The climate change impact on the water balance of the Curonian Lagoon

The Curonian Lagoon is the biggest fresh water basin in Lithuania influenced by the exchange of the fresh Nemunas and other smaller rivers’ water and saline water of the Baltic Sea. The lagoon ecosystem is influenced by fresh, brackish and brackish water masses. A long-term water balance of the Curonian Lagoon was calculated for the period of 1960–2009. The sum river inflow is 21.784 km³/year, precipitation—1.199 km³/year, evaporation—1.007 km³/year, inflow of brackish water from the Baltic Sea to the Curonian Lagoon—6.171 km³/year, and fresh water runoff from the Curonian Lagoon to the Baltic Sea—27.642 km³/year. The lagoon water balance elements have been influenced by climate change. The water balance forecasting has been performed for the period of 2011–2100. The climate change impact on the water balance of the Lagoon has been evaluated using Global Climate Models (ECHAM5 and HadCM3), greenhouse gas emission scenarios (A2, A1B and B1), and hydrological modelling by Hydrologiska Byrans Vattenbalansavdelning (HBV) software. One scenario was selected for the prediction of the Baltic Sea water level. Considerable changes of the Curonian Lagoon water balance are forecasted in the 21st century. Increase of weather temperature and changes in precipitation will influence the elements of water balance of the Curonian Lagoon. In the period of 2011–2100, the river inflow and outflow from the Baltic Sea into the Lagoon will decrease respectively by 20.4 and 16.6% in comparison with the baseline period (1961–1990). The amount of precipitation and evaporation will increase respectively by 3.8 and 25.1%, while inflow from the Baltic Sea into the Curonian Lagoon will increase up to 39.7% in comparison with the baseline period.     

Small‐Scale ASR Between Flow Barriers in a Saline Aquifer

Regular aquifer storage recovery, ASR, is often not feasible for small‐scale storage in brackish or saline aquifers because fresh water floats to the top of the aquifer where it is unrecoverable. Flow barriers that partially penetrate a brackish or saline aquifer prevent a stored volume of fresh water from expanding sideways, thus increasing the recovery efficiency. In this paper, the groundwater flow and mixing is studied during injection, storage, and recovery of fresh water in a brackish or saline aquifer in a flow‐tank experiment and by numerical modeling to investigate the effect of density difference, hydraulic conductivity, pumping rate, cyclic operation, and flow barrier settings. Two injection and recovery methods are investigated: constant flux and constant head. Fresh water recovery rates on the order of 65% in the first cycle climbing to as much as 90% in the following cycles were achievable for the studied configurations with constant flux whereas the recovery efficiency was somewhat lower for constant head. The spatial variation in flow velocity over the width of the storage zone influences the recovery efficiency, because it induces leakage of fresh water underneath the barriers during injection and upconing of salt water during recovery.     

频率域航空电磁法浅层水资源调查的试验研究

用航空电磁法进行浅层水资源调查的试验研究,并取得显著成效,在我国还是首次。本文简述了该方法的地质、地球物理前提与技术条件。并指出,HDY-3型双频航空电磁系统,用中比例尺进行航测,在平原的“有咸水”水文地质分区中,圈定咸水、淡水、半咸水,是一种快速、经济而有效的新的水文物探手段。该方法不但能划分咸、淡水及半咸水的界线,还能预测淡水的相对富水程度、研究古沉积环境和土壤粒度。文中还讨论了充实和改进该方法的途径。     

频率域航空电磁法浅层水资源调查的试验研究

用航空电磁法进行浅层水资源调查的试验研究,并取得显著成效,在我国还是首次。本文简述了该方法的地质、地球物理前提与技术条件。并指出,HDY-3型双频航空电磁系统,用中比例尺进行航测,在平原的“有咸水”水文地质分区中,圈定咸水、淡水、半咸水,是一种快速、经济而有效的新的水文物探手段。该方法不但能划分咸、淡水及半咸水的界线,还能预测淡水的相对富水程度、研究古沉积环境和土壤粒度。文中还讨论了充实和改进该方法的途径。     

