Runoff Collectors Research Articles

Surface runoff and losses of phosphorus from hydrophobic pastoral soils

The impact of soil water repellency (SWR) on soil phosphorus (P) mobility in surface water runoff remains contentious. Although SWR may cause a significant increase in surface runoff, especially in post-summer rainfall events, whether it contributes to background phosphorus losses remains unclear. Surface runoff and P concentrations in runoff were measured on hilly Allophanic pastoral soils with different water repellency levels using seven runoff collectors. Phosphorus fertilizer was broadcasted at 18 kg P ha−1 in the summer over dry soils. Runoff volumes and P concentrations were measured after each natural rain event prompting surface runoff. The highest runoff/rainfall ratios were observed at the early rainfall events following the dry summer and then decreased significantly by the end of autumn and winter. The post-summer surface runoff correlation with SWR had an R2 of 0.46, and hydrophobic soils had significantly higher runoff ratios than wettable soils. Measurements of the dissolved reactive phosphorus (DRP) and total phosphorus (TP) in the surface runoff showed decreasing exponential trends, with the highest values recorded in the first runoff event following P fertilizer application, where over 90% of losses occurred (incidental losses). After the incidental loss phase, DRP concentrations were related to surface runoff ratio, soil P extractability by water, and SWR. Our data point to non-incidental TP loads being related to SWR (R2 = 0.53). The present results will improve the understanding of the SWR effect on surface runoff and will reconcile the controversy regarding its contribution to non-incidental P losses.

Hydrological heterogeneity in agricultural riparian buffer strips

Riparian buffer strips (RBS) may protect surface water and groundwater in agricultural settings, although their effectiveness, observed in field-scale studies, may not extend to a watershed scale. Hydrologically-controlled leaching plots have often shown RBS to be effective at buffering nutrients and pesticides, but uncontrolled field studies have sometimes suggested limited effectiveness. The limited RBS effectiveness may be explained by the spatiotemporal hydrological heterogeneity near non-irrigated fields. This hypothesis was tested in conventional corn and soy fields in the St. Lawrence Lowlands of southern Quebec (Canada), where spring melt brings heavy and rapid runoff, while summer months are hot and dry. One field with a mineral soil (Saint-Roch-de-l’Achigan) and another with an organic-rich soil (Boisbriand) were equipped with passive runoff collectors, suction cup lysimeters, and piezometers placed before and after a 3m-wide RBS, and monitored from 2011 to 2014. Soil topography of the RBS was mapped to a 1cm vertical precision and a 50cm sampling grid. On average, surface runoff intersects the RBS perpendicularly, but is subject to substantial local heterogeneity. Groundwater saturates the root zones, but flows little at the time of snowmelt. Groundwater flow is not consistently perpendicular to the RBS, and may reverse, flowing from stream to field under low water flow regimes with stream-aquifer connectivity, thus affecting RBS effectiveness calculations. Groundwater flow direction can be influenced by stratigraphy, local soil hydraulic properties, and historical modification of the agricultural stream beds. Understanding the spatiotemporal heterogeneity of surface and groundwater flows is essential to correctly assess the effectiveness of RBS in intercepting agro-chemical pollution. The implicit assumption that water flows across vegetated RBS, from the field to the stream, should always be verified.

Phosphorus and nitrogen losses from poultry litter stacks and leaching through soils

Stacking poultry litter in fields prior to land application is a common practice that provides important logistical benefits to farmers, but may lead to environmental losses of nutrients. A 2-year field study was conducted to evaluate phosphorus (P) and nitrogen (N) losses from poultry litter stacks with and without a protective cover. Surface runoff from the litter stacks and leachate through two texturally contrasting soils (sand and silt loam) was monitored using a combination of runoff collectors and zero-tension lysimetry. Nutrient losses in surface runoff were small (total P < 3 g m−2; total inorganic N < 7 g m−2), particularly when compared with losses in leachate (total P < 60 g m−2; total inorganic N < 290 g m−2). Covering stacks reduced leachate total P losses by 25–100 times and total inorganic N losses by 25–770 times, such that leachate nutrient losses from covered stacks were similar to that in the controls with no manure stacking. Despite relatively small nutrient losses from litter stacks over the 2-year study, results point to substantial nutrient accumulation in soil after repeated stacking. Water-extractable P concentrations in upper 5-cm soils were similar between covered (120–240 mg kg−1) and uncovered stacks (140–250 mg kg−1), but soil nitrate-N concentrations were much higher under the covered stack (80–140 mg kg−1) than the uncovered stack (<5 mg kg−1). This study clearly points to benefits of covering litter stacks, but highlights long-term concerns with regard to soil nutrient accumulation.

