Assessment of models for estimation of land-derived nitrogen loads to shallow estuaries

The performance of several models used to estimate land-derived N loads to shallow receiving estuaries are compared. Models included in the comparison differed in complexity and approach, and predicted either loads or concentrations in estuary water. In all cases, model predictions were compared to measured loads or concentrations, as appropriate. Measured N loads to 9 estuaries on Cape Cod, MA, were obtained as the product of mean concentrations in groundwater about to seep into estuaries multiplied by the annual recharge of groundwater. Measured annual mean N concentrations in estuaries were obtained by extensive sampling surveys. The validity of this procedure to measure loads was verified by comparison against seepage meter data. Responsiveness of model predictions was generally good: predictions increased significantly as measured values increased in 8 of the 10 models evaluated. Precision of predictions was significant for all models. Three models provided highly accurate predictions; correction terms were calculated that could be applied to predictions from the other models to improve accuracy. Four of the models provided reasonable predictive ability. Simulations were run with somewhat different versions of two of the models; in both cases, the modified versions yielded improved predictions. The more complex models tended to be more responsive and precise, but not necessarily more accurate or predictive. Simpler models are attractive because they demand less information for use, but models with more comprehensive formulations, and emphasis on processes tended to perform better. Different models predicted widely different partitioning of land-derived N loads from wastewater, fertilizers, and atmospheric deposition. This is of concern, because mitigation options would be based on such partitioning of predictions. Choice of model to be used in management decisions or for research purposes therefore is not a trivial decision.     

Alternative water management options to reduce vulnerability for climate change in the Netherlands

Urbanization, land subsidence and sea level rise will increase vulnerability of the urbanized low-lying areas in the western part of the Netherlands. In this article possibilities are explored to reduce vulnerability of these areas by implementing alternative water management options. Two main water management fields are distinguished, water supply and flood control. A four-component vulnerability framework is presented that includes threshold capacity, coping capacity, recovery capacity, and adaptive capacity. By using the vulnerability framework it is shown that current water supply and flood control strategies in the Netherlands focus on increasing threshold capacity by constructing higher and stronger dikes, improved water storage and delivery infrastructure. A complete vulnerability decreasing strategy requires measures that include all four capacities. Flood damage reduction, backup water supply systems and emergency plans are measures that can contribute to increasing coping capacity. Recovery capacity can be increased by multi-source water supply, insurance, or establishing disaster funds. Adaptive capacity can be developed by starting experiments with new modes of water supply and urbanization. Including all four components of the vulnerability framework enables better understanding of water and climate related vulnerability of urban areas and enables developing more complete water management strategies to reduce vulnerability.     

Contribution of estuaries to commercial fisheries in temperate Western Australia and the concept of estuarine dependence

Fisheries catch statistics for temperate Western Australia are considered in conjunction with life cycle data to elucidate the importance of estuaries to the commercial and recreational fisheries in this region. The data are used to discuss whether the term estuarine-dependent is strictly applicable to all species of finfish found in abundance in estuaries. Between 1976 and 1984, 96 species of finfish, 7 species of crustaceans and 12 species of mollusks contributed to the large commercial fishery in estuaries, protected coastal areas and open marine waters of temperate Western Australia. The mean annual weight and monetary value (in 1984 terms) of this fishery was 21,355 t and $A151.3×10⁶. The contribution of the weight (4,340 t) and value ($A3.7×10⁶) of the estuarine-dependent species to the total fishery was 20.3 and 2.4%, respectively. Estuarine-dependent marine species frequently use protected inshore waters in temperate Western Australia, and have to do so when they occur in subtropical regions in Western Australia where there are no permanent estuaries. Even the semi-anadromous Perth herring and some species which are estuarinesensu stricto in south-western Australia complete their life cycle within the marine waters of this latter more northern region. Since virtually none of the commercially important marine species in temperate Western Australia can be considered to be entirely dependent on estuaries, and a similar conclusion is valid for many species of marine teleosts found in abundance in estuaries in temperate waters elsewhere in the world, these marine species would be best regarded as estuarine opportunists rather than estuarine dependents.     