Integrated geophysical and chemical study of saline water intrusion

Surface geophysical surveys provide an effective way to image the subsurface and the ground water zone without a large number of observation wells. DC resistivity sounding generally identifies the subsurface formations-the aquifer zone as well as the formations saturated with saline/brackish water. However, the method has serious ambiguities in distinguishing the geological formations of similar resistivities such as saline sand and saline clay, or water quality such as fresh or saline, in a low resistivity formation. In order to minimize the ambiguity and ascertain the efficacy of data integration techniques in ground water and saline contamination studies, a combined geophysical survey and periodic chemical analysis of ground water were carried out employing DC resistivity profiling, resistivity sounding, and shallow seismic refraction methods. By constraining resistivity interpretation with inputs from seismic refraction and chemical analysis, the data integration study proved to be a powerful method for identification of the subsurface formations, ground water zones, the subsurface saline/brackish water zones, and the probable mode and cause of saline water intrusion in an inland aquifer. A case study presented here illustrates these principles. Resistivity sounding alone had earlier failed to identify the different formations in the saline environment. Data integration and resistivity interpretation constrained by water quality analysis led to a new concept of minimum resistivity for ground water-bearing zones, which is the optimum value of resistivity of a subsurface formation in an area below which ground water contained in it is saline/brackish and unsuitable for drinking.     

Mathematical modelling of sea water intrusion,Nauru Island

A two-dimensional finite element model for density dependent groundwater flow was calibrated to simulate sea water intrusion in Nauru Island in the Central Pacific Ocean. Nauru Island occupies an area of 22 km² and supports a population of 8500. The island has been mined for its phosphate deposits and current reserves indicate that the mine has about eight years life remaining. The water supply of the island is about one third dependent on imported water which is also used as ballast on the phosphate ships. Imported water will not be available in the future, and a hydrogeological investigation shows that the island is underlain by a fresh water layer, less than 5 m thick. The freshwater layer overlies a thick transition zone of brackish water which in turn overlies sea water. Simulation of several management options shows that it is possible to substitute current importation of fresh water by careful extraction from the groundwater resources of the island.     

Organotins (TBT and DBT) in water, sediments, and gastropods of the southern Venice lagoon (Italy)

The release of tributyltin (TBT) from maritime traffic represents one of the main problems of direct, diffuse, and continued contamination of the marine environment. In the present survey, the concentrations of TBT and dibultytin (DBT) in brackish waters, sediments, and the gastropods Nassarius nitidus were evaluated in order to estimate the contamination of the southern part of the Venice lagoon. TBT and DBT were determined by GC-MS/MS. Recent contamination of TBT was found in brackish waters near marinas, whereas the highest concentrations of TBT and DBT were observed in surface sediments at dockyards and harbours. High content of organotin in the gastropods sampled near the dockyards, harbours, and marinas showed a mobilisation from the sediments through the food web. The present study allowed assessment of whether, despite the ban on the use of TBT paints, waters, sediments, and biota were still being contaminated by organotin compounds in the southern Venice lagoon.     

Intertidal spring dynamics and coastal nutrient loading revealed through geophysics,drone surveys,and in-situ monitoring

