Stream Water Concentrations Research Articles

Nitrogen Fertilization Effects on Stream Water Cadmium Concentration

High transition metal concentrations were previously unexpectedly observed in soil water extracted by suction lysimeters following forest N fertilization. This observation called for additional measurements to investigate if the finding is a general phenomenon and, if so, whether stream water concentrations of transition metals could increase as a result of N fertilization. The measured levels of Cd in the preliminary findings were well above health limits for drinking water. Hence, the problem could be of major concern. Here we report on soil water and stream water concentrations at two partly fertilized watersheds. All sites were situated in the central part of Sweden. The N application (150 kg N ha(-1) in the form of calcium ammonium nitrate) resulted in increased concentrations of nitrate, and a pulse of acidity through the soil profile, which increased the solubility of transition metals (mainly Cd and Zn) and Al. Stream water concentrations of transition metals, on the other hand, were not affected during the studied period by the increased solubility of transition metals in the soil. The data imply that the solubilized transition metals probably insolubilize further down the soil profile, and that there is no risk from forest N fertilization (at normal soil pH levels) of transition metal levels increasing in nearby surface waters. To our knowledge, this is the first time this side effect of N fertilization has been considered.

Simazine concentrations in soil, groundwater and stream water following application to Pinus plantations in the coastal lowlands of south-east Queensland

Summary A study was conducted to assess the fate of simazine applied to exotic Pinus plantations in the coastal lowlands of south-east Queensland. The study had two components, the first being a large-scale catchment study site (903 ha) which assessed the level of simazine residues being transported from the point of application to the shallow unconfmed aquifer and the major drainage stream over a 13-month period. The second component consisted of a separate study on a small-scale study site (0.1 ha) to assess simazine persistence and its potential to leach in the coarse textured and relatively infertile soils of the area. An 80 ha clearfelled area within the large-scale study catchment was re-established with a second rotation plantation and routinely treated with simazine at 2.5 kg a.i. ha1 over an 11—month period. A stream monitoring station at the base of the catchment sampled streamwater, and two piezometers provided access for groundwater monitoring. At the small-scale study site, simazine was applied to small plots at the above rate and the soil profile and shallow groundwater were routinely sampled. Simazine was regularly detected in streamwater after surface runoff events but was below the current Australian drinking water health value. The detection of simazine in the unconfined aquifers at both sites indicated that it has the potential to leach to groundwater. However, under routine applications it would seem that the groundwater concentrations were low and shortlived (persistence < 6 weeks). The results indicated that simazine has a relatively short half-life (mean 13 days) in the coarse textured soils of the coastal lowlands of south-east Queensland. Transport from point of application by runoff or leaching was thought to be a minor pathway for loss from these plantations. Recommendations for future monitoring and research directions are discussed.

Trace metal loss following whole-tree harvest of a northeastern deciduous forest, U.S.A.

We examined changes in the biogeochemistry of trace metals following a commercial whole-tree harvest (WTH) at the Hubbard Brook Experimental Forest in New Hampshire. Within 6 months after completion of the WTH, maximum streamwater concentrations of Ni, Cd, Ba, Sr, Mn, Zn and Fe increased two- to nine-fold. Streamwater concentration of Cu remained unchanged after harvest. Streamwater pH decreased from 5.2 to 4.5 after the harvest, and correlated strongly with trace metal concentrations except for Fe. The decrease in pH apparently resulted from increased nitrogen mineralization and nitrification following harvest. All streamwater metal concentrations (except Mn and Fe) in the disturbed watershed increased prior to the decrease in streamwater pH, suggesting that the loss of readily exchangeable metals, not increased mineral dissolution, was responsible for the initial increase in streamwater trace metal concentrations. In contrast, streamwater Mn concentrations did not increase until streamwater pH dropped to 4.5, due in part to increased mineral dissolution. Although pH related strongly to trace metal concentrations in the harvested watershed, it did not account for much of the variation in metal concentrations in the reference (W6) watershed. Annual flux of trace metals increased two- to eight-fold following WTH. Annual losses of Mn and Sr were 14% and 12%respectively of the forest floor pool for each element, and less than 10% of forest floor pools for all other elements. Except for Cd and Cu, annual trace metal losses in streamwater exceeded annual inputs in bulk precipitation.

Catchment-Scale Variation in the Nitrate Concentrations of Groundwater Seeps in the Catskill Mountains, New York, U.S.A.

