Sediment-free Water Research Articles

On the possible use of hydraulic force to assist with building the step pyramid of saqqara.

The Step Pyramid of Djoser in Saqqara, Egypt, is considered the oldest of the seven monumental pyramids built about 4,500 years ago. From transdisciplinary analysis, it was discovered that a hydraulic lift may have been used to build the pyramid. Based on our mapping of the nearby watersheds, we show that one of the unexplained massive Saqqara structures, the Gisr el-Mudir enclosure, has the features of a check dam with the intent to trap sediment and water. The topography beyond the dam suggests a possible ephemeral lake west of the Djoser complex and water flow inside the 'Dry Moat' surrounding it. In the southern section of the moat, we show that the monumental linear rock-cut structure consisting of successive, deep compartments combines the technical requirements of a water treatment facility: a settling basin, a retention basin, and a purification system. Together, the Gisr el-Mudir and the Dry Moat's inner south section work as a unified hydraulic system that improves water quality and regulates flow for practical purposes and human needs. Finally, we identified that the Step Pyramid's internal architecture is consistent with a hydraulic elevation mechanism never reported before. The ancient architects may have raised the stones from the pyramid centre in a volcano fashion using the sediment-free water from the Dry Moat's south section. Ancient Egyptians are famous for their pioneering and mastery of hydraulics through canals for irrigation purposes and barges to transport huge stones. This work opens a new line of research: the use of hydraulic force to erect the massive structures built by Pharaohs.

Measurement of rill and ephemeral gully flow velocities and their model expression affected by flow rate and slope gradient

Water flow velocities in rill and ephemeral gully are useful for estimating hydrodynamics in the study on soil erosion. Laboratory experiments were conducted to measure erosive rill and ephemeral gully flow velocities, including nine unit width flow rates of 0.17, 0.33, 0.67, 1.33, 2.67, 5.33, 10.67, 21.33, and 42.67×10-3 m2 s−1, and five slope gradients of 8.7%, 17.6%, 26.8%, 36.4%, and 46.6%, on sandpaper slope glued with silt loam soil materials to imitate fixed rill and ephemeral gully beds, using an electrolyte tracer method. The flow velocities measured in this research ranged from 0.31 to 3.34 m s−1 for sediment-free water flow. The flow velocity fitted well with unit width flow rate and slope gradient by a power function, yielding an improved model with higher coefficient of determination than that related flow velocity to flow rate alone. The improved model is applicable for flow velocity and soil erosion predictions.

Effect of sediment size on damage caused by cavitation erosion and abrasive wear in sediment-water mixture

Damage caused by cavitation erosion and abrasive wear is a significant problem for hydraulic machinery in rivers with high concentrations of sediment. In this study, experiments are performed using a vibratory apparatus and a custom-made particle-moving device. The specimens are ASTM 1045 carbon steel, and sediment particles with mean diameters of 0.026–0.531mm are mixed in water at concentrations of 25kg/m3, 50kg/m3, and 85kg/m3. Experimental results demonstrate that damage is indeed exacerbated with increasing sediment sizes. However, when the size of sediment particles is smaller than a critical number (Dc), the damage caused by the sediment-water mixture is slightly less than the cavitation damage caused by sediment-free water; furthermore, for this small sediment, the damage decreases as the concentration increases. The critical size for the cases in this study is approximately 0.035–0.048mm. The viscosity of the mixture is likely a key factor to this phenomenon because the viscosities of mixtures with sediment smaller than the critical size increase as the sediment size decreases or the concentration increases. Experiments with mixtures with two sediment sizes further demonstrate that smaller sediment can inhibit the damage by cavitation.

Performance of Cotton Mat as Pre-Filtration Unit for Groundwater Recharging

Recharging groundwater through rooftop-harvested rainwater has immense potential. In order to manage the instant increase in storm run-off generated from high-intensity rainfall events, a filtration system with high-flow rate is required. Filtration through sand beds is a technique accepted world-wide, but its filtration rate reduces drastically with increase in inflow sediment load. For maintaining the pace in filtration rate through sand bed, a highly efficient, low-cost pre-filtration unit fabricated using cotton mat is recommended. The performances of three- and four-layer cotton mat filters have been evaluated using inflow sediment concentration of 50 and 100 mg/l. Results show that the four-layer cotton mat filter starts delivering sediment-free water much earlier than the three-layer filter, especially at the lower inflow sediment concentration. Moreover, the sediment trapping pattern is influenced by inflow sediment load and the first layer of the cotton mat. Experimental results show that the performance of the cotton mat filter is excellent and can be used as a cost-effective and reliable pre-filtration unit for handling the instant increase in storm runoff during groundwater recharging.

