Temporal and Spatial Variability of Groundwater Nitrate in the Southern Willamette Valley of Oregon PDF Download
Are you looking for read ebook online? Search for your book and save it on your Kindle device, PC, phones or tablets. Download Temporal and Spatial Variability of Groundwater Nitrate in the Southern Willamette Valley of Oregon PDF full book. Access full book title Temporal and Spatial Variability of Groundwater Nitrate in the Southern Willamette Valley of Oregon by Jeffrey Glenn Mutti. Download full books in PDF and EPUB format.
Author: Jeffrey Glenn Mutti
Publisher:
ISBN:
Category : Groundwater
Languages : en
Pages : 346
Get Book Here
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: Jeffrey Glenn Mutti
Publisher:
ISBN:
Category : Groundwater
Languages : en
Pages : 346
Get Book Here
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: Christopher Flanders Vick
Publisher:
ISBN:
Category : Groundwater
Languages : en
Pages : 292
Get Book Here
Book Description
A relatively stable, persistent and historical problem with elevated NO3− concentrations in rural drinking wells in the southern Willamette Valley, Oregon is evident. What is the origin of NO3− in rural drinking water wells in this area? The answer to the question is not simple. Many non-point sources contribute to the elevated levels of NO3− in ground water, including residential and agricultural. The objective of this study was to use isotopes of NO3− and other chemical indicators to determine the sources of NO3− in drinking water wells in the southern Willamette Valley, OR. Criteria for wells to be included in the study were (1) less than 75 feet in depth (2) installed after 1960 and (3) domestic use. Four hundred sixty-six wells met the criteria of the study and 120 wells were sampled during the summer of 2003. Geologic units, dominant land use and soil types were determined for each well in an attempt to determine vulnerability of wells, for NO3− contamination. Twenty drinking water wells were selected to undergo isotopic and further chemical analyses. In order to determine the chemical and isotopic fingerprints of the dominant sources of NO3− contamination soil samples were augered from 10 septic drain fields and water samples were collected below 10 agricultural fields. NO3−N concentrations in the study area ranged from below detection (
Author: Frank A. Rinella
Publisher:
ISBN:
Category : Organic water pollutants
Languages : en
Pages : 78
Get Book Here
Book Description
Author: Robert W. Stogner
Publisher:
ISBN:
Category : Groundwater
Languages : en
Pages : 4
Get Book Here
Book Description
Author: Paul D. Bakke
Publisher:
ISBN:
Category : Bull Run River Watershed (Or.)
Languages : en
Pages : 460
Get Book Here
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: Irene Rolston
Publisher:
ISBN:
Category : Best management practices (Pollution prevention)
Languages : en
Pages : 248
Get Book Here
Book Description
Author: Frank A. Rinella, Mary L. Janet
Publisher:
ISBN:
Category :
Languages : en
Pages : 74
Get Book Here
Book Description
Author: F.S. Goderya
Publisher:
ISBN:
Category :
Languages : en
Pages : 11
Get Book Here
Book Description
Author: Audrey Eldridge
Publisher:
ISBN:
Category : Groundwater
Languages : en
Pages : 0
Get Book Here
Book Description
Author: Louis M. Arighi
Publisher:
ISBN:
Category : Groundwater
Languages : en
Pages : 184
Get Book Here
Book Description
Low-permeability geologic units may offer significant chemical and hydraulic protection of adjacent aquifers, and are important for managing groundwater quality, especially in areas with significant non-point source contamination. Nitrate in the Willamette Valley is attenuated across the Willamette Silt, a semi-confining unit overlying a regionally important aquifer. To quantify the main mechanism responsible for nitrate attenuation, soil cores were taken at 19 locations, and profiles of nitrate concentrations were constructed for each site. In 7 locations a sharp, major geochemical transition - a "redoxcline"--Is present near the base of the Willamette Silt; this redoxcline is characterized by a color change from red-brown to blue-gray, an increase in iron(II) concentration, a rise in pH, and the appearance of carbonate minerals. At all sites where a significant surface input of nitrate was detected, the nitrate signal was attenuated before reaching the base of the silt. Denitrifier Enzyme Activity assays from one site show no denitrification potential in the profile, suggesting that a non-biological mechanism is responsible. We suggest that iron(II) is reducing the nitrate abiotically to nitrite, and that the blue-gray reducing zone of Willamette Silt is indicative of the presence of sufficient iron(II) for the reaction to go forward. To increase the usefulness of this study to regional water management agencies, a thickness isopach map of the reduced zone was created both for the northern and southern Willamette Valley to help determine areas where nitrate is most likely to be attenuated.
