Long-term Changes In Water Quality Research Articles

A Variational Mode Decomposition–Grey Wolf Optimizer–Gated Recurrent Unit Model for Forecasting Water Quality Parameters

Water is a critical resource globally, covering approximately 71% of the Earth’s surface. Employing analytical models to forecast water quality parameters based on historical data is a key strategy in the field of water quality monitoring and treatment. By using a forecasting model, potential changes in water quality can be understood over time. In this study, the gated recurrent unit (GRU) neural network was utilized to forecast dissolved oxygen levels following variational mode decomposition (VMD). The GRU neural network’s parameters were optimized using the grey wolf optimizer (GWO), leading to the development of a VMD–GWO–GRU model for forecasting water quality parameters. The results indicate that this model outperforms both the standalone GRU model and the GWO–GRU model in capturing key information related to water quality parameters. Additionally, it shows improved accuracy in forecasting medium to long-term water quality changes, resulting in reduced root mean square error (RMSE) and mean absolute percentage error (MAPE). The model demonstrates a significant improvement in the lag of forecasting water quality parameters, ultimately boosting forecasting accuracy. This approach can be applied effectively in both monitoring and forecasting water quality parameters, serving as a solid foundation for future water quality treatment strategies.

Study the Impact of the Anthropogenic Activities on the Marine Environment of Fujairah Offshore Waters of UAE Based on Baseline Surveys and Buoy Data

As Fujairah comprises extremely diverse natural landscapes which enforce us to protect and understand possible risks and challenges faced by the coastal waters of Fujairah, it is critical to mitigate, reduce, and eliminate the risks. The aim of this study is to assess and evaluate the effect of such anthropogenic activities on the offshore waters of Fujairah. Accordingly, two buoys were deployed after conducting a baseline survey for 30 locations targeting areas affected by the anthropogenic activities. Furthermore, two sites were chosen for the buoy deployment, nearshore which is across the desalination plant (Qidfa) and offshore which is across the oil and gas facility port (Skamkam). After analyzing the water quality measurements taken for 1 year from both deployed buoys and compared it with the baseline survey measurements, an indication of water quality deterioration in nearshore and offshore buoys was evinced, and the nearshore site which located in Qidfa has a higher deterioration in water quality measurements compared to the offshore site located in Skamkam. A long-term monitoring program needs to be conducted to gather additional data on water quality over several years to help identify the seasonal variations, trends, and long-term changes in water quality.

Long-term changes in water quality and structure of benthic animal communities in the Neva estuary under anthropogenic stress

In the Neva River estuary, 188 species and taxa of a higher rank of benthic animals were found, of which 129 were found in the eastern part of the Gulf of Finland. At present, the zoobenthos of the estuary is dominated by eurybiont species inhabiting polluted waters. We used integrated index IP' specially devised for water-bodies and rivers of the north-western Russia to assess the water quality and a state of ecosystems of the Neva estuary. It is based on structural parameters of zoobenthic communities and makes it possible to take into consideration the pollution by toxic and organic substances. On average the water quality of the Neva Bay assessed from IP′ values was relatively stable during 1994–2021. It was assessed as “polluted” with the exception of 2006 and 2015 caused by large-scale dredging works. In the period 1982–2021, the average number of zoobenthos species at one station in the Neva Bay almost doubled, from 12 ± 1 species in 1982 to 23±2 species in 2020. In the resort area of the eastern Gulf of Finland, the values of species richness and the Shannon index were much lower than in the Neva Bay, and on average for one station varied from 5±0.6 to 14±4 species and from 1.1±0.2 to 2.3±0.2 bit/ind. This is caused by the influence of salinity, eutrophication and pollution, and invasion of alien species. In addition to intense anthropogenic impact, the dynamics of the state of zoobenthos in this part of the estuary was determined by climate fluctuations.

