SCADA and related technologies

Presented at SCADA and related technologies for irrigation district modernization, II: a USCID water management conference held on June 6-9, 2007 in Denver, Colorado.SCADA systems in irrigation districts have focused on remote monitoring and remote control. In many districts, the remote control is manual, but in others the automation of structures is enabled through the usage of distributed control for the automation of individual structures. This paper presents the concept of an expanded, "umbrella" SCADA system that will perform the standard functions of remote control and remote monitoring, and will also incorporate information flow in the field for operators. The umbrella SCADA system will mesh the equipment-equipment information into an equipment-program-personnel network

Comparison of Field Level and Regional Actual ETc Values Developed from Remote Sensing and Dual Crop Coefficient Procedure

Crop evapotranspiration (ETc) estimates are important for regional water planning as well as irrigation scheduling. Traditional ETc computations utilize published crop coefficients (basal) that are adjusted on a daily basis depending on soil water availability (i.e., dual crop coefficient method). Recent advancements include using remote sensing data such as LandSAT combined with a surface energy balance algorithm (METRIC), allowing crop evapotranspiration to be computed for each pixel throughout images taken during the season. There are limitations and advantages for both methods. Comparisons of soil water balance evapotranspiration values to METRIC values for two scenarios in different regions of California have been made. The comparisons show that when averaged either spatially or temporally, values estimated from the methods show a good relationship. However, there can be significant variability between the two methods when looking at instantaneous values (for a specific day that the LandSAT image was taken). The cause for this can be attributed to the inputs into the dual crop coefficient model. Both methods have advantages and disadvantages. If the user has good input information, both methods can provide accurate evapotranspiration estimates. Work is currently underway to leverage advantages from both methods by coupling them together

Spatial Variability in Evapotranspiration Related to Irrigation System Distribution Uniformity

Understanding the causes of variable ET in a field is critical for maximizing yield on a per-acre basis as well as for proper irrigation scheduling and regional water management. Since 2004, the ITRC has provided technical irrigation support and management for over 2,000 acres of center pivot irrigated forage crops being supplied by reclaimed water near Palmdale, California. Irrigation scheduling is conducted using a daily soil water balance dual crop coefficient approach. Detailed records on planting and harvest dates, daily water applications, pivot run speeds, and annual distribution uniformity evaluations are maintained along with daily reference evapotranspiration data from a station on site. Since accurate records on pivot distribution uniformity are available, and most of the pivots were under moderate deficit irrigation in one of the years analyzed, a portion of the spatial variability in ETc can be attributed (quantifiably) to this non-uniformity in irrigation distribution. During 2010, the same fields were fully irrigated (no water stress) during the evaluation period because a reservoir was constructed on site. The variability in ETc during the non-water stressed conditions can be attributed to causes other than irrigation DU. Comparing the uniformity of evapotranspiration from the same fields, with the same crops, under both water stressed conditions, the uniformity of evapotranspiration due to irrigation system DU (ET_UDU) was quantified. The results indicate that under moderate water stressed conditions, the ET_UDU contributes approximately 55% to the overall non-uniformity of evapotranspiration in a field

Center Pivot Sprinkler Distribution Uniformity Impacts on the Spatial Variability of Evapotranspiration

Understanding variable evapotranspiration (ET) throughout a field can help maximize yield on a per-acre basis, as well as assist with proper irrigation scheduling. The results from this study indicate that irrigation system distribution uniformity (DU) has a significant effect on the uniformity of ET during water-stressed periods. The study site involved intensely managed forage (alfalfa and winter grain hay) irrigated by center pivots being supplied with reclaimed water near Palmdale, California. During spring and early summer 2007 the center pivots were operating under deficit irrigation. In 2010, after the installation of reservoirs, water was applied to meet full evapotranspiration (ETc) demands. Using remote sensing of actual evapotranspiration, the variability in ETcfor the same pivots with the same crop was quantified. During the non-water-stressed period, ET uniformity was significantly better than during the water-stressed period (2007). The difference in uniformity was found to be attributable to irrigation system distribution uniformity. For the 540 ha used in this study, irrigation system DU was found to explain 55% of the ET nonuniformity during deficit irrigation. A method to predict the nonuniformity in ET as a result of irrigation system DU and water-stress level is presented

