Changes In Stream Water Quality Research Articles

Sulfate runoff processes during rainfall events in a small forested catchment on the sea of Japan side recovering from acidification under climate change

AbstractChanges in rainfall patterns due to climate change may accelerate the runoff of sulfate (SO42−), which is anthropogenically emitted and deposited as an air pollutant, cycled in forest ecosystems, and partly accumulated in forest soils. A forested catchment on the Sea of Japan side in central Japan is significantly affected by transboundary air pollution from the Asian continent due to northwesterly seasonal winds in winter. In this study, intensive 24‐h observations were conducted every hour eight times from 2019 to 2020 to clarify changes in stream water quality and runoff processes during rainfall events. The pH, electrical conductivity, and SO42− concentration in stream water decreased with increasing hourly average discharge rate (L sec−1). The SO42− concentration was negatively correlated with discharge rate. Hydrograph separations using the water isotopic parameter (deuterium excess, d‐excess = δ2H – 8 × δ18O) showed that most of the stream flow during the rain events was derived from pre‐storm water. A significant negative correlation between the d‐excess and stream water discharge was found for all six events where the water isotope analysis was applied. However, the S isotope ratio (δ34S) in stream water was not correlated with discharge rate during rainfall events and was obviously different (>1.5‰) from rainwater δ34S in the same month. This suggests that rainwater SO42− during rainfall events did not directly flow to the stream but was retained in the forest ecosystem. The isotopically well homogenized internal SO42− appeared to be mainly released into the stream during rainfall events. Future climate change may further accelerate SO42− runoff from forest catchments and disrupt material cycles in the ecosystem if warming causes more intense rainfall.

Hydroclimatic non-stationarity drives stream hydrochemistry dynamics through controls on catchment connectivity and water ages

We used data from 17 years of routine stream flow sampling to characterise hydrochemical dynamics in the Girnock Burn, an internationally important long-term catchment monitoring site. We combined hydrochemical time series analysis with hydrological modelling to understand short- and long-term dynamics in relation to dominant runoff processes. Isotopic tracer data employed within the model enabled flux tracking of water as it transited the catchment, facilitating water age estimates. The stream drains an upland 31 km2 catchment with complex topography and variable geology, which influences soil distributions; peaty soils dominate valley bottoms which receive drainage from more permeable podzolic soils on steeper slopes. Short-term hydrochemical dynamics largely reflect the relative dominance of hydrological sources: summer low flows are dominated by alkaline groundwater high in weathering products (Ca2+, Mg2+, SiO2) whilst high flows generated by overland flow from peaty soils are more acidic, DOC enriched, and dominated by atmospheric solutes (Na+, Cl-, SO42-). Baseflows are dominated by older groundwater (>∼3years) in contrast to storm runoff dominated by younger (<∼0.5 years), near-surface, waters. Usual seasonal distributions of stream flows, with high flows in winter and summer low flows, result in strong seasonality in most solutes. However, coupled effects of hydroclimatic variability and catchment heterogeneity dictates marked scatter in flow-concentration relationships for most determinands. A long-term decreasing trend was evident for SO42-concentrations, reflecting continuing effects of reductions in atmospheric deposition of pollutants from coal burning. Reductions in large storm event frequency post-2016 and protracted periods of low flows in the droughts of 2018 and 2022 have resulted in the catchment becoming dominated by low flows, derived from older groundwater with more alkaline chemistry for longer periods. Changing climatic conditions and stream flow responses seem likely to continue to cause changes in stream water quality and associated ecosystem services of the Girnock Burn and similar upland catchments.

