NITROGEN AND PHOSPHORUS CONCENTRATIONS IN FOREST STREAMS OF THE UNITED STATES1

ABSTRACT: Seventy to eighty percent of the water flowing in rivers in the United States originates as precipitation in forests. This project developed a synoptic picture of the patterns in water chemistry for over 300 streams in small, forested watersheds across the United States. Nitrate (NO₃^?) concentrations averaged 0.31 mg N/L, with some streams averaging ten times this level. Nitrate concentrations tended to be higher in the northeastern United States in watersheds dominated by hardwood forests (especially hardwoods other than oaks) and in recently harvested watersheds. Concentrations of dissolved organic N (mean 0.32 mg N/L) were similar to those of NO₃～, whereas ammonium (NH₄⁺) concentrations were much lower (mean 0.05 mg N/L). Nitrate dominated the N loads of streams draining hardwood forests, whereas dissolved organic N dominated the streams in coniferous forests. Concentrations of inorganic phosphate were typically much lower (mean 12 mg P/L) than dissolved organic phosphate (mean 84 mg P/L). The frequencies of chemical concentrations in streams in small, forested watersheds showed more streams with higher NO₃^? concentrations than the streams used in national monitoring programs of larger, mostly forested watersheds. At a local scale, no trend in nitrate concentration with stream order or basin size was consistent across studies.     

CHEMICAL COMPOSITION OF SOFTWATER FLORIDA LAKES AND THEIR SENSITIVITY TO ACID PRECIPITATION1

ABSTRACT: Based on alkalinity data for 596 lakes, 31 percent of Florida's 7300 lakes have < 100 μeq/l alkalinity and are sensitive to acid depostion. More than two-thirds of the lakes in 12 northern Florida counties fit this criterion. Increasing aluminum and decreasing nutrient and chlorophyll a concentrations were observed with decressing pH in a survery of 20 softwater lakes. Maximum measured aluminum values (100-150 μg/L) are below levels asociated with fish toxicity. Factor analysis showed that lake chemistry was related to three principal factors, representing three major processes: watershed weathering, acidification, and nutrient inputs. An acidification index defined as the difference between excess SO₄^2- and excess (Ca²⁺+Mg²⁺) accounted for 74 percent of the variance in lake pH. Comparison of historical (late 1950a) and present data for pH, alkalinity, and excess SO₄^2- indicated loss of alkalinity (>25 μeq/L) and increase in excess SO₄^2- (16-34 μeq/L) in several softwater lakes.     

BIOGEOCIIEMISTRY OF AN OLD-GROWTH FORESTED WATERSHED,OLYMPIC NATIONAL PARK,WASHINGTON1

ABSTRACT: The biogeochemistry of a coastal old-growth forested watershed in Olympic National Park, Washington, was examined. Objectives were to determine: (1) concentrations of major cations and anions and dissolved organic C (DOC) in precipitation, throughfall, stemflow, soil solution and the stream; (2) nutrient input/output budgets; and (3) nutrient retention mechanisms in the watershed. Stemilow was more acidic (pH 4.0–4.5) than throughfall (pH 5.1) and precipitation (pH 5.3). Organic acids were important contributors to acidity in throughfall and stemflow and tree species influenced pH. Soil solution pH averaged 6.2 at 40 cm depth. Stream pH was higher (7.6). Sodium (54.0 μeq L-¹) and Cl (57.6 μeq L^?1) were the dominant ions in precipitation, reflecting the close proximity to the ocean. Throughfall and stemflow were generally enriched in cations, especially K. Cation concentrations in soil solutions were generally less than those in stemilow. Ion concentrations increased in the stream. Dominant ions were Ca (759.7 μeq L^?1), Na (174.4 μeq L^?1), HCO₃ (592.0 μeq L^?1), and SO₄ (331.5 μeq L^?1) with seasonal peaks in the fall. Bedrock weathering strongly influenced stream chemistry. Highest average NO₃ concentrations were in the stream (5.2 μeq L^?1) with seasonal peaks in the fall and lowest concentrations in the growing season. Nitrogen losses were similar to inputs; annual inputs were 4.8 kg/ha (not including fixation) and stream losses were 7.1 kg/ha. Despite the age and successional status of the forest, plant uptake is an important N retention mechanism in this watershed.     

