone and to accurately explain the main factors influencing Calligonum mongolicum desert-oases transition areas. The results showed that monthly average salinity ranged from 2.0 to 8.0 g kg−1, with a peak in August (9.17 g kg−1). The presence of human activities (Salt Drainage Canal) and the distribution of Calligonum mongolicum resulted in a clear spatial salinity zonation. Moreover, analysis of environmental indicators using the TVGSSREM-3D model revealed strong correlations between the distribution of salinity in Calligonum mongolicum desert-oases transition areas and groundwater depth (GD), minimum relative humidity (MRH), and water vapor pressure (WVP). These findings provide a scientific basis for stabilizing, restoring, and reconstructing the ecosystem of the oasis-desert transition zone.

The Satellite‐Observed Linkages Between Large‐Scale Climate Fluctuations and Mesoscale Eddy Movements in the North Pacific

AbstractThe North Pacific Gyre Oscillation (NPGO), Pacific Decadal Oscillation, and El Niño‐Southern Oscillation are climate fluctuations in the Pacific. Mesoscale eddies dominate the ocean kinetic energy spectrum. By analyzing the altimetry data, a close linkage between these climate fluctuations and eddy propagation speed is found. Propagation speeds of both cyclonic and anticyclonic eddies in the regions of 10° ∼ 20°N, 120°–180°E and 35° ∼ 45°N, 160°E−160°W are faster in the NPGO negative phase than positive phase, while those in the area of 25° ∼ 35°N, 150°E−170°W are opposite. These differences between positive and negative phases are the response of large‐scale circulation modulated by NPGO. When these climate fluctuations support the same westward/eastward anomaly of circulation, the eddies can propagate much faster/slower than that only considering NPGO. Causality analysis verifies that climate fluctuations can have strong influences on eddy movement. These climate fluctuations can affect the water mass, heat and salt transport by eddy advection.

Effect of Soil Texture on Water and Salt Transport in Freeze—Thaw Soil in the Shallow Groundwater Area

Research on the variation in soil water, heat, and salt in unsaturated zones during the freeze–thaw process has great significance in efficiently utilizing water resources and preventing soil salinization. The freeze–thaw field experiment was carried out with the lysimeter as the test equipment to analyze characteristics of the soil freeze–thaw process, profile water content, main ion content, and salt content of three textured soils with the groundwater table depth of 0.5 m. The results showed that the soil temperature gradient and freezing depth were greater as the average soil particle size increased. The increment of water content at the depth of 0 to 30 cm in sandy loam and loamy sand decreased by 40.20~93.10% and 28.14~65.52% compared with that in sandy soil, and the average increment of salt content at the depth of 0 to 30 cm decreased as the average soil particle size increased during the freeze–thaw period. The average content of Ca2+, Na+, Cl−, and SO42− in loamy sand and sandy soil decreased by 4.37~45.50% and 22.60~70.42% compared with that in sandy loam at the end of the freeze–thaw period, and the correlation between soil salt content and water content decreased with the increase in the average soil particle size. The research results can provide a theoretical basis for soil salinization prevention and crop production in shallow groundwater areas.

North Atlantic Ocean Circulation and Related Exchange of Heat and Salt Between Water Masses

AbstractThe meridional transport of mass, heat, and salt in the North Atlantic Ocean is often described for separate regions and parts, but rarely are all components of the circulation followed at once. Lagrangian trajectories have here been used to divide the North Atlantic Ocean circulation into four different pathways. In the boundary between the Subpolar and Subtropical Gyres, we show that the northward flowing waters exchange heat and salt with the water originating from the subpolar regions. This subsurface water mass exchange takes place in the first 1,000 m and is a key piece of the puzzle of how the Atlantic Meridional Overturning Circulation transports heat and salt. Between 30° and 60°N the northward flowing water loses 8.8 Gg/s salt to the Subpolar Gyre and an equivalent loss of only 1.7 Gg/s to the atmosphere due to the net fresh water influx.