Catchment-scale impacts of shallow landslides on stream water chemistry

Catchment water quality plays an important role in ecosystem and water resource management in mountainous areas. Shallow landslides triggered by earthquakes or heavy rainfall can cause a sudden and long-term deterioration in stream water quality by releasing contaminants into streams. Although many studies have been undertaken on the relationship between a single landslide and the water chemistry of a nearby river, little is known about the impact of densely distributed shallow landslides on stream water chemistry at the catchment scale. To this end, this study determined the major ion concentrations and isotopic compositions of stream water along with the shallow landslide area/catchment area ratio (LCR) in 37 headwater subcatchments in the southern part of Hokkaido, Japan, where an earthquake caused more than 6000 shallow landslides on September 6, 2018. In subcatchments with a high LCR, stream water exhibited significantly higher Ca2+ and HCO3− concentrations, while there was no correlation between the LCR and concentrations of Na+ and Cl−. The δ18O and δD values of stream water plotted between the local meteoric water lines of summer and winter precipitation, indicating that they originated from meteoric water. Shallow landslides formed sliding surfaces, landslide deposits, and landslide-dammed lakes, which enhanced the interaction between the surface soil and stream water, leading to Ca–HCO3 type water. The results showed that shallow-landslide-driven changes in stream water quality could be linearly approximated by the fraction of the landslide area at the catchment scale, which is a more versatile approach than the local framework of a single landslide and a nearby stream. In future research, these findings could be combined with a slope stability model and the background climatic, geological, topographical, and water quality conditions of a watershed to evaluate water pollution triggered by shallow landslides at the catchment scale.

Effect of metal pollution from mining on litter decomposition in streams

Litter decomposition is critical to stream biogeochemical cycles. Metal pollution from past or present mining activities seriously threatens stream ecosystems. However, its effects on litter decomposition in streams remain unclear. A field litterbag experiment was conducted to determine the direct (i.e., via changes in stream water quality: a mine-affected vs. forest stream) and indirect (i.e., via changes in litter traits: polluted vs. non-polluted litter) effects of metal pollution from mining activities on leaf litter decomposition (total vs. microbial-driven) and the associated microbial activity and community composition in streams. Platanus acerifolia leaf litter collected from a polluted and a non-polluted site was enclosed in fine and coarse mesh bags and incubated in a mine-affected stream and a forest stream. The litter from the polluted site had a higher Pb, Zn, Cd, N, soluble sugar concentrations, specific leaf area and pH, and lower leaf toughness and lignin concentration than the litter from the non-polluted site. After incubation in situ, litter mass loss did not significantly differ between streams, but the mine-affected stream had a greater impact on total-driven decomposition rates than microbial-driven decomposition rates. Polluted litter had a significantly higher decomposition rate than non-polluted litter. The decomposition potential of polluted litter produces faster nutrient cycling and supports higher microbial colonization. Litter traits and decomposer community type modulate the influence of metal pollution on litter decomposition. The results suggest that the indirect effects of mining activities on litter decomposition were stronger than the direct effects.

Riparian wetland rehabilitation and beaver re-colonization impacts on hydrological processes and water quality in a lowland agricultural catchment

Quantifying the catchment water balance and the characterization of its water quality changes are effective tools for establishing the response of catchments to shifting land management practices. Here we assess long-term hydrological partitioning and stream water chemistry over a 30-year period in a rural mixed land use catchment in northern Germany undergoing riparian wetlands and widespread re-colonization by beavers (Castor fiber) along the river network. We used long-term spatially distributed stream discharge, groundwater levels and surface water quality data with a simple monthly water balance model, changes in the variability in discharge measurements, and statistical analysis of spatio-temporal changes in stream water quality to assess long-term changes. Water balance estimates indicated high proportions of evapotranspiration loss (~90% of total precipitation) and relatively low groundwater recharge (<5% of total precipitation) prior to riparian rehabilitation in 2000. Increasing groundwater levels from 2000 to 2017 and the relatively linear nature of the catchment storage – discharge relationship, indicate a gradual increase in groundwater recharge (buts still <10% of total precipitation). Wetland rehabilitation, greatly enhanced by increasing beaver populations, resulted in longer water transit times in the stream network, less linear storage-discharge relationship and a loss of daily stream variability, increased DOC concentrations, isotopic evaporative enrichment downstream, and moderated stream temperatures. There was limited long-term water quality improvements from wetland rehabilitation on either nitrate or total phosphorus concentrations, with unchanged seasonal summer and winter peak concentrations for phosphorus and nitrate, respectively. This likely reflects the long-term legacy of fertilizer use on nutrient reservoirs in the catchment's soils, aquifers, and stream network. These long-term changes in hydrology and stream chemistry resulting from riparian rehabilitation and changes in agricultural management practices provide invaluable insights into catchment functioning and an evidence base for future planning in relation to long-term climatic changes.

