Modelling the relative impact of rivers (Scheldt/Rhine/Seine) and Western Channel waters on the nutrient and diatoms/Phaeocystis distributions in Belgian waters (Southern North Sea)

The coastal areas of the Southern North Sea (SNS) experience eutrophication problems resulting from freshwater nitrogen (N) and phosphorus (P) inputs from rivers. In particular, massive blooms of Phaeocystis colonies occur in Belgian waters. In this region, water masses result from the mixing of Western Channel (WCH) waters transported through the Straits of Dover with nutrient-rich freshwater from the Scheldt, the Rhine and Meuse, the Seine, the Thames and other smaller rivers. However, the relative contribution of the WCH and each river to the inorganic nutrient pool and the impact on the phytoplankton community structure (diatoms and Phaeocystis) are not known. In order to effectively manage the eutrophication problems, it is necessary to know: (i) the relative contribution of the WCH and of each river impacting the region and (ii) the relative effect of a N and/or P nutrient reduction on the Phaeocystis blooms. To answer these questions, sensitivity tests (1% nutrient reduction) and nutrient reduction scenarios (50% nutrient reduction) have been performed with a three-dimensional (3D) coupled physical–biogeochemical model (MIRO&CO-3D).MIRO&CO-3D results from the coupling of the COHERENS 3D hydrodynamic model with the ecological model MIRO. The model has been set up for the region between 48.5°N, 4°W and 52.5°N, 4.5°E and run to simulate the annual cycle of carbon, inorganic and organic nutrients, phytoplankton (diatoms and Phaeocystis), bacteria and zooplankton (microzooplankton and copepods) in the SNS under realistic forcing (meteorology and river inputs) for the period 1991–2003. The relative contribution of the WCH waters and of the different rivers on the inorganic nutrient pool available for phytoplankton (diatoms and Phaeocystis) growth is assessed by decreasing by 1% the nutrient (dissolved inorganic nitrogen, DIN and inorganic phosphate, PO₄) inputs from the WCH and from, respectively, the Scheldt (and smaller Belgian rivers), the Rhine/Meuse and the Seine (and smaller French rivers) [sensitivity tests]. The relative role of N and P reduction on the diatoms/Phaeocystis distribution is further explored by simulations with 50% reduction of the total (inorganic and organic) N and total P river inputs [nutrient reduction scenarios]. These scenarios allow assessing the impact of the expected 50% reduction of river nutrient inputs resulting from the implementation of nutrient reduction policy.Results of the sensitivity tests suggest that the impact of a 1% reduction of river nutrient inputs on surface nutrients (DIN and PO₄) over the Belgian Exclusive Economic Zone (EEZ) area is similar for the Seine and the Scheldt, which are in turn greater than for the Rhine. However, a hypothetical 1% reduction of nutrient input from the WCH boundary would have a higher impact than for the Scheldt. The impact of nutrient reduction is higher for DIN than for PO₄ whatever the river (contrary to the WCH). DIN is more sensitive to riverine nutrient reduction because the rivers are over enriched in DIN compared to PO₄. The sensitivity tests suggest also that a PO₄ river input reduction would result in a N:P increase and a DIN river input reduction would result in a N:P decrease but that a combined (PO₄ and DIN) input reduction would reduce the N:P ratio at sea.From 50% nutrient reduction scenarios, model results suggest that a total P reduction would induce a significant decrease of diatoms and a small (coast) to negligible (offshore) decrease of Phaeocystis biomass. On the contrary, a total N reduction would induce a significant decrease of Phaeocystis biomass and a moderate increase of diatoms. When N and P river input reductions are combined, the model predicts a significant decrease of Phaeocystis biomass in Belgian waters and a significant decrease of diatom biomass in the coastal waters and a small increase offshore. A future management plan aiming at Phaeocystis reduction should thus prioritise N reduction.     

