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  • 1
    Language: English
    In: Journal of Hydrology, Feb 13, 2014, Vol.509, p.601(14)
    Description: To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.jhydrol.2013.12.005 Byline: Svenja Bartsch, Sven Frei, Marianne Ruidisch, Christopher L. Shope, Stefan Peiffer, Bomchul Kim, Jan H. Fleckenstein Abstract: acents Temporal variability of river-aquifer exchange fluxes is controlled by the monsoon. acents Monsoonal extreme precipitation events are dominant drivers for flow reversals. acents Frequent flow reversals affect the local water quality. Article History: Received 26 August 2013; Revised 3 December 2013; Accepted 5 December 2013 Article Note: (miscellaneous) This manuscript was handled by Peter K. Kitanidis, Editor-in-Chief, with the assistance of Philippe Negrel, Associate Editor
    Keywords: Aquifers ; Rain ; Climate
    ISSN: 0022-1694
    Source: Cengage Learning, Inc.
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  • 2
    Language: English
    In: Agriculture, Ecosystems and Environment, April 1, 2013, Vol.169, p.21(12)
    Description: To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.agee.2013.02.006 Byline: Marianne Ruidisch (a), Svenja Bartsch (b), Janine Kettering (c), Bernd Huwe (a), Sven Frei (b) Keywords: Nitrate leaching; Numerical modeling; Fertilizer best management practices; Ridge tillage; Plastic mulch; Groundwater Abstract: a* Nitrate leaching rates are 26% lower in a plastic mulched ridge cultivation system compared to uncovered ridges. a* Fertilizer placement only in ridges decreases nitrate leaching rates up to 36%. a* Split application decreases nitrate leaching rates up to 59%. a* Combing plastic mulch, a better fertilizer placement and split applications reduces nitrate leaching up to 82%. a* We recommend to apply plastic mulch and fertilizer best management practices for sandy soils in a flat terrain under monsoon climate. Author Affiliation: (a) University of Bayreuth, Soil Physics Group, Universitatsstr. 30, 95440 Bayreuth, Germany (b) University of Bayreuth, Department of Hydrology, Universitatsstr. 30, 95440 Bayreuth, Germany (c) University of Bayreuth, Department of AgroEcoSystem Research, Universitatsstr. 30, 95440 Bayreuth, Germany Article History: Received 13 September 2012; Revised 13 February 2013; Accepted 15 February 2013
    Keywords: Leaching -- Analysis ; Leaching -- Models ; Soil Biology -- Analysis ; Soil Biology -- Models ; Agroecosystems -- Analysis ; Agroecosystems -- Models ; Sandy Soils -- Analysis ; Sandy Soils -- Models ; Hydrology -- Analysis ; Hydrology -- Models ; Fertilizer Industry -- Analysis ; Fertilizer Industry -- Models ; Agricultural Chemicals -- Analysis ; Agricultural Chemicals -- Models
    ISSN: 0167-8809
    Source: Cengage Learning, Inc.
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  • 3
    Language: English
    In: Agriculture, ecosystems & environment, 2013, Vol.169, pp.21-32
    Description: Groundwater pollution by fertilizer NO₃ ⁻ is a major problem recognized in many parts of the world. The excessive use of mineral fertilizers to assure high yields in agricultural production intensifies the leaching problem especially in regions affected by a monsoon climate as in South Korea. The extent that leaching occurs depends on several factors such as climatic conditions, agricultural management practices, soil properties and the sorption characteristics of fertilizers and agrochemicals. In the South Korean monsoon season 2010, NO₃ ⁻ concentrations under varying nitrogen fertilizer rates were monitored in a plastic mulched ridge cultivation (RTₚₘ) with radish crops (Raphanus sativus L.). Based on these findings we calibrated a three-dimensional water flow and solute transport model using the numerical code HydroGeoSphere in combination with the parameter estimation software ParallelPEST. Subsequently, we used the calibrated model to investigate the effect of plastic mulch as well as different fertilizer best management practices (FBMPs) on NO₃ ⁻ leaching. We found that cumulative NO₃ ⁻ leaching under RTₚₘ was 26% lower compared to ridge tillage without coverage (RT). Fertilizer placement confined to the ridges resulted in 36% lower cumulative NO₃ ⁻-leaching rates compared to broadcast applied fertilizer. Splitting the total amount of 150kgNO₃ ⁻ha⁻¹ per growing season into three fertilizer applications (1–4–2.5 ratio) led to a reduction of NO₃ ⁻ leaching of 59% compared to the one-top dressing at the beginning of the growing season. However, the combination of a fertilizer rate of 150kgNO₃ ⁻ha⁻¹, plastic mulched ridges, fertilizer placement only in the ridges and split applications of fertilizer resulted in the lowest cumulative NO₃ ⁻ leaching rate (8.14kgha⁻¹) during the simulation period, which is equivalent to 5.4% of the total NO₃ ⁻ fertilizer input. Compared to RT with conventional one-top dressing fertilization in ridges and furrows, the NO₃ ⁻ leaching was reduced by 82%. Consequently, the combination of all FBMPs is highly recommendable to decrease economical costs for fertilizer inputs as well as to minimize nitrate leaching and its impact on groundwater quality. ; p. 21-32.
