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The study area is located in the arid section of Punjab province, Pakistan. The accessibility of freshwater is the main problem in this area. The area is mainly flat and alluvial deposits are present down to 800 m. The groundwater is not fit for drinking because of its salinity. Hence, it is essential to mark the transition between fresh water and saltwater. Resistivity models were used to locate freshwater areas. The saltwater areas are between 10 and 30 m deep. Salt flats and clayrich deposits are visible on resistivity maps and were identified by low resistance values. After linking resistivity data and maps, it is determined that the south portion of the area has a freshwater aquifer, especially at a depth of 200 m. At this depth, the quality of water is very good, regardless of its mild salinity in some areas. The margin between salty and freshwater is set to no degree. This is dependent upon the recharge and usage of an aquifer. Groundwater pollution poses a severe threat to the city’s residents. Results from the physio-chemical analysis of the water samples confirm the presence of arsenic in excessive amounts in water samples and are outside the limits set by the WHO and NDWQS. Just two out of 10 samples are within the limits for safe drinking water. The results of this research are valued for groundwater management and the installation of tubular wells in freshwater areas for households and irrigation purposes., Istraživano područje smješteno je u pustinjskome dijelu provincije Punjab u Pakistanu, obilježenome nedostatkom pitke vode. Područje je najvećim dijelom zaravnjeno i prekriveno aluvijem koji mjestimice može dosegnuti i 800 m debljine. Podzemna voda nije pogodna za piće zbog slanosti. Stoga je iznimno važno prepoznati prijelaznu zonu između slatke i slane vode. Za lociranje slatkovodnih područja korišteni su modeli otpornosti. Područja slane vode duboka su između 10 i 30 m. Taložine soli i gline opažaju se na kartama otpornosti niskim vrijednostima otpora. Uočeno je kako se na jugu područja javljaju vodonosnici slatke vode, čak na dubini od 200 m, s vrlo dobrom kvalitetom vode, uz rijetku pojavu bočatosti. Granicu između slatke i slane vode nije moguće jednoznačno odrediti, a ovisi o dotoku i uporabi vodonosnika. Njihovo zagađenje može biti ozbiljan problem, poglavito za gradska područja. Rezultati fizičko-kemijske analize pokazali su nazočnost prevelikih količina arsena, tj. u granicama iznad dopuštenih klasifikacijama WHO-a i NDWQS-a. Od 10 samo su 2 uzorka bila u granicama koje određuju pitku vodu. Rezultati su vrijedan doprinos za gospodarenje tom podzemnom vodom te projektiranje bušotina kojima bi se pitka/slatka voda dovodila kućanstvima ili koristila za navodnjavanje.

Desert playas, such as those in northern Utah, form a landscape often in stark contrast to surrounding mountain ranges due to their minimal topographic relief, lack of vegetation, and saline soils. Dry highly reflective halite surfaces, which make up many of the desert playas in northern Utah, are generally characterized by a surface albedo over 40%. However, their albedo can be reduced abruptly to less than 20% by flooding due to rainfall, runoff from surrounding higher terrain, or surface winds transporting shallow water across the playas. A weather station installed during September 2016 to study the Bonneville Salt Flats (BSF) in northern Utah provides estimates of surface albedo that can be related to cycles of flooding and desiccation of the halite surface. The normalized difference water index (NDWI) derived from the MODIS MOD09A1 land surface reflectance product estimates the fractional coverage of surface water over the BSF. NDWI values computed over 8-day periods from 2000 to 2018 highlight year-to-year and seasonal variations in playa flooding events over the BSF. Periods of playa flooding were observed with both ground-based observations and NDWI with sharp reductions in albedo when the surface is flooded.

The effect of elevation and seasonal variations on the elemental status of sediments was investigated along a semi-arid mangrove profile in the Heart of Voh, New Caledonia. As other mangroves in the world, this mangrove site experienced an increase of tidal range that led to the recent colonisation of salt flats at the highest elevations landward by Avicennia marina (Forsk.) Vierh subsp. australasica (Walp.) J. Everett. This young Avicennia stand was compared with an old Avicennia stand at lower elevations on its edge. Down the elevation profile, the sediment properties of a short Rhizophora stylosa Griff stand were compared with a taller Rhizophora stand seaward that experienced longer immersion periods. Our results show that centimetre-scale variation in elevation significantly affects all sediment properties along the semi-arid profile and induces a strong seasonal variation in reduction potential and pH at high elevations over the year. We suggest that during the dry season, the oxygenated sediments enhanced the oxidation of organic matter (OM), which led to the dissolution of Fe-S compounds and the subsequent acidification of the sediments. This in turn induced a loss of metal content (Fe, Cu Ni, Mn) compared to the sediments at lower elevation. Moreover, our results show that the accumulation of OM during the colonisation phase by Avicennia coincided with higher water content and higher total and exchangeable concentrations of N, P, Mg and K within the surface sediments than in the old Avicennia stand. The tall Rhizophora stand at the borders of the channel was characterized by an increase in elevation, denser sediments and a depletion of elements in several horizons of the depth profile compared to the short Rhizophora landward. These results provide a better understanding of i) the impact of elevation differences on major and minor elements in a semi-arid mangrove ecosystem, and ii) the changes of sediment properties mediated by a pioneer species within the early phase of succession in hypersaline mangroves.

Saline lakes occupy 44% and 23% of the volume and area of all lakes that are tending to suffer from extended dryness, reduced hydro period, or complete desiccation by 2025. The current study is conducted on Sambhar Salt Lake, the largest inland saline Ramsar, site of India, contributing to 9.86% of total salt production. The lake is under threat due to illegal salt pan encroachment, losing brine worth 300 million USD. The objective was to identify the key drivers that affect the lake at a landscape level. Geospatial modelling was conducted for 96 years (1963–2059) at a decadal scale, integrating ground data (birds-soil-water). Land Use Land Cover (LULC) classification was conducted using CORONA aerial imagery of 1963, along with Landsat imageries, using supervised classification for 1972, 1981, 1992, 2009, and 2019, and future prediction for 2029, 2039, 2049, and 2059. Further, images were classified into 8 classes that include the Aravali hills, barren land, saline soil, salt crust, salt pans, wetland, settlement, and vegetation. Past trends show a reduction of wetland from 30.7 to 3.4% at a constant rate (4.23%) to saline soil, which subsequently seemed to increase by 9.3%, increasing thereby the barren land by 4.2%; salt pans by 6.6%, and settlement by 1.2% till 2019. Future predictions show loss of 40% wetland and 120% of saline soil and net increase in 30% vegetation, 40% settlement, 10% salt pan, 5% barren land, and a net loss of 20%, each by Aravali hills and salt crust. Additionally, the ground result shows its alteration and reduction of migratory birds from 3 million to 3000. In the light of UN Decade on Ecosystem Restoration (2021–2030), restoration strategies are suggested; if delayed, more restoration capital may be required than its revenue generation.