Post-fire water-quality response in the western United States

Wildfires are increasing in size and severity in forested landscapes across the Western United States. Not only do fires alter land surfaces, but they also affect the surface water quality in downstream systems. Previous studies of individual fires have observed an increase in various forms of nutrients, ions, sediments and metals in stream water for different post-fire time periods. In this research, data were compiled for over 24 000 fires across the western United States to evaluate post-fire water-quality response. The database included millions of water-quality data points downstream of these fires, and was synthesised along with geophysical data from each burned watershed. Data from 159 fires in 153 burned watersheds were used to identify common water-quality response during the first 5 years after a fire. Within this large dataset, a subset of seven fires was examined further to identify trends in water-quality response. Change-point analysis was used to identify moments in the post-fire water-quality data where significant shifts in analyte concentrations occurred. Evaluating individual fires revealed strong initial increases or decreases in concentrations, depending on the analyte, that are masked when averaged over 5 years. Evidence from this analysis shows significant increases in nutrient flux (different forms of nitrogen and phosphorus), major-ion flux and metal concentrations are the most common changes in stream water quality within the first 5 years after fire. Dissolved constituents of ions and metals tended to decrease in concentration 5 years after fire whereas particulate matter concentration continued to increase. Assembling this unique and extensive dataset provided the opportunity to determine the most common post-fire water-quality changes in the large and diverse Western USA. Results from this study could inform studies in other parts of the world, will help parameterise and validate post-fire water-quality models, and assist communities affected by wildfire to anticipate changes to their water quality.

Structural and functional measures of leaf-associated invertebrates and fungi as predictors of stream eutrophication

Eutrophication is a major threat to freshwater ecosystems worldwide that affects aquatic biota and compromises ecosystem functioning. In this study, we assessed the potential use of leaf decomposition and associated decomposer communities to predict stream eutrophication. Because leaf quality is expected to affect leaf decomposition, we used five leaf species, differing in their initial nitrogen concentration. Leaves of alder, chestnut, plane, oak and eucalyptus were placed in coarse-mesh bags and immersed in six streams along an eutrophication gradient to assess leaf decomposition and the structure of associated decomposer communities. A hump-shaped relationship was established between leaf decomposition and the eutrophication gradient for all leaf species, except for eucalyptus. Invertebrate biomass and density as well as fungal biomass and sporulation were lowest at the extremes of the gradient. Leaf-associated invertebrate and fungal assemblages were mainly structured by stream eutrophication. The percentage of shredders on leaves decreased, whereas the percentage of oligochaeta increased along the eutrophication gradient. The Iberian Biological Monitoring Working Party Index (IBMWP) applied to benthic invertebrates increased from oligotrophic to moderately eutrophic streams and then dropped sharply at highly and hypertrophic streams. Overall, leaf decomposition was a valuable tool to assess changes in stream water quality, and it allowed the discrimination of sites classified by the IBMWP within class I and class IV. Moreover, decomposition of most leaf species responded in a similar way to eutrophication when decomposition was normalized by the quality of leaves.

Changes in stream water quality due to logging of the boreal forest in the Montmorency Forest, Québec