Linking Landscape Characteristics and High Stream Nitrogen in the Oregon Coast Range: Red Alder Complicates Use of Nutrient Criteria

Red alder (Alnus rubra), a nitrogen(N)‐fixing deciduous broadleaf tree, can strongly influence N concentrations in western Oregon and Washington. We compiled a database of stream N and GIS‐derived landscape characteristics in order to examine geographic variation in N across the Oregon Coast Range. Basal area of alder, expressed as a percent of watershed area, accounted for 37% and 38% of the variation in summer nitrate and total N (TN) concentrations, respectively. Relationships between alder and nitrate were strongest in winter when streamflow and landscape connections are highest. Distance to the coast and latitude, potential surrogates for sea salt inputs, and watershed area were also related to nitrate concentrations in an all‐subsets regression analysis, which accounted for 46% of the variation in summer nitrate concentrations. The model with the lowest Akaike's Information Criterion did not include developed or agricultural land cover, probably because few watersheds in our database had substantial levels of these land cover classes. Our results provide evidence, at a regional scale, that background sources and processes cause many Coast Range streams to exceed proposed nutrient criteria, and that the prevalence of a single tree species (N‐fixing red alder) exerts a dominant control over stream N concentrations across this region.     

WATER QUALITY FROM TWO SMALL FORESTED WATERSHEDS IN SOUTHERN ILLINOIS1

Two intermittent streams on oak-hickory watersheds in southern Illinois were gaged with a V-notched weir and sampled with an automatic water sampler. For three years data were collected on flow volume and water quality. Flow volumes show large variations between years and watersheds. Samples were analyzed for Na⁺, K⁺, Ca⁺⁺, Mg⁺⁺, P, and NO^-₃. Water quality was consistently high, although there were significant differences between watersheds. A baseline for water quality has been established for comparison after one of the watersheds is clearcut at a later date.     

EFFECTS OF FOREST HERBICIDE APPLICATIONS ON STREAMWATER CHEMISTRY IN SOUTHWESTERN BRITISH COLUMBIA1

ABSTRACT: The herbicide glyphosate was applied to portions of two watersheds in southwestern British Columbia to kill vegetation that was competing with Pseudotsuga menziesii (Douglas-fir) plantations. This application had little significant effect on streamwater chemistry (K⁺, Na²⁺, Mg²⁺, Ca²⁺, Cl^-, NOs₃^-, NH₄⁺, PO4^3-, SO₄⁼, and SiO₂ concentrations, electrical conductivity, and pH) when vegetation cover in a watershed was reduced by 4%, but had significant (P>0.05) effects, which lasted for at least five years, when cover was reduced by 43%. In this case, most parameters increased in value following the application, with K⁺ and Mg²⁺ concentrations and pH values exhibiting the most prolonged increases and NO₃^- concentrations exhibiting the greatest percentage increases. Sulphate and dissolved SiO₂ concentrations decreased following the application. Streamwater chemical fluxes showed similar trends to concentrations except that changes in fluxes were less significant and no decreases were observed. Forest management induced losses of NO₃-N in streamwater during the first five post-treatment years in the study area decreased in the order: herbicide application (approximately 40 kg/ha) < clearcutting and slashburning (approximately 20 kg/ha) < clearcutting (approximately 10 kg/ha). In watersheds similar to those of the study area, herbicide application is likely to have a greater impact on streamwater chemistry, in general, than would clearcutting or clearcutting followed by slashburning.     