Re-suspension of bed sediment in a small stream – results from two flushing experiments

Abstract. Streams draining small watersheds often exhibit multiple peaking sedigraphs associated with single peaking hydrographs. The process reasons of the multiple sediment peaks are not fully understood but they may be related to the activation of different sediment sources such as the stream bed itself, where deposited sediments from previous events may be available for resuspension. To understand resuspension of stream bed sediments at the reach scale we artificially flooded the small stream of the HOAL Petzenkirchen catchment in Austria by pumping sediment-free water into the stream. Two short floods were produced and flow, sediment and bromide concentrations were measured at three sites with high temporal resolution. Hydrologically, the two flood events were almost identical. The peak flows decreased from 57 to 7.9 L s−1 and the flow volumes decreased from 17 to 11.3 m2 along the 590 m reach of the stream. However, a considerably smaller sediment load was resuspended and transported during the second flood due to depletion of stream bed sediments. The exception was the middle section of the stream, where more sediment was transported during the second flood event which can be explained by differences between flow velocity and wave celerity and the resulting displacement of sediments within the stream. The results indicate that the first peak of the sedigraphs of natural events in this stream is indeed caused by the resuspension of stream bed sediments, accounting for up to six percent of the total sediment load depending on total flow volume.

Larval Pacific Herring (Clupea pallasi) Survival in Suspended Sediment

Pacific herring early life stages provide good model systems for studying effects of suspended sediments on estuarine organisms. To investigate effects on the herring larval stage, we used environmentally relevant particle concentrations for San Francisco Bay (200–400 mg/L of particles <50 μm in size) and exposure times of 16 h in a novel two-pump sediment suspension mesocosm. There were no mortalities during the 16-h suspended sediment incubation. Following sediment exposure, larvae were cultured in sediment-free water for up to 10 days during which survival and condition were measured. None were affected by previous sediment treatment. Four criteria for larval condition included growth, heart rate, prey capture, and critical swimming velocity. These results provide a framework for implementing regulatory decisions on anthropogenic activities such as dredging.

A method to adapt watershed-scale sediment fingerprinting techniques to small-plot runoff experiments

Suspended sediment in rivers, lakes, and streams has been identified as a problem for several reasons. Watershed-scale studies are often conducted to identify primary sediment sources utilizing scale-appropriate soil fingerprinting methods. However, fingerprinting has not been attempted in small-plot runoff experiments to better understand sediment dynamics related to management practices. The objective of this study was to apply sediment fingerprinting techniques to small-plot runoff experiments to determine the relative contribution of the plot and applied sediment to sediment exported from small plots. Sediment-free water was applied to the head and sides of constructed vegetated channels in March and September of 2008. A 10 L (2 gal) sample of the runoff was collected, the water was evaporated from it, and the remaining sediment was ground and analyzed for total carbon (C). Water mixed with soil material obtained from a different part of the landscape and with a higher soil C content than that of the plot soil was applied to the head and sides of the vegetated channels, the mixture was sampled as it was applied, and the resulting runoff from the plot was sampled. These runoff samples were processed and analyzed for total C similarly to those collected when sediment-free water was introduced to the upper end of the plot. Based on differences in total C of the plot soil and the introduced soil material, a linear relationship was developed, allowing the sediment exiting the plot to be partitioned between that soil material introduced with the inflow and that soil coming from the plot bed. The sediment C content was entered into the linear equation to determine the percent plot-derived sediment in the runoff. When soil material mixed with water was introduced to the plots, on average, 20.5% of the sediment in runoff was derived from within the plot. The sediment trapping efficiency of the vegetated channels was very high (over 90%), and accounting for percent plot-derived sediment had little effect on sediment-trapping efficiency.

The hydraulic geometry of narrow and deep channels; evidence for flow optimisation and controlled peatland growth