Heavy metal transport in large river systems: heavy metal emissions and loads in the Rhine and Elbe river basins

Pollutant transport and management in the Rhine and Elbe basins is still of international concern, since certain target levels set by the international committees for protection of both rivers have not been reached. The analysis of the chain of emissions of point and diffuse sources to river loads will provide policy makers with a tool for effective management of river basins. The analysis of large river basins such as the Elbe and Rhine requires information on the spatial and temporal characteristics of both emissions and physical information of the entire river basin. In this paper, an analysis has been made of heavy metal emissions from various point and diffuse sources in the Rhine and Elbe drainage areas. Different point and diffuse pathways are considered in the model, such as inputs from industry, wastewater treatment plants, urban areas, erosion, groundwater, atmospheric deposition, tile drainage, and runoff. In most cases the measured heavy metal loads at monitoring stations are lower than the sum of the heavy metal emissions. This behaviour in large river systems can largely be explained by retention processes (e.g. sedimentation) and is dependent on the specific runoff of a catchment. Independent of the method used to estimate emissions, the source apportionment analysis of observed loads was used to determine the share of point and diffuse sources in the heavy metal load at a monitoring station by establishing a discharge dependency. The results from both the emission analysis and the source apportionment analysis of observed loads were compared and gave similar results. Between 51% (for Hg) and 74% (for Pb) of the total transport in the Elbe basin is supplied by inputs from diffuse sources. In the Rhine basin diffuse source inputs dominate the total transport and deliver more than 70% of the total transport. The diffuse hydrological pathways with the highest share are erosion and urban areas. Copyright © 2002 John Wiley & Sons, Ltd.     

Nitrogen and phosphorus losses from agricultural systems in China: A meta-analysis

Studies worldwide have indicated that agricultural pollution is the main source of nitrogen and phosphorus (N and P) in surface waters. A systematic understanding of N and P sources and sinks in agricultural systems is important for selecting the appropriate remedial strategies to control nutrient losses and water pollution. Based on nationwide data and a long-term monitoring program in Southeast China, the nationwide spatial and temporal patterns of N and P losses and the relationships between such losses and N and P inputs and rainfall were analyzed. The results showed that the annual nutrient losses from agricultural systems in China strongly varied, and the N/P values ranged from 0.01 to 51.0, with a majority at approximately 0–20, and an arithmetic mean of 9.73; these values mostly overlap the suitable range of N/P (6–15) for red bloom algae.     

Phosphorus storage,transport and export dynamics in the Foron River watershed

Phosphorus (P) export from the Foron River watershed was intensively monitored. Water was analysed for total P, soluble total P, soluble orthophosphate and suspended solids. Watershed soils and river sediments were sampled and the size fraction <0·2 mm analysed for total P, water extractable P, bioavailable P, 1 minute exchangeable P and P fixation capacity. Interstitial waters were analysed for soluble total P. Four hydrological conditions recurred, two during low river flows and two during increased flow. The first occurs in dry weather with a constant or decreasing flow over at least seven days and when there is no surface runoff. Exported phosphorus, predominately soluble and bioavailable, is from point sources. Phosphorus inputs exceed P export so P accumulates in the river. The second condition occurs when a small storm flow increases the average seven-day flow to exceed the preceding weekly average. Phosphorus export exceeds P inputs and originates from urban runoff, point sources and release of P stored in the river. Exported P is largely particulate but highly bioavailable. The third condition is when substantial runoff follows at least a seven-day period of constant or decreasing flow. Phosphorus export is from diffuse urban runoff. All the P stored is exported. Exported P is highly bioavailable. High concentrations and fluxes of P export are often seen. The fourth condition happens when the soils are wet and increased flow is from both urban and agricultural runoff. Phosphorus export from diffuse agricultural runoff predominates and is largely not bioavailable. Phosphorus concentrations are low but export fluxes are high when flows are high. These hydrological conditions, when integrated with concepts of mass balance define a phosphorus export typology comprising four regimes. These regimes explain total phosphorus (TP) storage, transport and export patterns, changes in P speciation and allow identification of probable sources of TP in the Foron river watershed. © 1998 John Wiley & Sons, Ltd.     

