Canal Flow Research Articles

Phosphorus fractionation and distribution in sediments from wetlands and canals of a water conservation area in the Florida Everglades

Phosphorus (P) fractionation and distribution in sediments are of great concern in the Florida Everglades ecosystem because potential eutrophication of surface waters usually results from P external loading and stability. Intact core sediment samples were collected to a depth of 35 cm from wetlands and canals across Water Conservation Area 3 (WCA‐3) of the Florida Everglades. These sediment cores were sliced into 5 cm increments and analyzed for P contents in different fractions by sequential extraction. These fractions mainly included total P (TP), readily available P (Pi‐KCl), Fe/Al‐bound P (Pi‐NaOH), Ca/Mg‐bound P (Pi‐HCl), organic P (Po‐NaOH), and residual P (PoResidue). Results showed that the canal sediments had the highest concentrations of TP, with about 87% in the form of Ca/Mg‐bound fraction, and the concentrations of TP in these sediments increased with depth. In contrast, the wetland sediments contained the lowest concentrations of TP (predominantly in the organic fraction), with 43% residual P and 27% Po‐NaOH, and the concentrations of TP in these sediments decreased with depth. In addition, a large amount of the readily available P (up to 1500 mg kg−1) in the canal sediments was accumulated at the top layer of 0–5 cm. This study suggests that any disturbance and/or environmental alterations, such as high canal flow and dredging in canal sediments, could pose a potential risk of a P increase in the water column and, consequently, in the wetlands because of the release of readily available P despite the relatively stable nature of such P fractions in these sediments.

Design of water supply facilities for a tidal fish farm in the Niger Delta, Nigeria

Studies to redress the water supply problem by designing water supply facilities (inundation canal with sluice gate, a reservoir, and a pumping station) for African Regional Aquaculture Centre (ARAC) fish farm located in Aluu, Rivers State of Nigeria were carried out for twenty-four months. The topographic survey of the area indicated gentle sloping woodland, with the highest and lowest elevations of 11.00 and 1.00 m respectively above ordinance datum. The longitudinal section of the proposed canal indicated relatively flat tidally fed wetland, with the highest elevation of 1.70 m and lowest elevation of 0.47 m above ordinance datum. The mean peak heights of water in the study canal during spring tides ranged from 0.95 to 1.45 m. On the other hand, the mean peak height of water during neap tides ranged from 0.38 to 0.86 m. The floodtide and ebb tide velocities of canal water flow ranged from 0.40 to 0.75 m/s and 0.72 to 0.92 m/s respectively. Soil particles size analysis showed predominantly loamy clay soils. Mean surface water temperature readings ranged from 23.50 to 29.00 O C. Dissolved oxygen (DO) content ranged from 5.80 to 7.40 mg/L. The corresponding DO deficits ranged from 2.35 to 0.20 mg/L, indicating a moderate level of pollution. pH values of canal water flow ranged from 5.80 to 6.97 units, which is considered slightly acidic. The transparency of the river ranged from 95.00 to 199.00 cm, while total hardness values ranged from 12.90 to 50.20mg CaCO 3 /l. The water quality characteristics showed seasonal variations, attributed largely to the dilution effect of the rain. The baseline data were considered adequate for the design of water supply facilities for the farm. Keywords: Tidal water levels, fish farm, wetland, water supply, Niger Delta International Journal of Natural and Applied Sciences , 7(1): 94 - 103, 2011

First results of a study of the Etruscan tunnel and other hydraulic works on the Ponte Coperto stream (Cerveteri, Rome, Italy)

The Etruscan tunnel called Ponte Coperto is located NW of Rome, near the town of Cerveteri. The Ponte Coperto tunnel, mapped for the first time during the present research and dug mainly in volcanic tuff lying below the lava flow, was built to drain a valley of about 8.5 km2, probably between the VII and VI century B.C. Before the tunnel construction, part of the valley was occupied by a swamp, whose reclamation was carried out by digging a long rectilinear canal of about 800 metres to the tunnel opening. Several hundred metres upstream of the tunnel entrance a secondary canal flows into the main one; this tributary canal drains a secondary valley, next to the principal one. Nowadays the Ponte Coperto tunnel, 170 m long, looks much larger than its original shape due to natural erosion that has widened and deepened it: during the dry season its discharge is negligible, but some calculations show that the peak discharge can be in the order of several dozens of cubic metres per second. The efficiency of the Ponte Coperto system is outstanding, as the hydraulic setup of the area is still that left by the Etruscans engineers more than two millennia ago: the tunnel and the canals keep draining both the surface and the ground waters from the more permeable rocks, and the valley is still healthy and cultivated. The Ponte Coperto system is a good example of the fact that Roman water engineering has its roots in Etruscan technology.