Impact of an Invasive Exotic Species on Stream Nitrogen Levels in Southern Illinois1

Abstract: Autumn‐olive (Elaeagnus umbellata Thunb.) is an invasive, exotic shrub that has become naturalized in the eastern United States. Autumn‐olive fixes nitrogen (N) via a symbiotic relationship with the actinomycete Frankia. At the plot scale, the presence of autumn‐olive has been related to elevated soil water nitrate‐N (NO₃^?‐N) concentrations. This study examined the relationship between autumn‐olive cover in a watershed and stream water quality. Stream water nitrate‐N (NO₃^?‐N) and ammonium‐N (NH₄⁺‐N) concentrations were measured in 12 first order ephemeral streams draining watersheds with mixed forest cover and a range of 0‐35% autumn‐olive cover. Percent autumn‐olive cover was positively correlated with mean stream NO₃^?‐N concentrations, but was not correlated with mean stream NH₄⁺‐N concentrations. While other studies have demonstrated a significant relationship between native N‐fixers and stream NO₃^?‐N, this is the first study to document a relationship for an invasive, exotic N‐fixing species. Results suggest that this exotic species can be an additional source of NO₃^? in local and regional water bodies and demonstrates an additional negative ecosystem consequence of invasion beyond losses in biodiversity.     

FATE OF NITROGEN AND PHOSPHORUS ENTERING A GULF COAST FRESHWATER LAKE: A CASE STUDY1

ABSTRACT: Nitrogen and P fluxes, transformations and water quality functions of Lake Verret (a coastal Louisiana freshwater lake), were quantified. Ortho-P, total-P, NH₄⁺-N NO₃ -N and TKN in surface water collected from streams feeding Lake Verret averaged 104, 340, 59, 185, and 1,060 mg 1^?1, respectively. Lake Verret surface water concentrations of ortho-P, total-P, NH⁺-N, NO₃^?_-N and TKN averaged 66, 191, 36, 66, and 1,292 μg 1^?1. The higher N and P concentrations were located in areas of the lake receiving drainage. Nitrification and denitrification processes were significant in removing appreciable inorganic N from the system. In situ denitrification rates determined from acetylene inhibition techniques show the lake removes 560 mg N m^?2 yr^?1. Laboratory investigations using sediment receiving 450 μg NH⁺₄-N (N-15 labeled) showed that the lake has the potential to remove up to 12.8 g N m^?2 yr^?1. Equilibrium studies of P exchanges between the sediment and water column established the potential or adsorption capacity of bottom sediment in removing P from the overlying water. Lake Verret sediment was found to adsorb P from the water column at concentrations above 50 μg P 1^?1 and the adsorption rates were as great as 300 μg P cm^?2 day^?1 Using the ¹³⁷C s dating techniques, approximately 18 g N m^?2 yr^?1 and 1.2 g P m^?2 yr^?1 were removed from the system via sedimentation. Presently elevated nutrient levels are found only in the upper reaches of the lake receiving nutrient input from runoff from streams draining adjacent agricultural areas. Nitrification, denitrification, and adsorption processes at the sediment water interface over a relatively short distance reduces the N and P levels in the water column. However, if the lake receives additional nutrient loading, elevated levels will likely cover a larger portion of the lake, further reducing water quality in the lake.     

WATERSHED SCALING EFFECT ON BASE FLOW NITRATE,VALLEY AND RIDGE PHYSIOGRAPHIC PROVINCE1

ABSTRACT: A study of stream base flow and NO₃‐N concentration was conducted simultaneously in 51 subwatersheds within the 116‐square‐kilometer watershed of East Mahantango Creek near Klingerstown, Pennsylvania. The study was designed to test whether measurable results of processes and observations within the smaller watersheds were similar to or transferable to a larger scale. Ancillary data on land use were available for the small and large watersheds. Although the source of land‐use data was different for the small and large watersheds, comparisons showed that the differences in the two land‐use data sources were minimal. A land use‐based water‐quality model developed for the small‐scale 7.3‐square‐kilometer watershed for a previous study accurately predicted NO₃‐N concentrations from sampling in the same watershed. The water‐quality model was modified and, using the imagery‐based land use, was found to accurately predict NO₃‐N concentrations in the subwatersheds of the large‐scale 116‐square‐kilometer watershed as well. Because the model accurately predicts NO₃‐N concentrations at small and large scales, it is likely that in second‐order streams and higher, discharge of water and NO₃‐N is dominated by flow from smaller first‐order streams, and the contribution of ground‐water discharge to higher order streams is minimal at the large scale.     