Controls on surface water chemistry in two lake‐watersheds in the Adirondack region of New York: differences in nitrogen solute sources and sinks

The southwestern Adirondack region of New York receives among the highest rates of atmospheric nitrogen (N) deposition in the USA. Atmospheric N deposition to sensitive ecosystems, like the Adirondacks, may increase the acidification of soils through losses of exchangeable nutrient cations, and the acidification of surface waters associated with enhanced mobility of nitrate (NO₃^?). However, watershed attributes, including surficial terrestrial characteristics, in‐lake processing, and geological settings, have been found to complicate the relationships between atmospheric N deposition and N drainage losses. We studied two lake‐watersheds in the southwestern Adirondacks, Grass Pond and Constable Pond, which are located in close proximity (～26 km) and receive similarly high N deposition, but have contrasting watershed attributes (e.g. wetland area, geological settings). Since the difference in the influence of N deposition was minimal, we were able to examine both within‐ and between‐watershed influences of land cover, the contribution of glacial till groundwater inputs, and in‐lake processes on surface water chemistry with particular emphasis on N solutes and dissolved organic carbon (DOC). Monthly samples at seven inlets and one outlet of each lake were collected from May to October in 1999 and 2000. The concentrations of NO₃^? were high at the Grass Pond inlets, especially at two inlets, and NO₃^? was the major N solute at the Grass Pond inlets. The concentrations of likely weathering products (i.e. dissolved Si, Ca²⁺, Mg²⁺, Na⁺) as well as acid neutralizing capacity and pH values, were also particularly high at those two Grass Pond inlets, suggesting a large contribution of groundwater inputs. Dissolved organic N (DON) was the major N solute at the Constable Pond inlets. The higher concentrations of DON and DOC at the Constable Pond inlets were attributed to a large wetland area in the watershed. The DOC/DON ratios were also higher at the Constable Pond inlets, possibly due to a larger proportion of coniferous forest area. Although DON and DOC were strongly related, the stronger relationship of the proportion of wetland area with DOC suggests that additional factors regulate DON. The aggregated representation of watershed physical features (i.e. elevation, watershed area, mean topographic index, hypsometric‐analysis index) was not clearly related to the lake N and DOC chemistry. Despite distinctive differences in inlet N chemistry, NO₃^? and DON concentrations at the outlets of the two lakes were similar. The lower DOC/DON ratios at the lake outlets and at the inlets having upstream ponds suggest the importance of N processing and organic N sources within the lakes. Although an inverse relationship between NO₃^? and DOC/DON has been suggested to be indicative of a N deposition gradient, the existence of this relationship for sites that receive similar atmospheric N deposition suggest that the relationship between NO₃^? and the DOC/DON ratio is derived from environmental and physical factors. Our results suggest that, despite similar wet N deposition at the two watershed sites, N solutes entering lakes were strongly affected by hydrology associated with groundwater contribution and the presence of wetlands, whereas N solutes leaving lakes were strongly influenced by in‐lake processing. Copyright © 2006 John Wiley & Sons, Ltd.     

Some challenges of an "upside down" nitrogen budget--science and management in Greenwich Bay, RI (USA)

When nutrients impact estuarine water quality, scientists and managers instinctively focus on quantifying and controlling land-based sources. However, in Greenwich Bay, RI, the estuary opens onto a larger and more intensively fertilized coastal water body (Narragansett Bay). Previous inventories of nitrogen (N) inputs to Greenwich Bay found that N inputs from Narragansett Bay exceeded those from the local watershed, suggesting that recent efforts to reduce local watershed N loads may have little effect on estuarine water quality. We used stable isotopes of N to characterize watershed and Narragansett Bay N sources as well as the composition of primary producers and consumers throughout Greenwich Bay. Results were consistent with previous assessments of the importance of N inputs to Greenwich Bay from Narragansett Bay. As multiple N sources contribute to estuarine water quality, effective management requires attention to individual sources commensurate with overall magnitude, regardless of the political complications that may entail.     