The effect of apical preparation size on irrigant flow in root canals evaluated using an unsteady Computational Fluid Dynamics model

To evaluate the effect of apical preparation size on irrigant flow inside a root canal during final irrigation with a syringe and two different needles types, using a Computational Fluid Dynamics (CFD) model. A validated CFD model was used to simulate the irrigant flow from either a side-vented or a flat 30G needle positioned inside root canals having sizes of 25, 35, 45 and 55, all with a .06 taper, at 3 mm short of working length (WL). Velocity, pressure and shear stress in the root canal were evaluated. Different preparation sizes resulted in minor differences in the flow pattern in the apical root canal. Major differences were observed between the two needle types. The side-vented needle could not achieve irrigant replacement to the WL even in a size 55, .06 taper root canal. Significant irrigant replacement was evident almost to the WL in size 35, 45 and 55, .06 taper root canals with the flat needle. The maximum shear stress decreased as the preparation size increased. The flat needle developed higher mean pressure at the apical foramen. Both needles led to a similar gradual decrease in apical pressure as the preparation size increased. Apical preparation size affected irrigant replacement, the shear stress on the canal wall and the pressure at the apical foramen. Root canal enlargement to sizes larger than 25 appeared to improve the performance of syringe irrigation. Adequate space between the needle and the canal wall should be ensured to allow for an effective reverse flow of the irrigant towards the canal orifice.

The effect of harvesting strategy of grass silage on digestion and nutrient supply in dairy cows

This study examined the effects of primary growth (PG) and regrowth (RG) timothy-meadow fescue silages harvested at 2 stages of growth on feed intake, cell wall digestion and ruminal passage kinetics in lactating dairy cows. Four dairy cows equipped with rumen cannulas were used in a study designed as a 4 × 4 Latin square with 21-d periods. The experimental silages were offered ad libitum with 8 kg/d of concentrate. Ruminal digestion and passage kinetics were assessed by the rumen evacuation technique. Silages of PG were on average more digestible than RG silages. The concentration of neutral detergent fiber (NDF) and indigestible NDF (iNDF) increased and the concentration of digestible organic matter in dry matter (DM) of silages decreased with advancing maturity in PG and RG. Cows consumed more feed DM, energy, and protein and produced more milk when fed PG diets rather than RG diets. Delaying the harvest decreased DM intake and milk production in PG and RG. There were no differences between PG and RG in rumen pH, ammonia N, or total volatile fatty acid concentrations. The intake of N, omasal canal flow of total nonammonia N and microbial N, excretion of N in feces, and ruminal true digestibility of N were higher for PG than for RG diets. The efficiency of microbial N synthesis was not different between PG and RG. Intake and omasal canal flow of organic matter, NDF, and potentially digestible NDF (pdNDF) were higher in PG than in RG. Whole-diet digestibility of organic matter, NDF, or pdNDF in the rumen or in the total tract was not different between PG and RG despite the higher digestibility of PG silages measured in sheep. Rumen pool sizes of crude protein and iNDF were lower for PG diets, whereas the pool size of pdNDF was higher for PG diets than for RG diets. The rate of passage of iNDF was higher for PG diets than for RG diets, with no difference between them in rate of digestion or passage of pdNDF. The lower milk production in cows fed regrowth grass silages compared with primary growth silages could be attributed to the lower silage DM intake potential. Chemical composition of the silages, rumen fill, digestion and passage kinetics of NDF, or the ratio of protein to energy in absorbed nutrients could not explain the differences in DM intake between silages made from primary and regrowth grass.

Numerical simulation of the flow in semicircular canals with the method of fundamental solutions

AbstractWe present a numerical model for the simulation of the flow in semicircular canals (SCCs). The governing equations for the flow are solved with the method of fundamental solutions (MFS), a mesh free method for boundary value problems. We describe the flow field in a SCC with utricle, and we find a vortex that had not yet been reported in literature. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Effects of feeding grass or red clover silage cut at two maturity stages in dairy cows. 1. Nitrogen metabolism and supply of amino acids