    Keywords: Water Quality ; Input Costs ; Radishes ; Fertilizer Rates ; Monsoon Season ; Furrows ; Split Application ; Raphanus Sativus ; Nitrates ; Mathematical Models ; Mulching ; Growing Season ; Hydrologic Models ; Groundwater Contamination ; Mineral Fertilizers ; Condition Factor ; Agricultural Management ; Soil Properties ; Water Flow ; Leaching ; Plastic Film Mulches ; Climate ; Ridge Tillage
    ISSN: 0167-8809
    Source: AGRIS (Food and Agriculture Organization of the United Nations)
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  • 4
    Language: English
    In: Agriculture, Ecosystems and Environment, 01 April 2013, Vol.169, pp.21-32
    Description: ► Nitrate leaching rates are 26% lower in a plastic mulched ridge cultivation system compared to uncovered ridges. ► Fertilizer placement only in ridges decreases nitrate leaching rates up to 36%. ► Split application decreases nitrate leaching rates up to 59%. ► Combing plastic mulch, a better fertilizer placement and split applications reduces nitrate leaching up to 82%. ► We recommend to apply plastic mulch and fertilizer best management practices for sandy soils in a flat terrain under monsoon climate. Groundwater pollution by fertilizer NO is a major problem recognized in many parts of the world. The excessive use of mineral fertilizers to assure high yields in agricultural production intensifies the leaching problem especially in regions affected by a monsoon climate as in South Korea. The extent that leaching occurs depends on several factors such as climatic conditions, agricultural management practices, soil properties and the sorption characteristics of fertilizers and agrochemicals. In the South Korean monsoon season 2010, NO concentrations under varying nitrogen fertilizer rates were monitored in a plastic mulched ridge cultivation (RT ) with radish crops ( L.). Based on these findings we calibrated a three-dimensional water flow and solute transport model using the numerical code HydroGeoSphere in combination with the parameter estimation software ParallelPEST. Subsequently, we used the calibrated model to investigate the effect of plastic mulch as well as different fertilizer best management practices (FBMPs) on NO leaching. We found that cumulative NO leaching under RT was 26% lower compared to ridge tillage without coverage (RT). Fertilizer placement confined to the ridges resulted in 36% lower cumulative NO -leaching rates compared to broadcast applied fertilizer. Splitting the total amount of 150 kg NO ha per growing season into three fertilizer applications (1–4–2.5 ratio) led to a reduction of NO leaching of 59% compared to the one-top dressing at the beginning of the growing season. However, the combination of a fertilizer rate of 150 kg NO ha , plastic mulched ridges, fertilizer placement only in the ridges and split applications of fertilizer resulted in the lowest cumulative NO leaching rate (8.14 kg ha ) during the simulation period, which is equivalent to 5.4% of the total NO fertilizer input. Compared to RT with conventional one-top dressing fertilization in ridges and furrows, the NO leaching was reduced by 82%. Consequently, the combination of all FBMPs is highly recommendable to decrease economical costs for fertilizer inputs as well as to minimize nitrate leaching and its impact on groundwater quality.
