The Spatial and Temporal Variability of Nitrate in Streams of the Bull Run Watershed, Oregon PDF Download
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Author: Paul D. Bakke
Publisher:
ISBN:
Category : Bull Run River Watershed (Or.)
Languages : en
Pages : 460
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Book Description
An 18-year record of nitrate (NO3), orthophosphate, total nitrogen and total phosphorus in four streams of the Bull Run watershed, Oregon, was examined to determine its precision and time resolution. Of these four species, only NO3 was found to be known to a sufficient level of detail for modeling and inference purposes. The precision of precipitation NO3 and total nitrogen measurements at the Bull Run was found to be inadequately determined and much poorer than the precision of corresponding stream chemistry data. An autoregressive time-series multiple-regression model was developed to predict stream NO3 load (kg/ha/day) based on 14-day cumulative stream discharge, the current day's, previous day's and cumulative 7-day precipitation, the 14-day average maximum air temperature and a storm hysteresis factor. Coefficients of determination ranged from 0.66 to 0.75. The model was found to be of limited use in inference about watershed processes due to the coarse time resolution of the data (1 to 3 week sampling intervals). Although the 47 independent variables considered were known at much finer time scales (30 minutes to 1 day), this was insufficient to offset the problem of long sampling intervals and strengthen the inference capability. Complete description of the nutrient record would require sampling intervals of less than one day during periods of rapid change. Peak NO3 concentration and load events were found to be unrelated to suspended sediment concentration or the magnitude of snow melt. Stream NO3 showed a weak inverse relationship with precipitation NO3 or total nitrogen content. Where light and other non-nutrient factors are present in abundance, streams of the Bull Run watershed were found to be predominantly phosphorus limited, although nitrogen-limited conditions occur in 1 to 37 percent of the days sampled, depending on sub-basin.
Author: Paul D. Bakke
Publisher:
ISBN:
Category : Bull Run River Watershed (Or.)
Languages : en
Pages : 460
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Book Description
An 18-year record of nitrate (NO3), orthophosphate, total nitrogen and total phosphorus in four streams of the Bull Run watershed, Oregon, was examined to determine its precision and time resolution. Of these four species, only NO3 was found to be known to a sufficient level of detail for modeling and inference purposes. The precision of precipitation NO3 and total nitrogen measurements at the Bull Run was found to be inadequately determined and much poorer than the precision of corresponding stream chemistry data. An autoregressive time-series multiple-regression model was developed to predict stream NO3 load (kg/ha/day) based on 14-day cumulative stream discharge, the current day's, previous day's and cumulative 7-day precipitation, the 14-day average maximum air temperature and a storm hysteresis factor. Coefficients of determination ranged from 0.66 to 0.75. The model was found to be of limited use in inference about watershed processes due to the coarse time resolution of the data (1 to 3 week sampling intervals). Although the 47 independent variables considered were known at much finer time scales (30 minutes to 1 day), this was insufficient to offset the problem of long sampling intervals and strengthen the inference capability. Complete description of the nutrient record would require sampling intervals of less than one day during periods of rapid change. Peak NO3 concentration and load events were found to be unrelated to suspended sediment concentration or the magnitude of snow melt. Stream NO3 showed a weak inverse relationship with precipitation NO3 or total nitrogen content. Where light and other non-nutrient factors are present in abundance, streams of the Bull Run watershed were found to be predominantly phosphorus limited, although nitrogen-limited conditions occur in 1 to 37 percent of the days sampled, depending on sub-basin.