Long-term changes in water quality downstream of three abandoned metal mines

Abandoned metal mines pollute rivers with both acidic and circumneutral metal-rich waters, sometimes from well-mapped mines, but often from long-abandoned adits with limited historical records. Changes in water quality over the monitored timescales were calculated for three mines across Wales (Nantymwyn, Parys Mountain and Frongoch), each abandoned since the early 20th century. Using all available spot sampling data provided by the environmental regulator, it was found that there was a sustained input of metals to the receiving watercourses with no or limited reduction in the concentrations from the mines without remediation, despite the passage of time and impacts of weathering. At Nantymwyn, comparison with five months’ sampling in 2019 showed no significant change (p > 0.05) in metal concentrations compared to the same months in 1985. Parys Mountain showed an increase in filtered zinc concentrations of 2 % between 2004 and 2020. At Frongoch, however, a substantial reduction in its environmental impact was observed after remediation, including a 90 % reduction in total lead concentrations. Realisation that the pollution from these sites does not reduce over the decades since abandonment should galvanize the resolve to understand the highest priority sites, and where possible remediate them.

A climate-water quality assessment framework for quantifying the contributions of climate change and human activities to water quality variations

Water quality safety has attracted global attention and is closely related to the development of the social economy and human health. It is widely recognized that climate change and human activities significantly affect water quality changes. Therefore, quantifying the contributions of factors that drive long-term water quality changes is crucial for effective water quality management. Here, we built a climate-water quality assessment framework (CWQAF) based on climate-water quality response coefficients and trend analysis methods, to achieve this goal. Our results showed that the water quality improved significantly by 4.45%–20.54% from 2011 to 2020 in the Minjiang River basin (MRB). Human activities (including the construction of ecological projects, stricter discharge measures, etc.) were the main driving factors contributing 65%–77% of the improvement effect. Notably, there were differences in the contributions of human activities to water quality parameter changes, such as DO (increase (I): 0.12 mg/L, human contribution (HC): 66.8%), CODMn (decrease (D): 0.71 mg/L, HC: 67.2%), BOD5 (D: 1.10 mg/L, HC: 77.7%), CODCr (D: 4.20 mg/L, HC: 81.2%), TP (D: 0.13 mg/L,HC: 72.8%) and NH3–N (D: 0.40 mg/L, HC: 63.0%). Climate change explained 23%–35% of the variation in water quality. The water quality response to climate change was relatively significant with precipitation. For example, the downstream region was more susceptible to climate change than was the upstream region, as the downstream movement of precipitation centers strengthened the process of climatic factors affecting water quality changes in the MRB. Generally, although human activities were the main driving factor of water quality changes at the basin scale, the contribution of climate change could not be ignored. This study provided a manageable framework for the quantitative analysis of the influence of human activities and climate change on water quality to enable more precise and effective water quality management.

Long-Term Examination of Water Chemistry Changes Following Treatment of Cyanobacterial Bloom with Coagulants and Minerals.

The abundant growth in cyanobacterial blooms poses severe ecological threats with a high risk to aquatic organisms and global public health. Control of cyanobacterial blooms involves spraying cyanobacteria removal materials, including coagulants. However, little is known about the fate of the coagulated-cyanobacteria-laden water. Here, we examined long-term changes in water quality following treatment with various coagulants and minerals for cyanobacterial removal when the coagulated cyanobacterial cells were not removed from the water. An experiment in a controlled water system tested the effects of six different compounds, one conventional coagulant, two natural inorganic coagulants, and three minerals. All tested coagulants and minerals exhibited >75% of cyanobacterial removal efficiency. However, compared to the control, higher concentrations of nitrogen were observed from some samples treated during the experimental period. After 20 months, the final total phosphorus concentration of the raw water increased 20-fold compared to the initial concentration to 11.82 mg/L, indicating significant nutrient release over time. Moreover, we observed that the decomposition of sedimented cyanobacterial cells caused the release of intracellular contents into the supernatant, increasing phosphorous concentration over time. Therefore, cyanobacterial cells should be removed from water after treatment to prevent eutrophication and maintain water quality.

Factors affecting the seasonal succession of phytoplankton functional groups in a tropical floodplain reservoir in Vietnam