Coastal eutrophication poses an increasing risk to ecosystem health due to enhanced nutrient loading to the global coastline. Submarine groundwater discharge (SGD) represents a significant pathway for nitrate-nitrogen (NO₃-N) transport to the coast, but diffusive SGD transport is difficult to monitor directly, given the low flux rates and expansive discharge areas. In contrast, focused SGD from intertidal springs can potentially be sampled and directly gauged, providing unique insight into SGD and associated contaminant transport. Basin Head is a coastal lagoon in Prince Edward Island, Canada that is a federally protected ecosystem. Nitrate-nitrogen is conveyed from agricultural fields in the contributing watershed to the eutrophic lagoon via intertidal groundwater springs and groundwater-dominated tributaries. We used several field methods to characterize groundwater discharge, nutrient loading, and in-channel mixing associated with intertidal springs. The tributaries and intertidal springs were gauged and sampled to estimate a representative summer nitrate load to the lagoon. Our analysis revealed that NO₃-N export to the lagoon through tributaries and springs throughout summer 2023 was on average 401 kg N/month, with the combined spring loading comparable in magnitude to the combined tributary loading. We collected thermal infrared and visual imagery using drone surveys and found spatial overlap between cold-water plumes from the spring discharge and macroalgae blooms, indicating the local thermal and ecosystem impacts of the focused SGD. We also mapped the electrical resistivity (salinity) distribution in the water column around one large spring with electromagnetic geophysics at different tidal stages to reveal the three-dimensional spring plume dynamics. Results showed that the fresher spring water floated above the saline lagoon water with the brackish plume oriented in the direction of the tidal current. Collectively, our multi-pronged field investigations help elucidate the hydrologic, thermal, and nutrient dynamics of intertidal springs and the cascading ecosystem impacts.     

Effects of salinity variation on iron ore dust sedimentation rates

Time course measurements of iron ore dust sedimentation rates in sea-water of different salinities have shown that dust particle settlements occur at similar rates in normal sea-water and in that diluted to 50%. With salinities similar to those in brackish water conditions the sedimentation rates were rapid compared with those in fresh water.     

Conventional Oil—The Forgotten Part of the Water-Energy Nexus

The impacts of unconventional oil and gas production via high-volume hydraulic fracturing (HVHF) on water resources, such as water use, groundwater and surface water contamination, and disposal of produced waters, have received a great deal of attention over the past decade. Conventional oil and gas production (e.g., enhanced oil recovery [EOR]), which has been occurring for more than a century in some areas of North America, shares the same environmental concerns, but has received comparatively little attention. Here, we compare the amount of produced water versus saltwater disposal (SWD) and injection for EOR in several prolific hydrocarbon producing regions in the United States and Canada. The total volume of saline and fresh to brackish water injected into depleted oil fields and nonproductive formations is greater than the total volume of produced waters in most regions. The addition of fresh to brackish “makeup” water for EOR may account for the net gain of subsurface water. The total amount of water injected and produced for conventional oil and gas production is greater than that associated with HVHF and unconventional oil and gas production by well over a factor of 10. Reservoir pressure increases from EOR and SWD wells are low compared to injection of fluids for HVHF, however, the longer duration of injections could allow for greater solute transport distances and potential for contamination. Attention should be refocused from the subsurface environmental impacts of HVHF to the oil and gas industry as a whole.     

Isotopic and geochemical characterization of salinization in the shallow aquifers of a reclaimed subsiding zone: The southern Venice Lagoon coastland

The coastal plain bordering the southern Venice Lagoon is a reclaimed lowland characterized by high subsidence rate, and ground level and water-table depth below sea level. In this agricultural region, where the surface hydrologic network is entirely artificially controlled by irrigation/drainage canals, salinization problems have long been encountered in soils and groundwaters. Here we use isotopic and geochemical tracers to improve our understanding of the origin of salinization and mineralization of the semi-confined aquifer (0–40 m), and the freshwater inputs to this hydrological system. Water samples have been collected at different seasons in the coastal Adriatic Sea, lagoon, rivers and irrigation canals, as well as in the semi-confined aquifer at depths between 12 and 35 m (14 boreholes), and in the first confined aquifer (three boreholes drilled between 40 and 80 m depth). Stable isotopes (δ¹⁸O and δD) and conductivity profiles show that direct saline intrusion from the sea or the lagoon is observed only in a restricted coastal strip, while brackish groundwaters are found over the entire topographic and piezometric depression in the centre of the study area. Fresh groundwaters are found only in the most western zone. The sharp isotopic contrast between the western and central regions suggests disconnected hydrological circulations between these two parts of the shallow aquifer. The border between these two regions also corresponds to the limits of the most strongly subsiding zone.Our results can be interpreted in terms of a four end-member mixing scheme, involving (1) marine water from the lagoon or the open sea, (2) alpine and pre-alpine regional recharge waters carried either by the main rivers Adige, Bacchiglione and Brenta (irrigation waters) or by the regional groundwater circulation, (3) local precipitation, and (4) evaporated waters infiltrated from the surface. Infiltration from the surface is also revealed by the stratification of the electrical conductivity profiles, showing that the brackish groundwaters are overlain by a shallow layer of less saline water all over the central depression. In the first confined aquifer, the groundwaters have isotopic compositions similar to the deep groundwaters of the Venetian confined aquifers (40–400 m depth). The isotopic data and the Br/Cl ratio show that the origin of the salinization of the phreatic aquifer can be ascribed to seawater intrusion alone, with no indication of the involvement of deep brines (identified at 450 m depth) in the process.The chemical composition of the saline and brackish groundwaters is characterized by an excess of sodium and a deficit of calcium compared to conservative mixing between fresh groundwaters and seawater. This suggests that the phreatic aquifer is progressively freshening, as a consequence of the beneficial influence of the extensive irrigation/drainage network, including raised canals acting as a hydraulic barrier along the coast. This freshening tendency may have been lasting since the reclamation in the mid-twentieth century, and has probably been accelerated by the ban on groundwater abstraction since the 1970s.     