AbstractSummer stream water quality was monitored before and following the logging of 50% of the boreal forest within three small watersheds (&lt;50 ha) nested in the ‘Ruisseau des Eaux‐Volées’ Experimental Watershed, Montmorency Forest (Québec, Canada). Logging was conducted in winter, on snow cover according to recommended best management practices (BMPs) to minimize soil disturbance and protect advance growth. A 20‐m forest buffer was maintained along perennial streams. In watershed 7·2, cut‐blocks were located near the stream network and logging was partially allowed within the riparian buffer zone. In watersheds 7·5 and 7·7, logging occurred farther away from the stream network. Observations were also made for watershed 7·3 that collected the runoff from watersheds 7·2 and 7·5, and watershed 7·6, the uproad portion of watershed 7·7. The control watershed 0·2 was contiguous to the impacted watersheds and remained undisturbed. Following clearcutting, changes in summer daily maximum and minimum stream temperatures remained within ± 1 °C while changes in diurnal variation did not decrease by more than 0·5 °C. Concentrations of NO3− greatly increased by up to 6000% and concentrations of K+ increased by up to 300% during the second summer after logging. Smaller increases were observed for Fetotal (up to 71%), specific conductance (up to 26%), and Mg2+ (up to 19%). Post‐logging pH decreased slightly by no more than 7% while PO43− concentration remained relatively constant. Suspended sediment concentrations appeared to increase during post‐logging, but there was not enough pre‐logging data to statistically confirm this result. Logging of moderate intensity and respecting established BMPs may account for the limited changes of water quality parameters and the low exceedances of the criteria for the protection of aquatic life. The proximity of the cutover to the stream network and logging within the riparian zone did not appear to affect water quality. Copyright © 2008 John Wiley &amp; Sons, Ltd.

Modelling potential impacts of coalbed methane development on stream water quality in an American watershed

AbstractCoalbed methane (CBM) development raises serious environmental concerns and concerted efforts have been made to collect chemistry, salinity, and sodicity data on CBM produced water. A model is sorely needed to make use of this data to quantify potential changes in stream water quality resulting from directly and/or indirectly receiving CBM produced water, on which little information is available in the literature. However, the application of existing hydrodynamic and water quality models such as CE‐QUAL‐W2 is not straightforward because the number of outfalls is usually large and the channels poorly defined for intermittent streams in semiarid areas such as the Powder River watershed, located in the states of Wyoming and Montana. Hence, the objectives of this study were to: (1) develop a CBM produced water routing (CBMPRO) model, and (2) apply the new CBMPRO model, along with a CE‐QUAL‐W2 model, to examine potential changes in stream water quality due to CBM development in the Powder River watershed. The CBMPRO model was developed and used to chart the CBM discharge and the transport of its associated constituents (e.g. total dissolved solids and alkalinity) from an outfall to its inclusive subwatershed outlet. In turn, the outputs from the CBMPRO model were applied as inputs into the CE‐QUAL‐W2 model to predict changes in the water quantity and quality along the Powder River mainstem. The results indicate that discharges from CBM developments adversely affect the stream water quality. Compared with the baseline conditions, the developments would increase the stream flows as well as make the stream water warmer and more saline. In addition, the impacts were predicted to undergo seasonal and spatial variations and to become smaller with time, as expected. Copyright © 2007 John Wiley &amp; Sons, Ltd.

Recovery of Acidified Streams in Forests Treated by Total Catchment Liming

Reduced emissions of acidifying pollutants have changed the acidification process, and as a result, forest soils and surface waters are slowly recovering in Sweden. However, model calculations show that some areas may never recover completely unless further measures, such as liming, are undertaken. Liming of surface waters (lakes, rivers and wetlands) has been successfully practised in Sweden since the 1970s, but repeated treatments are necessary. A full recovery of acidified lakes and streams without frequent liming is however not possible until soil acidification is reversed in the most strongly affected areas. In this study, the recovery of acidified streams was examined using ‘the total catchment approach’ i.e. treatment of both recharge and discharge areas. The aim was to compare the quantitative effect of different treatments on run off chemistry and the recovery of brown trout. Catchments in southwest Sweden were treated with a combination of 2 tons of wood ash and 4, 6 or 12 tons of crushed limestone per hectare in 1998/1999. Treatment of both recharge and discharge areas resulted in fast and significant changes in stream water quality, e.g. increased concentrations of calcium, higher pH and ANC and a decreased concentration of inorganic aluminium. The initial changes were dependent on the distribution of the applied lime between discharge and recharge areas rather than the average dose on the total catchment. Treatment of recharge areas only, resulted in smaller but still significant effects on calcium, pH and ANC in stream water. Furthermore, there was an initial leaching of nitrate but it was only minor compared with the elevated leaching that occurs after a clear-cut. As a result of the treatments, brown trout is now successfully reproducing.