Diapycnal Mixing Induced by Rough Small‐Scale Bathymetry

AbstractDiapycnal mixing impacts vertical transport rates of salt, heat, and other dissolved substances, essential for the overturning circulation and ecosystem functioning in marine systems. While most studies have focused on mixing induced by individual obstacles in tidal flows, we investigate the net effect of non‐tidal flow over multiple small‐scale (<1 km) bathymetric features penetrating a strongly‐stratified density interface in a coastal region. We combine high‐resolution broadband acoustic observations of turbulence microstructure with traditional shear microstructure profiling, to resolve the variability and intermittency of stratified turbulence related to the rough bathymetry. Scale analysis and acoustic imaging suggest that underlying mixing mechanisms are related to topographic wake eddies and breaking internal waves. Depth averaged dissipation rates (1.1 × 10−7 Wkg−1) and turbulent vertical diffusivities (7 × 10−4 m2s−1) in the halocline exceed reference values by two orders of magnitude. Our study emphasizes the importance of rough small‐scale bathymetric features for the vertical transport of salt in coastal areas.

Balancing Volume, Temperature, and Salinity Budgets During 2014–2018 in the Tropical Pacific Ocean State Estimate

AbstractA state estimate of the tropical Pacific Ocean is used to analyze regional volume, temperature, and salinity budgets during 2014–2018. The simulated ocean state is constrained by both model dynamics and assimilated observations. Comparisons with independent mooring data show that the state estimate is consistent with the observed variability in temperature and velocity. Budgets are analyzed between 5°S and 5°N in the upper 300 m, inside a box defined to represent the central and eastern equatorial Pacific. Transports through the faces of this box are quantified to understand the processes responsible for variability in box‐mean properties. Vertical mixing across 300 m is negligible; temperature and salinity tendencies are balanced by surface fluxes and advective divergence, which is decomposed into geostrophic and ageostrophic components. The onset and recovery of the 2015/2016 El Niño event is found to be dominated by anomalous surface fluxes and horizontal advection. During the onset phase, weaker trade winds cause the shallow meridional overturning circulation to slow down, which reduces the poleward transport of heat and leads to upper ocean warming. Anomalous precipitation and advection of fresh water from the western Pacific drive the net freshening of the region. Relaxation from El Niño conditions is dominated by wind‐driven meridional advection at 5°N. As the meridional advection regains strength, Ekman advection efficiently exports the warm, fresh surface water out of the equatorial region. Quantifying the heat and salt transport changes in response to wind variability strengthens our understanding of global ocean heat transport.

Impact of Extreme Wind and Freshwater Runoff on the Salinity Patterns of a Mesotidal Coastal Lagoon

The interaction between tide, river runoff, and wind in coastal lagoons induces complex salinity gradients, which are remarkable when the meteorological forcing is exacerbated. This work aims to characterize the salinity structure under extreme freshwater and wind events in the Ria de Aveiro coastal lagoon (Portugal). The Delft3D model was implemented and validated in 3D mode and used to perform simulations forced with extreme freshwater and wind scenarios. Results show that forcing conditions determine salinity stratification intensity and location. Generally, stratification increases as the freshwater increases, while the salinity intrusion moves downstream. Extreme wind tends to destroy stratification but fails to promote full-depth mixing, which is also dependent on the wind direction, as shown for the Espinheiro channel. The salinity intrusion is also impacted by wind events, being NW storms responsible for an upstream salt transport along the Mira channel and a downstream transport along the Espinheiro channel, and SW storms for an upstream displacement of the salinity intrusion along the São Jacinto channel. Finally, it is observed that the advection of a freshwater plume from the Vouga River into the middle of the São Jacinto channel under high freshwater scenarios causes an unusual local salinity pattern. This plume can either be pushed upstream or prevented from entering the channel, depending on the wind direction.

Synergistic, adaptive, continuous-flow, and low-carbon solar evaporation and electrochemical treatment (SEET) system – a combined numerical and experimental study

A synergistic, adaptive, continuous-flow, and low-carbon solar evaporation and electrochemical treatment (SEET) system was proposed and researched for energy-efficient and sustainable decentralized water treatment. The hybrid system integrated anodic oxidation with solar evaporation to enhance organic degradation and optimize mass transport through the photo-thermal effect. A novel four-step numerical simulation method was proposed to design the system and examine the water evaporation process and mass transport of salts and organics. A case study was implemented, revealing that system parameters related to evaporation and organics degradation exhibited strong interdependence. The relationships between these parameters were well-established, and adaptive water flow rate ranges were also identified to prevent salt accumulation while ensuring efficient organic degradation. The adaptability demonstrated the system's potential for use in varying influent scenarios. A prototype of the system was constructed, and the experimental data matched well with the simulation results. In the experiments, the local water temperature reached 45–50 °C in the continuous-flow mode under one sun condition, resulting in a 2–5 times reduction in outlet organic concentrations compared to traditional electrochemical systems. Energy analysis confirmed that the system primarily relied on clean and sustainable solar energy, maintaining a low carbon footprint. In conclusion, this innovative approach offers significant potential for addressing the clean drinking water crisis and enhancing pollutant removal in future decentralized water treatment systems.

