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Rainfall Simulator (rainfall + simulator)

Distribution by Scientific Domains

Earth and Environmental Science	33%

Selected Abstracts

Soil infiltration, runoff and sediment yield from a shallow soil with varied stone cover and intensity of rain

EUROPEAN JOURNAL OF SOIL SCIENCE, Issue 4 2005
Uttam Kumar Mandal
Summary Stones on the surface of the soil enhance infiltration and protect the soil against erosion. They are often removed in modern mechanized agriculture, with unfortunate side-effects. We evaluated experimentally the influence of surface stones on infiltration, runoff and erosion under field conditions using a portable rainfall simulator on bare natural soil in semi-arid tropical India, because modernization and mechanization often lead to removal of these stones in this region. Four fields with varied cover of stones from 3 to 65% were exposed to three rainfall intensities (48.5, 89.2 and 136.8 mm hour,1). Surface stones retarded surface runoff, increased final infiltration rates, and diminished sediment concentration and soil loss. The final infiltration ranged from 26 to 83% of rainfall when the rainfall intensity was 136.8 mm hour,1. The reduction in runoff and soil erosion and increase in infiltration were more pronounced where stones rested on the soil surface than where they were buried in the surface layer. The sediment yield increased from 2 g l,1 for 64.7% stone cover with rainfall of 48.5 mm hour,1 to 70 g l,1 for 3.5% stone cover with rain falling at 136.8 mm hour,1. The soil loss rate was less than 2 t ha,1 hour,1 for the field with stone cover of 64.7% even when the rainfall intensity was increased to 136.8 mm hour,1. The effects of stones on soil loss under the varied rainfall intensities were expressed mathematically. The particles in the sediment that ran off were mostly of silt size. [source]

Physically based modelling of sediment generation and transport under a large rainfall simulator

HYDROLOGICAL PROCESSES, Issue 11 2006
Russell Adams
Abstract A series of large rainfall simulator experiments was conducted in 2002 and 2003 on a small plot located in an experimental catchment in the North Island of New Zealand. These experiments measured both runoff and sediment transport under carefully controlled conditions. A physically based hydrological modelling system (SHETRAN) was then applied to reproduce the observed hydrographs and sedigraphs. SHETRAN uses physically based equations to represent flow and sediment transport, and two erodibility coefficients to model detachment of soil particles by raindrop erosion and overland flow erosion. The rate of raindrop erosion also depended on the amount of bare ground under the simulator; this was estimated before each experiment. These erodibility coefficients were calibrated systematically for summer and winter experiments separately, and lower values were obtained for the summer experiments. Earlier studies using small rainfall simulators in the vicinity of the plot also found the soil to be less erodible in summer and autumn. Limited validation of model parameters was carried out using results from a series of autumn experiments. The modelled suspended sediment load was also sensitive to parameters controlling the generation of runoff from the rainfall simulator plot; therefore, we found that accurate runoff predictions were important for the sediment predictions, especially from the experiments where the pasture cover was good and overland flow erosion was the dominant mechanism. The rainfall simulator experiments showed that the mass of suspended sediment increased post-grazing, and according to the model this was due to raindrop detachment. The results indicated that grazing cattle or sheep on steeply sloping hill-country paddocks should be carefully managed, especially in winter, to limit the transport of suspended sediment into watercourses. Copyright © 2006 John Wiley & Sons, Ltd. [source]

Simulated rainfall evaluation of revegetation/mulch erosion control in the Lake Tahoe Basin,1: method assessment

