USCID/EWRI conference

Presented at the 2002 USCID/EWRI conference, Energy, climate, environment and water - issues and opportunities for irrigation and drainage on July 9-12 in San Luis Obispo, California.Includes bibliographical references.Calibration equations for free-flowing radial gates typically provide sufficient accuracy for irrigation district operations. However, many districts have difficulty in determining accurate discharges when the downstream water level begins to submerge the gate. Based on laboratory studies, we have developed a new calibration method for free-flowing and submerged radial gates that allows for multiple gates and widely varying upstream and downstream channel conditions. The method uses the energy equation on the upstream side of the structure and the momentum equation on the downstream side. An iterative solution is required to solve these two equations, but this allows calibration from free flow to submerged flow right through the transition. Adjustments to the energy equation for free flow are described, along with an additional energy adjustment for the transition to submerged flow. An application is used to describe the new procedure and how it overcomes the limitations of current energy-based methods

Canal pool resonance

Presented at Meeting irrigation demands in a water-challenged environment: SCADA and technology: tools to improve production: a USCID water management conference held on September 28 - October 1, 2010 in Fort Collins, Colorado.Includes bibliographical references.The Integrator-Delay (ID) model (Schuurmans et al 1999) is a simple model of canal response that is used for design of various canal controllers. It describes the change in water depth at the downstream end of a canal pool as a function of flow changes at the upstream and downstream gates. Canal pools are characterized by a Delay time and a backwater surface area (Integrator). This model works very well for canal pools where water is flowing under normal depth conditions for a portion of the length, or where there are drops. For canal pools where the upstream flow depth is influenced by the downstream flow depth (that is, where canal pool is under backwater) the ID model often does not properly represent the water-level response. Changes in gate flows often cause a step change in water level. Schuurmans (1997) and Miltenburg (2008) propose the use of filters to account for this step change (ID-F), where the filter effectively causes a delay in response. Litrico and Fromion (2004) proposed the IDZ model, where a gate flow change causes a step change in downstream water level, after which the water level response follows the integrator of the ID model. The IDZ model does not fully account for resonance. An IDZ model with Filtering (IDZ-F) is proposed to account for additional resonance. In this paper, we compare the resulting water level response when the ID-F and IDZ-F models are used to design canal controllers for canal pools under backwater. It is shown that controllers designed with the IDZ-F model provide slightly better control than when designed with the ID-F model, although differences are not significant

USCID water management conference

Presented at Upgrading technology and infrastructure in a finance-challenged economy: a USCID water management conference held on March 23-26, 2010 in Sacramento, California.Includes bibliographical references.The Central Arizona Irrigation and Drainage District (CAIDD) began delivering water to users in 1989. Although designed for automatic control, the system was run manually until a homemade SCADA (Supervisory Control and Data Acquisition) system was developed by district employees. In 2002, problems with radio communication and limitations of the homemade SCADA system prompted CAIDD to begin the process of modernization. New spread-spectrum radios and RTUs (Remote Terminal Units) were purchased along with a commercial SCADA package (iFix by GE-IP). In 2005, CAIDD decided to pursue implementation of full automated control of a majority of district check gates. Currently, 125 gates are under remote manual supervisory control and 129 water levels are remotely monitored. CAIDD chose to implement SacMan (Software for Automated Canal Management) under development by the U.S. Arid Land Agricultural Research Center, Maricopa, AZ. The decision was made to only apply full automation at gates that had gate position sensors. Thus purchase and installation of gate position sensors have slowed implementation. To date, five lateral canals have been set up for full automatic control, where SacMan routes flow changes through the canal and uses downstream water level feedback control to correct for any errors that occur. The ditchrider only makes changes at the farm turnouts and district-operated wells. Automation of the Central Main canal has been tested in simulation. Control of this canal requires special treatment, as described in a companion paper. The district is waiting until enough of the canal is ready for automation before it turns automatic controls on 24/7, since this will require some operator training and remote oversight when problems occur. We hope this occurs in the summer of 2010

USCID water management conference

Presented at Upgrading technology and infrastructure in a finance-challenged economy: a USCID water management conference held on March 23-26, 2010 in Sacramento, California.Includes bibliographical references.The operation of main irrigation canals is complicated in situations where the operator does not have full control over the canal inflow, or where there are very long transmission distances from the point of supply, or both. Experienced operators are able to control the canal, but often supply errors are simply passed to downstream, thus creating problems further down the system. In previous work, the senior author showed that it is important to contain such errors and not let them pass downstream. With automatic upstream level control, all flow errors are passed to the downstream end of the canal. Distant downstream water level control requires full control of canal inflow. Without this, most errors will occur toward the upstream end of the canal. An alternative scheme is offered here where the canal check gates are controlled based on the relative water level error between adjacent pools. The scheme uses a simple linear model for canal pool response. The scheme is implemented as a multiple-input, multiple-output scheme and solved as a Linear Quadratic Regulator (LQR). Thus all gates respond to relative deviations from water-level set point. The scheme works to keep the relative deviations in all pools the same. If the canal has more inflow than outflow, the scheme will adjust gates so the water levels in all pools will rise together with the same deviation from set point. It thus distributes the error over the entire canal. When in equilibrium, operators will be able to judge the actual flow rate mismatch by the rate of change of these levels. The scheme acts like a combination of upstream level and distant downstream level control. It was tested on a simulation model of the Central Main Canal at the Central Arizona Irrigation and Drainage District, Eloy, AZ