Abstract Phytoplankton communities can be classified into different groups based on physiological, morphological, and ecological functions. In this study, the responses of phytoplankton functional groups (PFGs) to physicochemical variables and hydraulic regimes were investigated and used as ecological indicators in the Tri An Reservoir (TAR), a eutrophic tropical floodplain reservoir located in southern Vietnam. Altogether, 148 phytoplankton taxa were identified and assigned to 16 PFGs; the four predominant PFG groups were M (Microcystis spp.), MP (filamentous cyanobacteria: Oscillatoria spp., and some other diatoms: Gomphonema angustatum, Navicula sp.), J (green algae: Coelastrum spp., Cosmarium spp., Pediastrum spp., Scenedesmus spp., Staurastrum spp., Tetradesmus spp., Tetraëdron spp., and Xanthidium spp.), and P (Closterium spp., Aulacoseira granulata, Fragilaria spp., Pinnularia spp., and Desmidium baileyi). The average PFG biovolume ranged from 79.6 ± 20.2 to 230.1 ± 69.1 mg/L with M being the dominant group. The trophic state index (TSI) indicated that the water condition was light-eutrophic to hyper-eutrophic. It was found that the large water level fluctuation resulted in seasonal nutrient dynamics, with higher nutrient concentrations and higher turbidity during the low water level period and vice versa. The redundancy analysis (RDA) indicated that the nutrient concentrations, water level fluctuation, and mixing regimes were critical factors in the PFG selection in the TAR. Therefore, we assumed that water level fluctuation management coupled with biological competition have the potential to control toxic cyanobacteria in the TAR. In conclusion, the PFGs are suitable for examining the effects of environmental conditions on phytoplankton dynamics in tropical floodplain reservoirs, but their sensitivity to long-term changes in water quality and eutrophication requires further investigation.

Long-term phosphorus reduction and phytoplankton responses in an urban lake (USA)

Eutrophication is one of the primary factors causing harmful cyanobacteria blooms in freshwater lakes. This study investigated the long-term changes in water quality and summer phytoplankton assemblages in Oswego Lake, OR, USA, in relation to phosphorus reduction through hypolimnetic aeration and alum applications. Both water quality and phytoplankton assemblages were sampled biweekly during the summers from 2001 to 2013. The concentrations of total phosphorus, soluble reactive phosphorus, and total nitrogen decreased 66%, 93% and 31%, respectively, in response to the hypolimnetic aeration and alum treatments since 2005. Summer phytoplankton assemblages showed a 62% reduction of cyanobacteria biovolume and a shift from cyanobacteria dominance (2001–2005) to diatom and chlorophyte dominance (2006–2013). Cluster analysis identified four statistically different groups of summer phytoplankton assemblages (denoted Groups 1–4). Nonmetric multidimensional scaling analysis indicated that the four groups were associated with different water quality conditions. Group 1 occurred prior to hypolimnetic aeration and was primarily comprised of cyanobacteria, associated with water conditions of high nutrients and high primary production. Group 2, dominated by cyanobacteria and chlorophytes, occurred between hypolimnetic aeration and alum surface application. Group 3 was dominated by diatoms and occurred after alum surface application. Group 4 included R-strategist phytoplankton that quickly respond to environmental changes and occurred in the years following alum injection, drawdown, and inflow alum treatment. Both Group 3 and 4 were associated with reduced nutrients in the lake. We conclude that these lake management practices had strong effects on both production and community compositions of phytoplankton, and advocate for future studies on large-scale climate impacts on lake ecosystems and to identify corresponding best management practices.

Trends in long-term water quality changes in Ivan’kovo and Uglich reservoirs

A comparative analysis of water quality indicators in the upper and lower parts of the Ivan’kovo and Uglich Reservoirs was carried out based on the analysis of long-term monitoring datasets on water quality condition in reservoirs. The observations were performed at the gauging stations of the State Observation Network and Mosvodokanal in the period from the mid-1980s to 2019 and 2004 accordingly. Over a long-term period, all studied hydrochemical indicators except for Zn and SO4 tend to decrease closer to the dam both in the Ivan’kovo and Uglich Reservoirs. Two periods with sufficiently different average values of considered parameters and their dynamics were distinguished for the Uglich Reservoir according to statistical analysis. A high level of pollution in the Uglich Reservoir is mainly associated with heavy metals (Cu, Zn, Fe), phenols and oil products and is typical for both the upper and lower parts of the reservoir. Such pattern is inherent to both heterogeneous periods (1985-2000 and 2001-2019) identified for the Uglich Reservoir. The main trends of long-term and seasonal variability in water quality of the Ivan’kovo and Uglich Reservoirs have been identified using the water pollution index.

