Major Runoff Events Research Articles

Application of GIS in Analysing Spatial Patterns of Multiple Runoff Events

Rainfall, topography and soil characteristics are considered to control spatial redistribution of phosphorus in catchments. To advance this research, a hydrology model is needed to describe spatial variation of soil moisture dynamics and runoff source areas in multiple runoff events. This study examined whether the spatially distributed, topographically based rainfall-runoff model, TOPMODEL provides superior performance for rainfall/runoff events in maritime climate and pastoral hill lands like New Zealand. Unlike previous efforts, we evaluate the hydrological model to identify runoff source areas for each individual runoff event. Geographical information system was used to analyse the model sensitivity on pattern dynamics of runoff, water tables and soil moistures of three major runoff events (low, medium and high). The model was tested for two catchments at Waipawa in Palmerston north, New Zealand. The study confirmed that TOPMODEL give high quality results (R2 of 84%) when validated against flow observations. Visual analysis on GIS systems showed that the predicted dynamics of variable source area and the component hydrological processes is realistic in the study area of pastoral farmlands. The TOPMODEL can be used to reflect both long-term evolutionary soil moisture content patterns and the short term forcing of flow dynamics during storm events in typical New Zealand mountainous and high rainfall volume (1200mm/year) regions.

Recent gully erosion in the El Cautivo badlands (Tabernas, SE Spain)

Detailed geomorphic observations in El Cautivo badland area, in the semiarid SE of Spain, show a recent renewal of linear channel erosion following a period of aggradation. Prior to this renewal, the landscape was characterized by smooth colluvial pediments on the north-east facing aspects and relatively steep crusted microhillslopes on south-west facing aspects. First-order valleys within the badland landscape were smooth-floored and filled with silty deposits connected with pediment colluvial deposits. The conditions under which valley bottom deposition was replaced by channel incision were analyzed by a study of flow hydraulics (magnitude–frequency of eroding events vs. resistance of valley floor to water flow) and the pollen sequence in the recently cut deposits. Changes in the vegetation-carpeting the valley bottom seem to be responsible for the deposition–erosion alternation rather than changes in the magnitude–frequency of major runoff events, given the high sensitivity of flow hydraulics to changes in roughness. Present rainfall rates would not, on their own, be able to erode a well-vegetated valley bottom. Yet, the pollen sequence in the valley fills demonstrates a progressive deterioration in climatic conditions with the eventual disappearance of groups that require a constant level of soil moisture ( Alnus, Corylus, Cyperaceae). An increase in yearly rainfall or a change in temporal patterns would increase infiltration leading to permanent denser vegetation on footslopes and valley floors, helped by the natural water harvesting system. This vegetation cover would reduce the flow velocity and induce the deposition of the colluvium and valley fills, whereas erosion on headslopes would have been active enough to supply the sediments that were deposited downslope or on the valley bottoms. The reactivation of linear erosion would seem, therefore, to be a consequence of the decay of this permanent vegetation, induced by an increase in the duration or severity of drought periods, which meant that the water storage capacity of the valley fillings was insufficient to support it.

Are Shifts in Herbicide Use Reflected in Concentration Changes in Midwestern Rivers?

In many Midwestern rivers, elevated concentrations of herbicides occur during runoff events for 1−3 months following application. The highest or “peak” herbicide concentration often occurs during one of these runoff events. Herbicide concentrations in rivers are affected by a number of factors, including herbicide use patterns within the associated basin. Changing agricultural practices, reductions in recommended and permitted herbicide applications, shifts to new herbicides, and greater environmental awareness in the agricultural community have resulted in changes to herbicide use patterns. In the Midwestern United States, alachlor use was much larger in 1989 than in 1995, while acetochlor was not used in 1989, and commonly used in 1995. Use of atrazine, cyanazine, and metolachlor was about the same in 1989 and 1995. Herbicide concentrations were measured in samples from 53 Midwestern rivers during the first major runoff event that occurred after herbicide application (postapplication) in 1989, 1990, 1994, and 1995. The median concentrations of atrazine, alachlor, cyanazine, metribuzin, metolachlor, propazine, and simazine all were significantly higher in 1989/90 than in 1994/95. The median acetochlor concentration was higher in 1995 than in 1994. Estimated daily yields for all herbicides and degradation products measured, with the exception of acetochlor, were higher in 1989/90 than in 1994/95. The differences in concentration and yield do not always parallel changes in herbicide use, suggesting that other changes in herbicide or crop management are affecting concentrations in Midwestern rivers during runoff events.