Effects of Land Use and Sample Location on Nitrate‐Stream Flow Hysteresis Descriptors during Storm Events

The U.S. Geological Survey's New Jersey and Iowa Water Science Centers deployed ultraviolet‐visible spectrophotometric sensors at water‐quality monitoring sites on the Passaic and Pompton Rivers at Two Bridges, New Jersey, on Toms River at Toms River, New Jersey, and on the North Raccoon River near Jefferson, Iowa to continuously measure in‐stream nitrate plus nitrite as nitrogen (NO₃ + NO₂) concentrations in conjunction with continuous stream flow measurements. Statistical analysis of NO₃ + NO₂ vs. stream discharge during storm events found statistically significant links between land use types and sampling site with the normalized area and rotational direction of NO₃ + NO₂‐stream discharge (N‐Q) hysteresis patterns. Statistically significant relations were also found between the normalized area of a hysteresis pattern and several flow parameters as well as the normalized area adjusted for rotational direction and minimum NO₃ + NO₂ concentrations. The mean normalized hysteresis area for forested land use was smaller than that of urban and agricultural land uses. The hysteresis rotational direction of the agricultural land use was opposite of that of the urban and undeveloped land uses. An r² of 0.81 for the relation between the minimum normalized NO₃ + NO₂ concentration during a storm vs. the normalized NO₃ + NO₂ concentration at peak flow suggested that dilution was the dominant process controlling NO₃ + NO₂ concentrations over the course of most storm events.     

Response of Soil Inorganic Nitrogen to Land Use and Topographic Position in the Cofre de Perote Volcano (Mexico)

This study addressed the effects of land use and slope position on soil inorganic nitrogen and was conducted in small watersheds. The study covered three land use types: tropical cloud forest, grassland, and coffee crop. To conduct this research, typical slope small watersheds were chosen in each land use type. Slopes were divided into three positions: shoulder, backslope, and footslope. At the center of each slope position, soil sampling was carried out. Soil inorganic nitrogen was measured monthly during a period of 14 months (July 2005–August 2006) with 11 observations. Significant differences in soil NH₄ ⁺–N and NO₃ ⁻–N content were detected for both land use and sampling date effects, as well as for interactions. A significant slope position-by-sampling date interaction was found only in coffee crop for NO₃ ⁻–N content. In tropical cloud forest and grassland, high soil NH₄ ⁺–N and low NO₃ ⁻–N content were recorded, while soil NO₃ ⁻–N content was high in coffee crop. Low NO₃ ⁻–N contents could mean a substantial microbial assimilation of NO₃ ⁻–N, constituting an important mechanism for nitrogen retention. Across the entire land use set, the relationship between soil temperature and soil inorganic N concentration was described by an exponential decay function (N = 33 + 2459exp^−0.23T, R ² = 0.44, P < 0.0001). This study also showed that together, soil temperature and gravimetric soil water content explained more variation in soil inorganic N concentration than gravimetric soil water content alone.     

IMPACTS OF URBANIZATION ON NUTRIENT CONCENTRATIONS IN SMALL SOUTHEASTERN COASTAL STREAMS1

ABSTRACT: Coastal watersheds in the southeastern United States are rapidly changing due to population growth and attendant increases in residential development, industry, and tourism related commerce. This research examined spatial and temporal patterns of nutrient concentrations in streams from 10 small watersheds (< 4 km²) that drain into Murrells Inlet (impacted) and North Inlet (pristine), two high salinity estuaries along the South Carolina coast. Monthly grab samples were collected during baseflow during 1999 and analyzed for total and dissolved inorganic and organic forms of nitrogen and phosphorus. Data were grouped into forested wetland creeks (representing predevelopment reference sites), urban creeks, and urban ponds. DON and NH4 concentrations were greater in forested streams than in urban streams. NO3 and TP concentrations were greatest in urban streams. Seasonally, concentrations were highest during summer for TN, NH4, DON, and TP, while NO3 concentrations were greatest during winter. Nutrient ratios clearly highlighted the reduction in organic nitrogen due to coastal development. Multiple regression models to predict instream nutrient concentrations from land use in Murrells Inlet suggest that effects are not significant (small r²). The findings indicate that broad land use/land cover classes cannot be used to predict nutrient concentrations in streams in the very small watersheds in our study areas.     