Effects of Organic Manure and Biochar-Based Fertilizer Application on Soil Water and Salt Transport in Brackish Water Irrigated Soil Profile

Effects of Organic Manure and Biochar-Based Fertilizer Application on Soil Water and Salt Transport in Brackish Water Irrigated Soil Profile

Progress of Water and Salt Transport in Saline Lands and Hydrus Model: A Review

The key to saline land management and improvement is to understand the soil water and salt transport laws and to carry out scientific regulation. In order to propose a scientific and reasonable model for soil salinity control, it is necessary to study the principle of water and salt transport in soil, the transport law with time and space, which is also the theoretical basis for understanding the occurrence and evolution of saline soils in the region and preventing secondary salinization of soil. In recent years, the study of water-salt transport and its simulation model has become one of the research hotspots in the field of agriculture, especially in the northwest of China. This paper systematically summarizes the research progress and applications of water-salt transport characteristics, models, influencing factors and the popular software Hydrus at home and abroad, and summarizes the advantages and disadvantages of the models and the influencing factors of water-salt transport, and introduces the research results of many scholars in the field of water-salt transport, and gives an outlook on the future research and development trend of water-salt transport.

Thermal effects of freshwater injection on flow and salinity distributions in tidally-affected coastal unconfined aquifers

Freshwater injection is a practical and efficient solution to mitigate seawater intrusion in coastal aquifers, but its thermal impacts on groundwater flow and salt transport are still poorly understood. This study investigates the dynamic characteristics of salinity distributions and seawater recirculation in coastal unconfined aquifers subjected to freshwater injection and tides. The results show that the seaward development of thermal plume modifies the transience of upper saline plume and saltwater wedge, significantly prolonging the aquifer response to injected freshwater. Three temporal variations of upper saline plume due to freshwater injection are driven by pressure waves of injected freshwater, thermal plume-induced changes of hydraulic gradients and saltwater wedge, and the hydraulic conductivity within the upper saline plume. Moreover, a delayed reduction in seawater recirculation in response to the thermal impacts of cold-water injection induces a significant and long-lasting overshoot of total water efflux. An increased tidal amplitude facilitates thermal effects on flow and salinity distributions. A deeper injection well extends the flow path of injected freshwater and thermally regulates discharge rates along the beach surface, thereby enhancing overshoot magnitude of total water efflux. These results improve the understanding of underlying processes related to freshwater injection in coastal aquifers and provide guidance for better managing coastal groundwater resources.

Salt enrichment and its deterioration in earthen sites in Emperor Qin’s Mausoleum Site Museum, China

Salt enrichment in the topsoil, owing to one-way migration of moisture from earthen sites to air environment, is an important inducement to weathering of sites and relics, such as efflorescence, recess, slice-peeling, which becomes the most important challenge to the preservation of unearthed sites and relics. Further, salt enrichments in the topsoil of undulating earthen sites are usually inhomogeneous such that it is difficult to precisely prevent the deterioration from happening of salt enrichment in the topsoil. A case study of salt enrichment at the K9901 funerary pit of Emperor Qin’s Mausoleum Site Museum was conducted by soil column experiment and numerical simulation. The water and salt transport in the earthen sites were simulated and analyzed by HYDRUS software. The simulation of the salt enrichment process at the earthen sites demonstrated that the enrichment of soluble salt ions mainly occurs on the surface of rammed earth and increases annually; the salt damage at the earthen sites can be effectively delayed by taking an environmental control measure. These results provide a reference for the prevention of salt damage at earthen sites and facilitate the daily management of earthen sites.