Assessing water-quality changes in US rivers at multiple geographic scales using results from probabilistic and targeted monitoring

Two commonly used approaches for water quality monitoring are probabilistic and targeted. In a probabilistic approach like the US Environmental Protection Agency’s National Rivers and Streams Assessment, monitoring sites are selected using a statistically representative approach. In a targeted approach like that used by many monitoring organizations, monitoring sites are chosen individually to answer specific questions. One important goal of both approaches is documenting long-term changes in water quality. Here, we compare chloride change results in US rivers and streams between the early 2000s and early 2010s from both approaches. The probabilistic approach provided an unbiased representation of change in all US rivers and streams, but was designed to measure low-streamflow conditions within a spring/summer index period during periodic survey years. The targeted approach was focused on larger, more developed watersheds but samples were collected frequently throughout the assessment period in different seasons and streamflows. The probabilistic results showed a small decrease in chloride concentrations in rivers and streams with the lowest concentrations, but no consistent increase or decrease in the remainder. The increased granularity of the targeted results showed that there was, in fact, a mix of changes occurring, with increases at 132 sites, decreases at 112 sites, and relatively stable conditions at 55 sites. The combined results suggest that chloride is not responding to a widespread, common driver across the USA and that management of chloride would be most effective when targeted regionally or locally.

Long-Term Water Quality Changes as a Result of a Sustainable Restoration—A Case Study of Dimictic Lake Durowskie

Nature-based solutions in lake restoration enable gradual ecosystem reconstruction without drastic and expensive intervention. Sustainable lake restoration involves limited external interference strong enough to initiate and maintain positive changes in the ecosystem. It was introduced in Lake Durowskie, an urban, flow-through lake situated in Western Poland, using hypolimnetic aeration, phosphorus precipitation with small doses of chemicals and biomanipulation in 2009, and is continued until today. Oxygen conditions in the lake hypolimnion after initial deterioration were gradually improved, and finally a shortening of the duration and range of oxygen deficits was observed. Nitrogen transformations were induced in the hypolimnion by water aeration as well, reducing ammonium N (30% during 2013–2017 in comparison to 2008) and increasing nitrates (90% in 2013–2017 in comparison to 2008). Phosphorus content was diminished (19% during 2015–2017 in relation to 2008 for SRP) due to effective iron-binding and a smaller amount of fresh organic matter being decomposed. Its reduction was related to lower phytoplankton biomass, expressed in a decrease of chlorophyll-a concentrations (55% reduction during 2013–2017 in comparison to 2008) and an increase in water transparency (two-fold during 2013–2017 in relation to 2008) throughout the nine years of treatment. A long-term restoration program, based on non-aggressive, multiple in-lake techniques was applied and, despite the lack of a reduction in total external loading, was able to suppress progressive eutrophication.

An Analysis of Long-term Changes in Water Quality of Geumho River using Statistical Techniques

In this study, water quality data of eight main sites in the Geumho River watershed were collected and analyzed for long-term changes in water quality over the period from 2005 to 2015. The results showed that BOD concentration was gradually improved by the Total Maximum Daily Load (TMDL), stages 1 and 2. Recently, a tendency of increasing BOD concentration was observed in the downstream section of the river. The concentration of COD was analyzed to be contaminated throughout the water system regardless of the water quality improvement project, and the TN concentration tended to increase in the midstream of the river from 2013. The TP concentration has clearly decreased from 2012 after the second stage of TMDL. For the statistical analysis of PCA ordination, monthly water qualities (pH, DO, Electrical Conductivity (EC), Water Temperature (WT), BOD, COD, TN, TP, TOC, and SS) and flow rate data for 5 years from 2012 to 2016 were used. Seasonally the Geumho River showed an increase in the TN concentration at point sources during the dry season (December to February). TP showed the effect of non-point sources in the summer, because rainfall has caused a rise in flow rate in the upstream. Besides, the origin of pollution source was changed from non-point sources with BOD, COD, and TOC.