A nutrient loading budget for Biscayne Bay, Florida

The water quality in Biscayne Bay has been significantly affected by past and continuing coastal and watershed development. The nutrient concentrations in the Bay have been dramatically changed by the conversion of natural creeks and sheet flow freshwater inputs to rapid and episodic canal inputs from the large and rapidly expanding Miami metropolitan area. This study is an evaluation of nutrient loadings to Biscayne Bay for 1994-2002 from canal, atmospheric, and groundwater sources. Dissolved inorganic nitrogen (DIN, as nitrate, nitrite, and ammonium) and total phosphorus (TP) loadings by the canals were influenced by their geographic locations relative to discharge amount, watershed land use, stormwater runoff, and proximity to landfills. Annual budgets showed that canals contributed the bulk of N loading to the bay as 1687.2 metric ton N yr(-1) (88% total load). Direct atmospheric DIN load for Biscayne Bay was only 231.7 ton N yr(-1), based on surface area. Of the canal DIN load, nitrate+nitrite (NO(x)(-)) loading (1294.5 ton N yr(-1)) made up a much greater proportion than that of ammonium (NH(4)(+), 392.6 ton N yr(-1)). In the urbanized north and central Bay, canal DIN load was evenly split between NO(x)(-) and NH(4)(+). However, in the south, 95% of the DIN load was in the form of NO(x)(-), reflecting the more agricultural land use. Contrary to N, canals contributed the only 66% of P load to the bay (27.5 ton P yr(-1)). Atmospheric TP load was 14 ton Pyr(-1). In the north, canal P load dominated the budget while in the south, atmospheric load was almost double canal load. Groundwater inputs, estimated only for the south Bay, represented an important source of N and P in this zone. Groundwater input of N (141 ton N yr(-1)) was about equal to atmospheric load, while P load (5.9 ton P yr(-1)) was about equal to canal load.     

Strontium isotope identification of water mixing and recharge sources in a river system (Oder River,central Europe): A quantitative approach

This study uses Sr isotope composition (⁸⁷Sr/⁸⁶Sr) and Sr content of waters of the Oder, one of the largest rivers in central Europe, to fingerprint natural and anthropogenic contributions to its Sr budget and to evaluate water mixing processes in its hydrological system. It also demonstrates a simple method of quantifying natural and anthropogenic Sr inputs in the watershed. The method has potential for environmental and archaeological research because past Sr geochemistry of river water can easily be reconstructed. For the first time, a catchment‐scale impact of anthropogenic sources on the Sr budget of a middle‐size river is shown in a quantitative way. The water of the Oder is characterized by a relatively uniform Sr isotope composition, from 0.7100 to 0.7108, contrasting with strong variations in Sr concentration, from 0.25 to 1.27 mg/L. There is a general seasonal trend in variability, with waters becoming more radiogenic and dilute with respect to the Sr in the spring time. This Sr systematics differs significantly from the Sr budgets of the majority of the Oder tributaries that exhibit more radiogenic composition and systematically lower Sr concentrations. A mixing scenario in the Oder involves Sr contribution from four principal water sources: (a) shallow ground waters with Sr derived from near‐surface weathering of silicates, (b) moderately radiogenic mine waters from the Upper Silesian Coal Basin, (c) unradiogenic mine waters from the Permian sequence of the copper district, and (d) unradiogenic ground waters from shallow‐seated Palaeogene, Neogene, and Mesozoic aquifers. The Sr budget of the Oder is primarily controlled by inputs of dissolved Sr from anthropogenic sources, which overprint the natural background, controlled by geology. Thus, about 47.5% of Sr originates from agriculture, industrial, and municipal additions, 31.5% from mine water inputs, and only 21% from natural sources, that is, rock weathering and atmospheric precipitation. Reconstruction of the past Sr chemistry of the Oder reveals that its present‐day Sr isotope composition is temporary and significantly different from that of the preindustrial times.     

Temporal and spatial variations in nutrient stoichiometry and regulation of phytoplankton biomass in Hong Kong waters: influence of the Pearl River outflow and sewage inputs