Impact of Agriculture on Water Quality in the North Carolina Middle Coastal Plain

Water quality in the Middle Coastal Plain of North Carolina has been impacted by agriculture; however, the water quality impacts in these areas over time have not been studied in detail. The surface water quality of several streams in the Neuse River Watershed along the Middle Coastal Plain of North Carolina was monitored for approximately five years, while shallow groundwater in cropped fields and adjacent to drainage ditches was monitored for three years. Surface water samples were collected biweekly and analyzed for nitrate nitrogen (N O3 -N) , ammonium nitrogen (N H4 -N) , total Kjeldahl nitrogen, orthophosphate (P O4 -P) , total phosphate, and total suspended solids, and approximately monthly groundwater samples were collected from wells and analyzed for N O3 -N . Trends relating to seasonal changes in stream water quality as a function of land use and soil type were analyzed, as well as long term changes. Generally, upstream sampling points showed low levels of all constituents. Nutrient and sedimen...

Development of Chemical Index as a Measure of In-Stream Water Quality in Response to Land-Use and Land Cover Changes

Water pollution in response to accelerated land-use/land cover changes has drawn concerns because of public health and environmental impacts. The study was conducted to evaluate the impact of land use/land cover changes, seasonal, and location on water quality of streams within the Wheeler Lake Watershed basin in northern Alabama. Temporal water samples from 18 sheppard streams were randomly collected in 2000 and 2001, processed and analyzed for pH, and total nitrogen (TN), dissolved (Dp), particulate (Pp) and total phosphorus (Tp), dissolved oxygen (DO) and soluble lead (Pb) concentration, employing standard methods of analysis. The data were normalized and integrated into a simple index (WQCIndex) to evaluate stream water quality. Results showed that the urban proportion of the total watershed basin had increased from 2.9 to 14.7% with an associated loss of agricultural (8.9%) and wetland (4.8%) covers from 1992 to 2000. A change in land-use/land covers in association with seasonal and location variation significantly affected stream water quality. Total nitrogen concentration in stream water had a peak during the summer at 34% above the annual mean. While both Pp and Tp concentrations peaking during the summer at 24% above the annual mean and about 25% below the annual mean during spring, the DO concentrations were 46% above the annual mean during the fall and 18 to 26% below annual mean during summer. The WQCIndex had responded very seasonal and showed significant identical trends, with 21% degradation in water quality during the summer above the annual mean and improvement during the spring at 20% above the annual mean. Upstream water had a significantly greater Pp and Tp (21 to 28%) concentration than at down- and middle streams water. Location and seasonal variations had significant interactive effects on Pp, Tp and DO concentration of stream water. Total amount of seasonal rainfall significantly accounted 99.6% of the variations in WQCIndex. Increasing seasonal mean relative humidity, air and soil temperature, evaporation and solar radiation had positive relationship with the variations in WQCIndex. Among the water quality parameters, both Pp and Tp were correlated (r 2 = 0.998∗*∗) to each other, and accounted for more than 80% variability of the WQCIndex. Highly significant positive linear relationship between Pp and Tp concentration suggested that 99.8% of the P in stream water is in Pp form which probably transported with sediments in surface runoff. In other words, Pp is the main pollutant responsible for degradation of stream water quality in the Wheeler lake basin. Routine measurement of either Pp or Tp concentration could be used as sensitive and early indicator of temporal changes in stream water quality even when the other parameters changed negligibly or remain unchanged.