Salt is a key solute in salt marshes and under the influence of evapotranspiration can accumulate to a high concentration level in the marsh soil and precipitate in the solid form to become a significant stressor for plants, affecting marsh plant productivity and ecological zonation. Numerical simulations of coupled pore water flow and salt transport were conducted to examine how spring-neap tides and evaporation combine to influence salt dynamics and distribution patterns in marshes. The salt pan formation was simulated with a sandy loam marsh soil subjected to a medium rate of potential evaporation. The critical condition for the salt pan formation was underpinned by hydraulic connection between the marsh surface and water table to sustain evaporation in the supratidal zone. Both low soil permeability and overly high potential evaporation were found to break the hydraulic connection. In this case, the surface soil salinity increased gradually over the intertidal zone to a maximum around the spring high tide mark followed by a rapid decrease to a lower constant level across the supratidal zone. This salinity distribution pattern has also been observed in the field. In both salt marshes with and without salt pans, excessive salt accumulated on the marsh surface due to evaporation was removed by tidally induced circulating flow and/or flow driven by density gradients associated with the accumulated salt. The salt dynamics and distribution patterns revealed here, especially the salt pan formation simulated for the first time, have important implications for studies of marsh plant growth and overall eco-functions.

The Bonneville Salt Flats (BSF) in Utah is a dynamic saline playa environment responding to natural and anthropogenic forces. Over the last century, the saline groundwater from below BSF has been harvested to produce potash via evaporative mining, mostly used as agricultural fertilizers, while the surface halite crust has provided a significant recreational site for land speed racing. Perceptions of changes in the salt crust through time have spurred debates about land use and management; however, little is known about the timescales of natural change as the salt crust responds to climatic parameters that drive flooding, evaporation, and desiccation (FED) cycles that control surface salt growth and dissolution. Climate data over the last ~ 30 years are examined to identify annual patterns in surface water balance at BSF to identify annual and seasonal climate constraints on FED cycles. Landsat satellite data from 1986 to the present are used to map the areal extent of the surface halite salt crust at BSF at the end of the desiccation season (between August 15 and October 30) annually. Overall, the observed area of the desiccation-stage BSF halite crust has varied from a maximum of 156 km2 in 1993 to a minimum of 72 km2 in 2014 with an overall trend of declining area of halite observed over the ~ 30 years of analysis. Climatic variables that influence FED cycles and seasonal salt dissolution and precipitation have also varied through this time period; however, the relationship between surface water fluxes and salt crust area do not clearly correlate, suggesting that other processes are influencing the extent of the salt. Intra-annual analyses of salt area and weather illustrate the importance of ponded surface water, wind events, and microtopography in shaping a laterally extensive but thin and ephemeral halite crust. Examination of annual to decadal changes in salt crust extent and environmental parameters at BSF provides insights into the processes driving change and the sustainability of land use in this dynamic environment.

Groundwater pollution from anthropogenic sources is a serious concern affecting several river basins and coastal aquifer environment. It is very important to acquire the impacts of the enhanced anthropogenic pressure and climatic changes on the evolution of groundwater characteristics in this study. The present study aims to concentrate on the hydrogeochemical characteristics by evaluating the groundwater quality through geographical information system (GIS) and multivariate statistical approach. Fifty groundwater samples were collected from the river basin and analyzed for major physicochemical parameters. The analytical results were interpreted in GIS and multivariate statistical techniques and demarcated the spatial variation of groundwater quality and their site-specific influencing factors over time. The presence of Na–Cl facies reflects the saline nature in groundwater in and around salt pan area. Factor analysis reveals the characteristics of four factors, and it accounted for 88.7% total variability. Significant correlation between TDS with major components of Na+, Mg2+, Cl− ions indicate the presence of saline influence on the groundwater. Cluster I and Cluster II represent fresh to slightly saline in nature, Cluster III mainly indicates the average concentration of EC (8615 µS/cm), chloride (2738 mg/l), and salinity (4.67 mg/l) is mainly due to small-scale industrial effluents, salt pan, agricultural activities, and rock–water interaction with related minerals in evaporite deposits.

Bento, L.; Masuda, L.S.M.; Peixoto, R.B., and Enrich-Prast, A., 2017. Regulation in the metabolism and community structure of a tropical salt flat after rainfall. Tropical salt flats typically lack a water column for most of the year, which means that rainfall is probably one of the major factors that regulate benthic microalgae and metabolism in areas subjected to periodic drought. Therefore, the goal of this study was to evaluate the effects of rainfall on the ecological function and community structure of a tropical mangrove salt flat area. This study showed that the highest primary production and respiration fluxes were recorded on the last day of sampling when it rained (−7.6 and 4.7 mmol C-CO2 m−2 h−1, respectively). Net primary production increased significantly compared with the dry period that preceded the rain event. The results also suggested that community structure was regulated by rainfall. After the rain event, abundance increased by one order of magnitude, but the diversity and ev...

Depression wetlands (colloquially referred to in South Africa (SA) as pans) are found worldwide and primarily occur in arid regions including North and South America, southern and central Africa and southern and western Australia. Surface water resources in SA, and specifically in Gauteng, are under pressure from urbanisation, poor agricultural practices and untreated mining and industrial effluent. Research of these wetlands will benefit the development of health assessment tools for these unique aquatic resources. The aim of this project was to determine the water quality and macroinvertebrate community structure for each perennial pan during consecutive dry and wet seasons and to establish a possible comparison between these pans that can be used as a baseline for future research on pans. The sampled pans in Gauteng presented higher TDS, Cl and Mg results compared to other South African studies, and similar SO4 results to pans in the Mpumalanga province. Ammonia, Al and Zn results of all pans through all sampling events exceed the Target Water Quality Range (TWQR) for aquatic ecosystems of the Water Quality Guidelines (WQG) from the Department of Water and Sanitation (DWS). The water quality from selected systems is suitable for livestock watering based on the DWS TWQR. Macroinvertebrate species of all sampled pans were mostly low water quality tolerant species with a predator dominant community structure. Seasonal variation of species was evident. Macroinvertebrate families found in the wet season include Hydrophilidae, Aeshnidae, Pleiidae, Ephemeroptera, Belostomatidae and Notonectidae. Families found in the dry season include Planaridae, Dysticidae, Hirudinidae and Daphnidae. Graphical representation of ordination analyses with Canoco version 5 (Ter Braak and Smilauer 2012) indicated that TDS, temperature, pH, sulphates and hardness are strong drivers of the existing macroinvertebrate community in most of the pans.

An attempt has been made in Nagapattinam and Karaikal Coastal aquifers to explain hydrochemical characteristics and salinization sources. A total of 122 groundwater samples were collected during southwest monsoon and summer seasons and analyzed for major and minor ions. Groundwater samples represents alkaline nature irrespective of seasons. Larger variations in conductivity might be due to multiple geochemical processes. Hill piper plot suggests evolution of groundwater from fresh to saline facies during both the seasons. The multi-rectangular facies evolution diagram identifies saline intrusion dominant during summer and freshening of waters during southwest monsoon. The Ionic ratio plot suggests saline intrusion, cation exchange and anthropogenic sources controlling the groundwater chemistry. Correlation and factor analysis suggests additional sources of salinization from salt pan and agricultural influences. The spatial distribution map suggests larger area influenced by saline water intrusion when compared with other sources.