Application of a multimetric fish index to assess the environmental condition of South African estuaries

A multimetric fish index, the Estuarine Fish Community Index (EFCI) of Harrison and Whitfield (2004), was applied to data collected for 190 South African estuaries. Estuaries spanned three biogeographic regions and included three distinct estuarine typologies. The EFCI is based on 14 metrics or measures that represent four broad fish community attributes: species diversity and composition, species abundance, nursery function, and trophic integrity. Metric reference conditions and scoring criteria were developed separately for each estuary type within each zoogeographic region. The final EFCI was applied to each estuary by comparing its fish community with the appropriate reference. Index values ranged between 18 (very poor) and 66 (very good). A comparison of the EFCI with independent measures of estuarine condition revealed that the index was able to effectively differentiate between poor and good quality sites. Applying the EFCI to estuaries in which multiple samples were taken also showed that the index is reproducible. The EFCI is both a robust and sensitive method for assessing the ecological condition of estuarine systems; it is also an effective communication tool for converting ecological information into an easily understood format for managers, policy makers, and the general public.     

Eutrophication,water management,and the functioning of Dutch estuaries and coastal lagoons

A number of major European rivers (especially the Rhine) have a prevailing influence on the nutrient cycling of most Dutch estuaries. Owing to the increased loading of the estuaries with nitrogen and phosphorus compounds, effects of eutrophication on the biological communities are most evident in the tidal Western Wadden Sea and in a nontidal brackish lagoon, Veerse Meer. Whether the relation between changed nutrient loadings and changed biomass and production of primary and secondary producers in the turbid tidal Dutch ecosystems should be considered as a causal relation is questionable. The very widespread practice of lagoon modification confuses the effects of nutrient loading.     

Comparison of different models of water quality index in the assessment of surface water quality

The method of water quality index is widely used in evaluation of the surface water quality because of its capability to summarize a number of water quality parameters into one numeric value, along with defined scale of water quality range. The current investigation includes application of modified model for calculating water quality index values, generated using experimental data and literary models. Software was created using modular design. Fourteen physical, chemical and biological parameters representing water quality state along with the assigned weights were elected. Comparison between models generated based on Serbian and American models of water quality index was done. Selected parameters differ mutually in number of parameters used in calculation of index, as well as in values of the weighting factors. In order to enable an efficient water quality analysis and to reconcile the requirements of both Serbian and American model, two software solutions were generated and processed on the example of the water quality of the Danube River in Serbia. Danube water quality was assessed at seventeen measuring locations along the river flow. Index values obtained from the two generated software applications were compared with the results of the official Serbian online calculator. Water quality determined using new generated models shows stricter approach and one class lower water quality compared to the existing Serbian model. Therefore, modular and open-generated simulation software is of great significance for the comparison and testing of different water quality models, not just those two shown in this study.     

Correction to: Assessing real options in urban surface water flood risk management under climate change

Windblown dust originating in China and Mongolia causes health effects and agricultural damage in its source areas and causes Asian dust events in Japan. An early warning system that could be combined with weather forecasts would be helpful in preventing serious damage. However, it is difficult to specify source areas of dust with current dust modeling systems because land surface information, including vegetation coverage and land surface soil water content, is inadequate. To find and monitor dust source regions, a semi-real-time dust erodibility map was developed based on MODIS satellite data that focuses particularly on the threshold wind speed in a target area of northeast Asia including China and Mongolia (35°–50°N, 75°–120°E). The mapping system incorporates satellite data on snow cover, areas of frozen soil, surface soil water content, and vegetation cover.     

A method to assess the freshwater inflow requirements of estuaries and application to the Mtata estuary, South Africa

The National Water Act (Act 36 of 1998) in South Africa recognizes basic human water requirements as well as the need to sustain the country's freshwater and estuarine ecosystems in a healthy condition for present as well as future generations. In this Act, provision is made for a water reserve to be estimated prior to the authorization of water use (e.g., for agriculture, large volume residential and industrial uses) through licensing. This reserve is the water required to satisfy basic human needs (i.e., 25 1 person^?1 d^?1) and to protect aquatic ecosystems to ensure present and future sustainable use of the resource. This led the Departments of Water Affairs and Forestry and estuarine scientists throughout South Africa to develop a method to determine the freshwater inflow requirements of estuaries. The method includes documenting the geographical boundaries of the estuary and determining estuarine health by comparing the present state of the estuary with a predicted reference condition with the use of an Estuarine Health Index. The importance of the estuary as an ecosystem is taken from a national rating system and together with the present health is used to set an Ecological Reserve Category for the estuary. This category represents the level of protections afforded to an estuary. Freshwater is then reserved to maintain the estuary in that Ecological Reserve Category. The Reserve, the quantity and quality of freshwater required for the estuary, is determined using an approach where realistic future river runoff scenarios are assessed, together with data for present state and reference conditions, to evaluate the extent to which abiotic and biotic conditions within an estuary are likely to vary with changes in river inflow. Results from these evaluations are used to select an acceptable river flow scenario that represents the highest reduction in freshwater inflow that will still protect the aquatic ecosystem of the estuary and keep it in the desired Ecological Reserve Category. The application of the Reserve methodology to the Mtata estuary is described.     