Author: Jeffrey Glenn Mutti
Publisher:
ISBN:
Category : Groundwater
Languages : en
Pages : 346
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Book Description
Groundwater nitrate contamination is a well-documented issue in the Southern Willamette Valley (SWV) of Oregon, as a Groundwater Management Area (GWMA) has recently been declared. As a GWMA, groundwater nitrate monitoring must occur until regional concentrations are below 7 mg/L NO3-N. However, the presence of temporal variability can make it difficult to determine if contamination exceeds a threshold and if contamination is increasing or decreasing over time. To examine the potential impact of temporal variability on groundwater nitrate monitoring in the SWV, a well network was created and sampled monthly for 15 months. Results indicate that substantial intra-well temporal variability is present, and that spatial variability of groundwater nitrate is greater than temporal variability. Generally, temporal variability was associated with recharge events, which flushed higher concentration soil-water into the aquifer. Though individual wells showed seasonality, network-wide seasonal trends were not statistically significant (which is believed to be caused by a dampening effect due to local heterogeneities). From a monitoring perspective, this implies that less frequent groundwater nitrate sampling (such as quarterly) can capture network-wide seasonal response to the same degree as monthly sampling. To determine how long-term land management practices are likely to impact regional nitrate leaching and future monitoring trends, a nitrogen loading model was created for the SWV. Present-day data were used to calibrate and validate the Soil and Water Assessment Tool (SWAT) model, with 3 alternative future scenarios then being evaluated. The effects of agrarian Groundwater Best Management Practices (GW-BMPs) were examined with respect to nitrate leaching in present and future scenarios. Modeled values indicate that agrarian GW-BMP implementation is a more effective agent for reduced nitrate leaching than land use change alone. Together, land use change and the adoption of GW-BMPs were found to decrease nitrate leaching values by 32 to 46% of their present-day rates. These predicted results do not include the impact of denitrification or changes in septic leaching, and therefore should be regarded with caution as they do not completely represent future conditions. Considering this, a conservative conclusion which can be drawn is that GW-BMP implementation is a safer alternative than reliance on projected land use/crop change alone for lessening groundwater nitrate concentrations in the GWMA. This is the first study to successfully apply SWAT as a tool to examine the spatial and temporal variability of nitrate leaching.
Author: Frank A. Rinella
Publisher:
ISBN:
Category :
Languages : en
Pages : 76
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Book Description
Author: Paul W. Adams
Publisher:
ISBN:
Category : Municipal water supply
Languages : en
Pages : 106
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Book Description
Author:
Publisher:
ISBN:
Category : Forests and forestry
Languages : en
Pages : 870
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Book Description
Author: Sade H Shafer
Publisher: Springer Science & Business Media
ISBN:
Category : Education
Languages : en
Pages : 440
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Book Description
Cited in Sheehy, Chen, and Hurt . Volume 38 (thesis year 1993) reports a total of 13,787 thesis titles from 22 Canadian and 164 US universities. As in previous volumes, thesis titles are arranged by discipline and by university within each discipline. Any accredited university or college with a grad
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 346
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Book Description
Author: V. Cody Hale
Publisher:
ISBN:
Category : Forest management
Languages : en
Pages : 220
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Book Description
Few studies have examined both long-term and fine-scale spatial variations in water quality of small streams in the Pacific Northwest. As such, a case study was conducted to determine if current physical and chemical properties of water in three streams located in the Oregon Coast Range differed from historically measured conditions, taking differences in past management regimes into account. In addition, this research provides an assessment of spatial and temporal variability in nitratenitrogen (N) concentrations and summer stream temperatures within each catchment. The three research catchments were part of the Alsea Watershed Study (1959- 1973), where effects of forest management practices were examined using a pairedwatershed study design. One catchment, Needle Branch, was clear-cut with no protection provided to the stream. Harvesting in Needle Branch was followed by an intense broadcast burn to remove logging slash. Another catchment, Deer Creek, was patch-cut in three small units resulting in a 25% harvest of the total catchment area, but buffers were retained along fish-bearing streams. The third catchment, Flynn Creek, was used as a control. In this revisit to the Alsea Watersheds, measurements were conducted continuously (discharge, turbidity), intermittently (suspended sediments), and at regular intervals (nitrate-N) for one year between October 2005 and September 2006. Summertime stream temperature was also measured every half-hour from mid-June to mid-September. Comparisons of recent data with historic data show no detectable changes over time for streamflow characteristics (annual runoff volume, peak flow discharges, and number of low-flow days), annual sediment yield, or summer maximum stream temperatures. Current nitrate-N export was similar to historically measured values for Flynn Creek and Deer Creek; however, export at Needle Branch was increased over past levels. This observation may be caused by dense colonization of the riparian area with red alder (Alnus rubra), a N-fixing species, following the 1966 harvest. Patterns of nitrate-N concentration varied throughout each catchment and are likely influenced by the current distribution of red alder stands. Synoptically measured stream temperatures were variable along each stream's longitudinal profile. The ability to meet Oregon's water quality standard for temperature was dependent on measurement location and method of analysis. Evaluating individual sampling points as discrete records resulted in each stream exceeding the standard for at least one measurement location, whereas evaluating the criteria based on the mean of all data collected within the mainstem stream excluded Flynn Creek and Needle Branch from violation. These results highlight the physical and chemical variability of stream water draining Oregon Coast Range headwater catchments and provide insight as to where future work should be focused to gain a more thorough understanding of these dynamic systems.