This study investigated the effects of plant species (red clover vs. timothy-meadow fescue) and forage maturity at primary harvest (early vs. late cut silage) on rumen fermentation, nutrient digestion, and nitrogen metabolism including omasal canal AA flow and plasma AA concentration in lactating cows. Five dairy cows equipped with rumen cannulas were used in a study designed as a 5×5 Latin square with 21-d periods. The diets consisted of early-cut and late-cut grass and red clover silage, respectively, and a mixture of late-cut grass and early-cut red clover silages given ad libitum with 9kg/d of a standard concentrate. Grass silage dry matter intake tended to decrease but that of red clover silages tended to increase with advancing maturity. Milk yields were unchanged among treatments, milk protein and fat concentrations being lower for red clover than for grass silage diets. Rumen fluid pH was unchanged but volatile fatty acid and ammonia concentrations were higher for red clover than for grass silage diets. Intake of N, and omasal canal flows of total nonammonia N (NAN), microbial NAN, and dietary NAN were higher for red clover than for grass silage diets but were not affected by forage maturity. However, microbial NAN flow and amount of N excreted in the feces decreased with advancing maturity for grass diets but increased for red clover diets. Apparent ruminal N degradability of the diets was unchanged, but true ruminal N degradability decreased and efficiency of microbial synthesis increased with red clover diets compared with grass silage diets. Omasal canal flows of AA, except those for Met and Cys, were on average 20% higher for red clover than grass silage diets. Omasal canal digesta concentrations of Leu, Phe, branched-chain, and essential AA were higher but those of Met lower for red clover than for grass silage diets. Plasma AA concentrations, except for His (unchanged) and Met (lower), were higher for red clover than for grass diets. However, none of these AA-related variables were affected by forage maturity. Total digestibility of N and excretion of N in the urine were higher for red clover than for grass diets and decreased with advancing maturity. It was concluded that despite the higher total AA supply of cows fed red clover versus grass silage diets, further milk production responses on red clover diets were compromised by an inadequate supply of Met as evidenced by lower Met concentration in the AA profile of omasal digesta and plasma.

Application of the relevance vector machine to canal flow prediction in the Sevier River Basin

This work addresses management of water for irrigation in arid regions where significant delays between the time of order and the time of delivery present major difficulties. Motivated by improvements to water management that will be facilitated by an ability to predict water demand, it employs a data-driven approach to developing canal flow prediction models using the relevance vector machine (RVM), a probabilistic kernel-based learning machine. A search is performed across model attributes including input set, kernel scale parameter and model update scheme for models providing superior prediction capability using the RVM. Models are developed for two canals in the Sevier River Basin of southern Utah for prediction horizons of up to 5 days.

Flow Discharge Modeling in Open Canals Using a New Fuzzy Modeling Technique (SMRGT)

AbstractThe main goal of this study was to research the answer to two important questions in flow modeling; i) how to optimally design the cross‐section of an open channel for a given flow, and ii) in the case of selecting the fuzzy method for modeling, how to construct the membership functions (MFs) and fuzzy rules (FRs) such that the system yields the best results. The first question is answered in order to minimize difficulties in excavation and related costs by using the appropriate flow velocity. To provide the best answer researchers use several methods. The second question is answered in order to minimize model error. For this aim, there are many algorithms proposed by researchers in the literature. In this paper, the fuzzy logic method was used for open canal flow modeling. Furthermore, a simple membership function and fuzzy rule generation technique (SMRGT) is introduced, and used for fuzzy modeling. Two fuzzy models, each for different cross‐sectional shape, are presented in this study as an application of SMRGT. The comparison depends on various statistics, mean absolute relative error, and contour maps showed that the fuzzy models were successful in open channel flow modeling and SMRGT is useful for MF (membership function) and FR (fuzzy rule) generation.

Generalized Flow Rating Equations at Prototype Gated Spillways

Gated spillways are used to control flow in canals, rivers, and estuaries. Despite their widespread use, available flow ratings at these gated structures are largely derived from reduced-scale laboratory models. In this paper, generalized flow rating equations are developed based on field flow measurements collected mostly with an Acoustic Doppler Current Profiler at about 90 prototype gated spillways in South Florida. The proposed ratings, developed using dimensional analysis, agree well with field measurements. A single generalized equation that is applicable to all flow conditions was also developed. This generalized equation addresses the limitation of continuity of the calculations as flow transitions from one condition to another.

Comparison of Flow-Boundary Effects on Critical Submergence of an Intake

In this study, the effects of canal bottom and dead-end wall on the critical submergence of a single rectangular or circular intake are investigated and compared. In order to find the functional relationship involving the critical submergence and the influencing dimensionless variables, dimensional analysis is utilized. Experiments were conducted on a rectangular or circular intake sited with different positions in a uniform canal flow. Experimental results have indicated that the flow boundaries considerably affect the critical submergence. The effect of the boundary cutting the free surface on the critical submergence is much larger than that of the sub-surface boundary not cutting the free surface.