Calculating optical water quality targets to restore and protect submersed aquatic vegetation: Overcoming problems in partitioning the diffuse attenuation coefficient for photosynthetically active radiation

Submersed aquatic vegetation (SAV) is an important component of shallow water estuarine systems that has declined drastically in recent decades. SAV has particularly high light requirements, and losses of SAV have, in many cases, been attributed to increased light attenuation in the water column, frequently due to coastal eutrophication. The desire to restore these valuable habitats to their historical levels has created the need for a simple but accurate management tool for translating light requirements into water quality targets capable of supporting SAV communities. A procedure for calculating water quality targets for concentrations of chlorophyll and total suspended solids (TSS) is derived, based on representing the diffuse attenuation coefficient for photosynthetically active radiation, K_d(PAR), as a linear function of contributions due to water plus colored dissolved organic matter (CDOM), chlorophyll, and TSS. It is assumed that K_d(PAR) conforms to the Lambert-Beer law. Target concentrations are determined as the intersection of a line representing intended reduction of TSS and chlorophyll by management actions, with another line describing the dependence of TSS on chlorophyll at a constant value of K_d(PAR). The validity of applying the Lambert-Beer law to K_d(PAR) in estuarine waters was tested by comparing the performance of a linear model of K_d(PAR) with data simulated using a more realistic model of light attenuation. The linear regression model tended to underestimate K_d(PAR) at high light attenuation, resulting in erroneous predictions of target concentrations at shallow restoration depths. The errors result more from the wide spectral bandwidth of PAR, than from irrecoverable nonlinearities in the diffuse attenuation coefficient per se. In spite of the failure of the Lambert-Beer law applied to K_d(PAR), the variation of TSS with chlorophyll at constant K_d(PAR) determined by the more mechanistic attenuation model was, nevertheless, highly linear. Use of the management tool based on intersecting lines is still possible, but coefficients in the line describing the dependence of TSS on chlorophyll at constant K_d(PAR) must be determined empirically by application of an optical model suitably calibrated for the region of interest. An example application of the procedure to data from the Rhode River, Maryland, indicates that approximately 15% reduction in both TSS and chlorophyll concentrations, or 50% reduction in chlorophyll alone, will be needed to restore conditions for growth of SAV to levels that existed in the late 1960s.     

Waste water management and water quality of river Yamuna in the megacity of Delhi

The present study aims at assessing water quality of river Yamuna in one of the world’s most polluted and populated megacities, Delhi. Conductivity, salinity and sodium content were within the permissible categories. Chloride concentration exceeded acceptable levels of drinking water guidelines. Water quality was poor at all locations with respect to heavy metal contamination, especially along the lower section of the Delhi stretch. Heavy metal concentrations were manifold higher than the acceptable limits of drinking water according to the BIS guidelines and reached ~29, 4.9, 10, 31, 27, 83, 7.3 and 27 times higher, respectively, for metals aluminum, copper, chromium, cadmium, iron, lead, manganese and nickel. The Najafgarh and the Shahdara drains are major point sources. Low oxidation–reduction potential reflected high organic loads and traces of eutrophication together with significant levels of nitrate and total phosphate. Discharges from agriculture, sewage and power plants could be important sources of high metal concentration. This calls for urgent measures to be taken for prevention of metal contamination in the river, through both, technology as well as implementation of regulations in order to sustain huge populations in megacities like Delhi. Waste water treatment from point sources needs tremendous improvement on the city. Treatment of the entire waste generated up to the tertiary level is required for minimizing dissolved solids, especially toxic metals, and rendering reuse in agriculture suitable. Treatment plants need proper operation, maintenance, uninterrupted power supply and regular monitoring. Various measure and programmes need to be undertaken to ensure safe reuse of wastewater.     