A Multi‐Year Study of Four Herbicides in Surface Water of a Small Prairie Watershed

AbstractTemporal trends of three phenoxy‐herbicides (2,4‐D, dichlorprop and MCPA) and bromoxynil were determined in the South Tobacco Creek, which drains a 70 km2 agricultural watershed near Miami, Manitoba, over a 4‐yr sampling program. The quantities of all pesticides used in the watershed and their application times were accurately recorded with the cooperation of landowners. Herbicide concentrations in South Tobacco Creek ranged from <0.01 ng/L to a maximum concentration of 680 ng/L (for 2,4‐D) and reflected local application times. Spring melt contributions were important when no significant runoff events occurred late in the previous growing season. Discharge of these herbicides in the South Tobacco Creek was calculated to be <0.01% of their quantities used within the watershed. No correlation was found between the water quality parameters: total organic C, total N, and total P and herbicide concentrations in South Tobacco Creek. Total N and P, however, were correlated to water flow, indicating runoff and ground water sources rather than atmospheric. We concluded that detailed temporal patterns of herbicides and nutrients could only be established if high sampling frequency was maintained during such critical periods such as application periods and during major runoff events. An unexpected finding was that herbicide concentrations were not related to runoff losses, but instead they did correspond to elevated levels in precipitation and air measured within the watershed.

The upper Hawkesbury River, New South Wales, Australia: a Holocene example of an estuarine bayhead delta

ABSTRACTHolocene deposits of the Hawkesbury River estuary, located immediately north of Sydney on the New South Wales coast, record the complex interplay between sediment supply and relative sea‐level rise within a deeply incised bedrock‐confined valley system. The present day Hawkesbury River is interpreted as a wave‐dominated estuarine complex, divisible into two broad facies zones: (i) an outer marine‐dominated zone extending 6 km upstream from the estuary mouth that is characterized by a large, subtidal sandy flood‐tidal delta. Ocean wave energy is partially dissipated by this flood‐tidal delta, so that tidal level fluctuations are the predominant marine mechanism operating further landward; (ii) a river‐dominated zone that is 103 km long and characterized by a well developed progradational bayhead delta that includes distributary channels, levees, and overbank deposits. This reach of the Hawkesbury River undergoes minor tidal level fluctuations and low fluvial runoff during baseflow conditions, but experiences strong flood flows during major runoff events. Fluvial deposits of the Hawkesbury River occur upstream of this zone.The focus of this paper is the Hawkesbury River bayhead delta. History of deposition within this delta over the last c. 12 ka is interpreted from six continuous cores located along the upper reaches of the Hawkesbury River. Detailed sedimentological analysis of facies, whole‐core X‐ray analysis of burrow traces and a chronostratigraphic framework derived from 10 C‐14 dates reveal four stages of incised‐valley infilling in the study area: (1) before 17 ka BP, a 0–1 m thick deposit of coarse‐grained fluvial sand and silt was laid down under falling‐to‐lowstand sea level conditions; (2) from 17 to 6·5 ka BP, a 5–10 m thick deposit composed of fine‐grained fluvial sand and silt, muddy bayhead delta and muddy central‐basin deposits developed as the incised valley was flooded during eustatic sea‐level rise; (3) during early highstand, between 6·5 and 3 ka BP, a 3–8 m thick bed of interbedded muddy central‐basin deposits and sandy river flood deposits, formed in association with maximum flooding and progradation of sandy distributary mouth‐bar deposits commenced; (4) since 3 ka BP, fluvial deposits have prograded toward the estuary mouth in distributary mouth‐bar, interdistributary‐bay and bayhead‐delta plain environments to produce a 5–15 m thick progradational to aggradational bayhead‐delta deposit. At the mouth of the Hawkesbury estuary subaqueous fluvial sands interfinger with and overlie marine sands. The Hawkesbury River bayhead‐delta depositional succession provides an example of the potential for significant variation of facies within the estuarine to fluvial segment of incised‐valley systems.