    Keywords: Nitrate Leaching ; Numerical Modeling ; Fertilizer Best Management Practices ; Ridge Tillage ; Plastic Mulch ; Groundwater ; Agriculture ; Environmental Sciences
    ISSN: 0167-8809
    E-ISSN: 1873-2305
    Source: ScienceDirect Journals (Elsevier)
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  • 5
    Language: English
    In: Journal of Hydrology, 13 February 2014, Vol.509, pp.601-614
    Description: An important prerequisite to better understand the transport of nutrients and contaminants across the river-aquifer interface and possible implications for biogeochemical transformations is to accurately characterize and asses the exchange fluxes. In this study we investigate how monsoonal precipitation events and the resulting variability in river discharge affect the dynamics of river-aquifer exchange and the corresponding flux rates. We evaluate potential impacts of the investigated exchange fluxes on local water quality. Hydraulic gradients along a piezometer transect were monitored at a river reach in a small catchment in South Korea, where the hydrologic dynamics are driven by the East-Asian Monsoon. We used heat as a tracer to constrain river-aquifer exchange fluxes in a two-dimensional flow and heat transport model implemented in the numerical code HydroGeoSphere, which was calibrated to the measured temperature and total head data. To elucidate potential effects of river-aquifer exchange dynamics on biogeochemical transformations at the river-aquifer interface, river water and groundwater samples were collected and analyzed for dissolved organic carbon (DOC), nitrate (NO ) and dissolved oxygen saturation (DO ). Our results illustrate highly variable hydrologic conditions during the monsoon season characterized by temporal and spatial variability in river-aquifer exchange fluxes with frequent flow reversals (changes between gaining and losing conditions). Intense monsoonal precipitation events and the associated rapid changes in river stage are the dominant driver for the observed riverbed flow reversals. The chemical data suggest that the flow reversals, when river water high in DOC is pushed into the nitrate-rich groundwater below the stream and subsequently returns to the stream may facilitate and enhance the natural attenuation of nitrate in the shallow groundwater.
    Keywords: River-Aquifer Exchange Fluxes ; Heat As a Natural Tracer ; Monsoonal-Type Climate ; Hydraulic Gradient Reversals ; Hydrogeosphere ; Natural Attenuation of Nitrate ; Geography
    ISSN: 0022-1694
    E-ISSN: 1879-2707
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  • 6
    In: Journal of Geophysical Research: Biogeosciences, September 2012, Vol.117(G3), pp.n/a-n/a
    Description: Although land‐water carbon (C) transport represents a critical link in the global C cycle, rare attempts have been made to compare hydrologic controls over storm pulses of dissolved organic C (DOC) and particulate organic C (POC) in mountainous watersheds. An immersible UV/Vis spectrophotometer was used to comparatively investigate the rapid storm responses of stream water DOC and POC in a small mountainous forested watershed in South Korea. High‐frequency measurements at 5‐min intervals during 42 hydrologic events, including monsoon storms and winter snowmelts, showed consistent patterns: POC concentrations were lower than DOC concentrations during base flow and small storm events but exceeded them during the peak flow periods of intense storm events. Although both the DOC and POC concentrations had hysteretic relationships with discharge, the POC concentrations showed larger increases and variations after crossing a threshold discharge on the rising limb of the storm hydrograph. Stronger responses to intense storms resulted in a disproportionately large export of POC at high flow, whereas a large portion of the total DOC flux was exported under prevailing low‐flow conditions. The results demonstrate the potential of in situ optical measurements for investigating fine‐resolution dynamics of the DOC and POC export during storm events. Stronger storm responses of the POC export compared to the limited response range of the DOC export suggest that erosion‐induced POC export will become more important as a major pathway for the hydrologic soil C loss from mountainous watersheds in response to an increasing occurrence of extreme storm events. In situ optical monitoring captured differential storm responses of DOC and POC POC export was more variable on rising discharge than limited DOC responses Strong storm responses lead to disproportionately large POC export at high flow
    Keywords: Dissolved Organic Carbon ; Extreme Events ; In Situ Sensors ; Mountainous Watersheds ; Particulate Organic Carbon ; Soil Carbon Loss
    ISSN: 0148-0227
    E-ISSN: 2156-2202
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  • 7
    Language: English
    In: Journal of Hydrology, 12 December 2013, Vol.507, pp.149-162
    Description: The linkage between hydrologic dynamics and the delivery of nitrate and DOC (dissolved organic carbon) to streams was studied in the Haean catchment, a mixed land-use mountainous catchment in South Korea. Three monsoonal precipitation events were analyzed, which varied in total rainfall amount (39–70 mm) and intensities (mean: 1.6–5.6 mm h ), by high-resolution (2–4 h interval) stream water-quality sampling along the topographic elevation gradient of the catchment, from an upland deciduous forest stream, over areas intensively used for agriculture (dryland farming and rice paddies) down to the catchment outlet. The dynamics of river-aquifer exchange were investigated at two piezometer transects at mid and lower elevations. DOC and nitrate sources and their transport pathways to the receiving surface waters differed between the forested and the agricultural stream site. In the forest stream, elevated DOC concentrations (max: 3.5 mgC l ) during precipitation events were due to hydrologic flushing of soluble organic matter in upper soil horizons, with a strong dependency on pre-storm wetness conditions. Nitrate contributions to the forested stream occurred along shallow subsurface transport pathways. At the agricultural sites stream DOC concentrations were considerably higher (max: 23.5 mgC l ) supplied from adjacent rice paddies. The highest in-stream nitrate concentrations (max: 4.1 mgN l ) occurred at river reaches located in the lower agricultural part of the catchment, affected by groundwater inputs. Groundwater nitrate concentrations were high (max: 7.4 mgN l ) owing to chemical fertilizer leaching from dryland fields forced by monsoonal rainfalls. Overall, this study demonstrates that the hydrologic dynamics resulting from the monsoonal climate drive the in-stream DOC dynamics in the forested 1st-order catchment whereas sources and mobilization of DOC in downstream agricultural areas are mainly controlled by the prevailing land-use type and irrigation management. Nitrate dynamics in higher order agricultural streams and their connected aquifers reflect combined effects of land-use type and monsoonal hydrology.