Assessment of groundwater-driven dissolved nutrient inputs to coastal wetlands associated with marsh-coastal lagoons systems of the littoral of the outer Río de la Plata estuary

In coastal wetlands the hydrological dynamics and in particular the groundwater flows play a critical role in the establishment of wetlands and in the transport of salts and nutrients. The aim of the work is to analyze the role that groundwater discharge has in the dynamics of the dissolved nutrients of the wetland associated with the coastal lagoon and marshes of the Punta Rasa Natural Reserve, which is located on the coastal sector of the southern end of the Río de la Plata estuary. A monitoring network in the form of transects was generated in order to define groundwater flows and take samples of dissolved species of N and P. The presence of sandy sediments with similar granulometric profiles in all geomorphological environments determines that the underground flow occurs in a homogeneous aquifer. From the dunes and beach ridges the fresh to brackish groundwater flows with a very low hydraulic gradient towards the marsh and coastal lagoon. The contributions of N and P would derive from the degradation of the organic matter of the environment, in the case of the marsh and coastal lagoon also from the tidal flow and discharge of groundwater, and possibly from atmospheric sources in the case of N. Since in all environments oxidizing conditions dominate, nitrification is the main process which is why the most abundant species of N is the NO3−. Under oxidizing conditions, P has a greater affinity for the sediments in which it is mostly retained, registering it in low concentrations in water. The discharge of groundwater from the dunes and beach ridges provides dissolved nutrients to the marsh and coastal lagoon. However, the low hydraulic gradient and the dominant oxidizing conditions determine that the flow is scarce and that it only acquires relevance in the contribution of NO3−.

Impact of initial and lateral open boundary conditions in a Regional Indian Ocean Model on Bay of Bengal circulation

This study uses three simulations (Exp-1, Exp-2, and Exp-3) from a nested basin-scale, regional, eddy-permitting Indian Ocean model forced with CORE-II inter-annual forcing, to study the impact of initial and lateral open boundary conditions on Bay of Bengal (BoB) circulation. It also evaluates the state of art reanalysis products from GODAS, SODA3 and ORAS5. Sensitivity studies using more realistic initial and lateral boundary conditions suggest that accurate initial conditions are essential for realistic simulation of the mean and the variability of temperature and salinity in the upper ocean. We also show that accurate lateral boundary conditions are also essential for realistic basin-scale simulations for the upper ocean circulation in the BoB. The model captured well the observed seasonal and inter-annual variability of salinity in the BoB. The comparison of surface currents from the regional simulations and reanalysis products with OSCAR analyses shows Exp-3 (with improved initial and lateral boundary​ conditions) to be the closest among all three. The summer monsoon current is also most realistic in Exp-3, while the reanalysis products are unable to reproduce the BoB Coastal Current structure and magnitude. This study also reports the first evidence of a coastally trapped, narrow boundary current at thermocline depth along the eastern boundary of BoB. The presence of this boundary current is noticed in all three regional solutions while most prominent in Exp-3 and nearly absent in the reanalysis products. The salt transport across 8°N shows large seasonal and inter-annual variations during 2003–2009 in the best simulation (Exp-3), with standard deviation ranging between 77–150 psu-m3/s up to 1000 m depth. Apart from summer and winter monsoon periods, which show the intrusion of salt into BoB from the equatorial Indian Ocean in the upper layers, we found significant salt transport at deeper depths (300–1500 m) as well. The integrated inter-annual variations of the seasonal salt flux at different depths across 8 °N show presence of strong seasonal cycle in the upper layer (0–200 m). However, the seasonality is most prominent in the upper 50 m. The intra-seasonal variation in the deeper layers are more prominent as compared to the upper layer.