Forested headwater streams in the Catskill Mountains of New York show significant among-catchment variability in mean annual nitrate (NO3-) concentrations. Large contributions from deep groundwater with high NO3-concentrations have been invoked to explain high NO3-concentrations in stream water during the growing season. To determine whether variable contributions of groundwater couldexplain among-catchment differences in streamwater, we measuredNO3- concentrations in 58 groundwater seeps distributed across six catchments known to have different annual average streamwater concentrations. Seeps were identified based on release from bedrock fractures and beddingplanes and had consistently lower temperatures than adjacentstreamwaters. Nitrate concentrations in seeps ranged from neardetection limits (0.005 mg NO3--N/L) to 0.75 mg NO3--N/L. Within individual catchments, groundwaterresidence time does not seem to strongly affect NO3-concentrations because in three out of four catchments therewere non-significant correlations between seep silica (SiO2) concentrations, a proxy for residence time, andseep NO3- concentrations. Across catchments, therewas a significant but weak negative relationship betweenNO3- and SiO2 concentrations. The large rangein NO3- concentrations of seeps across catchmentssuggests: 1) the principal process generating among-catchmentdifferences in streamwater NO3- concentrations mustinfluence water before it enters the groundwater flow system and 2) this process must act at large spatial scales becauseamong-catchment variability is much greater than intra-catchmentvariability. Differences in the quantity of groundwater contribution to stream baseflow are not sufficient to account for differences in streamwater NO3- concentrationsamong catchments in the Catskill Mountains.

Water chemistry in a number of mountainous streams of east Asia

To determine the processes and factors responsible for the chemical composition of mountainous stream waters, correlations among solute concentrations in streams were examined in 13 forested watersheds from Japan, Jiulianshan (southern China) and Chiang Mai (northern Thailand), which had different soil parent materials and climatic conditions. The Na + concentration in stream water was significantly correlated with both Cl − and Si concentrations in the regions near the sea (Kagawa and Shibecha), but was correlated with the Si concentration in the regions far from the sea (Mt. Hiei, Takayama, Jiulianshan and Chiang Mai). In some watersheds in Kagawa, the Si concentration was correlated with Cl −, probably reflecting the relatively dry climate conditions. In Kagawa and Mt. Hiei, SO 4 2− concentrations in stream water were inversely correlated with NO 3 − concentrations, suggesting that nitrification inhibited SO 4 2− discharge, and denitrification and root NO 3 − uptake enhanced it. The alkalinity was mainly carried by HCO 3 − and organic acid anions. According to the theory of ion exchange equilibrium, high alkalinity was closely related to divalent cations (Ca 2+ and Mg 2+) more than to Na +. In the streams where concentrations of SO 4 2− and divalent cations were low (Chiang Mai), alkalinity was closely related to Na + reflecting production by weathering.

Phosphorus Accumulation in Farm Ponds and Dams in Southwestern Australia

AbstractEutrophication of farm ponds and dams (earth tanks) due to elevated dissolved phosphorus concentrations causes death of fish, crustaceans, and animals. Phosphorus accumulation in water and sediment in 50 farm ponds and dams and 2 streams was investigated for a 4000‐ha area near York, Western Australia. Water, sediment, and soil samples were analyzed for total, inorganic, and organic P. Sediments contained between 4 and 54% clay. The major minerals in the clay fraction were quartz, kaolinite, and smectite with minor amounts of illite, felspars, calcite, and iron oxides. Sediments contained between 0.4 and 5.9 g kg−1 N, 6.0 and 14.3 g kg−1 AI, 15.0 and 77.0 g kg−1 Fe, and 3.0 and 80.0 g kg−1 organic carbon. The dissolved P concentration in pond, dam, and stream water ranged from 0.001 to 4.15 mg L−1 and suspended particulate P (&gt;0.22 µm) ranged from 0.016 to 2.78 mg L−1. Total P in sediments ranged from 29 to 1101 mg kg−1 compared with 134 to 554 mg kg−1 in soils. Inorganic P accounted for 57% of total P in sediments and 75% of total P in soils. Relationships between concentrations of total P, inorganic P, and organic P in sediments and dissolved P in dam water were linear, indicating a buffering action of the sediment constituents on dissolved P. There was a linear relationship between the concentrations of P in sediments and in soils of catchments.