应用单纯形-模拟退火混合算法估计河流水质参数

将由单纯形法(SM)与模拟退火(SA)两种算法构成的混合算法(SMSA),应用于求解分析瞬时投放示踪剂情况下的一维河流水团示踪试验数据,估计河流水质参数的函数优化问题。分别就不同的降温指数、内循环次数与新状态产生函数中的扰动系数等算法控制参数对混合算法和改进模拟退火法的收敛速度的影响,进行了数值实验。结果表明,SMSA混合优化算法对于求解估计河流水质参数的函数优化问题是非常有效的。在实验条件下,与单一具有记忆功能的改进模拟退火法的水质参数计算结果相比较,SMSA混合算法具有:①混合算法的收敛速度明显优于改进模拟退火法;②降温指数和内循环次数对SMSA混合算法的收敛速度影响非常微弱;③新状态产生函数中的随机扰动幅度大小对算法收敛速度具有较为明显的影响等特点。     

The historical context of water quality management for the Delaware estuary

The Delaware Estuary, bounded by the states of Delaware, New Jersey and Pennsylvania, is located in one of the most complex urban-industrial regions in the United States. Water pollution of the estuary was observable over two centuries ago and progressively worsened until after World War II. Four distinct governmental responses to the pollution have led to the vastly improved water quality of today. A fifth-generation response, now being initiated, is oriented toward remaining problems, including toxic contamination of the water column, bottom materials and aquatic life. Changes in water quality and the institutional responses to pollution are traced to demonstrate the evolutionary process of water pollution control.     

赣江下游污染负荷与水质响应关系模型

为了研究赣江下游入河污染物对河流水质的影响,建立了基于WASP（Water quality Analysis Simulation Program）模型富营养化原理和ELADI（Eulerian-Lagrangian Alternating Direction Implicit Method）有限差分方法的正交曲线平面二维水环境模型WESC2D（Two-Dimensional Water Environment Simulation Code）。模型采用基于双线性插值及亚网格技术的欧拉-拉格朗日方法求解对流项,在简单的浓度峰输运和赣江下游溶解氧变化过程算例检验的基础上,计算与分析了赣江下游入河排污口氨氮污染负荷与水质之间的动态响应关系。模拟与分析结果表明,WESC2D模型的计算结果与解析解吻合良好,有效地减少了欧拉-拉格朗日方法的数值耗散,并为赣江下游污染负荷与水质响应关系计算提供了重要工具。     

Using the VIKOR method to evaluate the design of a water quality monitoring network in a watershed

Water quality monitoring stations play critical roles for analyzing the information of water quality conditions in a watershed. The understanding of water quality conditions of a river system is very important for water resource management. This study applied the VIKOR method, a commonly used method in multiple criteria analysis, to evaluate the design of the water quality monitoring network in the Taipei Water Resource Domain (TWRD). Five criteria were selected for multiple criteria analysis: non-point source pollution, green cover ratio, landslide area ratio, over-utilization area ratio of hillsides, and density of water quality monitoring stations. This study recommended several areas where there is a need for sufficient monitoring records of water quality. The result shows that more monitoring stations are needed in the Bei-Shih Creek Basin. Although the Nan-Shih Creek Basin covers larger area than the Bei-Shih Creek Basin and the Sin-Dian Creek Basin, it can accept less density of water quality monitoring stations.     

Climate and hydrological models to assess the impact of climate change on hydrological regime: a review

Quantitative knowledge about the impacts of climate change on the hydrological regime is essential in order to achieve meaningful insights to address various adverse consequences related to water such as water scarcity, flooding, drought, etc. General circulation models (GCMs) have been developed to simulate the present climate and to predict future climatic change. But, the coarse resolution of their outputs is inefficient to resolve significant regional scale features for assessing the effects of climate change on the hydrological regimes, thus restricting their direct implementation in hydrological models. This article reviews hierarchy and development of climate models from the early times, importance and inter-comparison of downscaling techniques and development of hydrological models. Also recent research developments regarding the evaluation of climate change impact on the hydrological regime have been discussed. The article also provides some suggestions to improve the effectiveness of modelling approaches involved in the assessment of climate change impact on hydrological regime.     