In 2001, the Hong Kong government implemented the Harbor Area Treatment Scheme (HATS) under which 70% of the sewage that had been formerly discharged into Victoria Harbor is now collected and sent to Stonecutters Island Sewage Works where it receives chemically enhanced primary treatment (CEPT), and is then discharged into waters west of the Harbor. The relocation of the sewage discharge will possibly change the nutrient dynamics and phytoplankton biomass in this area. Therefore, there is a need to examine the factors that regulate phytoplankton growth in Hong Kong waters in order to understand future impacts. Based on a historic nutrient data set (1986-2001), a comparison of ambient nutrient ratios with the Redfield ratio (N:P:Si=16:1:16) showed clear spatial variations in the factors that regulate phytoplankton biomass along a west (estuary) to east (coastal/oceanic) transect through Hong Kong waters. Algal biomass was constrained by a combination of low light conditions, a rapid change in salinity, and strong turbulent mixing in western waters throughout the year. Potential stoichiometric Si limitation (up to 94% of the cases in winter) occurred in Victoria Harbor due to the contribution of sewage effluent with high N and P enrichment all year, except for summer when the frequency of stoichiometric Si limitation (48%) was the same as P, owing to the influence of the high Si in the Pearl River discharge. In the eastern waters, potential N limitation and N and P co-limitation occurred in autumn and winter respectively, because of the dominance of coastal/oceanic water with low nutrients and low N:P ratios. In contrast, potential Si limitation occurred in spring and a switch to potential N, P and Si limitation occurred in eastern waters in summer. In southern waters, there was a shift from P limitation (80%) in summer due to the influence of the N-rich Pearl River discharge, to N limitation (68%) in autumn, and to N and P co-limitation in winter due to the dominance of N-poor oceanic water from the oligotrophic South China Sea. Our results show clear temporal and spatial variations in the nutrient stoichiometry which indicates potential regulation of phytoplankton biomass in HK waters due to the combination of the seasonal exchange of the Pearl River discharge and oceanic water, sewage effluent inputs, and strong hydrodynamic mixing from SW monsoon winds in summer and the NE monsoon winds in winter.     

Nitrogen emissions into freshwater ecosystems: is there a need for nitrate elimination in all wastewater treatment plants?

Excessive inputs of phosphorus and nitrogen are the main reasons of eutrophication of inland waters and coastal areas. Large efforts have been made to control phosphorus, but the measures to reduce nitrogen emissions failed at least partly. While it was possible to reduce nitrogen emissions from industry and municipal wastewater treatment plants, diffuse sources are showing only very minor decline. Examples of limnetic, marine and coastal systems are given to review the current knowledge about nitrogen transformation and the effects of nitrate in the environment. When N is the limiting nutrient in a particular water body, this does not necessarily mean that phytoplankton is controllable by NO₃^– removal. In systems with problems due to a high redox‐sensitive internal phosphorus load and under certain constraints, nitrate may be used as an ecotechnological measure to prevent anaerobic phosphorus release from sediments. Model simulations are used to demonstrate this. A schematic model of redox‐mediated temporal phosphorus storage in riverine lake sediments with short retention time is proposed. We conclude that while anthropogenic nitrogen emissions are a global problem, no fast and simple single solution exists. Additional nitrogen removal in wastewater treatment will have no effect, as long as diffuse sources and nitrate concentrations in groundwater remain at a high level. Emission reductions should be achieved in an integrated way, taking direct and indirect effects into account. In this sense, case by case decisions and a new definition of “sensitive areas” are required.     

Temporal and spatial variations in nutrient stoichiometry and regulation of phytoplankton biomass in Hong Kong waters: Influence of the Pearl River outflow and sewage inputs

In 2001, the Hong Kong government implemented the Harbor Area Treatment Scheme (HATS) under which 70% of the sewage that had been formerly discharged into Victoria Harbor is now collected and sent to Stonecutters Island Sewage Works where it receives chemically enhanced primary treatment (CEPT), and is then discharged into waters west of the Harbor. The relocation of the sewage discharge will possibly change the nutrient dynamics and phytoplankton biomass in this area. Therefore, there is a need to examine the factors that regulate phytoplankton growth in Hong Kong waters in order to understand future impacts. Based on a historic nutrient data set (1986–2001), a comparison of ambient nutrient ratios with the Redfield ratio (N:P:Si = 16:1:16) showed clear spatial variations in the factors that regulate phytoplankton biomass along a west (estuary) to east (coastal/oceanic) transect through Hong Kong waters. Algal biomass was constrained by a combination of low light conditions, a rapid change in salinity, and strong turbulent mixing in western waters throughout the year. Potential stoichiometric Si limitation (up to 94% of the cases in winter) occurred in Victoria Harbor due to the contribution of sewage effluent with high N and P enrichment all year, except for summer when the frequency of stoichiometric Si limitation (48%) was the same as P, owing to the influence of the high Si in the Pearl River discharge. In the eastern waters, potential N limitation and N and P co-limitation occurred in autumn and winter respectively, because of the dominance of coastal/oceanic water with low nutrients and low N:P ratios. In contrast, potential Si limitation occurred in spring and a switch to potential N, P and Si limitation occurred in eastern waters in summer. In southern waters, there was a shift from P limitation (80%) in summer due to the influence of the N-rich Pearl River discharge, to N limitation (68%) in autumn, and to N and P co-limitation in winter due to the dominance of N-poor oceanic water from the oligotrophic South China Sea. Our results show clear temporal and spatial variations in the nutrient stoichiometry which indicates potential regulation of phytoplankton biomass in HK waters due to the combination of the seasonal exchange of the Pearl River discharge and oceanic water, sewage effluent inputs, and strong hydrodynamic mixing from SW monsoon winds in summer and the NE monsoon winds in winter.     