Spatial Convergence in Major Dissolved Ion Concentrations and Implications of Headwater Mining for Downstream Water Quality

Spatial patterns in major dissolved solute concentrations were examined to better understand impact of surface coal mining in headwaters on downstream water chemistry. Sixty sites were sampled seasonally from 2012 to 2014 in an eastern Kentucky watershed. Watershed areas (WA) ranged from 1.6 to 400.5 km² and were mostly forested (58%–95%), but some drained as much as 31% surface mining. Measures of total dissolved solutes and most component ions were positively correlated with mining. Analytes showed strong convergent spatial patterns with high variability in headwaters (<15 km² WA) that stabilized downstream (WA > 75 km²), indicating hydrologic mixing primarily controls downstream values. Mean headwater solute concentrations were a good predictor of downstream values, with % differences ranging from 0.55% (Na⁺) to 28.78% (Mg²⁺). In a mined scenario where all headwaters had impacts, downstream solute concentrations roughly doubled. Alternatively, if mining impacts to headwaters were minimized, downstream solute concentrations better approximated the 300 μS/cm conductivity criterion deemed protective of aquatic life. Temporal variability also had convergent spatial patterns and mined streams were less variable due to unnaturally stable hydrology. The highly conserved nature of dissolved solutes from mining activities and lack of viable treatment options suggest forested, unmined watersheds would provide dilution that would be protective of downstream aquatic life.     

Urea Fluctuations in Stream Baseflow across Land Cover Gradients and Seasons in a Coastal Plain River System

Urea‐N is a component of bioavailable dissolved organic nitrogen (DON) that contributes to coastal eutrophication. In this study, we assessed urea‐N in baseflow across land cover gradients and seasons in the Manokin River Basin on the Delmarva Peninsula. From March 2010 to June 2011, we conducted monthly sampling of 11 streams (4 tidal and 7 nontidal), 2 wastewater treatment plants, an agricultural drainage ditch, and groundwater underlying a cropped field. At each site, we measured urea‐N, DON, dissolved organic carbon (DOC), total dissolved nitrogen (TDN), NO₃^?‐N, and NH₄⁺‐N. In general, urea‐N comprised between 1% and 6% of TDN, with the highest urea‐N levels in drainage ditches (0.054 mg N/L) and wetland‐dominated streams (0.035–0.045 mg N/L). While urea‐N did not vary seasonally in tidal rivers, nontidal streams saw distinct urea‐N peaks in summer (0.038 mg N/L) that occurred several months after cropland fertilization in spring. Notably, the proportion of wetlands explained 78% of the variance in baseflow urea‐N levels across the Manokin watershed. In wetland‐dominated basins, we found urea‐N was positively related to water temperature and negatively related to DOC:DON ratios, indicating short‐term urea‐N dynamics at baseflow were more likely influenced by instream and wetland‐driven processes than by recent agricultural urea‐N inputs. Findings demonstrate important controls of wetlands on baseflow urea‐N concentrations in mixed land‐use basins.     

