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Four rectangular sluice gates were calibrated for submerged-flow conditions using nearly 16,000 field-measured data points on Canal B of the B-XII irrigation scheme in Lebrija, Spain. Water depth and gate opening values were measured using acoustic sensors at each of the gate structures, and the data were recorded on electronic data loggers. Several gate calibration equations were tested and it was found that the rectangular sluice gates can be used for accurate flow measurement. The Energy-Momentum (E-M) equations proved to be sound. The calibration of the contraction coefficient, to be used in the energy equation, allowed good estimations of the discharge for three of the four gates studied. The gate for which the E-M method did not perform satisfactorily was located at the head of the canal with a unique nonsymmetric approach flow condition. Alternatively, we investigated the performance of the conventional discharge equation. The variation of the discharge coefficient, Ca, with the head differential, [DELTA]h, and the vertical gate opening, w, suggests that [C.sub.d] be expressed as a function of these two variables. For the sluice gates considered in this study, the best empirical fit was obtained by expressing [C.sub.d] as a parabolic function of w, although an exponential expression tested previously by other writers also produced satisfactory results. The greatest uncertainty in the variables considered in this study was in the calculated coefficient of discharge, and based on the uncertainty analysis, it is possible to quantify the uncertainty in the estimated discharge through a calibrated sluice gate. The discharge uncertainty in each of the four gates in this study decreases with increasing gate opening, and it decreases slightly with increasing head differentials. DOI: 10.1061/(ASCE)IR.1943-4774.0000085 CE Database subject headings: Canals; Gates; Calibration; Open channel flow.

The hydraulic transition between nonorifice and orifice flow regimes at a rectangular sluice gate was analyzed to determine the value of a coefficient ([C.sub.o]) used to define the threshold between the two regimes. The transition coefficient was defined as the ratio of vertical gate opening to upstream water depth. Several dozen data sets were collected in a hydraulic laboratory, each including the measurement of upstream and downstream water depth for five different vertical gate openings, and 17 different steady- state discharges from 0.02 to 0.166 [m.sup.3]/s. Various approaches were tested to define the limits of the nonorifice-to-orifice regime transition, but the one presented herein uses the specific-energy equation for open-channel flow. After the transition limits were defined, an estimation of the nonorifice-to-orifice transition coefficient, [C.sub.o], was made. The experimental results indicate that orifice flow always exists when CO is less than 0.83, and nonorifice flow always exists when Co is greater than 1.00. A procedure was developed to determine the flow regime and the discharge at a rectangular gate in the range 0.83 < [C.sub.o] < 1.00. DOI: 10.1061/(ASCE)IR.1943-4774.0000071 CE Database subject headings: Gates; Water discharge; Calibration; Open channel flow.

A series of detailed laboratory measurements were made under steady-state flow conditions through a 0.914-m (3-ft) Cutthroat flume in an attempt to more accurately define transition submergence for four standard throat widths. It was found that the change from free to submerged flow, and vice versa, is gradual and that there is no easily observable transition point. The gradual transition between the flow regimes suggested a new calibration approach in which a single equation could more elegantly and more accurately fit the laboratory measurements, eschewing the need for separate tree- and submerged-flow equations, and obviating the need to define transition submergence. Such an equation was found, providing greater calibration accuracy up to 95% submergence in 0.914-In Cutthroat flumes. DOI: 10.1061/(ASCE)0733-9437(2008)134:4(521) CE Database subject headings: Flumes; Calibration; Measurement; Submerged flow; Steady flow.

A volume balance approach to determine the parameters of the Kostiakov or modified Kostiakov infiltration equations in border and furrow irrigation is presented. The approach requires measured data from the advance phase, the postadvance (wetting) phase, or both, resulting in three different procedures to characterize infiltration. Using the entire field length the procedures provide infiltration parameters that are more representative of an actual irrigation. The volume balance computation performed by the end of the wetting phase makes it possible to determine the accuracy of each equation that can represent the infiltration process for a particular application. Inflow discharge, water front advance, average flow cross-sectional area, and outflow discharge are the required field data. Several mathematical approximations are suggested in order to simplify the field work and the amount of computation. The use of empirical factors to improve data fitting is discussed. By providing irrigation system performance information during an irrigation, this procedure can be easily adapted to guide decisions during real-time operation.

USM is a hydraulic-simulation computer program developed by the U.S. Bureau of Reclamation to analyze unsteady-flow conditions in canals. The program USM uses the method of characteristics to solve the complete Saint Venant equations for unsteady flow in open channels. This solution method yields accurate numerical results but sometimes requires more computer execution time than other methods. USM analyzes canal systems with a variety of structural boundary conditions, including check gates, weirs, siphons, and pumps. Check gates can have either manual or automatic gate control. Branching canals, supercritical flow, and channel dewatering cannot be analyzed. This paper describes the model and compares its strengths and weaknesses with those of other models. Several test data sets compiled by the ASCE Task Committee on Irrigation Canal System Hydraulic Modeling were used in the evaluation. USM simulation results are compared to field data collected from the Central Arizona Project canal system.

This is one of several introductory papers resulting from work by the ASCE Task Committee on Irrigation Canal System Hydraulic Modeling. It is intended to serve as background for analyses by the Task Committee of several available programs. Irrigation-canal modeling is based on the same unsteady-flow equations used for river modeling. However, the canal and irrigation environment present several unique simulation problems generally not encountered in river modeling. These include zero-depth conditions, mixed-regime and reversing flow, gate submergence, flow in inverted siphons and culverts, multiple flow paths, and control-system interfaces. This paper outlines some of these special problems, discusses their importance, and reviews some solution approaches in general terms.

Laboratory experiments are performed to study the conditions under which concrete scaling occurs. Induced temperature gradients causes the concrete surface to spall off in sheets, replicating an ubiquitous form of damage to the transportation infrastructure in much of the United States. A mathematical model is developed to simulate temperature gradients in concrete during freeze-thaw cycles, and the calculated results are in excellent agreement with the laboratory data. By using a finite-difference model, the rate and depth of temperature changes during surface scaling are predicted.