Impacts of conservation agriculture-based farming systems on optimizing seasonal rainfall partitioning and productivity on vertisols in the Ethiopian drylands

Field water conservation practices are a way to build resilience against drought by increasing productive green water through reducing runoff and evaporation and thereby boosting crop yield. A field study was undertaken on permanently kept rainfed experimental plots established in 2005 on a vertisol in order to evaluate two resource saving cropping systems based on conservation agriculture (CA) that integrate in situ soil and water conservation tillage practices (derdero+ and terwah+) as compared to a conventional system in terms of soil moisture, runoff, water loss (drainage and evapotranspiration together), water productivity and crop yield. The experimental layout was a randomized complete block design with three replications and a plot size of 5m×19m. The farming systems differed in tillage practice, but all had wheat, teff, barley and grass pea crops grown in rotation. The tillage treatments were (i) derdero+ (DER+) with a furrow and permanent raised bed planting system, plowed only by refreshing the furrow once at planting with no tillage on top of the permanently kept raised beds, 30% standing crop straw retention, and with ∼20% of the crop residue being covered with soil during refreshing the furrow at planting, (ii) terwah+ (TER+) with furrows made at 1.5m intervals, plowed once at planting, 30% standing crop straw retention and fresh broad beds, and crop residue being partly covered with soil during tillage at planting, and (iii) conventional tillage (CT) with a minimum of three plain tillage operations and complete removal of crop straw. All plowing as well as the maintenance of the furrows of the permanent raised beds was done using a local ard plow called mahresha. Glyphosate was sprayed at 2lha−1 to control weeds before crop emergence, starting from 2007 with DER+ and TER+. Runoff was collected at the lower end of each plot in calibrated runoff collectors after each runoff event. Soil–water content was measured using the gravimetric method at 5–6 day intervals. Normalized Difference Vegetation Index (NDVI) was measured in the field at several phenological stages, using a handheld GreenSeeker™ Optical Sensor Unit. Soil–water storage (0–80cm soil depth) during the growing season was always highest with DER+ followed by TER+ and CT, whereas the opposite trend was observed for runoff. On the other hand, deep drainage and evapotranspiration was always highest in the DER+ compared to CT. NDVI records throughout the growing season were significantly highest with DER+ for wheat and grass pea, while the highest values were observed with TER+ when under teff. These values were directly proportional to the above ground crop biomass and yield. The grain and straw yield of wheat in 2009 was increased from 1.6 and 3.7tha−1 with CT to 2.6 and 5.2tha−1 with DER+, respectively. Our study demonstrates that field water conservation tillage practices that incorporate CA principles are effectively increasing green water in the root zone available for crops and thus, improve crop productivity and yields substantially on vertisols in drylands without other inputs.

The herbicide glyphosate and its metabolite AMPA in the Lavaux vineyard area, western Switzerland: Proof of widespread export to surface waters. Part II: The role of infiltration and surface runoff