Assessing a decade of phosphorus management in the Lake Mendota, Wisconsin watershed and scenarios for enhanced phosphorus management

A phosphorus (P) budget was estimated for the watershed of Lake Mendota, Wisconsin, to assess the effects of nutrient management on P accumulation in the watershed soils. We estimated how nutrient management programs and legislation have affected the budget by comparing the budget for 2007 to a budget calculated for 1995, prior to implementation of the programs. Since 1995, inputs decreased from 1,310,000 to 853,000 kg P/yr (35% reduction) and accumulation decreased from 575,000 to 279,000 kg P/yr (51% reduction). Changes in P input and accumulation were attributed primarily to enhanced agricultural nutrient management, reduction in dairy cattle feed supplements and an urban P fertilizer ban. Four scenarios were investigated to determine potential impacts of additional nutrient management tactics on the watershed P budget and P loading to Lake Mendota. Elimination of chemical P fertilizer input has the greatest potential to reduce watershed P accumulation and establishment of riparian buffers has the greatest potential to prevent P loading to Lake Mendota.     

基于湖库水质目标的流域氮、磷减排与分区管理——以天目湖沙河水库为例

湖库水环境保护在保障生产与生活用水、维系生态平衡、发展旅游等方面发挥着重要的作用.水质目标管理是保护湖库水质的最佳管理办法.本文以天目湖地区沙河水库及其流域为研究区域,建立模型模拟沙河水库流域的水文与水质,评估入库污染通量和主要来源;依据水质目标测算氮、磷污染的容量和减排量,结合土地的生态保护与开发适宜性评估,提出氮、磷污染分区减排和土地管控的对策和措施.研究结果表明,沙河水库氮、磷污染物入库通量分别为206.01和3.29 t/a,面源总氮和总磷分别占总入库量的85.7%和67.5%.不同土地利用类型氮、磷输出强度有显著差异,总氮输出强度依次为茶园 >耕地 >建筑用地 >裸地 >草地 >退耕地 >林地 >河湖漫滩,总磷输出强度与地表覆盖度有关,依次为裸地 >建筑用地 >茶园 >耕地 >草地 >退耕地 >林地和河湖漫滩.从氮、磷输移过程来看,沙河水库流域总氮排放量为321.64 t/a,进入河流的为255.53 t/a,在河道输送过程中损失19.4%,最终有206.01 t/a进入水库;沙河水库流域总磷排放量为13.42 t/a,进入河流的为7.90 t/a,在河道输送过程中损失58.3%,最终有3.29 t/a进入水库.不同分区河流氮、磷滞留降解率有很大的差异,中田河总氮、总磷滞留降解能力最强,分别为34.71%和84.31%.2009年的通量计算结果显示,沙河水库总氮达到Ⅳ类水质目标需要的入湖减少量为32.01 t/a,入湖削减比例为15.50%,总氮达到Ⅲ类水质目标需要的入湖减少量为59.66 t/a,入湖削减比例为29.00%;总磷达到Ⅲ类水需要的入湖减少量为0.682 t/a,入湖削减比例为20.70%,总磷达到Ⅱ类水需要的入湖减少量为1.479 t/a,入湖削减比例为44.90%.为了实现基于土地利用的面源污染减排管控,选定植被覆盖度、水源涵养能力、地形坡度、土地利用、氮磷分区贡献量、与道路和村落距离等指标综合评估生态保护价值和开发适宜性,并划定禁止开发区、限制开发区和保护性开发区3个管理分区,最终确定各分区的开发强度限制和管控方式.     