    Keywords: Nitrate ; Dissolved Organic Carbon ; Monsoonal-Type Climate ; Land-Use Type ; River-Aquifer Exchange Dynamics ; Topography ; Geography
    ISSN: 0022-1694
    E-ISSN: 1879-2707
    Source: ScienceDirect Journals (Elsevier)
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  • 8
    Language: English
    In: Journal of Hydrology, 28 June 2013, Vol.494, pp.72-82
    Description: River discharge is a commonly measured hydrologic variable; however, estimate uncertainty is often higher than acceptable limits. To quantify method limitations and spatiotemporal variability, a multi-year hydrologic flow partitioning investigation was completed under monsoonal conditions in the ungauged complex terrain of the Haean Catchment, South Korea. Our results indicate that sediment transport from a single annual monsoonal event can significantly modify the channel cross-sectional area resulting in inaccurate stage-discharge rating curves. We compare six discharge measurement methods at 13 locations that vary in slope from 1% to 80%, with discharge ranging up to four orders in magnitude, which enabled us to weight the accuracy of each method over a specific range in discharge. The most accurate discharge estimation methods are the weir, the acoustic Doppler current profiler, and the in-stream velocity area method; however, under certain conditions each of these methods is less desirable than other methods. The uncertainty in the three methods is on average 0.4%, 4.7%, and 6.1% of the total discharge, respectively. The accuracy of the discharge estimates has a direct influence on the characterization of basin-wide hydrologic partitioning, which can lead to significant variability in sediment erosion rates and nutrient fate and transport.
    Keywords: Terreco ; Korea ; Discharge ; Baseflow ; Topography ; River ; Geography
    ISSN: 0022-1694
    E-ISSN: 1879-2707
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  • 9
    Language: English
    In: Transactions of the ASABE, 2013, Vol.56(2), pp.667-679
    Description: Plastic-covered ridge-furrow cultivation (plastic mulch) can substantially influence runoff and soil erosion on agricultural land. However, the impact of this management practice in combination with complex farmland topography has...
    Keywords: Erosion ; Erosion Mechanisms ; Farmlands ; Sediment Transport ; Erosion Rate ; Runoff ; Topography ; Cultivation ; Land Development, Irrigation, and Drainage (CE);
    ISSN: Transactions of the ASABE
    ISSN: 21510032
    E-ISSN: 2151-0040
    Source: CrossRef
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  • 10
    Language: English
    In: Biogeosciences Discussions, 11/15/2016, pp.1-26
    Description: Mediterranean ecosystems are significant carbon sinks but are also particularly sensitive to climate change but the carbon dynamic in such ecosystem is still not fully understood. An improved understanding of the drivers of the carbon fixation by plants is needed to better predict how such ecosystems will respond to climate change. Here, for the first time, a large dataset collected through the FLUXNET network is used to estimate how the gross primary production (GPP) of different Mediterranean ecosystems was affected by air temperature and precipitation between the years 1996 and 2013. We showed that annual precipitation was not a significant driver of annual GPP. Our results also indicated that seasonal variations of air temperature significantly affected seasonal variations of GPP but without major impact on inter annual variations. Inter-annual variations of GPP seemed largely controlled by the precipitation during early spring (March-April), making this period crucial for the future of Mediterranean ecosystems. Finally, we also observed that the sensitivity of GPP in Mediterranean ecosystems to climate drivers is not ecosystem type dependent.
    Keywords: Biology;
    ISSN: Biogeosciences Discussions
    E-ISSN: 1810-6285
    Source: CrossRef
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