Two parcels of the Lavaux vineyard area, western Switzerland, were studied to assess to which extent the widely used herbicide, glyphosate, and its metabolite aminomethylphosphonic acid (AMPA) were retained in the soil or exported to surface waters. They were equipped at their bottom with porous ceramic cups and runoff collectors, which allowed retrieving water samples for the growing seasons 2010 and 2011. The role of slope, soil properties and rainfall regime in their export was examined and the surface runoff/throughflows ratio was determined with a mass balance. Our results revealed elevated glyphosate and AMPA concentrations at 60 and 80 cm depth at parcel bottoms, suggesting their infiltration in the upper parts of the parcels and the presence of preferential flows in the studied parcels. Indeed, the succession of rainy days induced the gradual saturation of the soil porosity, leading to rapid infiltration through macropores, as well as surface runoff formation. Furthermore, the presence of more impervious weathered marls at 100 cm depth induced throughflows, the importance of which in the lateral transport of the herbicide molecules was determined by the slope steepness. Mobility of glyphosate and AMPA into the unsaturated zone was thus likely driven by precipitation regime and soil characteristics, such as slope, porosity structure and layer permeability discrepancy. Important rainfall events (>10 mm/day) were clearly exporting molecules from the soil top layer, as indicated by important concentrations in runoff samples. The mass balance showed that total loss (10–20%) mainly occurred through surface runoff (96%) and, to a minor extent, by throughflows in soils (4%), with subsequent exfiltration to surface waters.

Runoff Water Quality from a Sierran Upland Forest, Transition Ecotone, and Riparian Wet Meadow

High concentrations of inorganic N, P, and S have been reported in overland and litter interflow within forested uplands of the Tahoe basin and surrounding watersheds. In this study we compared runoff nutrient concentration and load as well as soil nutrient fluxes at three watershed locations; an upland forest, a transitional ecotone consisting of forest and meadow vegetation, and a down gradient riparian wet meadow immediately adjacent to Sagehen Creek at the U.C. Berkeley Sagehen Experimental Forest near Truckee, CA. Three parallel transects (one at each watershed location) consisting of four sampling points each were delineated. Runoff collectors, rain gages, snowmelt collectors, and resin capsules were installed along each transect. Runoff, precipitation, snowmelt, and groundwater samples were collected and analyzed for NO3−−N, NH4+−N, PO43−–P, and SO42−. Both discharge concentrations and loads were statistically similar among the upland forest, ecotone, and riparian wet meadow locations, indicating little effect from differences in ecological or physical processes. Model estimated data trends, however, suggested the presence of higher discharge concentrations of NH4+−N for upland and wet meadow sites compared with the transition ecotone, and higher discharge loads of NO3−−N from the wet meadow compared with either the upland or transition ecotone sites. Overall, the wet meadow riparian zone at our Sierra Nevada study location did not appear to be as effective at intercepting and retaining high nutrient loads as commonly presumed, and by virtue of the observed data trends in some instances, may have been a contributing source.

The Effects of Slash Pile Burning on Soil and Water Macronutrients

Significant effects of slash pile burning on soil chemistry and water quality were observed in forested sites in the eastern Sierra Nevada Mountains of Nevada. Slash piles in upland and meadow sites were instrumented postburn with ceramic cup lysimeters, runoff collectors, and resin stakes (Plant Root Simulator™ probes) along transects from pile centers to unburned areas. Ash and soil samples also were collected along these transects. The pH and concentrations of most nutrients in the soil were highest in the centers of the piles. Larger piles had lower levels of total carbon and total nitrogen in the pile centers (indicative of high burn temperatures and volatilization) compared with smaller piles. There also were differences between meadow and non-meadow systems including higher soil NO3− and lower SO42− amounts in the meadow areas. Soil solution data indicated that peak concentrations exceeded US Environmental Protection Agency water quality standards for both NO2−-N and NO3−-N at all three sites and were 2.5 to 3 times the standards in two sites. Runoff solution peak concentrations also exceeded the standards but only in the meadow site.

Evaluating Cattle Manure Application Strategies on Phosphorus and Nitrogen Losses from a Florida Spodosol