Low stream nitrate concentrations associated with oak forests on the Allegheny high plateau of Pennsylvania

Stream nitrate (NO3−) concentrations were 2.6–7.0 times lower in watersheds in which red oak (Quercus rubra) stands were present than in other forested watersheds in northwestern Pennsylvania. Also, seasonal variations in NO3− concentrations were smaller in watersheds with oak stands than in watersheds without oak stands. Stream water concentrations of calcium, magnesium, potassium, sodium, chloride, and sulfate did not differ significantly between the two groups of watersheds. The variability in NO3− concentrations among streams did not appear to be due to differences in atmospheric nitrogen deposition among watersheds. Low stream NO3− concentrations occurred even if only 10–20% of a watershed was covered by oak stands. We suggest that oaks, rather than directly controlling NO3− losses, instead merely occur on soils which have low NO3− losses.

Fecal Bacteria in the Waters of an Upland Area in Derbyshire, England: The Influence of Agricultural Land Use

AbstractLong‐term data on the dynamics of sanitary indicator bacteria in fresh waters is limited. This paper provides a data record of fluctuations in fecal bacterial concentrations in the waters of an upland area of northern England that can be examined in relation to agricultural land use practices and standards for contact recreation. Concentrations of fecal coliforms (FCs) were monitored in the waters of semi‐improved sheep pasture on the edge of a limestone karst system in north Derbyshire, England for a 21‐mo period. Data were obtained for three small streams and six water inflows to streams, comprising the end points of shallow subsurface tile drainage networks and natural, semi‐permanent, channelized overland flows. All sites showed significant contamination by fecal indicator bacteria. A consistent pattern of seasonal FC concentration change was observed at all sites, with concentrations generally highest during the summer and lowest during the winter. This may be explained by land use factors, including higher summer sheep stocking densities and the application of farmyard manure and sewage sludge. Correlations between changes in bacterial concentration at inflow sites and downstream changes in streamwater concentration were generally highly significant, providing strong empirical evidence for the assumed causal relationship between inflow and streamwater quality. The degree of fecal bacterial contamination of the streams, particularly during summer months, may constitute a real health risk to recreational cavers using parts of the limestone karst system into which the streams drain.

Effects of hurricane disturbance on stream water concentrations and fluxes in eight tropical forest watersheds of the Luquillo Experimental Forest, Puerto Rico

Stream water chemistry responds substantially to watershed disturbances, but hurricane effects have not been extensively investigated in tropical regions. This study presents a long-term (2.5–11 y) weekly record of stream water chemistry on eight forested watersheds (catchment basins) in the Luquillo Mountains of Puerto Rico. This includes a period before and at least 2 y after the disturbance caused by the 1989 Hurricane Hugo. Nitrate, potassium and ammonium concentrations increased after the hurricane and remained elevated for up to 2 y. Sulphate, chloride, sodium, magnesium and calcium showed smaller relative significant changes. Average stream water exports of potassium, nitrate and ammonium increased by 13.1, 3.6 and 0.54 kg ha−1 y−1 in the first post-hurricane year across all watersheds. These represent increases of 119, 182 and 102% respectively, compared to the other years of record. The increased stream outputs of potassium and nitrogen in the first 2 y post-hurricane are equivalent to 3% (potassium) and 1% (nitrogen) of the hurricane-derived plant litter. Effects of hurricanes on tropical stream water potassium and nitrogen can be greater than those caused by canopy gaps or limited forest cutting, but less than those following large-scale deforestation or fire.

Epilithic diatoms as indicators of stream total N and total P concentration

Patterns of diatom species distribution in relation to total N (TN), total P (TP), and other environmental variables from riffle sites on 2 streams in southern Ontario, Canada, were determined using canonical correspondence analysis (CCA). Relationships with TN and TP were sufficiently strong to develop weighted-averaging (WA) regression-calibration models for inferring stream water concentrations of these nutrients. The models were accurate within ±2.4 μg/L for TP (apparent r2 = 0.52) and ±2 mg/L for TN (apparent r2 = 0.53). An evaluation of the goodness of fit of these models with and without bootstrapping indicated that they performed better (bootstrapped r2 = 0.44 for TP and bootstrapped r2 = 0.42 for TN) than published TN and TP inference models for which similar assessments were made. Based on Organisation for Economic Cooperation and Development eutrophication ratings, the TP model predicted 76% of the mesotrophic and 57% of the eutrophic samples correctly. The model correctly predicted only 20% and 33%, respectively, of oligotrophic and hypereutrophic samples. WA inference models were improved when seasonal variation was removed by using mean summer water quality and diatom data (apparent r2 = 0.76 and bootstrapped r2 = 0.61 for TP; apparent r2 = 0.82 and bootstrapped r2 = 0.70 for TN). Overall, we conclude that epilithic diatoms can be related to TN and TP using these methods, and that WA inference models have utility for indicating eutrophication in southern Ontario lowland streams.