PLOT-SCALE RAINFALL-RUNOFF CHARACTERISTICS AND MODELING AT SIX SITES IN AUSTRALIA AND SOUTHEAST ASIA

During major runoff events when most soil loss occurs, runoff is likely to dominate the rainfall-driven erosionprocesses. Thus accurate estimation of the runoff rate is critical to soil loss predictions. At plot scale, the Green-Amptinfiltration model is commonly assumed to be able to describe the temporal variation of the infiltration rate over a stormevent. Field measurements of both rainfall intensity and runoff rate at 1-min intervals at six sites in the tropical and subtropicalregions of Australia and Southeast Asia, however, strongly suggest that the apparent infiltration rate is closelyrelated to the rainfall intensity and it is essentially independent of the cumulative infiltration amount, features not accordwith the Green-Ampt infiltration equation. Furthermore, the storage effect and runoff rate attenuation are not negligibleat the plot scale. With an initial infiltration amount to determine when runoff begins, an exponential distribution todescribe the spatial variation in the maximum infiltration rate and a linear storage formulation to model the lag betweenrunoff and rainfall, we were able to develop a satisfactory three-parameter model for the runoff rate at 1-min intervalswithin a storm event.

Phosphorus in runoff from a fertile dairy pasture

Losses of phosphorus (P) from grazed pastures in runoff can significantly reduce the water quality in streams draining agricultural catchments. Many preventative strategies depend for their success on the association of the P with large soil particles (>0·45 mm). We investigated the forms of P in runoff from a dairy pasture of high fertility. A 3·6-ha paddock at Darnum in West Gippsland, Victoria, was set up to measure runoff volume and rainfall, and to sample runoff water. Runoff from the site was restricted to 3 months in late winter and spring. Total runoff for 1994 of 660 m3 had an average total P concentration of 5·2 mg/L. Runoff from a single storm system over 8 days in early November accounted for 56% of the total runoff volume and 69% of the P lost. Of the total P in the runoff, 93% passed through a filter with 0·45-µm pores and 91% was reactive in an ascorbic acid–molybdate medium, without digestion; 89% of the P was both reactive in the ascorbic acid{molybdate medium and in the <0·45-µm fraction. There was no apparent relationship (P > 0·05) between P concentration and soil cover. In the Darnum catchment, the major runoff events occurred when the soil was saturated. The low settling velocities of materials <0·45 µm and the amount of P moving in larger storms would suggest that buffer strips and riparian zones are unlikely to decrease P losses substantially from dairy pastures in this area. Further, since erosion is unlikely to be the major process by which P is lost, control measures which simply limit erosion will be similarly ineffective at preventing P losses under the conditions that prevailed in this study.

Determination of Atrazine and Hydroxyatrazine in Agricultural Runoff Waters by Liquid Chromatography and Fast Atom Bombardment-High Resolution Mass Spectrometry

Abstract Agricultural surface water samples were collected after the first 2 major runoff events in 1994 for determination of atrazine (ATR, 2-chloro-4-ethylamino-6-isopropylamino-s-triazine) and hydroxyatrazine (HA, 2-ethylamino-4-hydroxy-6-isopropylamino-striazine). After addition of. 13C3-labeled ATR and 13C3-labeled HA as internal standards, the chemicals were quantitatively extracted and eluted from water samples by liquid-solid extraction with a carbon black cartridge. Liquid chromatography and fast atom bombardment-high resolution mass spectrometry were used to analyze the sample extracts. Concentrations of ATR ranged from 8.2 to 15.1 parts per billion (ppb) in the samples collected after both runoff events from a highly agricultural watershed in south-central Nebraska. HA concentrations ranged from 0.25 to 2.7 ppb in the water samples. Results obtained from both analytical procedures agreed within a 15% deviation. As predicted from runoff events, the highest levels occurred in samples from the first collection on June 24,1994, for both ATR and HA, whereas samples collected on July 5,1994, contained much lower levels of HA.