从沉积物特征谈太湖的演变

通过太湖湖底淤泥层中的微体古生物及其物理化学分析,在西太潮W1孔发现多门类海相化石。海相化石出现的时间约在1100—5000aB.P.之间。据此提出西太湖在全新世期间曾遭受海侵,因而支持了太湖形成于泻湖的说法,同时,还提出海水进入太湖的时间,比以往学者推测的早2000多年。     

青藏高原陆相介形类的分布特征及其对生态环境的响应

统计分析了青藏高原不同区域水体环境表层沉积物陆相介形类的属种分布特征,探讨了介形类在不同水环境下（盐度、pH值及水深）对生态环境的响应.结果显示,青藏高原现生介形类共计21属67种,其中Candona candida、Ilyocypris bradyi、Eucypris inflata、Limnocythere dubiosa、Limnocythere inopinata、Paracypricerus angulata、Leucocytherella sinensis和Leucocythere mirabilis为青藏高原地区的常见种.湖泊、河流、洼地和湿地4类水体环境中,湖泊中介形类最为丰富,达19属62种;青藏高原东北部（祁连山和柴达木盆地）、北部（昆仑山）、西部和南部不同区域的介形类常见种存在较大差异,可能是区域海拔、pH值和盐度综合作用的结果.淡水和微咸水环境介形类属种数量较咸水及盐湖中丰富,分别有17属41种和13属42种,Limnocythere dubiosa （0.52~90.6 g/L）和Leucocythere mirabilis（0.51~174.63 g/L）在淡水、咸水及盐湖中均有出现,适应盐度范围较广;pH值在8.0~10.0范围内介形类属种多样性最丰富,表明大部分介形类具有嗜碱性的特征;青藏高原陆相介形类属种多样性随水深的增加而降低,浅湖（0~15 m）中介形类属种最为丰富,达到17属52种,其中Candona candida（0.2~80 m）和Leucocythere dorsotuberosa（0.3~110 m）从滨湖至深湖区均有分布,二者均具有较大的水深适应范围.     

Implications of rate-limited mass transfer for aquifer storage and recovery

Pressure to decrease reliance on surface water storage has led to increased interest in aquifer storage and recovery (ASR) systems. Recovery efficiency, which is the ratio of the volume of recovered water that meets a predefined standard to total volume of injected fluid, is a common criterion of ASR viability. Recovery efficiency can be degraded by a number of physical and geochemical processes, including rate-limited mass transfer (RLMT), which describes the exchange of solutes between mobile and immobile pore fluids. RLMT may control transport behavior that cannot be explained by advection and dispersion. We present data from a pilot-scale ASR study in Charleston, South Carolina, and develop a three-dimensional finite-difference model to evaluate the impact of RLMT processes on ASR efficiency. The modeling shows that RLMT can explain a rebound in salinity during fresh water storage in a brackish aquifer. Multicycle model results show low efficiencies over one to three ASR cycles due to RLMT degrading water quality during storage; efficiencies can evolve and improve markedly, however, over multiple cycles, even exceeding efficiencies generated by advection-dispersion only models. For an idealized ASR model where RLMT is active, our simulations show a discrete range of diffusive length scales over which the viability of ASR schemes in brackish aquifers would be hindered.     