Repeated application of cattle (Bos taurus) manure to agricultural areas often results in soil P accumulation, which may pose risks to surface waters. We evaluated seven different application strategies on P and N losses from an established bahiagrass (Paspalum notatum Flügge) pasture: control (no N applied); two N sources [manure alone or manure plus ammonium nitrate (AN) (50/50% combination)]; two application frequencies (single or split); and two N rates (200 and 400 kg N ha−1). Shallow groundwater P was monitored using piezometers installed at 60 cm (shallow wells) and 120 cm (deep wells). Surface runoff collectors were used to monitor runoff N and P from naturally occurring rainfall events. Soil samples were analyzed for Mehlich‐1 P and KCl‐extractable NH4–N and NO3–N concentrations. Application of manure in combination with AN suppressed leachate P, but no effect was observed on leachate NO3–N concentrations in the shallow wells. Application of manure alone or in combination with AN did not affect P and N concentrations in the deep wells. Applying manure plus AN resulted in approximately 50% reduction in runoff N and P loads than treatments receiving manure alone. Manure applied alone or in combination with AN increased soil test P in upper soil horizons relative to control plots. Conversely, application of either manure or manure plus AN had no effect on soil NH4–N and NO3–N concentrations. Results demonstrate that combining manure application with inorganic N fertilizer represents an environmentally sound application strategy to reduce soil P and N accumulation and subsequent risks of nutrient transport.

Assessment of the Georgia Phosphorus Index on farm at the field scale for grassland management

In order to better manage agricultural phosphorus (P), most states in the United States have adopted a “P indexing” approach that ranks fields according to potential P losses. In Georgia, the Georgia P Index was developed to estimate the risk of bioavailable P loss from agricultural land to surface waters, considering sources of P, transport mechanisms, and management practices. Nine farm fields, managed as pasture or hay systems, were outfitted with 28 small in-field runoff collectors. Runoff P, soil P, and field management practices were monitored from 2004 to 2007. Fields varied from those rich in P (broiler litter or dairy slurry) to those without P amendments (inorganic nitrogen [N] or no amendments). Data relating to nutrient applications, soil properties, soil P, and management were used as input values to determine a Georgia P Index value estimating the risk of P export from each field. Results indicated that the Georgia P Index underrated the risk in only 2% of the cases when considering loads or mass losses of P, partly due to the influence of small annual runoff volumes and thus greater flow-weighted concentrations from some fields. While measured P export was generally low to moderate (

Concentración de nutrientes en la escorrentía de diferentes predios del trópico enmendados con residuos animales bajo condiciones de lluvia natural.

La pérdida excesiva de nutrientes de suelos agrícolas representa una fuente primaria de contaminación de los cuerpos de agua. En este estudio se cuantificaron las concentraciones de nitrógeno total Kjeldahl (NTK), fósforo total y disuelto (PD, PT), y carbón orgánico disuelto (COD) en la escorrentía de dos fincas productoras de animales de Puerto Rico. Las fincas, una vaquería y una avícola, son representativas de las condiciones típicas (i.e., topografía, zona ecológica, sistema de manejo) de estos sistemas de producción. En cada finca se seleccionaron dos predios para estudios de escorrentía y en cada predio se instalaron dos fraccionadores de escorrentía. Se recolectaron muestras de escorrentía generadas por eventos de lluvia natural. La concentración promedio de fósforo en la escorrentía de los predios avícolas (5.87 mg TP/L, 4.82 mg PD/L) fue significativamente mayor que la observada en los predios de la vaquería (2.29 mg PT/L, 1.79 mg PD/L). La concentración de PD representó cerca del 90% de la concentración de PT observada en ambas fincas, situación que puede agravar el impacto en las aguas circundantes. La concentración de PD promedio excedió 1 mg/L, límite propuesto para controlar la escorrentía de fósforo de predios agrícolas, en 70% de los eventos de escorrentía en el caso de la vaquería y en un 100% de los casos en la finca avícola. La magnitud de las concentraciones en ambas fincas se afectó significativamente por el lapso de tiempo transcurrido entre la aplicación de los residuos orgánicos y el primer evento de lluvia. La concentración de nutrientes en la escorrentía también se afectó significativamente con la profundidad de la lámina de lluvia.