Longitudinal and lateral circulation and tidal impacts in salt-plug estuaries

This study presents a comparison of forcings between density gradient and tides in idealized funnel-shaped salt-plug estuaries. Three-dimensional numerical model results also examine longitudinal and lateral circulations. In salt-plug estuaries, a positive longitudinal estuarine circulation is observed landward of a salinity maximum zone or salt plug. Seaward of the salt plug, the estuary shows an inverse circulation cell. The longitudinal flows show a fortnightly variability inside the salt plug. Also, the salt plug is saltier in spring tides than in neap tidal cycles mainly owing to higher landward salt transport by tidal advection during the spring tides. The lateral circulation and divergence dv/dy have the influence of Coriolis acceleration. In the absence of Earth’s rotation, the tidally averaged lateral circulations have nearly the same directions within the positive and inverse cells. Directions of lateral flow reverse in the salt-plug area. Inside this area, the lateral circulation also shows clear neap–spring variability, including downwelling cells during spring tides and upwelling in neap tides. The salinity maximum zone exhibits a vertically homogeneous condition particularly in meso-tidal salt-plug estuaries. Finally, this study introduces the threshold of “log(tidal Froude number)=3” (tidal forcing 3 orders of magnitude ≥ density gradients) for salt-plug estuaries as the condition under which the tidal forcing can overcome the density gradient, and consequently salinity inside the salt plug zone is reinforced by tides with a landward movement. This robust salinity maximum zone is also identified by a high Ekman number (log(Ekman number)>0.25).

Spatial-temporal distribution and accumulation characteristics of residual plastic film in cotton fields in arid oasis area and the effects on soil salt transport and crop growth

Plastic film residue pollutes farmland ecosystems and the natural environment though the plastic film employed in drip irrigation increases the utilization coefficient of irrigation water efficiency. Extensive studies have been conducted on soil pollution arising from residual films in northwest China, whereas the limits of the positive effect of plastic films on crop growth and the negative effect of residual plastic films remains unclear. To investigate the effects of residual films on soil salt transport and crop growth, the soil was collected from cotton fields under long-term film mulching and drip irrigation in arid oasis areas in this study to determine the distribution and accumulation of residual plastic films in the soil layers of an agricultural ecosystem. A plot experiment with eight residual film densities was performed in a cotton field at the experimental station, given the correlation between the film mulching year and residual film density. The effects of the residual film on soil salt migration and crop growth were elucidated through the observation of soil and cotton growth indicators, biomass, and yield. As indicated by the results, the density of residual mulching film in cotton fields under continuous mulching for five years exceeded the limit value of the determination standard (75 kg/ha). With the increase of the film mulching years, the residual film accumulated at a rate of 15.0 kg/ha annually, and it tended to migrate to the deep soil each year. The amount of the residual film of size < 4 cm2 was risen markedly, resulting in a problem of increasing fragmentation. Notably, the amount of the residual film was positively correlated with the variability in soil salinity. The growth index, biomass, and yield tended to be decreased with the increase of the mulching years. The yield reduction rate attributed to the residual film exceeded the yield increase arising from film mulching at the residual film density of 1210 kg·ha−1. This study takes on a critical significance to increasing the recycling efficiency of the residual films and ensure sustainable agricultural development in an oasis.

Numerical and experimental study on water-heat-salt transport patterns in shallow bare soil with varying salt contents under evaporative conditions: A comparative investigation

Soil salinization is aggravated by evaporation, resulting in salt crystallizing on the soil surface. Soil salinization is harmful to agriculture and has significant implications for the engineering and construction industry. Therefore, this paper investigates water and salt transport in saline soils through comparison of numerical simulations with indoor evaporation tests. Based on Darcy's law, ideal gas law, mass conservation law, and energy conservation law, a one-dimensional transient mathematical model of coupled water-heat-salt transport is derived. The bottom of the model represents a recharge boundary condition, the sides of the soil column are insulated and impermeable, and the top serves as a heat source. The results show that the greater the salinity of the soil, the more drastic the temperature change, and at the same time, the greater the water retention of the soil. The temperature gradient along the height of the soil column provides a tremendous driving force for water-salt transport, and although the volumetric water content of the soil column at 3 ∼ 4 cm dissipates quickly, there is a gradient of increasing salt concentration towards the ends and decreasing towards the middle. The modeled results agree with the experimental data, indicating that the model can effectively simulate the water-heat-salt transport process for different saline sites under evaporation conditions. The model is essential for the improvement of saline soils and for finding new methods to prevent further soil salinization.