Studies about wetlands have been identified as a key component of environmental change. The present study assesses the spatio-temporal changes in the wetlands of the Great Rann of Kachchh, in the Kachchh Biosphere Reserve, India, using remote sensing and GIS techniques. Satellite time-series data from Landsat (1977, 1990 and 1999) and IRS P6 (2006, 2008–2012) were used. The Normalised Difference Water Index (NDWI) was derived for each year and the layers were manually edited to obtain a high classification accuracy. The analysis found that the area has undergone considerable change from 1977 to 2011. The natural wetland area of 30.6 km2 was converted to salt pans. An area of about 255 km2 (41.6 %) of natural grassland was invaded by Prosopis juliflora, which raises further conservation concerns and emphasises the importance of having intervention plans to manage this ecosystem. The highest water spread of 1171 km2 was observed in September 2011, followed by 2010, 2009 and 2008 in the same month. The present study is useful in planning the long-term management and conservation of the Great Rann of Kachchh wetland.

Summary The major groundwater resources of the Arabian Peninsula are stored in the large sedimentary basins in its eastern part. Evaporation from continental salt pans (playas) is an important process in water resources assessments of its upper principal aquifers – the Upper Mega Aquifer system – as it constitutes a significant sink. However, literature values on evaporation rates vary widely and usually report about coastal salt pans where seawater evaporation is assumed. The present study applies different methods to provide a comprehensive picture of groundwater evaporation from salt pans of the Upper Mega Aquifer system. A remote sensing approach provided the spatial distribution and total salt pan area of about 36,500 km 2 . Hydrochemical and isotopic investigations revealed that from about 10% (3600 km 2 ± 1600 km 2 ) of the mapped salt pan area seawater evaporates. To estimate the groundwater evaporation rate from continental salt pans a laboratory column experiment was set up, implying a mean annual evaporation rate of about 42 mm ± 13 mm. In-situ analysis of water table fluctuations in the field suggested about 3 mm a −1 originate from recently infiltrated rainwater leading to an annual net groundwater evaporation of 39 mm ± 13 mm. Relating this number to the mapped salt pan area, from which groundwater evaporates, provides a total annual groundwater loss of 1.3 km 3 ± 0.5 km 3 for the Upper Mega Aquifer system.

Seawater intrusion is a major threat to the water quality in the coastal aquifers. A hydrogeochemical survey was conducted in and around the Point Calimere wetland with an objective to delineating the impact and sources of groundwater salinization. These objectives were met by a combined hydrochemical and multivariate statistical approach. Groundwater samples showed an alkaline nature throughout the area. It was substantiated by the observed positive correlation of TDS with Na, Mg and Cl and a negative correlation with HCO3. Ionic changes during the saline water-freshwater mixing were analyzed. It was detected that the mixing rate of seawater with the fresh groundwater was 31%. A negative e.change was observed for the samples collected near the coast as well as salt pans. The sources of salinity identified through factor analysis exhibited a clear segregation between freshwater and saline water. The presence of Ca and SO4 in the factor 2 shows the dissolution of gypsum minerals. The dendrogram generated through cluster analysis classified the total groundwater samples into two groups which agrees with the results obtained from the hydrochemical and factor analysis. The wells that are near the coast and salt pans, which are grouped under cluster 1, have influence of saline intrusion.

Water in Utah and Nevada is important for agriculture, municipal use, solute transport, and ecosystem preservation. Large spring wetland systems occur on the playa margin of the Bonneville basin, including Blue Lake, 15 km south of the Bonneville Salt Flats on the Utah-Nevada state border. Large spring systems have historically been studied as water budgets don't apparently balance from direct mountain front recharge (Nelson and Mayo, 2014; Gardner and Heilweil, 2014; and others). Blue Lake is no exception; prior studies here have suggested discharge rates 0.04 - 0.05 km3/yr (Louderback and Rhode, 2009), greater than expected for modelled recharge in the surrounding mountain range (0.03 km3/yr). Three hypothesized recharge mechanisms for Blue Lake are tested: mountain-front recharge, interbasinal groundwater flow, and infiltration from historic Lake Bonneville. Remote sensing suggests that a conservative estimate of Blue Lake discharge constitutes 50-64% of modelled mountain-front recharge (Flint et al., 2011). Major ions, δ18O, δ2H, dissolved gases (14C, 3He, 4He, Ne, Ar, Kr, Xe) and trace elements (Sr and 87Sr/86Sr isotopes) comprehensively constrain recharge conditions, water-rock interactions, flowpaths, and groundwater provenance of this large spring system. 14C signatures suggest that Blue Lake discharge has a transit time between 5,600 and 12,200 years, older than that of Fish Springs. Noble gas concentrations in Blue Lake water suggest an elevated recharge temperature greater than 19°C and low salinity, indicating a deep water table and high geothermal gradient in the recharge area. 87Sr/86Sr ratios of playa-margin springs are elevated from that of mid-playa groundwaters, springwaters from the adjacent mountain range, and alluvial fill groundwater from the valley directly south of Blue Lake. Playa-margin spring Sr isotope values (0.713-0.714) are most similar to direct runoff from the Deep Creek Range granodiorite outcrop (>0.713). Interbasinal groundwater flow in combination with mountain-front recharge is best supported by chemical data rather than mountain-front recharge alone or the slow discharge of regional aquifers recharged by lacustrine infiltration from Lake Bonneville.

The Salar de Atacama is one of the most well-known saline endorheic basins in the world. It accumulates the world main lithium reserves and contains very sensitive ecosystems. The objective of this work is to characterize the hydrodynamics of the Salar de Atacama, and to quantify its complex water balance prior to the intense brine extraction. The methodology and results can be extrapolated to the groundwater flow and recharge of other salt flats. A three-dimensional groundwater flow model using low computational effort was calibrated against hundreds of hydraulic head measurements. The water infiltrated from the mountains ascends as a vertical flux through the saline interface (mixing zone) produced by the density contrast between the recharged freshwater and the evaporated brine of the salt flat nucleus. This water discharges and is largely evaporated from lakes or directly from the shallow water table. On the other hand, the very low hydraulic gradients, coupled with the presence of the mixing zone that operates as barrier, leads the salt flat nucleus to act as a hydrodynamically quasi-isolated area. The computed water table shows the lowest hydraulic head in the salt flat nucleus near the discharge at the mixing zone. The groundwater balance of the Salar de Atacama in its natural regime was quantified resulting in an inflow/outflow of 14.9 m3·s−1. This balance considers the basin as an endorheic system. The very low infiltration values that are generally assumed for hyperarid basins are not consistent with the hydrogeology of the Salar de Atacama. Indeed, very high infiltration rates (up to 85% of rainfall) occur because of the high degree of fracturing of rocks and the scarce vegetation. This high infiltration is consistent with the light isotopic composition of the water from the recharge area (Altiplano). Therefore, the existence of additional inflows outside the basin is unlikely. © 2018, The authors acknowledge Sociedad Química y Minera de Chile S.A. (SQM) for their support and sharing data throughout the hydrogeological characterization of the SdA site. M.A. Marazuela gratefully acknowledges the financial support from the AGAUR (Agència de Gestió d'Ajuts Universitaris I de Recerca, Generalitat de Catalunya) and the European Union (grant number 2017FI B1 00194). Finally, we thank three anonymous reviewers for their valuable comments.