Responses of the aleppo pine (Pinus halepensis Mill.) and the holm oak (Quercus ilex L. subsp. ballota (Desf.) Samp.) to the collection of overland runoffs through minicatchments in different Mediterranean environments

Water is one of the most limiting factors in the forestation of Mediterranean areas, so that the survival and development of these areas is always connected to the availability of water resources. The aim of this study is to assess the efficiency of a series of hydraulic structures linked to land preparation, called minicatchments, as runoff collectors meant to increase water availability in the forestation. In order to do so, the amount of overland runoff reaching every seedling, as well as the survival of the reforestation in four places with different climatic and edaphic characteristics have been assessed. Results obtained show how water availability depends both on the amount of water reaching the bank and on the physical properties of the land. The areas that have normally been considered more difficult to restore due to a de-structured profile, to the presence of superficial physical crusts and to a scarce vegetal cover are the ones showing a better response to the technique of runoff collection trough minicatchments.

Performance of grass and eucalyptus riparian buffers in a pasture catchment, Western Australia, part 1: riparian hydrology

Rainfall takes many flowpaths to reach a stream, and the success of riparian buffers in water quality management is significantly influenced by riparian hydrology. This paper presents results from hydrometric monitoring of riparian buffer hydrology in a pasture catchment. Runoff processes and riparian flowpaths were investigated on two planar hillslopes with regenerating grass and E. globulus buffers. Surface runoff and subsurface flows (A- and B-horizons) were measured for 3 years using surface runoff collectors, subsurface troughs and piezometers. Water volumes moving through the riparian buffers via the measured flowpaths were ranked B-horizon ≫ surface runoff ≈ A-horizon. Runoff volumes through the B-horizon troughs were an order of magnitude greater than those recorded for the most productive surface runoff plots or the A-horizon troughs. Subsurface runoff and saturation-excess overland flow (SOF) were limited to the winter months, whereas infiltration-excess overland flow (IEOF) can occur all year round during intense storms. Surface runoff was recorded on 33 occasions, mostly during winter (late May–early October), and total annual surface runoff volumes collected by the 20 unconfined (2 m wide) runoff plots varied between > 80 and < 20 m3. Subsurface flow only occurred in winter, and the 6 m wide B-horizon subsurface troughs flowed above 1 l s−1 continuously, whereas the A-horizon troughs flowed infrequently (<6 days per year). In summer, surface runoff occurred as IEOF during intense storms in the E. globulus buffer, but not in the grass buffer. Observations suggest that surface crusting reduced the soil's infiltration capacity in the E. globulus buffer. During winter, SOF and seepage were observed in both buffers, but subsurface flow through the B-horizon was the dominant flowpath. Key hydrologic differences between the grass and tree buffers are the generation of IEOF in the E. globulus buffer during intense summer storms, and the smaller subsurface runoff volumes and fewer flow days in the E. globulus buffer. Low surface runoff volumes are likely to limit the potential of these buffers to filter pollutants from surface runoff. High subsurface flow volumes and saturated conductivities are also likely to limit the residence time of water in the subsurface domain. Based on their hydrologic performance, the key roles of riparian buffers in this landscape are likely to be displacing sediment and nutrient-generating activities away from streams and stabilizing channel morphology. Copyright © 2006 John Wiley & Sons, Ltd.

EVALUATI ON OF PERCENT FLOW CAPTURED BY A SMALL IN?FIELD RUNOFF COLLECTOR

Increased environmental concern about nutrient loadings in runoff and surface water has heightened the need for evaluation of management practices at the field scale. Thus, there is a need for small in–field runoff collectors to assess nutrient migration at the field scale on various land management systems. A runoff sampler previously designed for the relatively flat terrain of the Coastal Plain was modified to accommodate steeper slopes (5% to 12%), larger flow rates, and channelized flow common in the Southern Piedmont. We conducted a laboratory study with the modified sampler to evaluate the effect of flow rate (1 to 5.5 L min –1 ) and slope (5% and 12%) on percent flow capture. Our results show that slope and flow rate had little to no effect on the percent flow capture of the modified runoff collector. The 95% confidence interval for percent flow capture in a single observation was 10.4 µ 2.5% for the 10x splitter and 2.0 µ 1.7% for the 100x splitter. Because of the potential errors for single observations, several runoff collectors should be used if runoff volume needs to be quantified. The use of this small in–field runoff collector would be fairly unobtrusive, inexpensive in different management systems, and could help further our knowledge of migration of nutrients, pesticides, microorganisms, and sediments from fields into streams.

