Influences of the unsaturated, saturated, and riparian zones on the transport of nitrate near the Merced River, California, USA

Domagalski, Joseph L.; Phillips, Steven P.; Bayless, E. Randall; Zamora, Celia; Kendall, Carol; Wildman, Richard A.; Hering, Janet G.

doi:10.1007/s10040-007-0266-x

Cited by 22 publications

(23 citation statements)

References 42 publications

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“…Groundwater discharge to streams, as indicated by the base‐flow index, was not significant. Groundwater can be a source of phosphorus to streams (Domagalski et al ., ; Holman et al ., ) but this was not significant over the study area.…”

Section: Resultsmentioning

confidence: 99%

Sources and Transport of Phosphorus to Rivers in California and Adjacent States, U.S., as Determined by SPARROW Modeling

Domagalski

Saleh

2015

J American Water Resour Assoc

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The SPARROW (SPAtially Referenced Regression on Watershed attributes) model was used to simulate annual phosphorus loads and concentrations in unmonitored stream reaches in California, U.S., and portions of Nevada and Oregon. The model was calibrated using de-trended streamflow and phosphorus concentration data at 80 locations. The model explained 91% of the variability in loads and 51% of the variability in yields for a base year of 2002. Point sources, geological background, and cultivated land were significant sources. Variables used to explain delivery of phosphorus from land to water were precipitation and soil clay content. Aquatic loss of phosphorus was significant in streams of all sizes, with the greatest decay predicted in small-and intermediate-sized streams. Geological sources, including volcanic rocks and shales, were the principal control on concentrations and loads in many regions. Some localized formations such as the Monterey shale of southern California are important sources of phosphorus and may contribute to elevated stream concentrations. Many of the larger point source facilities were located in downstream areas, near the ocean, and do not affect inland streams except for a few locations. Large areas of cultivated land result in phosphorus load increases, but do not necessarily increase the loads above those of geological background in some cases because of local hydrology, which limits the potential of phosphorus transport from land to streams.(KEY TERMS: nutrients; phosphorus; geology; transport and fate; simulation; watersheds; SPARROW.) Domagalski, Joseph and Dina Saleh, 2015. Sources and Transport of Phosphorus to Rivers in California and Adjacent States, U.S., as Determined by SPARROW Modeling.

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Section: Resultsmentioning

confidence: 99%

Sources and Transport of Phosphorus to Rivers in California and Adjacent States, U.S., as Determined by SPARROW Modeling

Domagalski

Saleh

2015

J American Water Resour Assoc

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“…N itrate is one of the most pervasive contaminants in groundwater, and its potential for transfer through the unsaturated zone has been investigated in numerous modeling studies (Domagalski et al, 2008; Green et al, 2008a; Jabro et al, 2006; Ma et al, 2007a,b,c; Malone et al, 2007a,b; Saseendran et al, 2007; Schmied et al, 2000). The ability to quantify N losses in relation to loads at the land surface is essential for the development of strategies to protect groundwater from excessive leaching.…”

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confidence: 99%

Predicting Unsaturated Zone Nitrogen Mass Balances in Agricultural Settings of the United States

Nolan

Puckett

et al. 2010

J of Env Quality

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Unsaturated zone N fate and transport were evaluated at four sites to identify the predominant pathways of N cycling: an almond [Prunus dulcis (Mill.) D.A. Webb] orchard and cornfield (Zea mays L.) in the lower Merced River study basin, California; and corn-soybean [Glycine max (L.) Merr.] rotations in study basins at Maple Creek, Nebraska, and at Morgan Creek, Maryland. We used inverse modeling with a new version of the Root Zone Water Quality Model (RZWQM2) to estimate soil hydraulic and nitrogen transformation parameters throughout the unsaturated zone; previous versions were limited to 3-m depth and relied on manual calibration. The overall goal of the modeling was to derive unsaturated zone N mass balances for the four sites. RZWQM2 showed promise for deeper simulation profiles. Relative root mean square error (RRMSE) values for predicted and observed nitrate concentrations in lysimeters were 0.40 and 0.52 for California (6.5 m depth) and Nebraska (10 m), respectively, and index of agreement (d) values were 0.60 and 0.71 (d varies between 0 and 1, with higher values indicating better agreement). For the shallow simulation profile (1 m) in Maryland, RRMSE and d for nitrate were 0.22 and 0.86, respectively. Except for Nebraska, predictions of average nitrate concentration at the bottom of the simulation profile agreed reasonably well with measured concentrations in monitoring wells. The largest additions of N were predicted to come from inorganic fertilizer (153-195 kg N ha(-1) yr(-1) in California) and N fixation (99 and 131 kg N ha(-1) yr(-1) in Maryland and Nebraska, respectively). Predicted N losses occurred primarily through plant uptake (144-237 kg N ha(-1) yr(-1)) and deep seepage out of the profile (56-102 kg N ha(-1) yr(-1)). Large reservoirs of organic N (up to 17,500 kg N ha(-1) m(-1) at Nebraska) were predicted to reside in the unsaturated zone, which has implications for potential future transfer of nitrate to groundwater.

