Download or read book Temporal and Spatial Variability of Groundwater Nitrate in the Southern Willamette Valley of Oregon written by Jeffrey Glenn Mutti and published by . This book was released on 2006 with total page 346 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Download or read book Chemical and Isotopic Patterns of Nitrate Variability in the Southern Willamette Valley Oregon written by Christopher Flanders Vick and published by . This book was released on 2004 with total page 292 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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 (
Download or read book Seasonal and Spatial Variability of Nutrients and Pesticides in Streams of the Willamette Basin Oregon 1993 95 written by Frank A. Rinella and published by . This book was released on 1998 with total page 78 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Variability of Nitrate Concentrations in the Shallow Ground Water in a Selected Area of the San Luis Valley South central Colorado written by Robert W. Stogner and published by . This book was released on 1997 with total page 4 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Spatial and Temporal Variability of Nitrate in Streams of the Bull Run Watershed Oregon written by Paul D. Bakke and published by . This book was released on 1993 with total page 460 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Download or read book Who s Afraid of a Little Nitrate written by Irene Rolston and published by . This book was released on 2006 with total page 248 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Seasonal and Spatial Variability of Nutrients and Pesticides in Streams of the Willamette Basin written by Frank A. Rinella, Mary L. Janet and published by . This book was released on 1998 with total page 74 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Consideration of Spatial Variability in Nitrate Contamination to Groundwater written by F.S. Goderya and published by . This book was released on 1994 with total page 11 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Southern Willamette Valley Groundwater Summary Report written by Audrey Eldridge and published by . This book was released on 2004 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Quantification of the Nitrate Attenuation Capacity of Low permeability Missoula Flood Deposits in the Willamette Valley of Oregon written by Louis M. Arighi and published by . This book was released on 2004 with total page 184 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Download or read book Southern Willamette Valley Groundwater Management Area Declared written by Audrey Eldridge and published by . This book was released on 2004 with total page 2 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Short Term Termporal and Spatial Variability of Nitrogen and Phosphorus in Two Oregon Coast Range Streams written by Robert A. Scherer and published by . This book was released on 1995 with total page 254 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Download or read book Impact of Climate and Management Practices on Nitrate Contamination in Groundwater written by Zhi-Jun Liu and published by . This book was released on 1995 with total page 464 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Southern Willamette Valley 2002 Groundwater Study written by Audrey Eldridge and published by . This book was released on 2003 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Spatial Analysis of In Season Site Specific Nitrogen Management Effects on Groundwater Nitrate and Agronomic Performance written by and published by . This book was released on 2004 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: In-season, site-specific (SS) N management based on remote sensing (RS) has been suggested as a way of reducing groundwater NO3-N contamination. In-season N management seeks to match the temporal variability of crop N needs by applying appropriate amounts of N at critical crop growth stages. Site-specific N management attempts to match the spatial variability of crop N requirements by applying appropriate, spatially variable N rates within fields. We evaluated the environmental and agronomic benefits of two in-season, RS-informed N management strategies applied on a uniform field-average (FA) or SS basis. We compared these to current uniform N recommendations based on "Realistic Yield Expectations" (RYE) in a typical coastal plain cropping system. We also sought to understand the spatial and temporal dynamics of shallow groundwater NO3-N. An additional objective was to develop a statistical procedure for the analysis of spatially dense, georeferenced subsample data in randomized complete block designs, a common characteristic of precision agriculture research. The experiment was established in a 12-ha North Carolina field with a 2-yr winter wheat double-crop soybean-corn rotation. The three N management treatments were applied to 0.37 ha plots in a randomized complete block design with 10 replications. Groundwater NO3-N and water table depth were measured every two weeks at 60 well nests (two per plot) sampling 0.9- to 1.8-, 1.8- to 2.7-, and 2.7- to 3.7-m depths from 2001 to 2003. We developed a statistical procedure for selecting an appropriate covariance model in randomized complete block analyses in the presence of spatial correlation. When warranted, incorporating spatial covariance in the statistical analysis provides greater efficiency in estimating treatment effects. Elevations, soil organic matter (SOM), and water table elevations (WTE) were spatial covariates used for explaining NO3-N spatial correlation. Compared to RYE, SS achieved: (i) less groundwater.
Download or read book Bibliography of Agriculture written by and published by . This book was released on 1990 with total page 886 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Brackish Groundwater in the United States written by Jennifer S. Stanton and published by . This book was released on 2017 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