Seasonal variability of dissolved organic carbon in a Mediterranean stream

The seasonal variability of dissolved organic carbon(DOC) flux in a Mediterranean stream subjected todischarges of wide range of intensities and variabledry period was studied as a function of the hydrologicconditions, and the relationship between surface andsubsurface (hyporheic and groundwater) DOCconcentration. DOC concentration in stream water(2.6 mg l−1 ±1.5 SD) was higher thangroundwater (1.3 mg l−1 ± 1.2 SD) and lower thanhyporheic water (3.8 mg l−1 ±1.7 SD),suggesting that, at baseflow, stream DOC concentrationincreases when groundwater discharges through thehyporheic zone. Storms contributed to 39% of annualwater export and to 52% of the total annual DOCexport (220 kg km−2). A positive relationship wasobserved between Discharge (Q) and stream DOCconcentration. Discharge explained only 40% of theannual variance in stream DOC, but explained up to93% of the variance within floods. The rate of streamDOC changes with discharge change during storms (dDOC/dQ), ranged between 0 and 0.0045 C mgl−1 s l−1, with minimum values during Springand Summer, and maxima values in Fall and Winter.These dynamics suggest that storm inputs ofterrigenous DOC vary between seasons. During floods inthe dormant season, DOC recession curves were alwayssteeper than discharge decline, suggesting shortflushing of DOC from the leaching of fresh detritusstored in the riparian zone.

Dissolved organic nitrogen budgets for upland, forested ecosystems in New England

Relatively high deposition of nitrogen (N) in the northeastern United States has caused concern because sites could become N saturated. In the past, mass-balance studies have been used to monitor the N status of sites and to investigate the impact of increased N deposition. Typically, these efforts have focused on dissolved inorganic forms of N (DIN = NH4-N + NO3-N) and have largely ignored dissolved organic nitrogen (DON) due to diffi- culties in its analysis. Recent advances in the measurement of total dissolved nitrogen (TDN) have facilitated measurement of DON as the residual of TDN DIN. We calculated DON and DIN budgets using data on precipitation and streamwater chemistry collected from 9 forested watersheds at 4 sites in New England. TDN in precipitation was composed primarily of DIN. Net retention of TDN ranged from 62 to 89% (4.7 to 10 kg ha 1 yr 1 ) of annual inputs. DON made up the majority of TDN in stream exports, suggesting that inclusion of DON is critical to assessing N dynamics even in areas with large anthropogenic inputs of DIN. Despite the dominance of DON in streamwater, precipitation inputs of DON were approximately equal to outputs. DON concentrations in streamwater did not appear significantly influenced by seasonal biological controls, but did increase with discharge on some watersheds. Stream- water NO3-N was the only fraction of N that exhibited a seasonal pattern, with concentrations increasing during the winter months and peaking during snowmelt runoff. Concentrations of NO3-N varied considerably among watersheds and are related to DOC:DON ratios in stream- water. Annual DIN exports were negatively correlated with streamwater DOC:DON ratios, indicating that these ratios might be a useful index of N status of upland forests.

Nitrogen solutes in an Adirondack forested watershed: Importance of dissolved organic nitrogen