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“…Groundwater with nitrate concentrations of up to 93 mg/L (as NO 3 -) is transported toward the Merced River where it discharges to the river at an estimated rate of 18 L/s per river km. Some denitrification takes place within the shallow aquifer but subsequent transport of nitrate across a riparian zone and to the stream/groundwater interface results in higher rates of denitrification (Domagalski et al, 2008). Discharging groundwater near the center of the river channel contains no nitrate and only excess nitrogen gas from denitrification.…”

Section: Introductionmentioning

confidence: 99%

“…Two recent studies carried out in California are particularly instructive for comparing nitrate dynamics in a gaining (the Merced River near Turlock, CA; Domagalski et al, 2008) versus a losing stream (the Parajo River; Ruehl et al, 2007). These two studies employ natural and introduced geochemical and isotopic tracers to assess water exchange and nitrate source and transformation in stream water and shallow groundwater.…”

Section: Introductionmentioning

confidence: 99%

California GAMA Special Study: Nitrate Fate and Transport in the Salinas Valley

Moran

Esser

Hillegonds

et al. 2011

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Executive SummaryThe Groundwater Ambient Monitoring and Assessment (GAMA) Program is a comprehensive groundwater quality monitoring program managed by the California State Water Resources Control Board (SWRCB). Under the GAMA program, Lawrence Livermore National Laboratory carries out special studies that address groundwater quality issues of statewide relevance. The study described here is one in a series of special studies that address the fate and transport of nitrate in basins where groundwater is the main source of water for both irrigation and public drinking water supply.The Salinas Valley, known as 'the salad bowl of the world', has been an agricultural center for more than 100 years. Irrigated row crops such as lettuce and strawberries dominate both land use and water use in the valley. The most common water quality issue that arises from this type of intensive agriculture is contamination of groundwater by nitrate from fertilizers. This study focuses on three key aspects of nitrate fate and transport in the Salinas Valley groundwater basin: 1) establishing background conditions for nitrate in a comparatively un-impacted portion of the basin, 2) examining the fate and transport of nitrate near the recharging Salinas River, and 3) determining the source of nitrate in a highly impacted drinking water well.Establishing an approximate background nitrate concentration is important because native plants, certain rocks and sediments, and rainwater are natural sources of nitrate which may have highly variable inputs to surface water and groundwater. Furthermore, geochemical processes such as denitrification can decrease nitrate concentrations in surface water and groundwater, masking contributions from both natural and non-natural sources. For the Salinas Valley, the Arroyo Seco (a tributary to the Salinas River) serves as a "background" location with respect to nitrate because land cover is predominantly natural and the river and groundwater are relatively pristine. Very low concentrations of nitrate (less than 4 mg/L as NO 3 -) are observed in wells adjacent to Arroyo Seco and in Arroyo Seco surface water. Nitrate concentrations in groundwater (mean of 1.21 mg/L) and surface water (mean of 0.11 mg/L), along with other chemical and isotopic indicators, suggest that nitrate found in these samples comes from rain, with a small additional contribution of nitrate from the soil zone found in groundwater samples. The isotopic composition of nitrate in these samples also reflects its natural source. Nitrate Fate and Transport in the Salinas Valley California GAMA Special StudyTransport of water and solutes in areas adjacent to the Salinas River was examined in three ways: 1) physical measurements of groundwater elevation compared to stream elevation and streamflow with time over the past four years, 2) comparison of geochemical and isotopic constituents measured in Salinas River water over a seasonal hydrograph with the same constituents measured in monitoring wells adjacent to the river, and 3) comparison of geochem...

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Influences of the unsaturated, saturated, and riparian zones on the transport of nitrate near the Merced River, California, USA

Cited by 22 publications

References 42 publications

Sources and Transport of Phosphorus to Rivers in California and Adjacent States, U.S., as Determined by SPARROW Modeling

Sources and Transport of Phosphorus to Rivers in California and Adjacent States, U.S., as Determined by SPARROW Modeling

Predicting Unsaturated Zone Nitrogen Mass Balances in Agricultural Settings of the United States

California GAMA Special Study: Nitrate Fate and Transport in the Salinas Valley

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