Quantifying the effects of hydrological changes on long-term water quality trends in temperate reservoirs: insights from a multi-scale, paleolimnological study

Declining water quality in reservoirs is of growing concern in many regions, yet there is still little understanding of long-term water quality trends in these systems. Across the landscape, reservoirs have diverse origins, functions, and operational strategies. In temperate environments, winter water-level drawdown is a common operational practice in reservoirs but the long-term impacts of this hydrological modification has not been extensively studied. We paired a comparative, pre-dam-to-contemporary study (i.e. a top–bottom design) of 12 reservoirs with a detailed paleolimnological study of a focal lake to generate quantitative insights into the relative effect of hydrological changes vs. landscape and climatic drivers on water quality. The focal reservoir, Grand Lac Saint-Francois, is of relatively similar morphometry, geography, and limnology to our other sites, and has experienced annual winter water-level drawdown of ~ 5 m since it was dammed approximately 100 years ago. Based on our top–bottom analysis, we did not find strong correlations between long-term changes in water quality (i.e. diatom-inferred TP estimates) and winter water-level drawdown amplitudes. Instead, reservoir morphometry and watershed characteristics (i.e. geography, maximum depth, and cropland areas) appeared to be stronger drivers of trends across the region. From the detailed paleolimnological analysis, we found that sedimentary pigments and DI-TP concentrations significantly increased over the last century based on Mann–Kendall trend analyses. Breakpoint analyses showed that changes in biological-proxy trends, as well as the sedimentology (i.e. lithology and accumulations rates), coincided with dam construction and the onset of water level regulation. However, given the high variability in metrics and the extent of water level monitoring records, we were unable to quantitatively associate the impacts of drawdown with water quality trends at Grand Lac Saint-Francois. Conversely, we did find that watershed nutrient surpluses from livestock farming, and warming temperatures were significant explanatory variables of water quality metrics.

Changes in Water Quality of Grand Lake St. Marys Watershed Following Implementation of a Distressed Watershed Rules Package.

Grand Lake St. Marys watershed has drawn attention over the past decade as water quality issues resulting from nutrient loading have come to the forefront of public opinion, political concern, and scientific study. The objective of this study was to assess long-term changes in water quality (nutrient and sediment concentrations) following the distressed watershed rules package instituted in 2011. Since that time, a variety of rules (e.g., winter manure ban) and best management practices (cover crops, manure storage or transfers, buffers, etc.) have been implemented. We used a general linear model to assess variation in total suspended solids, particulate phosphorus, soluble reactive phosphorus (SRP), nitrate N, and total Kjeldahl nitrogen concentrations from daily Chickasaw Creek (drains ∼25% of watershed) samples spanning 2008 to 2016. Parameters were related to flow (higher values during high flows), timing (lower values during winter months), and the implementation of the distressed watershed rules package (lower values following implementation). Overall, reductions following the distressed designation for all parameters ranged from 5 to 35% during medium and high flow periods (with exception of SRP). Reductions were even more pronounced during winter months covered by the manure ban, where all parameters (including SRP) exhibited decreases at medium and high flows between 20 and 60%. While the reductions seen in this study are significant, concentrations are still highly elevated and continue to be a problem. We are optimistic that this study will serve to inform future management in the region and elsewhere.

Storms do not alter long-term watershed development influences on coastal water quality

A twelve year (2000−2011) study of three coastal lagoons in the Gulf of Mexico was conducted to assess the impacts of local watershed development and tropical storms on water quality. The lagoons have similar physical and hydrological characteristics, but differ substantially in the degree of watershed urban development and nutrient loading rates. In total the lagoons experienced 22 storm events during the period studied. Specifically, we examine (1) whether there are influences on water quality in the lagoons from watershed development, (2) whether there are influences on water quality in the lagoons from storm activity, and (3) whether water quality is affected to a greater degree by watershed development versus storm activity. The two urbanized lagoons typically showed higher water-column nitrate, dissolved organic nitrogen, and phosphate compared with the non-urbanized lagoon. One of the urbanized lagoons had higher water-column chlorophyll a concentrations than the other two lagoons on most sampling dates, and higher light extinction coefficients on some sampling dates. The non-urbanized lagoon had higher water-column dissolved oxygen concentrations than other lagoons on many sampling dates. Our results suggest long-term influences of watershed development on coastal water quality. We also found some evidence of significant storm effects on water quality, such as increased nitrate, phosphate, and dissolved oxygen, and decreased salinity and water temperature. However, the influences of watershed development on water quality were greater. These results suggest that changes in water quality induced by human watershed development pervade despite the storm effects. These findings may be useful for environmental management since they suggest that storms do not profoundly alter long-term changes in water quality that resulted from human development of watersheds.