The Salar de Atacama is used as a case study to analyse and quantify coupled natural (evaporation and recharge) and anthropogenic processes (pumping of lithium-rich brine) to abstract their patterns to other salt flats using a three-dimensional groundwater flow model. Important changes in the dynamics of the water table between the pre-operational period (1986–1994) and operational period (1994–2015) are observed. The water table exhibited a gradual drawdown during the pre-operational period because the evaporation was greater than the recharge for most of these periods. This negative balance was counteracted by some sharp rises that were produced by direct rainfall events on the salt flat. The deep lateral recharge that arrived from the mountains did not produce abrupt changes in the water table because the rainfall events in the mountains were damped by the distance of the recharge zone and great thickness of the unsaturated zone. The natural evolution of the water table was modified by the intensive brine pumping that was performed in the south-western Salar de Atacama during the operational period. As evaporation depends on the water table depth, the pumping caused a drawdown of the water table, resulting in an evaporation rate reduction that partially compensated for the pumped brine in the water balance of the basin. This effect is defined as the damping capacity of salt flats. Thus, salt flats have a high capacity for dampening oscillations in their water table in response to both natural and anthropogenic disturbances which is of great importance for the management of lake and wetland ecosystems and brine exploitation. The limit of the dampening capacity of salt flats is defined by the evaporation extinction depth, which is in the range of 0.5–2 m. © 2018 Elsevier B.V., The authors acknowledge Sociedad Química y Minera de Chile S.A. for their support and sharing data throughout the hydrogeological characterization of the SdA site. M.A. Marazuela gratefully acknowledges the financial support from the AGAUR (Agència de Gestió d’Ajuts Universitaris i de Recerca, Generalitat de Catalunya) and the European Union (grant number 2018FI B2 00068). Finally, we thank four anonymous reviewers for their valuable comments.

Inverse geochemical modelling with PHREEQC and multivariate statistical methods were used to determine the origin of groundwater chemical constituents and identify the source of salinity in parts of Ajabshir alluvial aquifer, East Azerbaijan, Iran. Q mode hierarchical cluster analysis (HCA) was used to partition groundwater in the study area into hydrochemical facies. Three major water groups were identified by HCA. Groundwater samples collected from the study area were classified as recharge area waters (Group 1: Na–Ca–HCO 3 water; Group 2: Ca–Na–HCO 3 water) in the northern, central and northeastern areas. Discharge area waters were identified in the vicinity of Urmia Lake and in southern parts of the study area (Group 3: Na–Cl water). Principal components analysis (PCA) with varimax rotation using the Kaiser criterion identified three principal sources of variation in the hydrochemistry. Factor 1 accounts for the salinity of the water, factor 2 represents silicate mineral weathering, and factor 3 represents calcite dissolution and incongruent silicate mineral weathering. Inverse modelling for major ions and the results of HCA confirmed the results obtained with PCA. The results of this study showed that water–rock interaction is an important mechanism in the evolution of water chemistry. The results also identified the following phenomena as important mechanisms in the composition of Group 3 waters: saline water upconing, mixing between freshwater and saline water, reverse flow from the salt flats toward the aquifer, flatness of the ground surface and very low velocity of the groundwater, shallow depth of the groundwater and evaporation from it, a silt–clay boundary at the outlet of groundwater flow from the aquifer, and airborne transport of salt particles from the salt flats.

Research on land use cover change (LUCC) has reached a mature stage and has formed a relatively complete scientific system. However, most studies analyzed the LUCC process from the view of land use types ignoring the integrality and systematicness of the land use system, which brought certain constraints to understanding the complexity and systematicness of land use process scientifically. Using the Modern Yellow River Delta (MYRD) of China as the study area, this research introduced the complex network analysis method to the study of the LUCC process by using 9 periods of land use data between 1976 and 2014 to build 8 stages of complex networks. The values of node degree, betweenness, changing proportions, and average shortest path in the networks were calculated to identify the key land use types, changing models of land use types, and the stability of land use system. Additionally, main parts of complex networks of the period from 1976 to 1995 and the period from 1995 to 2014 were selected to evaluate the changing characteristics of the LUCC process. The results indicated the area and proportion of natural wetland kept reducing, but the area and proportion of artificial wetland or non-wetland continued rising. The bare land, reed, bush, and cultivated land were the key land use types of the LUCC process. In the past 38 years, beach, bare land, reed and bush had been the output types, and the building land and salt pan had been the input types. The LUCC process has been a transfer process of natural wetland to artificial wetland and non-wetland in the past 38 years, which could be divided into land accretion process (1976 to 1995) and construction process (1995 to 2014). The land ecosystem was unstable for the period from 1990 to 2006.

Long-term intensive land use/cover changes (LUCCs) of the Yellow River Delta (YRD) have been happening since the 1960s. The land use patterns of the LUCCs are crucial for bio-diversity conservation and/or sustainable development. This study quantified patterns of the LUCCs, explored the systematic transitions, and identified wetland change trajectory for the period 1976–2014 in the YRD. Landsat imageries of 1976, 1984, 1995, 2006, and 2014 were used to derive nine land use classes. Post classification change detection analysis based on enhanced transition matrix was applied to identify land use dynamics and trajectory of wetland change. The five cartographic outputs for changes in land use underlined major decreases in natural wetland areas and increases in artificial wetland and non-wetland, especially aquafarms, salt pans and construction lands. The systematic transitions in the YRD were wetland degradation, wetland artificialization, and urbanization. Wetland change trajectory results demonstrated that the main wetland changes were wetland degradation and wetland artificialization. Coastline change is the subordinate reason for natural wetland degradation in comparison with human activities. The results of this study allowed for an improvement in the understanding of the LUCC processes and enabled researchers and planners to focus on the most important signals of systematic landscape transitions while also allowing for a better understanding of the proximate causes of changes.

The present study investigates the hydrogeochemical characteristics of groundwater quality in Agastheeswaram taluk of Kanyakumari district, Tamil Nadu, India. A total of 69 groundwater samples were collected during pre- and post-monsoon periods of 2011–2012. The groundwater quality assessment has been carried out by evaluating the physicochemical parameters such as pH, EC, TDS, HCO3 −, Cl−, SO4 2−, Ca2+, Mg2+, Na+ and K+ for both the seasons. Based on these parameters, groundwater has been assessed in favor of its suitability for drinking and irrigation purpose. Dominant cations for both the seasons are in the order of Na+ > Ca2+ > Mg2+ > K+ while the dominant anions for post monsoon and pre monsoon have the trends of Cl− > HCO3 − > SO4 2− and HCO3 − > Cl− > SO4 2−, respectively. Analytical results observed from various indices reveal that the groundwater quality is fairly good in some places. Analytical results of few samples show that they are severely polluted and incidentally found to be near the coasts, estuaries and salt pans in the study area. The Gibbs plot indicates that the majority of groundwater samples fall in rock dominant region, which indicates rock water interaction in the study area. The United States salinity (USSL) diagram shows that the groundwater is free from sodium hazards but the salinity hazard varies from low to very high throughout the study area. This reveals that the groundwater is moderately suitable for agricultural activities. The observed chemical variations in pre-monsoon and post-monsoon seasons may be the effect to rock-water interactions, ion-exchange reactions, and runoff of fertilizers from the surrounding agricultural lands.