Impact of riparian buffer zones on water quality and associated management considerations

Recent attention has focused on riparian forest buffer systems for filtering sediment, nutrients, and pesticides entering from upland agricultural fields. This paper summarizes the results of a field monitoring study done in Tokachikawa watershed in Hokkaido, Japan, Cisadane, Cianten and Citamyang sub-watersheds in Indonesia and Cauvery watershed, India to quantify the impact of riparian buffer zones on changes in stream water quality. A watershed approach was used to compare land use indicators – uplands, forests, riparian forest, livestock areas – to a wide range of surface water physical and chemical properties. Stream water physical property values increased from upstream to the confluence point, influenced by the upland and livestock land use activities. The greatest reduction in impairment of water quality was observed in buffer zones located along higher order streams where the gradient is very low, leading to slow groundwater movement. The lower stream water temperature in riparian buffer zones suggests that the shading effect is most pronounced in this area of the watershed. The results demonstrate the positive impact of forest buffer zones in reducing the influence of agricultural nutrients and chemicals on surface stream waters. Design and management considerations for establishing riparian zone land use are discussed.

Modelling Changes in Stream Water Quality Due to Climate Change in a Southern Ontario Watershed

This research represents a pilot project to establish a methodology for assessing the sensitivity of watershed stream water quality to changes in water quantity caused by climate change. The pilot watershed is the Duffins Creek watershed, located 20 km east of the City of Toronto, Canada. Scenarios of climate change analyzed in this project were drawn from two internationally recognized climate models: the Canadian Centre for Climate Modelling and Analysis (CCCma) CGCM1 and the Hadley Centre HadCM2. The AGNPS (Agricultural Non-Point Source) model was used to predict changes in stream water chemistry. The results are compared to baseline conditions as well as future conditions based on 2020 land use scenarios. It was determined that 2020 land use scenarios typically result in much smaller changes in peak flows than are predicted for the climate change scenarios, especially the wet climate change scenarios. Understanding climate change responses is critical for the development of watershed plans and drinking water source protection studies. Currently, watershed studies are completed using climate information based on relatively short-term monitoring databases that reflect past weather patterns. It is widely understood that management actions advocated in watershed studies could be improved if consideration were given to the implication of climate changes.

Characterization of environmental gradients using physico-chemical measurements and diatom densities in Nairobi River, Kenya

Degradation of water resources due to anthropogenic activities is a major problem all over the world. Monitoring changes in water quality is expensive but essential for management of water resources. Diatom assemblages can serve as useful indicators of changes in water quality. In order to determine changes in stream water quality in an urban environment, densities of epilithic diatom communities on both natural and artificial substrates were sampled in Nairobi River, Kenya in September 2000. Sampling of water and diatoms was carried out in almost equidistant sites along a 60 km stretch of the Nairobi River. Environmental (water physico-chemical and nutrients) data was explored by Principal Correspondence Analysis (PCA) and sites split into three groups of upper-, mid- and lower stream. Most abundant diatom taxa on both substrates were selected and their relationship with environmental variables determined. On artificial substrates, Gomphonema parvulum, Nitzschia palea and Nitzschia umbonata were the most abundant and were significantly related with total dissolved solids, nitrate, conductivity and turbidity. Temperature, altitude and pH interacted significantly with dominant diatom species on natural substrates, which included Gomphonema parvulum, Nitzschia palea and Navicula subminuscula. Non-parametric analyses showed that diatom densities in natural and artificial substrates were significantly different and were affected by different environmental variables. Our results indicate that abundant diatom species can be used to describe major types of aquatic environmental gradients and can serve as good indicators of ecological conditions in tropical streams and rivers. This study also showed that diatoms from artificial and natural substrates can be used to provide complementary information.

Assessing TMDL Effectiveness Using Flow-Adjusted Concentrations: A Case Study of the Neuse River, North Carolina