The Deethylatrazine/Atrazine Ratio as an Indicator of the Onset of the Spring Flush of Herbicides into Surface Water of the Midwestern United States

Abstract The ratio of deethylatrazine to atrazine (DAR) may be used to record the first major runoff of herbicides from non-point-source corn fields to surface water in the Midwestern United States. The DAR dramatically decreases from ∼0.5 to < 0.1 upon application of herbicide and the first major runoff event of a basin. The DAR then gradually increases to values of approximately 0.4–0.6 during the harvest season. Furthermore, the DAR may be used in studies of surface water movement to give a temporal indicator of water moving into reservoirs for possible storage of herbicides. It is hypothesized that deethylatrazine, which accounts for only 6% of the degradation of atrazine, becomes a significant metabolite in surface water (∼ 50% of parent compound) because of its selective removal from soil. This removal process may be an important concept for consideration in studies of herbicide contamination of rivers and reservoirs.

Soil management options to reduce runoff and erosion on a hardsetting Alfisol in the semi-arid tropics

Improved farming systems are needed to enhance productivity and reduce degradation on hardsetting Alfisols in the semi-arid tropics. A long-term experiment was started in July 1988 at ICRISAT, Hyderabad, India, to evaluate practices to improve infiltration and reduce erosion by stimulating biological activity and protecting soil in the rainy season. This paper outlines the rationale for the experiment, describes it, and summarises early results. Fifteen treatments in a randomised block design were applied to plots 28.5 m long by 5 m wide on a 2% slope. Nine annual treatments made up a factorial sub-set: tillage by tined implement to three depths (0, 10 and 20 cm) combined with three mulch treatments (no mulch, farmyard manure (FYM) at 15 t ha −1, and rice straw at 5 t ha −1). Pearl millet ( Pennisetum glaucum) was sown in the factorial sub-set in July 1988. Six perennial species ley treatments (combinations of perennial pigeonpea ( Cajanus cajan), verano stylo ( Stylosanthes hamata), and buffel grass ( Cenchrus ciliaris)) completed the randomised block design. All treatments were replicated three times making 45 plots in total. Plots were instrumented to measure runoff and soil loss. Millet straw yield was reduced by tillage to 20 cm and grain yield was significantly reduced by tillage to both 10 and 20 cm. Mulches had no effect on millet straw yield but FYM significantly increased millet grain yield. The proportion of rainfall running off plots ranged from 15.8 to 39.1%. Perennial species treatments tended to have higher runoff than treatments under millet, but this was not consistent as zero tillage without mulch, and tillage to 10 cm either with mulch or with FYM mulch, also had relatively high runoff. Rice straw mulch significantly reduced runoff by comparison with FYM and no mulch. Soil was lost mainly as suspended load, indicating that raindrop detachment was the main erosion process. Effects of perennial species were variable and probably reflected the degree of surface protection provided in this establishment phase. Tillage significantly increased suspended load concentration in the first major runoff event but not in an event later in the season. Rice straw mulch significantly reduced bed load concentration in the first event and reduced suspended load in the later event. The ability of straw mulch to reduce runoff volume and sediment concentration suggests mulch-based systems may be able to contribute to sustainability of farming systems in the semi-arid tropics. The lack of beneficial effects from tillage suggests a limited role for tillage-based systems. Results from subsequent years are needed to form definite conclusions and to show effects of slower biologically-induced changes in the soil.

Hydrological pathways of metolachlor export from an agricultural watershed

Hydrological pathways of metolachlor [2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl) acetamide] transport from a 5.5 ha−1 corn field in southern Ontario were examined. Metolachlor was applied as an early post-emergence surface broadcast treatment at a rate of 334.1 mg active ingredient m−2. Persistence in soils decreased exponentially following application, with slower dissipation in footslope areas. Metolachlor concentrations in runoff from experimental plots also decreased exponentially with time, and were strongly associated with herbicide levels in surrounding soils. Differences between concentrations and yields in saturation overland flow and Horton overland flow during the monitoring period were controlled by near-stream water table conditions. Total herbicide losses in runoff from the plots were in the order of 1% of applied a.i. Metolachlor was rapidly leached to depths of 1 m, such that peak concentrations and instantaneous metolachlor loads in tile drainage were observed within 14 days following application. Peak concentration in streamflow (125 µg L-1) occurred during the first major runoff event 13 days following application; peak concentrations in succeeding events followed an exponential decay during the growing season. Export of metolachlor from the field was in the order of 1% of applied a.i., with overland flow serving as the dominant transport mechanism from site of application. Near-stream hydrologic conditions may determine whether field exports of herbicide enter receiving water courses.