The carbon cycle in salt pans is complex and poorly understood. Field-based data are needed to improve regional estimates of C storage and land-atmosphere CO2 fluxes from dryland environments where pans are prevalent. This paper provides a first estimate of C stores and CO2 efflux within the salt pan, grassland and woodland of Ntwetwe Pan in the Makgadikgadi Basin, Botswana. C fluxes and stores associated with cyanobacteria-salt crusts are also determined. Total C stores are approximately an order of magnitude greater than on neighbouring Kalahari Sands at 675±41, 760±94 and 274±15 tonsha-1 to 1m depth in the woodland, grassland and salt pan respectively. Most of the C is found as carbonate, with organic C comprising 4.6-10% of total C. CO2 efflux increased with temperature and also increased for a few hours after flooding of the pan surface. Crusts were a small net contributor to CO2 efflux in the dry season but could be a net CO2 sink in the wet season. The biogeochemistry of the sediment is likely to facilitate rapid conversion of organic C from aquatic organisms, biological crusts and algal mats into inorganic carbonates. Although further work is required to improve estimates of the spatial and temporal distribution of C, our data have demonstrated the substantial C store with the Makgadikgadi environment and the important role of biological crusts in the C cycle.

article Sabkhat(Salt flats)are common geographic featuresof low-lyingmarinecoastalareas thatdevelopunder hyper- aridclimaticconditions.Theyare characterizedby thepresenceof highlyconcentratedsalinesolutions and evap- oritic minerals, and have been cited in the geologic literature as present-day representations of hyper-arid regional paleohydrogeology, paleoclimatology, coastal processes, and sedimentation in the geologic record. It is therefore important that a correct understanding of the origin and development of these features be achieved. Knowledge of the source of solutes is an important first step in understanding these features. Historically, two theories have been advanced as to the main source of solutes in sabkha brines: an early concept entailing seawa- ter as the obvious source, and a more recent and dynamic theory involving ascending geologic brine forced upward into the base of the sabkha by a regional hydraulic gradient in the underlying formations. Ra-226 coulduniquely distinguish betweenthese sourcesunder certain circumstances,asitistypically present atelevat- ed activity of hundreds to thousands of Bq/m 3 (Becquerels per cubic meter) in subsurface formation brines; at exceedingly low activities in open ocean and coastal water; and not significantly supplied to water from recently formed marine sedimentary framework material. The coastal marine sabkha of the Emirate of Abu Dhabi was used to test this hypothesis. The distribution of Ra-226 in 70 samples of sabkha brine (mean: 700 Bq/m 3 ), 7 sam- ples of underlying deeper formation brine (mean: 3416 Bq/m 3

Over a period of 44 years, we observed the vegetation changes in the western part of the lagoon system of the Cienaga Grande de Santa Marta, which is situated on the Caribbean coast of Colombia and is separated from the sea by a sandy barrier. Since the construction of the Barranquilla-Cienaga Road between 1956 and 1960, the lagoon system has been exposed to different interventions in its hydrological make-up, as well as changes to the vegetation. During the time of our investigations, four periods with different plant cover were distinguished. In 1965, the road was bordered by dense mangrove forests. The low surface water salinity and the presence of freshwater plants indicated the influence of the Magdalena River. At the beginning of the seventies, the second period was marked by a decrease in the freshwater in-flow from the river, which led to an increase in salinity and a gradual decay of vegetation. In 1988, the areas formerly covered by mangroves had converted into salt flats. The third period began with the reconstruction of several channels (1995–1998) which renewed the freshwater in-flow from the river to the lagoons. The subsequent vegetation development was characterized by the establishment of Typha domingensis Pers. In 1999, a year with an unusually high amount of rainfall, this species covered most of the former mangrove area in the western part of the lagoon system. The very low surface water salinity favored its spread. The last period began in 2001/2002, when growth conditions for T. domingensis became unfavorable due to an increase in salinity. Instead, conditions for mangrove regeneration improved. This process was slower than expected and is still ongoing. The striking vegetation changes indicate the sensitivity of the coastal lagoon system to hydrological variability.

Lake Urmia is one of the most important salt lakes in the world and the largest in Iran. At present, because of the recession of Lake Urmia and deposition of lacustrine sediments on the lake bed, a large part of the surrounding areas has become flat with several playa surfaces. So far, there have been very few studies related to Lake Urmia playa and its geomorphology. Therefore, the aim of this research was to field study of playa surfaces of Lake Urmia in its eastern part and also to identify areas susceptible to wind erosion. In this study, different playa surfaces from the northeast to the south of the lake were identified and mapped using satellite imagery. Then, boundaries of the mapped surfaces were checked during field observations. Moreover, physical soil properties, such as texture, bulk density, saturation percentage, resistancy, particle size distribution and soil aggregate stability, were determined. Next, the correlation of the studied properties with each surface resistance to wind erosion was investigated, and finally the geomorphic surfaces of Urmia Playa and their resistance to wind erosion were mapped using ARCGIS software. Based on the results, the study area included agricultural lands, shrub-grass zones, sand and gravel zones, mud-clay salt flats, sand-salt crusts, puffy grounds, delta-fans and wet zones. Results showed that approximately 25% of the surfaces had high resistance to wind erosion and they are therefore stable surfaces with no potential for generating dust in the future. About 35% of the surfaces were strongly susceptible to wind erosion, highly prone to generate saline dusts and sand storms. These areas were located in the east and southeast of the lake. Also, 40% of playa surfaces had moderate resistance to wind erosion. These areas can become very sensitive to wind erosion if ground water depth or the roughness of the surface changes. In conclusion, sandy-salt surfaces in the east and southeast of the lake are the most susceptible to wind erosion with high potential for generating dust, sand, and salt storms, which can affect agricultural lands and human health in the near future. Keywords: dust, erosion, geomorphology, Inceptisols, playa, Lake Urmia

Restoration of the industrial salt flats in the San Francisco Bay, California is an ongoing wetland rehabilitation project. Remote sensing maps of suspended sediment concentration, and other GIS predictor variables were used to model sediment deposition within these recently restored ponds. Suspended sediment concentrations were calibrated to reflectance values from Landsat TM 5 and ASTER using three statistical techniques -- linear regression, multivariate regression, and an Artificial Neural Network (ANN), to map suspended sediment concentrations. Multivariate and ANN regressions using ASTER proved to be the most accurate methods, yielding r2 values of 0.88 and 0.87, respectively. Predictor variables such as sediment grain size and tidal frequency were used in the Marsh Sedimentation (MARSED) model for predicting deposition rates for three years. MARSED results for a fully restored pond show a root mean square deviation (RMSD) of 66.8 mm (