At-a-station and bankfull hydraulic geometry analyses of peatland channels at Barrington Tops, New South Wales, Australia, reveal adjustments in self-forming channels in the absence of sediment load. Using Rhodes ternary diagram, comparisons are made with hydraulic geometry data from self-forming channels carrying bedload in alluvial settings elsewhere. Despite constraints on channel depths caused at some locations by the restricted thickness of peat, most stations have cohesive, near-vertical, well-vegetated banks, and width/depth (w/d) ratios of ∼2 that are optimal for sediment-free flow. Because banks are strong, resist erosion and can stand nearly vertical, and depth is sometimes constrained, adjustments to discharge are accommodated largely by changes in velocity. These findings are consistent with the model of maximum flow efficiency and the overarching least action principle in open channels. The bankfull depth of freely adjusting laterally active channels in clastic alluvium is well known to be related to the thickness of floodplain alluvium and a similar condition appears to apply to these swamps that grow in situ and are formed almost entirely of organic matter. The thickness of peat in these swamps rarely exceeds that required to form a bankfull channel of optimum w/d ratio for the transport of sediment-free water. Swamp vegetation is highly dependent on proximity to the water table. To maintain a swamp-channel and associated floodplain system, the channels must flow with sufficient water much of the time; they not only offer an efficient morphology for flow but do so in a way that enables bankfull conditions to occur many times a year. They also prevent the swamp from growing above a level linked to the depth of the channel. Once the channel attains the most efficient cross section, further growth of the swamp vertically is restricted by enhanced flow velocities and limited flow depths. This means that the volume of peat in such swamps is determined by the hydraulic efficiency of their channels. The development and maintenance of the hydraulic geometry of these swamp channels is biogeomorphic and biohydraulic in nature and yet accords to the same optimising principles that govern the formation of self-adjusting channels and floodplains in clastic alluvium.

A Probabilistic Screening Model for Evaluating Pyrethroid Surface Water Monitoring Data

Synthetic pyrethroids have been detected in recent California surface water monitoring. Filtration is avoided during sample workup because pyrethroids are extremely hydrophobic, tending to sorb to most surfaces. The resultant analytical pyrethroid concentrations reflect both dissolved pyrethroid and pyrethroid associated with suspended sediment in the water column. Such "whole-water" analytical data are not directly comparable to aquatic acute toxicity effect concentrations measured in laboratory sediment-free water. Consequently, any potential aquatic toxicity risk is indeterminate. In this study a simple probabilistic model was developed to allow a screening-level assessment of pyrethroid whole-water monitoring data. The results suggest that water column toxicity of pyrethroids is possible in California's agriculturally-dominated tributaries, and indicate that additional monitoring to better characterize pyrethroid water-column concentrations are warranted. Model refinement will depend on future work that more firmly establishes the relationship between pyrethroid partitioning and bioavailability, and that addresses the potential influence of dissolved organic carbon on pyrethroid sorption and bioavailability.

Experimental studies of food and suspended sediment effects on growth and reproduction of six planktonic cladocerans

Life-long somatic growth and egg production responses of Daphnia barbata, Daphnia gibba, Daphnia laevis, Daphnia pulex, Moina micrura and Diaphanosoma excisum were examined in relation to different food and suspended sediment levels, in factorial experiments at 20°C. Food treatments involved additions of 0, 100, 500 and 2500 μg C l−1 of Selenastrum to 20 μm filtered water, generally from source lakes. These food levels were tested at two suspended sediment levels in all species, viz. (i) natural source-lake nephelometric turbidities of 7–65 nephelometric turbidity units (NTU) (˜10–70 mg l−1 TSS) and (ii) ˜3- to 4-fold enrichment of natural levels (8-fold in D.excisum). A third sediment-free treatment was tested in all species of Daphnia other than D.gibba. Growth in body length and reproductive output were assessed daily for individual animals. Main and interactive effects of food and sediment on growth were assessed at selected ages from day 3 through subsequent life using analysis of variance (ANOVA). Strong and highly significant positive food effects were apparent at all ages in all species examined, with the curious exception of D.excisum. The onset of maturity and fecundity were also positively related to food level. Sediment effects on growth, age of maturity and fecundity were variable, but tended to be much weaker than food effects. Both stimulatory (positive, especially at low food levels) and inhibitory (negative) effects of sediment on growth were apparent, both between and within species. Performance in sediment-free water was very poor, except in D.pulex. Food-sediment interaction effects were variable. Generally, turbidwater species were influenced less adversely by sediment than clear-water species, indicating the existence of environmentally appropriate adaptive responses. Overall, the findings indicate that light limitation of algal resources by suspended sediments, rather than the condition of high turbidity per se, is responsible for the apparently negative impact of suspended sediments frequently observed on natural populations of cladoceran zooplankters.