LAND DEGRADATION AND DEVELOPMENT, Issue 6 2004
M. E. Grismer
Abstract Revegetation of road cuts and fills is intended to stabilize those drastically disturbed areas so that sediment is not transported to adjacent waterways. Sediment has resulted in water quality degradation, an extremely critical issue in the Lake Tahoe Basin. Many revegetation efforts in this semiarid, subalpine environment have resulted in low levels of plant cover, thus failing to meet project goals. Further, no adequate physical method of assessing project effectiveness has been developed, relative to runoff or sediment movement. This paper describes the use of a portable rainfall simulator (RS) to conduct a preliminary assessment of the effectiveness of a variety of erosion-control treatments and treatment effects on hydrologic parameters and erosion. The particular goal of this paper is to determine whether the RS method can measure revegetation treatment effects on infiltration and erosion. The RS-plot studies were used to determine slope, cover (mulch and vegetation) and surface roughness effects on infiltration, runoff and erosion rates at several roadcuts across the basin. A rainfall rate of ,60,mm,h,1, approximating the 100-yr, 15-min design storm, was applied over replicated 0·64,m2 plots in each treatment type and over bare-soil plots for comparison. Simulated rainfall had a mean drop size of ,2·1,mm and approximately 70% of ,natural' kinetic energy. Measured parameters included time to runoff, infiltration, runoff/infiltration rate, sediment discharge rate and average sediment concentration as well as analysis of total Kjeldahl nitrogen (TKN) and dissolved phosphorus (TDP) from filtered (0·45,,m) runoff samples. Runoff rates, sediment concentrations and yields were greater from volcanic soils as compared to that from granitic soils for nearly all cover conditions. For example, bare soil sediment yields from volcanic soils ranged from 2,12 as compared to 0·3,3,g,m,2,mm,1 for granitic soils. Pine-needle mulch cover treatments substantially reduced sediment yields from all plots. Plot microtopography or roughness and cross-slope had no effect on sediment concentrations in runoff or sediment yield. RS measurements showed discernible differences in runoff, infiltration, and sediment yields between treatments. Runoff nutrient concentrations were not distinguishable from that in the rainwater used. Copyright © 2004 John Wiley & Sons, Ltd. [source]

Numbers and transported state of Escherichia coli in runoff direct from fresh cowpats under simulated rainfall,

LETTERS IN APPLIED MICROBIOLOGY, Issue 2 2006
R.W. Muirhead
Abstract Aims:, To investigate the number of Escherichia coli in runoff derived directly from fresh cowpats and to determine if the E. coli are attached to dense particles, in flocs or as individual cells. Methods and Results:, Three cowpats were collected monthly from the same farm for 13 months and the number of E. coli in them estimated. A rainfall simulator was used to generate runoff from the individual cowpats, which was fractioned to determine the transported state of any E. coli present. The number of E. coli in the cowpat runoff was highly variable and was strongly correlated with the number of E. coli in the cowpat. Only a small percentage (approx. 8%) of the E. coli in runoff were attached to dense (>1·3 g ml,1) particles and there was no evidence of flocculation of the cells. Conclusions:,Escherichia coli in runoff from cowpats are transported predominantly as individual cells. Significance and Impact of the Study:, Mitigation strategies to reduce the number of faecal bacteria in overland flow from agricultural land need to be designed to trap single bacterial cells. [source]

Runoff transport of faecal coliforms and phosphorus released from manure in grass buffer conditions

LETTERS IN APPLIED MICROBIOLOGY, Issue 3 2005
W.L. Stout
Abstract Aims:, To test the hypothesis that faecal coliform (FC) and phosphorus (P) are transported similarly in surface runoff through the vegetative filter strip after being released from land-applied manure. Methods and Results:, The Hagerstown soil was packed into boxes that were 10 cm deep, 30 cm wide and 100, 200 or 300 cm long. Grass was grown in boxes prior experiments. Same-length boxes were placed under rainfall simulator and tilted to have with either 2% or 4% slopes. Dairy manure was broadcast on the upper 30-cm section. Rainfall was simulated and runoff samples were collected and analysed for Cl, FC and total phosphorus (TP). Mass recovery, the concentration decrease rate k, and the ratio FC : TP showed that there was a consistent relationship between FC and TP in runoff. Conclusion:, The FC and TP transport through simulated vegetated buffer strips were highly correlated. Significance and Impact of the Study:, As a knowledge base on the effect of the environmental parameters on P transport in vegetated buffer strips is substantially larger than for manure-borne bacteria, the observed similarity may enhance ability to assess the efficiency of the vegetated buffer strips in retention of FC currently used as indicator organisms for manure-borne pathogens. [source]