Critical submergence for dual pipe intakes

The effects of dimensions and relative positions of two (a dual) pipe intakes on the critical submergence are investigated. A dimensional analysis provided the relationship between the critical submergence and the governing dimensionless variables. Also, the potential flow solution was utilized to predict the critical submergence(s) for dual pipe intakes without partition walls located in the canal axis. Experiments were conducted on two vertical intakes at various relative positions. The experimental results indicate that the critical submergence is considerably affected by the relative positions and dimensions of an intake. The critical submergence for dual pipe intakes is larger than that of a single intake under identical conditions. The agreement between the potential flow solution and the experimental data related to the dual intakes on the same axis as the canal flow was found to be good.

Nonlinear Observer-Based Feedback for Open-Channel Level Control

This paper is devoted to nonlinear observer and controller design for water level control of open-channel flow in irrigation canals or dam-river systems. A finite-dimensional model, previously developed by orthogonal collocation methods, based on Saint Venant equations and used for control design, is now further used for online flow rate and water infiltration estimation. This is done by a so-called state observer. In particular, the estimates obtained in this way can successfully be used in a controller previously proposed, resulting in a water level control law using only two level measurements along the canal (instead of the four measurements previously needed). The study is restricted to the case of a rectangular wetted section and subcritical flow. The results have been validated by simulations, on an implicit finite difference simulator based on a Preissmann scheme for various scenarios.

A control tool for irrigation canals with scheduled demands

The problem of adjusting the discharges of a free surface flow canal to meet demand by farmers at particular diversion points requires a certain ability to control the canal and also needs a study of flow transients. This article presents an algorithm for feed forward control of the free surface flow in canals based on computational techniques for optimizing problem-solving in unsteady conditions. Once the irrigation demands in a given period of time are known, this algorithm makes it possible to define the movements of all the gates in the canal so as to provide the required discharge at the required time, thereby optimizing use of the volumes of water involved. Use of the algorithm is illustrated by solving two classical canal control problems.

Investigation of Integrated Management of Large-Scale Irrigation and Aquaculture Systems

The importance of nonirrigation uses of irrigation water to the livelihoods of the rural poor living close to irrigation systems has generally been ignored both in planning and operating these systems. An improved understanding of competition and complementarity of irrigation and nonirrigation uses is essential for increased productivity of irrigation water. This paper selected two typical types of large-scale irrigation systems as case study sites, i.e., the Lower Bhavani Project in Tamil Nadu, India—a canal-based irrigation system and Mahaweli System H, Sri Lanka—a tank-based irrigation system, and explored their potential for and constraints to integrated management for irrigation and aquaculture. The results revealed that for irrigation canals water supply reliability, canal flow velocity, and cage anchorage but for irrigation tanks water, supply reliability may impose constraints to integration of cage-based fish farming. However, the potential can be improved through more responsive operation and ma...

Alternative Rotational Delivery Scheduling for Better Water Regime in Canal Command

A model for modifying the canal delivery schedule during the dry season has been formulated to overcome the problem of low irrigation efficiency in a major irrigation project in India. Phulnakhara Distributary of the Puri main canal system (a run-of-the-river scheme) in the state of Orissa was chosen for this study. The model adopts a procedure of daily water balance simulation in paddy field and daily moisture balance simulation in nonpaddy crops field in the crop root zone. The historical canal flow data show that the prevailing delivery schedule is continuous. In addition to prevailing a continuous delivery schedule, five alternative rotational (variable discharge, constant duration, and constant frequency) schedules were considered. The alternatives considered are: 7 days canal operation followed by 7 days canal closure (7_7); 10 days canal operation followed by 10 days canal closure (10_10); 15 days canal operation followed by 15 days canal closure (15_15); 10 days canal operation followed by 7 days canal closure (10_7); and 15 days canal operation followed by 7 days canal closure (15_7). Considering both paddy and nonpaddy crops to be grown in the command during the dry season, 7 days canal operation followed by 7 days canal closure rotational schedule were found to be the best alternative. The alternative schedule 7_7 has registered weighted average seasonal evapotranspiraton (ET) of 354 mm in comparison to 347, 342, and 352 mm in 10_10, 15_15, and 10_7 schedules, respectively. In the paddy field, schedule 7_7 registered maximum of 4 days of disappearance of water as compared to 5 days and 6 days for 15_7 and 10_7 schedule, respectively. Besides creating a favorable water regime and better crop ET, this schedule saves about 10.31% of water over prevailing (actual) water supplies.