How much does dry‐season fog matter? Quantifying fog contributions to water balance in a coastal California watershed

The seasonally‐dry climate of Northern California imposes significant water stress on ecosystems and water resources during the dry summer months. Frequently during summer, the only water inputs occur as non‐rainfall water, in the form of fog and dew. However, due to spatially heterogeneous fog interaction within a watershed, estimating fog water fluxes to understand watershed‐scale hydrologic effects remains challenging. In this study, we characterized the role of coastal fog, a dominant feature of Northern Californian coastal ecosystems, in a San Francisco Peninsula watershed. To monitor fog occurrence, intensity, and spatial extent, we focused on the mechanisms through which fog can affect the water balance: throughfall following canopy interception of fog, soil moisture, streamflow, and meteorological variables. A stratified sampling design was used to capture the watershed's spatial heterogeneities in relation to fog events. We developed a novel spatial averaging scheme to upscale local observations of throughfall inputs and evapotranspiration suppression and make watershed‐scale estimates of fog water fluxes. Inputs from fog water throughfall (10–30 mm/year) and fog suppression of evapotranspiration (125 mm/year) reduced dry‐season water deficits by 25% at watershed scales. Evapotranspiration suppression was much more important for this reduction in water deficit than were direct inputs of fog water. The new upscaling scheme was analyzed to explore the sensitivity of its results to the methodology (data type and interpolation method) employed. This evaluation suggests that our combination of sensors and remote sensing allows an improved incorporation of spatially‐averaged fog fluxes into the water balance than traditional interpolation approaches.     

Improved water quality in response to pollution control measures at Masan Bay, Korea

The total pollution load management system (TPLMS) was first applied in 2007 to the highly developed Masan Bay watershed, Korea. To evaluate the effect of TPLMS on water quality improvement, we analyzed the water qualities in rivers and bay during 2005-2010, targeting chemical oxygen demand (COD), suspended sediment (SS), total nitrogen (TN), and total phosphorus (TP) loads. Land-based pollutant loading all decreased during this period, with a significant reduction in COD and SS loads (p<0.01). The COD reduction in seawater, following the TPLMS implementation, was also significant (p<0.01). Time-lagged responses in COD and Chl-a supported an estimated seawater residence time of ~1 month. Land-based nutrient loads were also significantly reduced for TN (p<0.01) and TP (p<0.05), however, significant reductions were not observed in the bay, indicating potential alternative nutrient inputs from non-point sources into the bay system.     

Sources and fate of nutrients in a subtropical reservoir

This study examined the sources and fate of nutrient inputs from two principal tributaries to the eutrophic subtropical Wivenhoe reservoir: an unregulated river and a dammed river with regular releases, during a period of declining reservoir water levels. Nutrient budgets were constructed over a period of 6 years, and combined with short-term data on nutrient concentrations and forms, and δ¹⁵N stable isotope data. Our study found that over a 6 year period, there was net retention of phosphorus (P) in the reservoir, with 60% of inputs retained. Most of the P input load came from the unregulated river, with an agricultural catchment, during periods of high flow. During one event half of the total TP load from the unregulated river in the study period was delivered in only 12 days. Much of the P was dissolved inorganic P (DIP) and was derived from high P concentrations in soils and sediments. This highlights the importance of appropriate catchment management practices to reduce P losses from terrestrial systems because retention of P in reservoir sediments reduces the availability of this nutrient for agricultural production. In contrast, there was negligible retention of nitrogen (N). The unregulated river was an important source of N derived from N fixation in the river and adjacent soils, while the source from the dammed river was mostly reprocessed N. The high retention of P relative to N is consistent with relatively higher accumulation of P in sediments.     

Copper,zinc, cadmium,nickel, iron and manganese in the Southern Bight of the North Sea

Ni, Cd, Cu, Zn, and Fe were determined in water and suspended matter samples and Mn in suspended matter samples from the Southern Bight region of the North Sea. Four distinct areas, comprising the Rhine estuary, the Dutch coastal waters, the centre of the Bight, and the English coastal water can be distinguished on the basis of the distribution of the trace metals. The total concentrations of all metals were high in the Rhine estuary, decreased in a seaward direction to reach very low values, comparable to continental shelf water, in the centre of the Bight, and increased again towards the English coast. Elevated concentrations of dissolved Cu, Ni, Cd and Zn near the English coast are not only due to river inputs. Over the entire region, the fraction of Cd, Ni and Zn in solution was consistently more important than the fraction in the suspended particulate phase. In contast, the fraction of Fe and Mn in the solid phase was consistently greater than the fraction in solution. Total concentrations of Fe, Mn and Cu are more dictated by the suspended particulate matter concentration than Cd, Ni and Zn.     