Capillary rise induced salt deterioration on ancient wall paintings at the Mogao Grottoes

Salt deterioration has been found to be a major threat to wall paintings at culture heritage sites in arid areas along the Silk Road. However, the routes of water migration that cause the efflorescence have not been identified, and consequently, effective preservation measures have not been developed. Our microanalysis, by interrogating 93,727 individual particles collected in a Mogao cave in Dunhuang, China, revealed that capillary rise of water in the earthen plasters drives the deterioration of wall paintings. The vertical distribution of chloride and sulfate particles in the salt efflorescence and their morphologies implied a migration of salts through capillary rise and subsequent crystal growth under environmental conditions exerts sufficient pressure to cause surface decay and loss. These results indicate that blocking the water capillary rise under the porous structures is likely the most effective route to prevent rapid deterioration of the ancient wall paintings. These salt transport and deterioration mechanisms in an arid environment, suggests that a wide range of management strategies and protective measures could be developed to effectively preserve heritage sites in arid regions, especially along the Silk Road.

RARE: The Regional Arctic Reanalysis

Abstract This paper describes the new Regional Arctic Ocean/sea ice Reanalysis (RARE) with a domain that spans a subpolar/polar cap poleward of 45°N. Sequential data assimilation constrains temperature and salinity using World Ocean Database profiles as well as in situ and satellite SST, and PIOMAS sea ice thickness estimates. The 41-yr (1980–2020) RARE1.15.2 reanalysis with resolution varying between 2 and 5 km horizontally and 1–10 m vertically in the upper 100 m is examined. To explore the impact of resolution RARE1.15.2 is compared to a coarser-resolution SODA3.15.2, which uses the same modeling and data assimilation system. Improving resolution in the reanalysis system improves agreement with observations. It produces stronger more compact currents, enhances eddy kinetic energy, and strengthens along-isopycnal heat and salt transports, but reduces vertical exchanges and thus strengthens upper ocean haline stratification. RARE1.15.2 and SODA3.15.2 are also compared to the Hadley Center EN4.2.2 statistical objective analysis. In regions of reasonable data coverage such as the Nordic seas the three products produce similar time-mean distributions of temperature and salinity. But in regions of poor coverage and in regions where the coverage changes in time EN4.2.2 suffers more from those inhomogeneities. Finally, the impact on the Arctic of interannual temperature fluctuations in the subpolar gyres on the Arctic Ocean is compared. The influence of the subpolar North Pacific is limited to a region surrounding Bering Strait. The influence of the subpolar North Atlantic, in contrast, spreads throughout the Nordic seas and Barents Sea in all three products within two years. Significance Statement The Arctic Ocean/sea ice system plays crucial roles in climate variability and change by controlling the northern end of the oceanic overturning circulation, the equator to pole air pressure gradient, and Earth’s energy balance. Yet the historical ocean observation set is sparse and inhomogeneous, while ocean dynamics has challengingly fine horizontal and vertical scales. This paper introduces a new Regional Arctic Ocean/sea ice Reanalysis (RARE) whose goal is to use the combined constraints of mesoscale ocean dynamics, historical observations, surface meteorology, and continental runoff in a data assimilation framework to reconstruct historical variability. RARE is used to produce a 41-yr ocean/sea ice reanalysis 1980–2020 whose results are described here.

Predicting the risk of saltwater contamination of freshwater aquifers during aquifer thermal energy storage

Aquifer thermal energy storage (ATES) is an underground thermal energy storage technology with a large potential to decarbonise the heating and cooling of buildings. ATES installations typically store thermal energy in aquifers that are also exploited for potable water, so a major consideration during development is ensuring that system operation will not lead to groundwater pollution. In this study, the risk of contamination due to upconing of a shallow freshwater/saltwater interface during ATES operation is investigated. Fluid flow, and heat and salt (chloride ion) transport are simulated in a homogeneous aquifer during ATES operation via a well doublet. The impact of geological, hydrological and operational parameters is investigated in a sensitivity analysis. Two new dimensionless numbers are proposed to characterise salt upconing and redistribution during ATES operation and provide a close match to simulated concentrations: CR,w characterises the contamination risk at the ATES installation, and CR,d characterises the risk at locations downstream of the ATES installation with respect to background groundwater flow. ATES systems with CR,w and CR,d < 10 introduce low risk of contamination in a homogenous aquifer, with chloride concentration at, and downstream of, the ATES system, remaining below the World Health Organisation’s advised limit. ATES installations with CR,w and CR,d > 10 cause a rapid increase in aquifer chloride concentration. The results are used to estimate an exclusion distance beyond which ATES system operation will not cause contamination in a homogenous aquifer. The dimensionless parameters proposed allow rapid assessment of the potential for saltwater contamination during ATES operation.