STREAM WATER CHEMISTRY IN WATERSHEDS RECEIVING DIFFERENT ATMOSPHERIC INPUTS OF H+, NH4, NO3−, AND SO42−1

ABSTRACT: Weekly precipitation and stream water samples were collected from small watersheds in Denali National Park, Alaska, the Fraser Experimental Forest, Colorado, Isle Royale National Park, Michigan, and the Calumet watershed on the south shore of Lake Superior, Michigan. The objective was to determine if stream water chemistry at the mouth and upstream stations reflected precipitation chemistry across a range of atmospheric inputs of H⁺, NH₄⁺, NO₃^?_?, and SO₄^2?. Volume-weighted precipitation H⁺, NH₄⁺, NO₃^?_?, and SO₄^2? concentrations varied 4 to 8 fold with concentrations highest at Calumet and lowest in Denali. Stream water chemistry varied among sites, but did not reflect precipitation chemistry. The Denali watershed, Rock Creek, had the lowest precipitation NO₃^?_? and SO₄^2? concentrations, but the highest stream water NO₃^?and SO₄^2? concentrations. Among sites, the ratio of mean monthly upstream NO₃^?_? concentration to precipitation NO₃^?_- concentration declined (p < 0.001, R²= 0.47) as precipitation NO₃^?_? concentration increased. The ratio of mean monthly upstream to precipitation SO₄^2? concentration showed no significant relationship to change in precipitation SO₄^2? concentration. Watersheds showed strong retention of inorganic N (> 90 percent inputs) across inputs ranging from 0.12 to > 6 kg N ha^?1 y^?1. Factors possibly accounting for the weak or non-existent signal between stream water and precipitation ion concentrations include rapid modification of meltwater and precipitation chemistry by soil processes, and the presence of unfrozen soils which permits winter mineralization and nitrification to occur.     

Spatial Variability of Nitrate Concentrations Under Diverse Conditions in Tributaries to a Lake Watershed1

Abstract: Nitrate‐nitrogen (NO₃‐N) concentrations in stream water often respond uniquely to changes in inter‐annual conditions (e.g., biological N uptake and precipitation) in individual catchments. In this paper, we assess (1) how the spatial distribution of NO₃‐N concentrations varies across a dense network of nonnested catchments and (2) how relationships between multiple landscape factors [within whole catchments and hydrologically sensitive areas (HSAs) of the catchments] and stream NO₃‐N are expressed under a variety of annual conditions. Stream NO₃‐N data were collected during two synoptic sampling events across >55 tributaries and two synoptic sampling periods with >11 tributaries during summer low flow periods. Sample tributaries drain mixed land cover watersheds ranging in size from 0.150 to 312 km² and outlet directly to Cayuga Lake, New York. Changes in NO₃‐N concentration ratios between each sampling event suggest a high degree of spatial heterogeneity in catchment response across the Cayuga Lake Watershed, ranging from 0.230 to 61.4. Variations in NO₃‐N concentrations within each of the large synoptic sampling events were also high, ranging from 0.040 to 8.7 mg NO₃‐N/l (March) and 0.090 to 15.5 mg NO₃‐N/l (October). Although Pearson correlation coefficients suggest that this variability is related to multiple landscape factors during all four sampling events, partial correlations suggest percentage of row crops in the catchments as the only similar factor in March and October and catchment area as the only factor during summer low flows. Further, the strength of the relationships is typically lower in the HSAs of catchment. Advancing current understanding of such variations and relationships to landscape factors across multiple catchments – and under a variety of biogeochemical and hydrological conditions – is important, as (1) nitrate continues to be employed as an indicator of regional aquatic ecosystem health and services and (2) a unified framework approach for understanding individual catchment processes is a rapidly evolving focus for catchment‐based science and management.     

WATER QUALITY AFTER LOGGING SMALL WATERSHEDS WITHIN THE BULL RUN WATERSHED,OREGON1

ABSTRACT: Road building, clearcutting 25 percent of the watershed, and slash disposal by broadcast burning or by natural decomposition caused changes in water quality of two small streams in the Bull Run Watershed in Oregon, which supplies water to the Portland, Oregon, metropolitan area. Concentrations of suspended sediment increased slightly, primarily owing to construction of a permanent logging road that crossed streams. Changes in nutrient cycling occurred due to logging and slash disposal in both watersheds where cutting was done. NO₃-N concentrations, which increased most where logging residue was left to decompose naturally, increased more than sixfold and commonly exceeded 100 pg/i during the October-June high-flow season for seven years after logging. Where logging slash was broadcast burned, NO₃-N concentrations increased roughly fourfold, but rarely exceeded 50 μg/l, and increases had mostly disappeared six years after slash burning. Changes in outflows of cations and other anions were not apparent. Annual maximum stream temperatures increased 2–3°C after logging, but temperature increases had mostly disappeared within three years as vegetation regrowth shaded the streams.     