Morphological Deformities in Brown Bullheads Administered Dietary β-Naphthoflavone

Abstract Brown bullheads Ameiurus nebulosus were exposed for 28 d to chemically contaminated sediments from tributaries of the Great Lakes. The fish were subsequently transferred to sediment-free water and fed a diet containing 500 mg (β-naphthoflavone/kg for 90 d in an effort to promote neoplasms. Following the β-naphthoflavone treatment, the fish were given untreated feed for an additional 150 d. The fish had no abnormalities after exposure to sediment for 28 d and no neoplasms after 268 d. However, fish fed β-naphthoflavone exhibited profound and unexpected external lesions and greatly reduced body weight. These morphological deformities resembled abnormalities found in brown bullheads from chemically contaminated sites in the natural environment, where in some instances the fish have unusually high frequencies of neoplasms. Our results suggest that morphological deformities observed in fishes from chemically contaminated sites could result from long-term exposure to compounds with mechanisms of action...

HYDRAULICS OF FLOW THROUGH A ROCKHLL DAM USING SEDIMENT-FREE WATER

ABSTRACT Rockfill dams can be used to slowly dewater sediment detention ponds. Currently, there is no suitable relationship to describe flow rate through rockfiU in terms of rockfill characteristics. This woric describes the flow of clean water through rockfill sections of different lengths, mean particle sizes, and standard deviations of particle size. Sixteen rockfill structures of varying gradations were used to define the hydraulics of turbulent flow for sediment-free water. Using the friction factor-Reynolds number relationship, five equations were developed to relate design parameters (length of rockfill, width of rockfill, flow rate, average diameter of rockfill, and standard deviation of the rockfill) to the unknown values (head loss through the rockfill, average hydraulic head within the rockfill, average velocity, friction factor, and Reynolds number). These equations were adequate for developing a stage-discharge curve and a design procedure for a rockfill structure.

Preliminary investigations on the influence of suspended sediments on the bioaccumulation of two chlorobenzenes by the guppy (Poecilia reticulata)

In this study the uptake by guppies (Poecilia reticulata) of 1,2,3-trichlorobenzene (TCB) and hexachlorobenzene (HCB) from sediment-free water was compared with uptake in the presence of suspended sediment. The results show that the influence of suspended sediment on the uptake of chlorobenzenes varies with test compound. For TCB uptake was not influenced by the presence of suspended sediment. This is probably due to the large amount of the chemical which is dissolved relative to the amount which is present in the sorbed state. For the more hydrophobic HCB, the concentration found in the fish from the system with suspended sediment was significantly higher than in fish from the control experiment.

Effects of discharge fluctuation and the addition of fine sediment on stream fish and macroinvertebrates below a water-filtration facility

A small, coastal stream in the San Francisco Bay area of California, USA, received the discharges from a drinking-water filtration plant. Two types of discharges were present. Discharges from filter backwashing were 3–4 times base stream flow, occurred 10–60 times per day, contained fine sediments, and each lasted about 10 min. The other discharge was a large, steady flow of relatively sediment-free water from occasional overflow of the delivery aqueduct which generally lasted several hours a day. Samples of invertebrates from natural substrates had significantly fewer taxa and lower density at the two stations below the backwash than at the two above. However, when stable artificial substrates were used, there were no significant differences among all four stations. The aqueduct apparently had no effect because the. invertebrate community at the station upstream of the backwash but downstream of the aqueduct was statistically similar to the station above the aqueduct. To test for acute toxicity, we exposed additional artificial substrates to short-term simulated backwash conditions. These exposures had no effect on invertebrate density or drift. Three-spine stickleback (Gasterosteus aculeatus) populations were also significantly reduced at the two downstream stations and were made up mostly of larger, adult fish. Prickly sculpins (Cottus asper), restricted to the most downstream station, were emaciated and had poor growth, probably as a result of scarce benthic food organisms. Artificial redds with eggs of rainbow trout (Salmo gairdneri) had significantly lower survival at two stations below the plant backwash (30.7% and 41.8%) than at the one above it (61.4%). Hatchery rainbow trout held in cages below the treatment plant from 7 to 37 days survived and continued to feed. Thus, the major effect of the water treatment plant on fish and invertebrates probably was not from acute toxicity in the discharges or the occasionally large discharge of clean water from the aqueduct, but was from the fluctuating backwash flows containing fine sediment that displaced small fish downstream and created unstable benthic substrates for invertebrates. The filter plant that we studied is a direct-feed type (that is, no sedimentation before filtration). These generally require greater frequencies of backwashing than do conventional plants and may therefore have greater biological impacts. Direct-feed plants are becoming increasingly popular throughout the world, for the most part because they are cheaper to build and operate. But if the associated biological problems are mitigated, then the cost savings of direct-feed compared to conventional plants may be lost.

Seepage Characteristics of Stable Channels

A channel in which no erosion occurs at a given design discharge is called a stable channel. Such channels are required to transport sediment-free water. The maximum bed shear stress does not exceed the critical shear stress at any place on the surface of the channel.