Hydrological characteristics of a moso-bamboo (Phyllostachys pubescens) forest in south china

Since 1986 the multiple benefits of moso-bamboo forest, a special forest type found mainly in south China, have been investigated in a small 11.7 ha watershed in Fenyi County, Jiangxi Province. The mean annual precipitation in the study area is 1593.3 mm. For the 0–60 cm soil layer the average soil bulk density is 1.00 g/cm³, and the mean values for other soil properties are: total porosity 71.74%; non-capillary porosity 5.81%; and water retention capacity 430 mm. The maximum effective water retention capacity of 313 mm is 28% higher than that for Chinese fir (Cunninghamia lanceolata) plantations and natural broadleaved forest in the neighbouring area. The parameters f₀, f_c and k, in Horton's infiltration equation, measured using the double-ring method under drought conditions, are 29.10 mm/min, 8.28 mm/min and 0.2391, respectively. These infiltration properties are more favourable than those under nearby Chinese fir plantations. Compared with a Chinese fir plantation, the canopy interception ratio of moso-bamboo is lower, but the stemflow ratio is higher. The annual canopy interception ratio is 11.1%. Because of snowfall, the interception ratios in January, February and March are higher, with values of 12.1–17.2%, whereas during the period of leaf fall in April, May and June the interception ratios are lower with values of 9.2–9.5%. During the other months they are relatively constant. The annual stemflow ratio is 4.4%. Again, because of snowfall, the stemflow ratios in January, February and March are lower with values of 2.8–2.9%, whereas during the remaining months they are fairly constant. Runoff analysis shows that the annual runoff ratio in this research watershed is 54.8%, but the ratio for quick runoff, composed of direct runoff and surface runoff, is only 0.8%. The upper interflow ratio is 15% and the ratio for the slow runoff composed of deeper interflow and underflow is 39%. The moso-bamboo forest is very effective in reducing peak runoff and increasing low flows. The annual nutrient element inputs (kg/ha) to the moso-bamboo forest ecosystem associated with throughfall and stemflow are N 17.7, P 0.38, K 56.5, Ca 31.,4, Mg 4.8 and SiO₂ 26.2, respectively. All the measured element inputs, with the exception of P, are higher than those associated with precipitation in the open, where typical values are N 10.1, P 0.89, K 18.8, Ca 25.8, Mg 3.1 and SiO₂ 10.1. The annual outputs in streamflow are N 3.0, P 0.28, K 16.6, Ca 38.9, Mg 8.3 and SiO₂ 125.7, indicating that for N, P and K the moso-bamboo forest ecosystem is an accumulating system, whereas for Ca, Mg and SiO₂ the reverse applies. All the pH values associated with precipitation in the open, throughfall, stemflow, surface runoff from runoff plots and streamflow in the research watershed vary between 6.45 and 7.60 and are close to neutral.     

Cross-Media Models of the Chesapeake Bay Watershed and Airshed

A continuous, deterministic watershed model of the Chesapeake Bay watershed, linked to an atmospheric deposition model is used to examine nutrient loads to the Chesapeake Bay under different management scenarios. The Hydrologic Simulation Program - Fortran, Version 11 simulation code is used at an hourly time-step for ten years of simulation in the watershed. The Regional Acid Deposition Model simulates management options in reducing atmospheric deposition of nitrogen. Nutrient loads are summed over daily periods and used for loading a simulation of the Chesapeake estuary employing the Chesapeake Bay Estuary Model Package. Averaged over the ten-year simulation, loads are compared for scenarios under 1985 conditions, forecasted conditions in the year 2000, and estimated conditions under a limit of technology scenario. Limit of technology loads are a 50%, 64%, and 42% reduction from the 1985 loads in total nitrogen, total phosphorus, and total suspended solids, respectively. Urban loads, which include point source, on-site wastewater disposal systems, combined sewer overflows, and nonpoint source loads have the highest flux of nutrient loads to the Chesapeake, followed by crop land uses.on assignment from NOAA Air Resources Laboratory