A hydrogeochemical study was conducted in Thoothukudi district situated in the southeast coast of Tamil Nadu, India to identify the influence of saltwater intrusion and suitability of groundwater for domestic and agricultural purposes. Scattered studies of this coastal region have reported signs of seawater intrusion, salt pan and industrial activity together with natural weathering process. To have a holistic picture of geochemical processes in the entire district, a total of 135 groundwater samples were collected and analyzed for major cations and anions. The geochemical parameters were compared with world and Indian standards and it was found that most samples are unsuitable for drinking purpose. The geochemical facies of the groundwater showed Na–Cl as the dominant water type indicating the saline nature of the groundwater. Chadda’s plots show that most of the samples fall in the Na–Cl type of water due to seawater intrusion. The samples were classified with parameters like sodium absorption ratio, residual sodium carbonate, total hardness, chloride, index to base exchange, electrical conductivity and facies to determine their suitability for irrigation purpose. It was inferred that the samples falling along the coast are not suitable for the irrigation purpose. The seawater-mixing percentage indicates that strong mixing was observed in the near shore and at the proximity of the salt pan. The permanent hardness was predominant in all the samples compared to the carbonate hardness reducing its domestic usability.

The ratio of archaeol to caldarchaeol (the ACE index) has been proposed recently as an index for paleosalinity reconstruction and is based principally on archaeal core lipids (CLs) from coastal salt pans (Turich, C., Freeman, K.H., 2011. Archaeal lipids record paleosalinity in hypersaline systems. Organic Geochemistry 42, 1147–1157). We have examined possible relationships between salinity and ACE in both CLs and intact polar lipids (IPLs) from suspended particulate matter (SPM) and surface sediments of lakes and surrounding soils on the northeastern Qinghai–Tibetan Plateau. Our results showed that ACE values were positively correlated with salinity in all samples; however, CL ACE values were systematically higher than IPL ACE values, probably due to different degradation kinetics of intact polar (IP) archaeol and IP caldarchaeol. On the other hand, surface sediment ACE values from both CLs and IPLs were lower than SPM ACE values, probably due to enhanced production of caldarchaeol relative to archaeol in the sediment. Our results demonstrate that the ACE proxy reflects changes in salinity in diverse environments on the Qinghai–Tibetan Plateau, which is promising for paleosalinity reconstruction; however, caution should be used when applying the salinity proxy before we have a better understanding of degradation kinetics of archaeal IPLs and in situ production of caldarchaeol and archaeol in sediments.

Salt pans in Indonesia are commonly set in batch operation and highly depend on the meteorological condition. Moreover, the common salt pans are considerably limited in the area (averagely 0.5-1 Ha) as it is not organized by industries or governments; local farmers instead. However, with such confinement, there are some salt pans particularly with filtering-threaded technology system (TUF system) that successfully produce salt with high production (>100 tons/Ha/season) and grade-1 quality. The present study was aimed to get insight on the meteorological condition at the salt pans using TUF system and the physical condition of the sea brine obtained from the TUF in the local salt pans in Cirebon Regency. Measurements on temperatures (air, brine and soil), humidity, wind direction and speed, brine conductivity, brine density and salinity were conducted at the pre-crystallizer pond, brine storage pond, channels, the condenser, and the reservoir. The meteorological parameters were recorded hourly using Automatic Weather Station and the data were taken during 49 hours ly, from August 26-28, 2014 started at 04.00 pm. Meanwhile, the physical parameters of the brine were measured every three hours using water quality meter. The results showed that the meteorological condition, brine physical condition, and the process occurred during salt production were still in agreement and met the theoretical condition or modeling. Even though the relative humidity and some wind speed in the present study area were out of the standard criteria recommended (5m/s for wind speed), the study showed that salt still can be produced in condition of relative humidity (52-88%), wind speed (0.2-5.7 m/s), and ambient temperature (23.2-32.4 oC). Interestingly, it is found that brine thickness and volume could be adjusted to get an optimum temperature of brine (reached 36.2 oC), in order to enhance the evaporation process. The highest soil temperature (34.7 oC) was found at 15.00 in the pre-crystallizer ponds. Meanwhile, the lowest temperature (26.7oC) was found early morning at 04.00 in the reservoir pond. Brine in the pre-crystallizer had highest thermal storage capacity during daytime (06.00-16.00), whereas soil in the pre-crystallizer tended to store heat during the nighttime (18.00-22.00). Brine and soil temperature fluctuation indicate that solar irradiation and convection process transferring heat energy from soil to brine occurs and also took an important part in the evaporation process. It therefore can be concluded that by understanding the condition of meteorology at the salt pan areas and the brine characteristic obtained, the appropriate technology resulting high-quality and quantity salt production could be devised.

Freshwater input to estuaries may be greatly altered by the river barrages required to meet human needs for drinking water and irrigation and prevent salt water intrusion. Prior studies have examined the salt plugs associated with evaporation and salt outwelling from tidal salt flats in single-channel estuaries. In this work, we discovered a new type of salt plug formation in the multi-channel Pasur River Estuary (PRE) caused by decreasing river discharges resulting from an upstream barrage. The formation of a salt plug in response to changes in river discharge was investigated using a conductivity-temperature-depth (CTD) recorder during spring and neap tides in the dry and wet seasons in 2014. An exportation of saline water from the Shibsa River Estuary (SRE) to the PRE through the Chunkhuri Channel occurred during the dry season, and a salt plug was created and persisted from December to June near Chalna in the PRE. A discharge-induced, relatively high water level in the PRE during the wet season exerted hydrostatic pressure towards the SRE from the PRE and thereby prevented the intrusion of salt water from the SRE to the PRE.

This paper serves to document a thermal spring, called Gaet’ale, that was reactivated in 2005, during the majorseismo-volcanic crisis in the Danakil Depression of the Afar region of northern Ethiopia. Many dead birds surrounding the spring attest to deadly gas emanations (almost certainly CO2) coming from this spring, reminiscent of those from other volcanic lakes, and the Pamukkale springs in Turkey. Gae’tale currently features among the tourist attractions of the Dallol region of the northern Afar, but it may pose a potentially dangerous, and even deadly, hazard for tourists and their guides. Some suggestions are made to help mitigate the risks, and to allow for sustainable geotourism in this environmentally sensitive region. These include ensuring that tour operators in the area are made aware of the hazards, and are communicating these to their tourist clients (who should also be aware of these hazards through websites, tour guidebooks and open-access scientific journals), and avoiding the areas closest to the lake, and periodic testing, with lit flames, for the presence of excess CO2 in the area, with plans for quick and safe evacuation if needed. Guidelines for proper conduct are given for geotourists who are planning to visit the region, to ensure their health and safety in the vicinity of the thermal springs.