Evaluating the accuracy of ANN and LR models to estimate the water quality in Zarivar International Wetland,Iran

One of the most important qualitative aspects of wetland ecosystem management is preserving the natural quality of water in such environments. This would not be achievable unless continuous water quality monitoring is implemented. With the recent advances in remote sensing technology, this technology could assist us to produce accurate models for estimating water quality variables in the ecosystem of wetlands. The present study was carried out to evaluate the capability of remote sensing data to estimate the water quality variables [pH, total suspended solids (TSS), total dissolved solids (TDS), turbidity, nitrate, sulfate, phosphate, chloride and the concentration of chlorophyll a] in Zarivar International Wetland using linear regression (LR) and artificial neural network (ANN) models. For this purpose, spectral reflectance of bands 2, 3, 4 and 5 of the OLI sensor of Landsat 8 was utilized as the input data and the collected chemical and physical data of water samples were selected as the objective data for both ANN and LR models. Based on our results overall, ANN model was the proper model compared with LR model. The spectral reflectance in bands 5 and 4 of OLI sensor revealed the best results to estimate TDS, TSS, turbidity and chlorophyll in comparison with other used bands in ANN model, respectively. We conclude that OLI sensor data are an excellent means for studying physical properties of water quality and comparing its chemical properties.     

Use of geographical information system and water quality index to assess groundwater quality in El Khairat deep aquifer (Enfidha, Central East Tunisia)

Groundwater is the most important natural resource used for drinking by many people around the world, especially in rural areas. In Tunisia, since the quantity and the quality of water available for different uses is variable from one place to another, groundwater quality in El Khairat deep aquifer was evaluated for its suitability for drinking purposes. To this end, an attempt has been made for the first time in order to determine spatial distribution of groundwater quality parameters and to identify places with the best quality for drinking within the study area based on: (1) an integrated analysis of physical?Cchemical parameters, (2) use of Geographical Information System, and (3) Water Quality Index (WQI) calculation. The physical?Cchemical results were compared with the World Health Organization (WHO) standards for drinking and public health, in order to have an overview of the present groundwater quality. According to the overall assessment of the basin, almost all the parameters analyzed are above the desirable limits of WHO. Using GIS contouring methods with Arcview 3.2a, spatial distribution maps of pH, TDS, EC, TH, Cl, HCO₃, SO₄, NO₃, Ca, Mg, Na, and K have been created. The spatial analysis of groundwater quality patterns of the study area shows that the TDS value increases from north-west to south-east following the general trend of the Khairat aquifer flow direction. The spatial distribution map of TH shows that a majority of the groundwater samples falls in the very hard category. WQI was used to assess the suitability of groundwater from the study area for human consumption. From the WQI assessment, over 82% of the water samples fall within the ??Poor?? and ??Very poor?? categories, suggesting that groundwater from the south-eastern of the El Khairat deep aquifer is unsuitable for drinking purposes.     

Use of alternative conceptual models to assess the impact of a buried valley on groundwater vulnerability

A buried valley incised into a sequence of pre-Quaternary sediments is shown to seriously affect the vulnerability of groundwater. Often the existence of buried valleys is not known or is not described explicitly in a hydrogeological model. In the present study, two numerical groundwater models, representing two alternative conceptual models, were produced to help quantify the effect of the valley on groundwater vulnerability. One model included the buried valley and the other did not. Both models were subjected to calibration and were found to describe hydraulic head and river discharge equally well. Even though the two models showed similar calibration statistics; fluxes, travel paths and travel times were affected by the inclusion of the buried valley. The recharge area and the groundwater age of potential abstraction wells placed in the pre-Quaternary deep aquifers surrounding the buried valley were different for the two models, with significantly higher vulnerability when the valley was included in the model. Based on the results of the present study, it is concluded that a buried valley may not always be detectable when calibrating a wrong conceptual model. If reliable results should be obtained a good geological model has to be constructed.     

Application of formation water geochemistry to assess seal integrity of the Gotnia Formation,Kuwait

A very large database of formation water geochemistry has been acquired for the Kuwait petroleum system. This database makes it possible to explore the geological history of Kuwait’s formation and ground waters in a way that is not possible by other means. Working at this regional scale spatial and formational variation in groundwater chemistry in Kuwait identifies lithostratigraphy and physical barriers to flow that can be explored in the context of Kuwait’s geological history. Cretaceous oil reservoirs in north Kuwait have formation water saturated with Na (>50%) that is anomalously abnormal in salinity for its depth. The most likely subsurface source of such saline water is the Upper Jurassic Gotnia Formation which comprises beds of evaporite halite, and/or pre-Gotnia formations of deeper reservoirs. To reach their current location, both parts of the Gotnia and Hith formations must have been breached. To date, this is the only evidence to show that the sealing capacity of the Gotnia Formation has been overcome, implying that the formation, and therefore units beneath, are capable of sourcing fluids to younger and shallower reservoirs. Given the ubiquity of samples of formation water in many other regions, applying formation water geochemistry to other petroleum systems would appear a good method for evaluating basin models and understanding of fluid migration in mature petroleum provenances.