Integrated control of both point and nonpoint source water pollution using Total Maximum Daily Load (TMDL) assignments will be a major regulatory focus over the next decade. We propose the use of "flow-adjusted" pollutant concentrations to evaluate the effectiveness of management actions taken to meet approved TMDLs. Pollutant concentrations are usually highly correlated with streamflow, and flow is strongly weather-dependent. Thus, pollutant loads, which are calculated as pollutant concentration multiplied by streamflow, have a large weather-dependent variance component. This natural variation can be removed by calculating flow-adjusted concentrations. While such values are not a direct measure of pollutant load, they make it easier to discern changes in streamwater quality. Additionally, they are likely to be a better predictor of pollutant concentrations in the receiving waterbody. We demonstrate the use of this technique using long-term nutrient data from the Neuse River in North Carolina. The Neuse River Estuary has suffered many eutrophication symptoms, and a program to reduce nutrient loading has been in place for several years. We show that, in addition to revealing recent reductions in nutrient inputs, annual flow-adjusted riverine nutrient concentrations show a more pronounced relationship with estuarine nutrient concentrations than do annual nutrient loads. Thus, we suggest that the calculation of flow-adjusted concentrations is a useful technique to aid in assessment of TMDL implementation.

A simple stream monitoring technique based on measurements of semiconservative properties of water.

Correlative relationships exist among conductivity, alkalinity, and hardness in streams due to natural geological and climatological controls, but the relationships among these three water-quality factors can be altered strongly by inputs of ion-rich wastewaters. The degree of alteration can be monitored conveniently by use of a simple chemical perturbation index, computed by subtracting the sum of rank pairwise correlations among the conductivity, alkalinity, and hardness (for observations on each of these variables, measured through time) from 3.0. The chemical perturbation index can be used to document or characterize spatiotemporal changes in stream water quality. This study explains the development of the index's concept and provides examples of its application in an extensive stream monitoring program used to assess ecological conditions in streams on the Department of Energy's Oak Ridge Reservation in east Tennessee, USA. The chemical perturbation index technique may be particularly useful in community-based stream monitoring programs because to its simplicity and low cost.

Effects of clear-cutting on streamwater quality in forest catchments in central Sweden

Hydrochemical studies were conducted in three forested catchments in central Sweden during a 12-year period (1977–1989). During this period, 50% and 95% of the surface of two of the areas were clear - felled. The third area was left untouched as a control for reference. A qualitative analysis of clear-cut effects was conducted to investigate changes in streamwater quality by use of Principal Component and SIMCA analyses. During the 8 years of clear-cutting, with reference to the control period, the average runoff increased by 85% and 110% (220 mm and 274 mm year −1), respectively, in the two areas felled to 50% and 95%. Significant changes in the status of the streamwater were detected for the two clear-felled catchments, whereas the changes detected in the control catchment were not significant, and within the limits of natural variation. In relation to the reference period, the changes in the clear-felled catchments were identified as dependent mainly on increased concentrations of K +, NH 4 +, NO 3 −, org-N, and tot-N. Concentrations of H + decreased, while changes in concentrations of Ca 2+, Mg 2+, Na +, SO 4 2−, and Cl − were less distinct. At the end of the 8 year investigation period, run-off and chemical composition of the streamwater successively returned to pre-cut conditions.

Water Quality Effects of Excavation and Diversion

Water quality data collected from Yellow Creek in northeast Mississippi before and during construction of the Divide Cut of the Tennessee‐Tombigbee Waterway provide information regarding the water quality effects of stream channelization and large‐scale construction projects. Simple graphical and statistical procedures for detecting changes in stream water quality are demonstrated. Data analysis was hindered by missing data, inconsistencies in the list of variables monitored, and changes in sampling frequency. Observed water quality changes were evidently due to increased inputs of sediment and reduced shade. Statistically significant changes in variances and means were observed for most grab‐sample variables. Mean values of specific conductance, turbidity, color, COD, and total alkalinity, hardness, ammonia, phosphorus, sulfate, iron, lead, and manganese were 50–100% greater during construction than before construction. Estimated average daily loadings of total metals, nutrients, and dissolved solids wer...

Biomonitoring networks operated by schoolchildren

The considerable logistical problems involved in large-scale monitoring networks could be overcome in part by establishing a biological water quality network of stations, operated by high schools. Measurement of benthic invertebrate community structure obtained in a pilot project involving five schools produced results that were reliable with regard to collecting and identification efficiency. Early results from a network that includes more than 20 teachers and 500 students at 12 schools show an ability to identify changes in stream water quality.