Reducing the computational cost of unconfined groundwater flow in conjunctive-use models at basin scale assuming linear behaviour: The case of Adra-Campo de Dalías

The optimization of conjunctive-use management models (with different competing demands, several reservoirs and aquifers, and a high interconnection among elements) over long time horizons requires the use of computationally-efficient groundwater flow models. A review of conjunctive use models and some methods applied to reduce the computational cost of the groundwater flow model has been performed, with special attention to the assumption of linear behaviour. The effect of considering invariant transmissivity in a conjunctive-use management model at the basin scale has been analyzed using as case study the Adra-Campo de Dalías system (Southeast of Spain). The system includes an unconfined aquifer not hydraulically connected to the river in which significant drawdown, relative to the saturated thickness, can appear. The basin scale system also includes storage in a reservoir, flows in several river segments and canals, and a second simpler aquifer. The management formulation seeks the best conjunctive operation of reservoir and aquifer to meet urban and irrigation demands while satisfying minimum flow and aquifer head constraints over a time horizon of several years. The effect of the linear assumption has been studied by comparing and analyzing management model results obtained modeling the aquifer as confined and as unconfined. Groundwater flow is simulated in the optimization model using the response matrix method. The optimization problem is solved using sequential linear programming (SLP) in the unconfined case and using linear programming (LP) when confined behaviour is assumed. Although the drawdown are significant, the difference in results is minor, suggesting that the use of a linear assumption may be valid in many basin scale conjunctive management problems in which the aquifer is not hydraulically connected to the river system. Nevertheless, the assumption should be tested, if possible, in each management problem with unconfined aquifers in which significant drawdown appears.

Water Scarcity Effects on Equitable Water Distribution and Land Use in a Major Irrigation Project—Case Study in India

In many river basins, upstream development and interannual variations in rainfall can cause both episodic and chronic shortages in water supplies downstream. Continued rapid development of surface and groundwater throughout the Krishna Basin in southern India resulted in historically low inflows to the main canals of the Nagarjuna Sagar irrigation project 8,955 km 2 during a recent drought 2002-2004. This paper presents an integrated approach to assess how cropping patterns and the spatial equity of canal flow changed with water supply shocks in the left canal command area 3,592 km 2 of Nagarjuna Sagar. We combined 3 years 2000-2003 of canal release data with census statistics and high temporal resolution 8-10 days moderate resolution imaging spectrometer MODIS 500-m resolution satellite imagery. The impact of water scarcity on land use pattern, delineated by MODIS images with moderate spatial resolution, was comparable with the census statistics, while the MODIS data also identified areas with changes and delays in the rice crop area, which is critical in assessing the impact of canal operations. A 60% reduction in water availability during the drought resulted in 40% land being fallowed in the left-bank canal command area. The results suggest that head reach areas receiving high supply rates during a normal year experienced the highest risks of fluctuations in water supply and cropped area during a water short year compared to downstream areas, which had chronically low water supply, and better adaptive responses by farmers. Contrary to expectations, the spatial distribution of canal flows among the three major zones of the command area was more equitable during low-flow years due to decreased flow at the head reach of the canal and relatively smaller decreases in tail-end areas. The findings suggested that equitable allocations could be achieved by improving the water distribution efficiency of the canal network during normal years and by crop diversification and introduction of alternative water sources during water shortage years. The study identified areas susceptible to decreases in water supplies by using modern techniques, which can help in decision-making processes for equitable water allocation and distribution and in devel- oping strategies to mitigate the effects of water supply shocks on cropping patterns and rural livelihoods.

Numerical simulation of the endolymph flow in a semicircular canal

AbstractWe present a concept for the simulation of the fluid flow in the semicircular canals of the inner ear. Based on the temporal dynamics of an idealized model configuration we formulate the governing equations and devise a strategy for their numerical solution. We analyze the proposed method and find a numerical instability. This instability is characterized by an error bound which can serve as a guideline for tuning the numerical method to the specific boundary conditions. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

ODE solution to the characteristic form of the Saint-Venant equations

An ordinary differential equation algorithm was formulated to approximate the solution to the characteristic form of the Saint-Venant equations for one-dimensional, gradually varied, unsteady open-channel flow in prismatic irrigation canals. The algorithm was applied by developing a network of characteristics using difference equations for randomly spaced intervals in the x − t (space–time) plane. Consistency, convergence and numerical stability of the equations are demonstrated, and a method to estimate the error of the predictor–corrector scheme is proposed. A mathematical model was developed to test the algorithm using a hypothetical case of unsteady flow, and it was compared to the results from two other mathematical simulation models, providing a high degree of agreement.