Seasonal dynamics of nutrients concentration and dissolved oxygen content in the rivers of southern Primorye

Rivers are the main source of terrigenous nutrients to the coastal sea which could be responsible for such adverse impacts as red tides or hypoxia in the estuarine areas. To evaluate the rivers influence on chemical environments in the coastal zone, monitoring of water properties in the rivers of southern Primorye was conducted in 2016 (and continues till nowadays). Retrospective data of chemical measurements on the Razdolnaya, Artemovka, Knevichanka and Ryazanovka rivers in different seasons of 1985 were used for comparison with modern data. Prominent seasonal dynamics of chemical parameters is revealed that generally corresponds to seasonal changes of freshwater discharge caused by monsoon cycle of precipitations. The seasonal dynamics of water temperature is conditioned by climate features of the region and geographic location of the rivers: the temperature at the surface is about 0 о C in February, then rises in spring-summer and decreases in autumn, with the maximum values in August as 26-27 о С for the flat rivers and 18-20 о С for the mountain rivers. The pH variations are conditioned by the carbon dioxide saturation in water, so its level is 6.1-7.2 in winter and 7.4-8.2 in summer. Nutrients, except iron, have the maximum concentration in winter (DIN ~2.5 µM/L, DIP ~0.5 µM/L, silicates ~115.0 µM/L) but the iron concentration is the highest in spring (~0.1 mg/L). However, natural seasonal variation of nutrients is distorted by anthropogenic load for some rivers with industrial and agricultural activity in the basins, including the territories of P.R. China (Suifen/Razdolnaya River): their waters are the richest by nitrogen and phosphorus in summer (DIN ~45.0 µM/L, DIP ~0.5 µM/L) and by dissolved iron in autumn-winter (~0.9-1.3 mg/L). Spatial variability is very similar between all nutrients in any season (correlation coefficients between DIN and Fe concentrations are 0.75-0.99, between DIP and Fe - 0.83-0.99) that means that their growth in the polluted rivers has common nature, presumably a decomposition of organic wastes Being transferred. Transferred to the sea, the nutrient elements of terrestrial origin are converted back to organic matter enhancing the coastal waters productivity, but consequences of this impact are principally different for the natural regime with the winter-spring maximum and for the distorted regime with the summer-fall maximum. Huge oxygen demand determines the lowered DO in the Suyfen/Razdolnaya and Knevichanka in winter. Other rivers of southern Primorye (Ryazanovka, Barabashevka, Kievka, Partizanskaya, Sokolovka, Artemovka) could be considered as «clean» ones, following to Russian standards of water quality. Seasonal variability of oxygen content in their waters is driven by changes of water temperature and photosynthesis. Comparison of the long-term changes in water quality for the rivers Razdolnaya, Artemovka, Knevichanka and Ryazanovka over the last 30 years (relative to 1985) has revealed unfavorable changes of dissolved oxygen content for the Razdolnaya and Knevichanka, whereas the changes are not significant for the Artemovka and the oxygen content has increased for the Ryazanovka. The latter indicates the Ryazanovka water quality improvement that is important since a fish farm is located on the river.

Long-term changes in water quality and ecological status of lakes in the Wielkopolska National Park and its buffer zone with special reference to effectiveness of the lakes’ protection

Abstract This paper evaluates water quality and ecological status of lakes located in the Wielkopolska National Park and its buffer zone. Changes in water quality were analyzed from 1974 to 2012 in order to assess the effectiveness of the protection strategies implemented on the studied lakes since 1957, i.e. the date when the park was established. The ecological status of the lakes was assessed with the use of macrophytes as well as hydromorphological and physicochemical analyses performed in 2012. Changes in water quality of the studied lakes within the last 40 years were analyzed based on available published and unpublished data, as well as field studies. All water bodies are characterized by advanced eutrophication. However, evaluation of the ecological status showed good status of the charophyte-dominated lakes, i.e. Lake Wielkowiejskie and Lake Budzyńskie. Lack of significant differences in physicochemical water qualities between the park and its buffer zone indicated that measures implemented to protect the water, particularly in the park, are ineffective. This study shows that more radical conservation measures are necessary to protect and improve the water quality, not only in WPN and its buffer zone but also in the whole catchment area.