Nitrogen (N) dynamics were evaluated from 1 June 1995 through 31 May 1996 within the Arbutus Lake watershed in the Adirondack Mountains of New York State, U.S.A. At the Arbutus Lake outlet dissolved organic nitrogen (DON), NO 3 and NH C contributed 61%, 33%, and 6% respectively, to the total dissolved nitrogen (TDN) flux (259 mol ha 1 yr 1 ). At the lake inlet DON, NO 3 ,a nd NH C constituted 36%, 61%, and 3% respectively, of TDN flux (349 mol ha 1 yr 1 ). Differences between the factors that control DON, NO 3 ,a nd NH C stream water concentrations were evaluated using two methods for estimating annual N flux at the lake inlet. Using biweekly sampling NO 3 and NH C flux was 10 and 4 mol ha 1 yr 1 respectively, less than flux estimates using biweekly plus storm and snowmelt sampling. DON flux was 18 mol ha 1 yr 1 greater using only biweekly sampling. These differences are probably not of ecological significance relative to the total flux of N from the watershed (349 mol ha 1 yr 1 ). Dissolved organic N concentrations were positively related to discharge during both the dormant (R 2 = 0.31; P < 0.01) and growing season (R 2 = 0.09; P < 0.01). There was no significant relationship between NO 3 concentration and discharge during the dormant season, but a significant negative relationship was found during the growing season (R 2 = 0.29; P < 0.01). Biotic controls in the growing season appeared to have had a larger impact on stream water NO 3 concentrations than on DON concentrations. Arbutus Lake had a major impact on stream water N concentrations of the four landscape positions sampled, suggesting the need to quantify within lake processes to interpret N solute losses and patterns in watershed-lake systems.

Atmospheric deposition and watershed nitrogen export along an elevational gradient in the Catskill Mountains, New York

Cumulative effects of atmospheric N deposition may increase N export from water- sheds and contribute to the acidification of surface waters, but natural factors (such as forest productivity and soil drainage) that affect forest N cycling can also control watershed N export. To identify factors that are related to stream-water export of N, elevational gradients in atmo- spheric deposition and natural processes were evaluated in a steep, first-order watershed in the Catskill Mountains of New York, from 1991 to 1994. Atmospheric deposition of SO 2 , and probably N, increased with increasing elevation within this watershed. Stream-water concentrations of SO 2 increased with increasing ele- vation throughout the year, whereas stream-water concentrations of NO 3 decreased with increasing elevation during the winter and spring snowmelt period, and showed no relation with elevation during the growing season or the fall. Annual export of N in stream water for the overall watershed equaled 12% to 17% of the total atmospheric input on the basis of two methods of estimation. This percentage decreased with increasing elevation, from about 25% in the lowest subwatershed to 7% in the highest subwatershed; a probable result of an upslope increase in the thickness of the surface organic horizon, attributable to an elevational gradient in temperature that slows decomposition rates at upper elevations. Balsam fir stands, more pre- valent at upper elevations than lower elevations, may also affect the gradient of subwatershed N export by altering nitrification rates in the soil. Variations in climate and vegetation must be considered to determine how future trends in atmospheric deposition will effect watershed export of nitrogen.

Temporal trends of bulk precipitation and stream water chemistry (1977–1997) in a small forested area, Krusné hory, northern Bohemia, Czech Republic

The Krusné hory (Erzgebirge or Ore Mountains) has been heavily affected by high atmospheric pollutant deposition caused by fossil fuel combustion in an adjacent Tertiary coal basin. Long-term routine sampling of bulk precipitation (1977–1996) and stream water (1977–1998) in a forested area on the south-eastern slope of the mountains were used to evaluate trends and patterns in solute concentration and flux with respect to controlling processes. From 1977 to 1996, the annual volume-weighted Ca2+ and SOconcentrations decreased in bulk precipitation. However, after 1989, when a pronounced and continuous decrease occurred in coal production, annual volume-weighted concentrations decreased for most solutes, except H+. The concentration decreases were marked, with 1996 levels at or below 50% of those in 1989. The lack of a trend in H+ is attributed to similar decreases in both acid anions and neutralizing base cations. Stream water concentrations of most solutes, i.e. H+, Ca2+, Mg2+, SONOwere highest at the onset of sampling in 1977, decreased markedly from 1977 to 1983 and decreased more gradually from 1983 to 1998. The spruce forest die-back and removal reduced dry deposition of these solutes by reducing the filtering action, which was provided by the forest canopy. A notable decrease in stream water Ca2+ concentrations occurred after 1995 and may be due to the depletion of Ca2+, which was provided by catchment liming in 1986, 1988 and 1989. Solute flux trends in bulk atmospheric deposition and stream water generally were not significant and the lack of trend is attributed to the large interannual variability in precipitation quantity and runoff, respectively. All solutes except Na+ varied seasonally. The average seasonal concentrations varied between the solutes, but for most solutes were highest in winter and spring and lowest in summer, correlating with the seasonal trend in runoff. For Ca2+, Mg2+ and SOthe concentration minimum occurs in September and the maximum occurs in February or March, correlating with the seasonal baseflow. These solutes are primarily controlled by the contribution of soil water and groundwater to stream flow. During snowmelt, the meltwater generally causes concentrations to decrease as soil water and groundwater are diluted. For NO3 , average minimum concentrations occur in August at the end of the growing season concurrent with the lowest stream flow, and the maximum occurs in February and March with high stream flow during snowmelt. Seasonal stream water NOconcentration variations are large compared with the long-term decrease. Copyright © 1999 John Wiley & Sons, Ltd.