Three Phase Runoff Model for Small Prairie Rivers: I. Frozen Soil Phase Assessment

The Conceptual Model used in this study attributes virtually all major runoff events from small prairie basins to snowmelt and rainfall on frozen soil. To model these events, two parameters are estimated: the frozen soil (snowmelt) contributing area, and the related depression storage losses. A method for assessing these parameters is developed using a small watershed in east central Alberta, Ribstone Creek near Czar. A climatic model with a daily time step has been utilized to predict the spring runoff depths at 34 climate stations for 13 years. These data are interpolated with spatial analysis techniques to a one kilometre grid over the study area to develop estimates of runoff depth for a watershed. Inclusion of estimates of winter ET and spring infiltration to frozen soils improves the statistical significance of the results. The analysis supports the argument that the frozen soil contributing area and depression storage losses are relatively constant, and that the principal factor determining runoff variability is the spring snow-water equivalent.

Atrazine and simazine in runoff from conventional and no-till corn watersheds

A study was initiated to compare the surface runoff of atrazine and simazine from adjacent conventional tillage (CT) and no-tillage (NT) corn watersheds that were otherwise identical. Runoff was collected in H-type flumes and Coshocton wheels. Atrazine [2-chloro-4-(ethylamino)-6-(isopropylamino) - s-triazine] and simazine [2-chloro-4,6-bis(ethylamino)- s-triazine] were applied at 2.2 kg a.i. ha −1 to both watersheds annually from 1979 to 1982. There was less runoff of water, atrazine and simazine from the NT watershed compared to the CT watershed each year that a major runoff event occurred during the growing season. Between 1979 and 1982, total volume of runoff was 27% less from the NT compared to the CT watershed. Most of the herbicide loss in surface runoff occurred during the first runoff event after application. The concentration of simazine in runoff was much less than that of atrazine. The greatest runoff of herbicides occurred in 1979 when 1.6 and 1.1% of the atrazine applied moved from the CT and NT watershed, respectively, and 0.52 and 0.36% of the simazine applied moved from the CT and NT watershed, respectively.

Effect of Crop Residue Management and Tillage on Water Use Efficiency and Yield of Winter Wheat1

AbstractDirect drilling of winter wheat (Triticum aestivum L.) into surface cereal residues reduces soil erosion but frequently has resulted in stunted plants and lower grain yields than conventional planting methods. Phytotoxins produced during decomposition of surface crop residues have been implicated as the cause of these reduced yields. Field plots were established on spring and winter wheat stubble to compare plant stands, water storage, grain yields, and water‐use efficiency between direct drill seeded and conventionally seeded winter wheat. Residue management treatments included: standing stubble, complete residue removal, moving the crop residue from the seed row, and residue incorporation. New sites were used each year with the spring and winter wheat stubble maintained on Naff silt loam (fine‐silty, mixed, mesic Ultic Argixerolls) and Palouse silt loam (finesilty, mixed, mesic pachic Ultic Haploxerolls), respectively. Water soluble phytotoxins from the surface crop residues were not found during the 3‐year study. Furthermore, moving the crop residues from the seed row did not affect yields, but did alleviate the high crown node set which in turn reduced visual injury from soil active herbicides. Surface crop residues significantly improved water storage during the one season with a major runoff event, which increased grain yields and water use efficiencies, but had no effect when soil profiles were filled by spring. During the 3‐year study, winter wheat yields from plots direct drilled into surface cereal residues were equal to those from plots tilled and seeded conventionally.

A Study of Factors Influencing the Nitrogen and Phosphorus Contents of Nebraska Waters

AbstractThe purpose of this investigation was to determine magnitude and sources of nutrient N and P in Nebraska waters. Correlation studies reveal little relation between N and P concentrations of the water and agricultural use of fertilizers. Nutrient levels in the water are governed more by human and livestock densities and intensity of irrigation development than by agronomic production factors. Only at sites of intensive irrigation development on very sandy soils and with irrigation of valley positions of shallow water table has fertilizer N contributed substantially to a reduction in ground‐water quality.Nutrient concentrations in streams fluctuate widely with (i) varied time and rate of organic waste intrusions and subsequent biological assimilation and (ii) major runoff events. Reservoirs on streams also have a major modifying action in reducing sediment and fertility load. The observed higher N content of streams during periods of peak flow can be attributed partially to the high N content of precipitation and its direct runoff into streams during periods of high rainfall intensity.