Spatial analysis of bacteria in brackish lake sediment

The spatial distribution of bacterial communities inhabiting sediment is heterogeneous at different spatial scales,but mostly unexplored.Here,it is postulated that the heterogeneity of the bacterial community composition varies at the same scale of the heterogeneity of sediment chemical properties.The large spatial scale(km) diversity in sediment from a brackish water lagoon(Chilika Lake,India) is studied,considering the large scale physical and chemical characteristics of land cover,climate,pH,and salinity.Seventy-two samples(24 stations,3 seasons:winter,rainy,and summer) of sediment from Chilika Lake were analyzed by 16 S ribosomal ribonucleic acid(rRNA) gene sequencing,and the relations with land cover and other physico-chemical paramete rs are discussed.Mo re samples were collected after a severe cyclonic storm(Phailin) passed near the lagoon in 2013,to see the impact of the tropical storm on the spatial and tempo ral distribution of bacteria in the sediment.The results demonstrate clear spatial relations between physico-chemical parameters(e.g.,salinity),land surfaces(e.g.,drainage area),and the distribution of sediment microbial communities.     

Locating the zone of saline intrusion in a coastal karst aquifer using springflow data

Coastal fresh water aquifers are an increasingly desirable resource. In a karstic aquifer, sea water intrusion occurs as a salt water wedge, like in porous media. However, preferential flow conduits may alter the spatial and temporal distribution of the salt water. This is typically the case when the outlet of the aquifer is a brackish spring. This paper shows that salinity and flow rate variations at a spring, where salinity is inversely proportional to discharge, can help to understand the hydrodynamic functioning of the aquifer and to locate the fresh water-sea water mixing zone deep inside the aquifer. The volume of water-filled conduit between the sea water intrusion zone and the spring outlet is calculated by the integral over time of the flow rate during the time lag between the flow rate increase and the salinity decrease as measured at the spring. In the example of the spring at Almyros of Heraklio (Crete, Greece), this time lag is variable, depending on the discharge, but the volume of water-filled conduit appears to be constant, which shows that the processes of salt water intrusion and mixing in the conduit are constant throughout the year. The distance between the spring and the zone where sea water enters the conduit is estimated and provides an indication of the position where only fresh water is present in the conduit.     

Geophysical Investigation of Fresh‐Saline Water Interface: A Case Study from South Punjab,Pakistan

The importance of the study of fresh‐saline water incursion cannot be over‐emphasized. Borehole techniques have been widely used, but they are quite expensive, intrusive, and time consuming. The electrical resistivity method has proved very successful in groundwater assessment. This advanced technique uses the calculation of Dar‐Zarrouk (D‐Z) parameters, namely longitudinal unit conductance, transverse unit resistance, and longitudinal resistivity has been employed by using 50 vertical electrical sounding points to assess the groundwater and delineate the fresh‐saline water interface over 1045 km² area of Khanewal in Southern Punjab of Pakistan. The x‐y plots and maps of D‐Z parameters were produced to establish a decipherable vision for the occurrence and distribution of different water‐bearing formations of fresh‐saline water aquifers through a complicated situation of intermixing of different resistivity ranges for fresh‐saline water bodies. This technique is useful to reduce the ambiguity produced by the process of equivalence and suppression which cause intermixing in differentiating fresh, brackish, and saline aquifers during interpretation. The fresh‐saline water interface is correlated very well with the previous studies of water quality analysis carried out in Khanewal area. The results suggest that the D‐Z parameters are useful for demarcating different aquifer zones. The behavior and pattern of D‐Z parameters with respect to occurrence and distribution of different water‐bearing formations were effectively identified and delineated in the study area.     