Long-Term Changes in Water Quality and Eutrophication of China’s Liujiang River

Long-Term Changes in Water Quality and Eutrophication of China’s Liujiang River

Editorial: Understanding change in the ecological character of wetlands

The world’s wetlands of international importance are overseen by host nations under processes established through the intergovernmental Convention on Wetlands, commonly known as the Ramsar Convention. Signatory nations to the Convention are required to list at least one wetland as internationally important (known as Ramsar sites) and describe and maintain their ecological character (Gardner and Davidson 2011). Wetlands that satisfy one of a suite of ecological criteria, many of which relate to wetland biodiversity, may be listed as internationally important; the list of internationally important wetlands currently contains 2231 sites covering 214 936 005 ha (17March 2016). The signatories are also required to report on any likely and actual variations in the ecological character of the wetland that may bring it to a state where it may be considered degraded (Finlayson 1996). They are then required to mitigate this degradation or follow prescriptions to delist and offset, with the former being potentially biophysically complex (Alexander et al. 2011) and the latter potentially bedevilled by complex processes (Pittock et al. 2010). As outlined in theMillenniumEcosystemAssessment (MEA 2005), many wetlands, including those listed as Ramsar sites, are increasingly under pressure from (1) anthropogenic climate change causing changes in their hydrology, and (2) the direct impacts of people, notably by modification to their water regimes (increasing water use and/or decreasing water quality), changes in land use, and the introduction or facilitation of invasive species. The Ramsar site description, which is provided at the time of listing of a wetland as internationally important, provides a baseline against which change can be measured. However, as outlined in thisSpecial Issue ofMarineF MacKay et al. 2009). Other techniques to understand the condition or trajectory of change in a wetland include palaeoecology. While these approaches, which are largely sediment-based, may not reconstruct the nature of waterbird or fish populations over time, they are capable of reporting on long-term changes in water quality, sediment load, plant and algal communities and invertebrates, particularly ostracods, cladocerans and chironomids. These records can extend the knowledge of change back centuries or even millennia, but with decreasing resolution over longer periods. With the scope or potential of these approaches being increasingly articulated (Gell 2012), there is an opportunity, or even a need, for contemporary ecologists andmanagers to explore the ecological heritage of their wetlands. Finlayson et al. (2016) also report that there are now many palaeoecological records from sediment sequences collected from Ramsar wetlands across the world, as shown by the papers included in this special issue (Gell and Finlayson 2016). These records show the extent of change through time, with some revealing variation in response to low-frequency climate cycles and others revealing the pervasive andmore recent impacts from industrial development. These studies can be used to reveal how well the ecological condition of awetland at the time of listing as internationally important represents the historical condition and variability of the wetland or if it is a consequence of more recent humanmodification. As explained by Gell et al. (2016), this can create considerable tension in discussions about the ‘ecological character’ of Ramsar-listed wetlands, as well as the ‘limits of acceptable change’, and what constitutes a ‘degraded state’, and can obfuscate the obligations of a signatory nation to remediate or offset adverse ecological change in a wetland of international significance. These issues provided the background for the workshop ‘RamsarWetlands: Understanding Change in Ecological Character’ at Queenscliff, Victoria, Australia, 5–8 November 2013. Sponsored by the International Geosphere-Biosphere Programme (now Future Earth) project PAGES (Past Global Changes), this meeting brought together what was possibly an eclectic group of palaeoecologists andwetlandmanagers andecologists. It included representatives from PAGES and from the Ramsar Convention’s CSIRO PUBLISHING

Management of BWRO systems using long-term monitoring of feed water quality to avoid future membrane process failure

AbstractPumping of wells from aquifers that are used to supply brackish-water reverse osmosis (BWRO) treatment systems commonly causes increases of water salinity in time. Some key aspects of assuring operational security are the magnitude of the water quality changes to assure that treatment can continue without failure of the process, reduction in installed capacity, or the necessity to modify the process by increasing the operational pressure and changing the membranes. An example of a BWRO system that uses a leaky aquifer system as a source of feed water located in Florida shows that careful monitoring of the well water quality and individual well pumping rates over a 10-year operating period can be used to assess the projected long-term changes in water quality with regard to the treatment facility design. The total dissolved solids concentration of the wellfield began with an average TDS of 2,461 mg/L which changed over 10 years to an average of 2,855 mg/L. The variation in time is linear and the pr...