Watershed- and plot-scale tests of the mobile anion concept

Anion fluxes from a forest soil are usually correlated with those of base cations (BC). Declines in base cation deposition or long-term depletion from the soil may change these relationships. We used multiple regression to identify biogeochemical variables predicting annual volume-weighted concentrations of BC in streamwater draining a forested watershed, and analysis of variance to compare the effects of Ca and Cl inputs on BC fluxes out of soil horizons in irrigated plots. For the watershed, anion concentrations in streamwater predicted BC export most precisely (R2 = 0.84). The best two-variable model (adjusted R2 = 0.91) also included BC concentration in bulk deposition. Consistent with predictions from equations governing exchange chemistry, the proportion of charge contributed by Ca2+ increased with increasing total anion concentration, while that of Na+ decreased. At the plot scale, Cl- concentrations in treatment solutions had a stronger effect (p = 0.06) on BC concentration in Oa-horizon solutions than did Ca2+ concentrations (p = 0.33). In individual horizons of individual plots, BC and total ion concentrations were correlated, but cation composition was not consistent within horizons from different plots. This study detected no evidence of long-term cation depletion in the soils controlling streamwater, but did detect extremely base-poor plots. Because acid deposition affects surface horizons first, streamwater chemistry may not be an adequate way to assess nutrient supply of forest soils.

Application of environmental models to different hydrological systems

In recent years global problems such as climatic change, acid rain, and water pollution in surface and subsurface environments dominate discussions of world environmental problems. In this paper, the roles of hydrologic processes and hydrogeochemical processes are investigated through development, modification, and application of mathematical models for addressing point and non-point source water quality modelling of receiving waters: surface water, subsurface water and lake water. The paper describes the use of models to simulate the movements of pollutants and water: subsurface water, surface water and lake sediments. A hydrological model was applied to Northeast Pond River watershed to understand climate change effects in the watershed. Four watershed acidification models were applied to compute hydrogen ion, alkalinity and sulphate concentrations from Turkey Lakes watershed, Canada. The computed hydrogen ion was used to estimate acidic events, magnitude of hydrogen ion, and duration using a stochastic model. There exist uncertainties in environmental models due to imperfect knowledge of processes controlling water quality parameters as well as errors in data. Monte Carlo, first order, and inverse method analyses were used to assess uncertainty in models. SUTRA (saturated–unsaturated transport) and SUTRA −1 models were applied to Lambton county, Ontario, Canada to locate groundwater discharge areas for St. Clair River, calculate discharge rates, and hydrogeologic parameters. A sediment contamination model was developed and applied to Great Lakes sediment data to estimate transport parameters by 210Pb data. It was then coupled with fatty acid data and results were compared with observed data. A contaminant transport model was developed and applied to two North American streams to compute stream water concentration. The computed data was compared with observed data using a simple statistical method. A hydrological model was coupled with water quality models and RAISON (regional analysis by intelligent systems on) expert system and applied to Canadian watersheds. Digital satellite data was used to locate groundwater discharge and recharge areas in the watershed. This data is useful as observed data for hydrological modelling and GIS (Geographical Information System) system.

Seasonal change in precipitation, snowpack, snowmelt, soil water and streamwater chemistry, northern Michigan