Localized thermal anomalies in haloclines of coastal Yucatan sinkholes

A temperature spike is reported in the haloclines of three Yucatan sinkholes along a 1 km NW-SE transect from 5 to 4 km inland from the Caribbean coast. The temperature spike decreases in magnitude from 3.5 degrees C to 0.2 degrees C, approaching the coast. The anomaly does not vary diurnally and does not extend down into the underlying sea water. These conditions are inconsistent with explanations such as radiation absorption within the halocline, in situ microbially mediated sulfate reduction within the halocline and the underlying sea water, and sulfide oxidation by photosynthetic purple and green bacteria within the halocline. One explanation consistent with the shape and halocline location of the temperature spike involves a localized sea water convection cell operating near the coast. Cold sea water from the Caribbean Sea enters the coastal limestone at depths of a few hundred meters and heats up because of the geothermal gradient, buoyantly rising in vertical fractures within the unconfined aquifer. Blocked by the less dense fresh water, the movement stops in the halocline where the warm sea water mixes with brackish water. The convection cycle would be completed by the coastward movement of cooling brackish water. The observed temperature anomalies could possibly be snapshots of this warm layer moving coastward.     

Holocene evolution of a rock‐bounded barrier‐lagoon system,Cíes Islands,northwest Iberia

Coastal geomorphology results from the combined effects of contemporary dynamics, sea‐level rise and the inherited geological framework, yet the relative importance of these driving mechanisms may change throughout the evolutionary history of coastal deposits. In this contribution, we analyse the depositional history of the Cíes Islands barrier‐lagoon system, based on lithofacies, radiocarbon ages, and pollen analysis. Our results reveal a sedimentary sequence that provides evidence for striking changes in the dynamical functioning of this complex since the mid‐Holocene. The sedimentary sequence commenced about 7700 cal years bp by fresh‐water ponding of an upland depression located about 4 m below present mean sea‐level. Fresh‐water ponds were infilled by aeolian sediments following a gradual lowering of the water‐table 4000 cal years bp . Post‐3600 cal years bp sea‐level rise allowed water oscillations to reach the elevation of the bedrock causing the inundation of fresh‐water ponds and subsequent lagoonal and marine sedimentation. Subsequently, landward and upward migration of a sand‐barrier led to overwash and deposition of sand in the newly formed lagoon. The resultant sedimentary sequence suggests that climatic conditions played an important role controlling the sedimentation regime during the entire history of the basin; changing water‐table levels during early stages of evolution and increasing storminess during more recent times. In addition, background sea‐level rise related to the Holocene transgression was a key factor in controlling the evolution of the system, yet its influence depended to an extent on the relative elevation of the bedrock topography. Copyright © 2009 John Wiley & Sons, Ltd.     

Multivariate Analysis of Species Distribution: A Survey on Occurence of Mangrove Molluscs in the Bonny and New Calabar Rivers of the Niger Delta Multivariate Analyse von Verbreitungsmustern: Ein Überblick über das Vorkommen von Mangroven-Mollusken im Bonny River und New Calabar River des Niger-Deltas

Studies on distribution and habitats of mangrove molluscs of the Bonny and New Calabar rivers (Niger Delta) were made at ten shore stations from the river mouth to the tidal fresh water zone. Forty-three species were collected and thirty-nine were identified. Investigations into tidal zonation patterns showed that molluscs inhabited the high, mid and low intertidal stretches of the shore. In the tidal fresh water and low-salinity brackish water zone, the low intertidal is poor in molluscs. Many species have restricted salinity ranges occuring either in the high or low salinity limits. The collected data on occurence of species were analyzed by different methods from multivariate data analysis, namely cluster analysis, principal component analysis and partial least squares. These allowed to visualize structures among mollusc species and stations according to distribution patterns and to estimate the degree of relation between these patterns and salinity.