We examined controls on water levels and salinity in a mangrove on a carbonate barrier island along the Indian River Lagoon, east-central Florida. Piezometers were installed at 19 sites throughout the area. Groundwater was sampled at 17 of these sites seasonally for three years. Head measurements were taken at the other two sites at 15-minute intervals for one year. Water levels in the mangrove are almost always lower than lagoon water levels. Spectral analysis of water levels showed that mangrove groundwater levels are not tidally influenced. Salinities vary spatially, with values of ∼10 psu in uplands, ∼30 psu in regularly-flushed mangroves, and ∼75 psu in irregularly-flushed mangroves. Cation and anion concentrations and stable isotope compositions indicate that water salinities are largely controlled by enrichment due to evapotranspiration. A shore-perpendicular electrical resistivity survey showed that the freshwater lens is restricted to uplands and that hypersaline waters extend deeply below the mangrove. These results indicate that evapotranspiration lowers water levels in the mangrove, which causes Indian River Lagoon water to flow into the mangrove where it evapoconcentrates and descends, forming a thick layer of high-salinity water below the mangrove.

Groundwater quality in the relatively small Yamagata Basin exhibits considerable variation. The water obtained from artesian wells in the downstream of the Midaregawa Fan in Hairi district is referred to as donko-sui, and is one of the selected 100 exquisite and well-conserved waters. The donko-sui is used for fish farming and daily life water in this district. On the other hand, kanake-mizu from the Sagae district is not potable due to the high Fe content. The kanake-mizu is often used for snow melting in winter, and the iron hydroxide changes the color of road surfaces to redblown. In the Hirashio district on the western margin of the basin, salt is produced in a salt pan fed by a saline spring with a Cl- concentration of more than 10,000 ppm. To clarify the hydrogeological reasons why such various interesting groundwaters exist in the Yamagata Basin, the authors examined a three dimensional distribution of chemistry of groundwater including in Tertiary sediments, which has been assumed to a hydrological basement, by field surveys and reviews of previous studies. The results are summarized as follows.(1) The hydrogeology of the Hairi district is characterized as the discharge zone of very active groundwater flow system in the Midaregawa watershed. Donko-sui is confined and has low electric conductivity and oxidative potential due to the very short residence time.(2) Kanake-mizu is found not only in the Sagae district but in the lowland area where it becomes reductive and Fe-rich after a long residence time.(3) Groundwater from the deep zone in Tertiary sediments (>400 m) could be classified into two groups based on hydrochemical characteristics. One group had lowδ18O, δD and d values, and was obtained from the eastern, southern, and northern parts of the basin. The δ values and Cl- concentration suggested that the groundwater from this group was formed by mixing with paleo sea-water and precipitation in an ice age, which has low δ and d values. The other group had high δ value and low d values, respectively. The properties are similar to saline spring at the Hirashio district but differed markedly from the water samples of the first group. The second group would be originated from paleo seawater but needs some mechanism to form the high δ value.(4) Groundwater from the shallow zone in Tertiary sediments (

In this paper, laboratory-based bidirectional reflectance distribution function (BRDF) analysis of vegetation leaves, soil, and leaf-litter samples is presented. The leaf litter and soil samples, numbered 1 and 2, were obtained from a site located in the savanna biome of South Africa (Skukuza: 25.0deg S, 31.5deg E). A third soil sample, number 3, was obtained from Etosha Pan, Namibia (19.20deg S, 15.93deg E, altitude of 1100 m). In addition, BRDF of local fresh and dry leaves from tulip polar tree (Liriodendron tulipifera) and black locust tree (Robinia pseudoacacia) were studied. It is shown how the BRDF depends on the incident and scatter angles, sample size (i.e., crushed versus whole leaf), soil samples fraction size, sample status (i.e., fresh versus dry leaves), vegetation species (i.e., poplar versus locust), and the vegetation's biochemical composition. As a demonstration of the application of the results of this paper, airborne BRDF measurements acquired with NASA's Cloud Absorption Radiometer over the same general site where the soil and leaf-litter samples were obtained are compared to the laboratory results. Good agreement between laboratory and airborne-measured BRDF is reported.

The Aral Sea has shrunk and become a large salt pan, because the water from the two rivers that used to feed the lake (Amu Darya and Syr Darya) is almost entirely used for irrigation. In this paper some possibilities to return to the original (1960) situation are studied. After discussing some of the alternatives, it is proposed to construct a canal along a more southerly route than the original Sibaral canal, starting from the Zaisan Lake along the Irtysh river. This solution requires the construction of a major tunnel through the Khrebet Tarbagataj mountain range. Thereafter, it will flow through the Balkash Lake, saving several hundred kilometers of canal construction, and discharge its water in the lower reaches of the Syr Darya. From here it will flow into Aral Sea, slowly restoring it towards its original (1960) level. Several flanking water saving measures are considered. Most of the drive to restore the Aral Sea is for ecological reasons. There may also be a serious climatic threat to avoid, although this is a matter of debate. It is found that the discharge of the major Siberian rivers into the Arctic Ocean is on the increase, and this may affect the great world ocean conveyor belt. This would have dire consequences for the climate in Western and Northern Europe. This could be avoided by diverting part of the water towards the Aral Sea. A restoration of the Aral Sea will have beneficial effects on climate, human health, fishery and ecology in general.

Landsat enhanced thematic mapper imagery (ETM) of 2002 and aerial photography of 1955, combined with published charts and field observations were used to interpret coastal changes in the zone between Kitchener drain and Damietta spit in the northeastern Nile delta, previously recognized as a vulnerable zone to the effects of any sea level rise resulting from global warming. The interpretation resulted in recognition of several changes in nine identified geomorphological land types: beach and coastal flat, coastal dunes, agricultural deltaic land, sabkhas, fish farms, Manzala lagoon, saltpans, marshes and urban centers. Reclamation of vast areas of the coastal dunes and of Manzala lagoon added about 420 km² to the agricultural deltaic land. About 48 km² of backshore flats, marshes, salt pans and Manzala lagoon have been converted to productive fish farms. The main urban centers have expanded; nearly 12.1 km2 have been added to their areas, and new urban centers (Damietta harbor and the New Damietta city) with total area reach of ~35.3 km2 have been constructed at the expense of vast areas of Manzala lagoon, coastal dunes, and backshore flats. As a consequence of human activities, the size of Manzala lagoon has been reduced to more than 65%. Shoreline changes have been determined from beach profile survey (1990–2000), and comparison of 1955 aerial photographs and ETM satellite image of 2002 reveal alongshore patterns of erosion versus accretion. The short-term rate of shoreline retreat (1990–2000) has increased in the downdrift side of Damietta harbor (≃14 m/year), whereas areas of accretion exist within the embayment of Gamasa and in the shadow of Ras El Bar detached breakwaters system, with a maximum shoreline advance of ~15 m/year. A sandy spit, 12 km long, has developed southeast of Damietta promontory. These erosion/accretion patterns denote the natural processes of wave-induced longshore currents and sediment transport, in addition, the impact of man-made coastal protection structures.