We have studied weekly precipitation, snowpack, snowmelt, soil water and streamwater chemistry throughout winter for over a decade in a small (176 ha) northern Michigan watershed with high snowfall and vegetated by 60 to 80 year-old northern hardwoods. In this paper, we examine physical, chemical, and biological processes responsible for observed seasonal change in streamwater chemistry based upon intensive study during winter 1996-1997. The objective was to define the contributions made to winter and spring streamwater chemical concentration and flux by processes as snowmelt, over-winter forest floor and surface soil mineralization. immobilization, and exchange, and subsurface flowpath. The forest floor and soils were unfrozen beneath the snowpack which permitted most snowmelt to enter. Over-winter soil mineralization and other biological processes maintain shallow subsurface ion and dissolved organic carbon (DOC) reservoirs. Small, but steady, snowmelt throughout winter removed readily mobilized soil NO 3 - which resulted in high over-winter streamwater concentrations but little flux. Winter soil water levels and flowpaths were generally deep which increased soil water and streamwater base cation (C B ), HCO 3 - , and Si concentrations. Spring snowmelt increased soil water levels and removal of ions and DOC from the biologically active forest floor and shallow soils. The snowpack solute content was a minor component in determining streamwater ion concentration or flux during and following peak snowmelt. Exchangeable ions, weakly adsorbed anions, and DOC in the forest floor and surface soils dominated the chemical concentration and flux in soil water and streamwater. Following peak snowmelt, soil microbial immobilization and rapidly increased plant uptake of limiting nutrients removed nearly all available nitrogen from soil water and streamwater. During the growing season high evapotranspiration increased subsurface flowpath depth which in turn removed weathering products, especially C B , HCO 3 - , and Si, from deeper soils. Soil water was a major component in the hydrologic and chemical budgets.

Application of the forest–soil–water model (PnET-BGC/CHESS) to the Lysina catchment, Czech Republic

In this study a fully linked plant-soil-water model PnET-BGC/CHESS (Santore, R.C., 1996. PnET-BGC/CHESS model. Version P3NC115; Santore, R.C., 1999. Modeling forest soil response to chemical treatment at three sites in the Adirondack Mountains, New York) was evaluated and applied. Forest growth, hydrologic, and biogeochemical processes with emphasis on element cycling in forest and adjacent aquatic ecosystems were simulated for the Lysina catchment, Czech Republic. The PnET-BGC submodel expands calculations of forest productivity and water use of the earliest version of the PnET model to include decomposition processes and cycling of major nutrients and other elements. The CHESS submodel simulates abiotic soil chemical processes. The study catchment consists of Norway spruce ( Picea abies) plantations on Spodosols located in a granitic highland of western Bohemia. Forest growth, hydrology and biogeochemistry of the catchment were simulated for the period 1550–2050. Simulated concentrations of SO 4 2−, F −, Ca 2+, Mg 2+, Na +, K +, Fe T, Si, and monomeric Al were similar to streamwater concentrations measured in 1990–1994. The model moderately overpredicted H +, Cl − and DOC, and highly overpredicted NO 3 − and especially NH 4 +. A scenario of reductions of S inputs by 67% of 1991–1994 values in 1995–2050 showed a decrease in base saturation of soil of 2.5% between 1995 and 2050. Inputs of S reduced by 90% of current values showed an increase in soil base saturation after 2030. Scenarios of improved deposition of S showed desorption of previously stored S to drainage water which delayed recovery from inputs of acidic deposition.

Water quality impacts of forest fertilization with nitrogen and phosphorus

The drinking-water quality of streamwater in forests is typically very good, exceeding the quality of water in areas with other types of land use. Streams draining agricultural lands in the United States average about nine times greater concentrations of nitrate and phosphate than streams draining forested areas. Forest fertilization commonly increases nutrient concentrations in streamwater, and large increases could lead to unacceptable degradation of water quality. This review summarizes information from studies of forest fertilization around the world, and evaluates the responses of streamwater chemistry. In general, peak concentrations of nitrate-N in streamwater increase after forest fertilization, with a few studies reporting concentrations as high as 10–25 (mg N)/l as nitrate. Increases in average concentrations of nitrate are much lower than the peak values, and the highest annual average nitrate-N concentration ever reported was 4 (mg N)/l. Relatively high concentrations of streamwater nitrate-N tend to occur with repeated fertilization, use of ammonium nitrate (rather than urea), and fertilization of N-saturated hardwood forests. Ammonium-N concentrations may also show large peaks following fertilization (up to 15 (mg N)/l), but annual averages remain <0.5 (mg N)/l. Fertilization with phosphate can lead to increased peak concentrations of >1 (mg P)/l, but annual averages remain <0.25 (mg P)/l. No evidence has been reported of detectable effects of forest fertilization on the composition or productivity of stream communities, but more detailed studies may be warranted (especially in relation to P fertilization). Major limitations in current knowledge include the effects of repeated fertilization in short-rotation plantations, fertilization of large landscapes rather than small stands, and the effects of fertilization on streamwater chemistry in tropical plantations.