Soil and Water Characteristics in Restored Canebrake and Forest Riparian Zones1

Andrews, Danielle M., Christopher D. Barton, Randall K. Kolka, Charles C. Rhoades, and Adam J. Dattilo, 2011. Soil and Water Characteristics in Restored Canebrake and Forest Riparian Zones. Journal of the American Water Resources Association (JAWRA) 47(4):772‐784. DOI: 10.1111/j.1752‐1688.2011.00555.x Abstract: The degradation of streams has been widespread in the United States. In Kentucky, for instance, almost all of its large streams have been impounded or channelized. A restoration project was initiated in a channelized section of Wilson Creek (Nelson Co., Kentucky) to return its predisturbance meandering configuration. A goal of the project was to restore the native riparian corridor with giant cane and bottomland forest species. The objective of this study was to evaluate the use of giant cane in riparian restoration and to compare water quality and soil attributes between restored cane and forested communities. Comparison of data to replicated sites of similar size in undisturbed upstream areas (control) was also examined to evaluate restoration success. Vegetation establishment was initially hindered by frequent flooding in 2004, but mean survival was good after two growing seasons with rates of 80 and 61% for forest and cane plots, respectively. Results showed an improvement in stream water quality due to restoration activities. Significant differences between the cane and forested plots in shallow groundwater dissolved oxygen, NO₃^?‐N, NH₄⁺‐N, and Mn concentrations suggest that soil redox conditions were not similar between the two vegetation types. Retention and transformation of carbon (C) and nitrogen (N) within the restored riparian system also differed by vegetation treatment; however, both communities appeared to be advancing toward conditions exhibited in the control section of Wilson Creek.     

BEDLOAD TRANSPORT IN AN OREGON COAST RANGE STREAM1

Bedload transport was measured with two sampler types (vortex tube and Helley-Smith pressure differential) for three major storms at Flynn Creek, which drains a 2.2-km² forested watershed in the Oregon Coast Range. The largest flow during two winters of monitoring had a peak discharge of 0.79 m³ s^-1 km^-2, with an associated recurrence interval of ? 1.3 yr. The median particle diameter of sediment in transport was generally < 1 mm. The vortex tube and its associated sample box were relatively inefficient at trapping particles < 10 mm in diameter; however, even after transport rates were adjusted to account for sampling deficiencies of the sample box, they still averaged 42–47 percent of those obtained with the Helley-Smith sampler. Organic matter and sand sized sediments in transport also were observed to partially plug the 0.2-mm-mesh bag of the Helley-Smith sampler. Large temporal variability in bedload transport rates was measured during periods of high flow.     

Nutrients and suspended solids in dry weather and storm flows from a tropical catchment with various proportions of rural and urban land use

The results of an investigation characterizing the nutrients and suspended solids contained in stormwater from Kranji Catchment in Singapore are reported in this paper. Stormwater samples were collected from 4 locations and analyzed for the following eleven analytes: TOC, DOC, TN, TDN, NH₄⁺, NO₂⁻ + NO₃⁻ (NO_x), TP, TDP, OP, SiO₂ and TSS. Stormwater was sampled from catchments with various proportions of rural and urban land use, including forested areas, grassed areas, agricultural and residential and commercial areas. The event mean concentrations (EMCs) of nutrients and TSS from sampling stations which have agricultural land use activities upstream were found to be higher. Comparison of site EMCs (SMCs) with published data showed that the SMCs of the nutrients and TSS are generally higher than SMCs reported for forested areas but lower than published SMCs for urban areas. Positive correlations (p < 5%) were found between loading and peak flow at locations most impacted by ubanisation or agricultural activities. Correlation between loading and rainfall variables was less distinct. EMC was found to correlate less with rainfall and flow variables compared to pollutant loading. Unlike loading, no consistent pattern exists linking EMC to any particular storm or flow variable in any of the catchments. Lastly, positive correlations were obtained between the particulate forms of nitrogen and phosphorus and TSS.