Benchmarking of Flexibility and Needs - 2004

ITRC interviewed irrigation district personnel from 25 agricultural districts in eastern Washington, northern Idaho and western Montana. Data were analyzed to determine the degree of water delivery flexibility provided to farmers and the extent of existing and planned district modernization. This is the fourth such report the Irrigation Training and Research Center (ITRC) has published for irrigation districts in the western US. The first two evaluations were conducted on behalf of the Mid-Pacific Region of the US Bureau of Reclamation (USBR) and included California irrigation districts that had long-term federal contracts. The third report was prepared on behalf of the California Department of Water Resources (DWR) and did not include irrigation districts with long-term federal contracts. The first three evaluations were conducted in 1996, 2000 and 2002, respectively. All three reports can be downloaded from the ITRC’s Reports web page (http://www.itrc.org/reports/reportsindex.html). This report was prepared on behalf of the USBR Yakima Office of Water Conservation, Upper Columbia Area of the Pacific Northwest Region and includes districts that receive at least some water from federal facilities. The interview process identified a strong perceived need by the districts for more direct technical assistance and training. This perceived need is greater than what ITRC has seen in California irrigation districts. These needs varied by district and region. In addition to general support, some districts acknowledged interest in small, specialized training efforts customized for single or small groups of districts at local facilities. Interest is especially high for information about automation and Supervisory Control and Data Acquisition (SCADA) systems. The data also indicated that more Rapid Appraisal Process (RAP) visits are needed to determine possible physical and operational improvements (modernization and efficiency) for districts to accommodate the ever-changing needs of their consumers and the environment. Direct technical assistance to individual districts has been and will continue to be a key element of continuing success in modernization. Other key items include: Many of the districts, and their farmers, are heavily dependent upon electric power to convey and distribute irrigation water. Presently, the power rates are lower than in other areas of the West. Irrigation district personnel, on the average, consider on-farm water usage/conservation to be beyond their scope of responsibility. This indicates that the “Bridging the Headgate” initiative by USBR and others may need more effort. Although 24 of the 25 districts provide water on at least an “arranged” basis, there is still room for improvement of the water delivery flexibility provided to farmers. The overall Flexibility Index was 11.5 (max. possible = 15; min. possible = 3). This compares with an overall Flexibility Index of 10.9 for sixteen non-Federal irrigation districts ranked by ITRC in 2002, and an Index of 12.9 for 58 Federal irrigation districts ranked by ITRC in 2000. Since 1995 the irrigation districts have made numerous improvements, including both software and hardware. This report summarizes the results and provides brief comments on various aspects of those results

Planetary Rings

Planetary rings are the only nearby astrophysical disks, and the only disks that have been investigated by spacecraft. Although there are significant differences between rings and other disks, chiefly the large planet/ring mass ratio that greatly enhances the flatness of rings (aspect ratios as small as 1e-7), understanding of disks in general can be enhanced by understanding the dynamical processes observed at close-range and in real-time in planetary rings. We review the known ring systems of the four giant planets, as well as the prospects for ring systems yet to be discovered. We then review planetary rings by type. The main rings of Saturn comprise our system's only dense broad disk and host many phenomena of general application to disks including spiral waves, gap formation, self-gravity wakes, viscous overstability and normal modes, impact clouds, and orbital evolution of embedded moons. Dense narrow rings are the primary natural laboratory for understanding shepherding and self-stability. Narrow dusty rings, likely generated by embedded source bodies, are surprisingly found to sport azimuthally-confined arcs. Finally, every known ring system includes a substantial component of diffuse dusty rings. Planetary rings have shown themselves to be useful as detectors of planetary processes around them, including the planetary magnetic field and interplanetary impactors as well as the gravity of nearby perturbing moons. Experimental rings science has made great progress in recent decades, especially numerical simulations of self-gravity wakes and other processes but also laboratory investigations of coefficient of restitution and spectroscopic ground truth. The age of self-sustained ring systems is a matter of debate; formation scenarios are most plausible in the context of the early solar system, while signs of youthfulness indicate at least that rings have never been static phenomena.Comment: 82 pages, 34 figures. Final revision of general review to be published in "Planets, Stars and Stellar Systems", P. Kalas and L. French (eds.), Springer (http://refworks.springer.com/sss

Accuracy of Global Microirrigation Distribution Uniformity Estimates

Emitter pressures and flow rates were systematically and extensively sampled in one drip and one microspray field. The data distributions are presented. The accuracy of rapid (limited samples) evaluation pressure sampling procedures was found to be quite good if the pressure distribution was systematic, but erroneous if the pressure distribution throughout a field was random. A simple mathematical combination of two nonuniformity components (due to pressure differences, and other causes of flow variation) provided a better estimate of overall system distribution uniformity than more complex mathematics

Electric Motor Efficiency under Variable Frequencies and Loads

This paper details a study performed by the Irrigation Training and Research Center to determine motor performances under varying speeds [induced by a variable frequency drives (VFD) controller] and loads. A further goal of the study was to provide sufficient information to designers so that they could estimate total pumping plant power usage with a VFD-controlled installation. Motors were tested with a VFD as well as across-the-line. On average, the relative efficiency of the electrical system with a VFD may be approximately 8% lower than the relative efficiency of a properly designed, full-load across-the-line system. If one considers actual field operating conditions this 8% is misleading because overall energy savings can be obtained with VFDs due to their ability to properly adjust speeds to meet actual field conditions