Downstream water-level feedback control

Presented at the 2002 USCID/EWRI conference, Energy, climate, environment and water - issues and opportunities for irrigation and drainage on July 9-12 in San Luis Obispo, California.Includes bibliographical references.Over the last 40 years researchers have made various efforts to develop automatic feedback controllers for irrigation canals. However, most of this work has concentrated on feedback controllers for single, in-line canals with no branches. In practice it would be desirable to automate an entire canal network and not just one of the branches. Because the branches in a network are hydraulically coupled with each other, a branching canal network cannot be controlled by designing separate controllers for each branch and then letting them run simultaneously. Changing the gate position in one pool on one branch can affect the water levels in pools on other branches. Because of this effect, the controllers designed for each of the in-line branches of the network will interfere with each other and potentially create instabilities in the branching canal network. Thus, the controller must be designed for the network as a whole and the branching flow dynamics must be explicitly taken into account during the controller design process. This paper presents preliminary simulation results on three different downstream feedback controllers on a branching canal network. The first controller is a series of Proportional-Integral (PI) controllers, one per pool. The second is a fully centralized PI controller. The third controller uses Model Predictive Control (MPC) to determine the appropriate control actions

SACMAN automated canal control system

Presented during the Third international conference on irrigation and drainage held March 30 - April 2, 2005 in San Diego, California. The theme of the conference was "Water district management and governance."Includes bibliographical references.Many irrigation districts currently operate their main canals, pumping plants, etc. remotely with Supervisory Control and Data Acquisition (SCADA) software. This is usually manual operation with perhaps a few local automatic control features. SacMan (software for automated canal management) is a software package that adds canal automation logic to commercially-available, windows-based SCADA packages. It allows the user to implement a variety of automatic control features, including complete automatic control, where feasible. It was developed through research at the U.S. Water Conservation Laboratory in Phoenix, AZ. SacMan has several levels of implementation ranging from manual control to full automatic control, including upstream level control, flow rate control, routing of known demand changes, and full (distant) downstream level control. SacMan interfaces with commercial Supervisory Control and Data Acquisition (SCADA) software, currently iFix by GE Fanuc (formerly Intellution, Inc.), but potentially applicable to other SCADA packages. SacMan was field tested on the WM lateral canal at the Maricopa Stanfield Irrigation and Drainage District (MSIDD) in central Arizona. In July/August 2004, SacMan successfully operated the WM canal for a period of 30 days, nearly continuously. This paper describes the features of this canal automation software and some results from this long-term testing.Sponsored by USCID; co-sponsored by Association of California Water Agencies and International Network for Participatory Irrigation Management

Infiltration parameters

Presented at the 2002 USCID/EWRI conference, Energy, climate, environment and water - issues and opportunities for irrigation and drainage on July 9-12 in San Luis Obispo, California.Includes bibliographical references.Infiltration characteristics are a major source of uncertainty in the design and management of surface irrigation systems. Understanding the sensitivity of the design to errors or variation in the design inputs is needed to develop management recommendations that account for this uncertainty. This paper further analyzes the sensitivity of the level basin design procedure proposed by Clemmens (1998). Results show that the recommended management approach, cutting off inflow when the water advances a fixed distance relative to the field length, works best when actual advance time is more than predicted. If actual advance time is the same or less than predicted, then cutoff based on time may be a better approach, independent from variations due to differences in infiltration, roughness, inflow, or all of these factors combined

Discharge Coefficients for Rectangular Suppressed and Submerged Sluice Gates

Two sizes of sluice gates were tested in submerged conditions with a variety of flow rates and gate openings. A new equation was developed for flow rate prediction

Flow Rate Equation for Suppressed and Submerged Sluice Gates

In irrigation projects, the control and measurement of flow rates at key bifurcation points is essential. Sluice gates at the heads of irrigation canals are used by operators to control the flow into these canals. In US irrigation districts, canal operators often estimate flow rate at the heads of canals by “experience” unless they have a flume downstream. For example, they may open a gate a certain number of turns for a change in flow rate, regardless of upstream and downstream conditions. Theoretical estimates of discharge are often inaccurate in field situations. Problems include varying and uncertain discharge coefficients, entrance and exit conditions, floor steps, gate orientation, sensor locations, free and submerged conditions, etc. Automatic control of flow rate with electronic devices (for example, programmable logic controllers) has been challenging at canal headgates because of uncertainties of what formulas and coefficients to use. Other devices are often not practical at these locations (flumes may require too much head loss, ultrasonic meters need long averaging periods, etc.). This paper develops calibration equations for one particular sluice gate configuration so that it can be used for automation of canal headgates. It modifies empirical methods used by others. With this method, the standard deviation of discharge predication is within 4.5 percent

Volume compensation

Presented at the 2002 USCID/EWRI conference, Energy, climate, environment and water - issues and opportunities for irrigation and drainage on July 9-12 in San Luis Obispo, California.Includes bibliographical references.Using the gate-stroking method, this paper shows that a complex open-channel flow feedforward control problem can be treated as a series of linearly additive single flow-change control problems. A key element of this approach is determining the initial conditions for each single flow-change problem. An inadequate choice of initial conditions will result in under or overestimation of the canal storage volume change needed for the new steady-state conditions. These findings provide support to a simple feedforward control scheme based on volume compensation and time delay. An example is used to demonstrate that the simple scheduling approach is nearly as effective in controlling water levels as the complex gate-stroking approach