Sambhar Lake in Rajasthan, India is the major inland salt water lake producing salt for centuries. The present study addresses the monitoring changes in and around the lake and its consequent effect on the lake water ecology. For this, satellite images of the years 1976, 1981, 1997, and 2013 are analyzed for land use land cover classes. Significant reduction in the water body is observed in contrast with the increase in salt pan around the periphery of lake and wetland classes. Further, the extent of water body and algae in the lake are delineated as per normalized difference water index and normalized difference vegetation index. Rainfall data do not indicate any major change in the pattern, but drastic decrease in the extent of water body and significant increase in algal bloom are serious concerns for the lake's existence. This may be due to surrounding anthropogenic activities and construction of check dams and anicuts in the lake catchment which curtail the runoff into the lake and provide favorable growth of algae. Sambhar Lake, being declared as a wetland according to the Ramsar Convention, is necessary to protect and conserve the ecological importance of the lake through sustainable planning and management.

Closed basins are catchments whose drainage networks converge to lakes, salt flats or alluvial plains. Salt flats in the closed basins in arid northern Chile are extremely important ecological niches. The Salar del Huasco, one of these salt flats located in the high plateau (Altiplano), is a Ramsar site located in a national park and is composed of a wetland ecosystem rich in biodiversity. The proper management of the groundwater, which is essential for the wetland function, requires accurate estimates of recharge in the Salar del Huasco basin. This study quantifies the spatio-temporal distribution of the recharge, through combined use of isotopic characterization of the different components of the water cycle and a rainfall-runoff model. The use of both methodologies aids the understanding of hydrological behavior of the basin and enabled estimation of a long-term average recharge of 22 mm/yr (i.e., 15 % of the annual rainfall). Recharge has a high spatial variability, controlled by the geological and hydrometeorological characteristics of the basin, and a high interannual variability, with values ranging from 18 to 26 mm/yr. The isotopic approach allowed not only the definition of the conceptual model used in the hydrological model, but also eliminated the possibility of a hydrogeological connection between the aquifer of the Salar del Huasco basin and the aquifer that feeds the springs of the nearby town of Pica. This potential connection has been an issue of great interest to agriculture and tourism activities in the region.

Wind-tidal flats are the dominant coastal wetland type in southern Texas, USA. Succulent vascular plants are colonizing the flats in some locations, often where past dredge disposal along navigation channels and other activities have interrupted natural water communication between hypersaline bays and large areas of wind-tidal flats. The objective of this study was to test the feasibility of proposed removal of a causeway at Laguna Atascosa National Wildlife Refuge to restore the historic hydrologic regime and eradicate encroaching vascular plants, mostly Salicornia bigelovii, on the assumption that high sediment salt excluded these vascular plants under natural conditions. Assessment in spring 1998 of the density of Salicornia in relation to elevation and sediment salt of bare and vegetated zones on the vegetated flats on one side of the causeway and entirely barren flats with unimpaired connection to Laguna Madre on the other side of the causeway suggested that sediment salt > 0.1 g ml−1 excluded vascular plants. However, bimonthly sampling in 1999–2000 revealed that sediment salt concentrations were > 0.1 g ml−1 throughout the vegetated zone in July and more locally in the period of winter low water, with little impairment to established plants. This indicates that if control is desired, it must be exerted at germination and early establishment during and after fall high water. Continuous monitoring of water levels on either side of the causeway suggests that, even with removal of the causeway, flooding with hypersaline lagoon water will be too infrequent to counteract the freshening effect of a permanent hydraulic connection to the main agricultural drain of the lower Rio Grande Valley that has developed at the other end of the salt flat. Monitoring Salicornia distribution over six years documented huge variation between years but no trend toward increasing dominance of the flats. The results of this study illustrate that the most obvious alterations to a site may not be the most influential on function and that the scale of analysis may have to extend far beyond the site in space and time to evaluate a proposed restoration properly.

Saline lakes are widespread throughout the arid and semi-arid regions of the world and have considerable ecological importance. They are also very vulnerable to climatic changes or changes in their hydrological regimes. Most saline lakes of Turkey are close to the verge of extinction due to natural and anthropogenic impacts. This study analyzes the spatial and temporal changes at a relatively pristine saline lake (Tuzla (Palas) Lake) in Kayseri, Turkey, from 1987 to 2011 using satellite imagery techniques. Landsat Thematic Mapper images acquired in 1987, 2000, 2003, and 2011 were used in the analysis. The images were geometrically corrected by registering them to ground control points. The study area on each image was classified into seven information classes, i.e., water, watery ground, dry lake, mud/vegetated flats, salt flats, shrubs/sedges, and agriculture. The accuracies of the classifications were evaluated using a standard error matrix and kappa statistics. The analysis showed that the surface area of Tuzla Lake was highly variable during the 1987–2011 period. Lake surface area was the largest in 1987 and the smallest in 2003. Analysis of the climatic conditions for 4 years showed that the surface area of the lake is highly vulnerable to changes in precipitation and air temperatures.

While many wetlands form along floodplains of rivers, streams, lakes, and estuaries, others have developed in depressions far removed from such waters. Depressional wetlands completely surrounded by upland have traditionally been called ''isolated wetlands.'' Isolated wetlands are not confined to basins, as some occur on broad flats and others form on slopes. The term ''geographically isolated wetlands'' better describes these wetlands, since many are hydrologically connected to other wetlands and waterbodies through ground-water flows or by intermittent overflows (spillovers). Numerous types of geographically isolated wetlands occur throughout the United States. They may be naturally formed or the result of human action. Naturally formed types include prairie pothole wetlands, playas, Nebraska's Rainwater Basin and Sandhills wetlands, West Coast vernal pools, sinkhole wetlands, Carolina bays, interdunal and intradunal wetlands, desert springs, terminal basins in the Great Basin, and kettle-hole bogs in glaciated regions. Human-caused isolated types may be intentionally built, such as ponds designed for various purposes and wetlands built on mined lands, or they may be accidentially created (e.g., natural wetlands that were once connected to rivers and streams but are now isolated by roads, railroads, and other development or isolated by altered river hydrology). Many of the functions and benefits attributed to non-isolated wetlands are present in isolated wetlands.

On 21 January 2000, a release of an estimated 100 barrels of diesel was reported from a product transportation pipeline north of Great Salt Lake in Utah. During the next few days, due to weather related conditions (freeze/thaw periods and wind), the product spread over 38 acres of salt flat and wetlands. Initial oil containment efforts were successful in reducing the risk of oil impacts to natural resources in a nearby national migratory bird refuge, but the risk remained to migratory waterfowl that were expected to arrive at the impacted wetland within approximately 6 weeks. As a result, in situ burning was proposed to remove the free-phase diesel and destroy the hydrocarbon-impacted vegetation. Upon approval of a Site Remediation Plan and Fire Management Plan, a Heli-Torch was used on 10 March, 2000 to burn the most-highly impacted 12.8 acres. The following month (late-April), 3.2 acres of remaining lightly oiled vegetation were burned using drip torches and propane wands. It was estimated that 75–80% of the spilled diesel was burned in these operations. Because burning of the free-phase hydrocarbons and impacted vegetation would not remove product that had penetrated into the soils, bioremediation techniques were subsequently implemented, in order to further reduce hydrocarbon levels in the soil and attain the regulatory cleanup level of 20 mg/kg total polycyclic aromatic hydrocarbons.