NITROGEN ASSIMILATION BY RIPARIAN BUFFER SYSTEMS RECEIVING SWINE LAGOON WASTEWATER

A three-year study was conducted to determine the feasibility of using riparian buffer systems to assimilatenitrogen (N) from swine lagoon effluent. Replicated 30 4 m plots were established at the interface of a pasture andriparian forest. Wastewater from the third lagoon of the University of Georgia Coastal Plain Experiment Station mainswine research unit was applied to each plot by overland flow from tanks at the top end of each plot. The wastewater,which contained an average N concentration of 160 mg L1 N, primarily as ammonium (NH4-N), was applied to the plotsat two different rates (either once per week [1 , 1285 L/plot] or twice per week [2 , 2570 L/plot]). Three differentvegetative buffer treatments were evaluated: (1) 10 m grass buffer draining into 20 m existing riparian zone vegetation;(2) 20 m grass buffer draining into 10 m existing riparian zone vegetation; and (3) 10 m grass buffer draining into 20 mmaidencane (Panicum hematomon). The effects of the wastewater on surface runoff and groundwater quality wereevaluated by transects of surface runoff collectors, suction lysimeters, and shallow groundwater wells which extendedfrom the top to the bottom of each plot. Data analyses showed differences due to wastewater application rate and distancedownslope from the wastewater application pipe. Nitrogen concentrations increased over time at the top ends of the plotsbut showed little increase at the bottom ends of the plots. Overall, all three vegetative treatments were successful inassimilating N from the wastewater. The study showed that riparian buffer systems, where wastewater is applied byoverland flow, can be effective in assimilating N contained within lagooned animal wastes.

Hydrological structure and erosion damage caused by concentrated flow in cultivated catchments

This study analyses the between-catchment variability of rill volumes produced by concentrated flow erosion during winter in the northern part of the Paris Basin. The working hypotheses were that (i) runoff concentrates along channels determined by topography or by agricultural practices; (ii) rill length is a major component of rill volume variability on a catchment scale; (iii) rill cross-sectional areas are controlled by the size of upslope runoff-contributing areas connected to the corresponding channels. Two samples, one of 20 zero order catchments and the other of 15 catchments, were surveyed. For each catchment, the runoff collector network was modelled from topographical and agricultural information, and split into homogeneous segments. Each segment was characterized by its slope gradient ( SL), the soil susceptibility to rill erosion ( SSE) and the size of the upslope runoff-contributing areas ( RCA) connected to it. These areas were identified by the structural state of their soil surface. The frequency of rill occurrence was highly correlated with RCA and SL. The rill cross-sectional areas of eroded channels were correlated with RCA, SL and SSE. Catchment erosion rates were estimated by adding together the predicted rill volumes for each segment within the catchment. These estimations were closely correlated with observed rill erosion rates. The relative spatial position of runoff collectors must be taken into account when examining the damage caused by concentrated flow erosion.

A quantitative approach for measuring N and P concentration changes in surface runoff from a restored riparian forest wetland

A recently restored riparian wetland is being evaluated as a bioremediation site for nutrients moving downslope from an animal waste application site. In question is the short-term effectiveness of the restored wetland in enhancing the quality of the water leaving the site. Networks of shallow ground-water wells and surface runoff collectors are being used to monitor nutrients concentrations and nutrient assimilation as surface and grounds water moves through the wetland. A 450-mm H-flume at the wetland outlet measures the quantity and quality of surface-water discharged from the wetland. Runoff is sampled at two locations entering the wetland and at two locations near the stream flow. At each location, the runoff is collected in a gutter, passed through a flume, and redistributed through a slotted gutter. Composite samples from each runoff event are collected with a low-cost automated sampler and analyzed for NO3-N, NH4-N, TKN, PO4-P, Total P, and Cl. Recorded hydrographs are used to determine total runoff volume and peak runoff rates of each runoff event. The runoff collectors have operated reliably and seem to be quantifying both hydrologic characteristics of runoff events and nutrient concentration changes in surface runoff as it migrate through the wetland. The simple design, low cost, and dependability of the runoff collection and automated sampling system make it suitable for a variety of research and industrial applications.