Author: Nancee Christine Hunter
Publisher:
ISBN:
Category : Climatic changes
Languages : en
Pages : 182
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Author: Robert A. Scherer
Publisher:
ISBN:
Category : Rivers
Languages : en
Pages : 254
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Book Description
High intensity sampling was undertaken to characterize the temporal and spatial variability of oxidized nitrogen (NO3-N + NO2-N), ammonia-nitrogen (NH3-N), total dissolved phosphorus, total unfiltered phosphorus and orthophosphorus (PO4-P) from two adjacent small streams in Western Oregon's Coast Range, Deer Creek (303 ha) and Flynn Creek (203 ha). Deer Creek has been 39 % clearcut from 1966 to 1987 while, Flynn Creek has never been logged and remains a "control" watershed for various research projects. A sequential wet-deposition precipitation sampler was also used to determine the temporal variability of oxidized-nitrogen, ammonia-nitrogen, total dissolved phosphorus and orthophosphorus entering a watershed during two storm events. Samples collected every one hour over a 25 to 26-h period during summer low flows indicated that oxidized nitrogen, ammonia-nitrogen, total unfiltered phosphorus, and orthophosphorus remained relatively constant. Total dissolved phosphorus concentrations were the most variable but did not have a discernible diel pattern. On a spatial scale, total unfiltered phosphorus and total dissolved phosphorus remained relatively constant or showed no discernable patterns when sampled over five 250-m intervals on each creek during summer low flow. Oxidized nitrogen and orthophosphorus concentrations increased on Deer Creek and decreased on Flynn Creek in an downstream direction. Ammonia-nitrogen concentrations decreased in a downstream direction on Deer Creek and remained constant on Flynn Creek. Nutrient constituent concentrations observed during high intensity sampling of three storm events had a variable response with stream discharge. Oxidized nitrogen concentration levels collected during the first fall storm appeared to be consistent with other research that has shown a flush of oxidized nitrogen out of the forest soil profile during the first fall storm. Sample concentrations from the first sampled storm had a 36 % decrease in concentration with the falling limb of the first sampled storm on both Deer Creek and Flynn Creek. Whereas, oxidized nitrogen concentrations had a 9 to 25 % decrease with an increase in discharge on the two studied creeks and returned to pre-storm levels with a decrease in discharge during two winter storms. Total unfiltered phosphorus concentrations had a 90 to 1150 % (0 to 10 fold) increase with a rise in storm discharge and decreased with the fall in storm discharge depending on the storm event and creek sampled. Ammonia-nitrogen, total dissolved phosphorus and orthophosphorus concentrations were not related to changes in discharge. Precipitation concentrations of oxidized nitrogen and ammonia-nitrogen either had a variable response or became diluted with an increase in rainfall amounts. The different responses appear to be related to storm intensity, with greater dilution in higher intensity storms. Results from this study indicate that the input and output of nitrogen and phosphorus into forested streams can be quite variable on both small temporal and spatial scales depending on the particular nutrient sampled, the particular creek sampled, stream flow conditions and season. It appears that sampling schemes designed for monitoring water chemistry or nutrient flux should initially presume significant short interval (2 to 20-h) variation until intensive sampling is able to prove otherwise.
