Charles M. Burt

Leaching of Accumulated Soil Salinity Under Drip Irrigation

ITRC conducted a reclamation leaching experiment in a drip-irrigated pistachio orchard south of Huron, California, during the winter of 2002-2003. The study was conducted to quantify the leaching water required to remove salts from the effective root zone of trees. This experiment tested a new reclamation leaching technique: multiple lines of low-flow drip tape were used to apply water to the area of salinity accumulation along a tree row. This new technique allows water to be applied where there is salt accumulation along the tree row, as opposed to putting water on the entire area of the field. Since reclamation leaching requires a relatively large depth of water, this technique offers the potential for significant water savings for reclamation leaching.

Characterization of Pumps for Irrigation in Central California: Potential Energy Savings

AbstractMany pumps are used for irrigation in central California, but a great number of them are operating inefficiently. In this paper, the information recovered from over 15,000 electric irrigation pump tests in central California is analyzed. The objectives of this study are to define the common characteristics attributed to pumps with best and worst performance and to identify the possible target groups that might benefit from improvements, obtaining potential energy savings. The results showed that pumps with lower reported total dynamic head (TDH) and flow rate (Q) usually have poorer overall pumping plant efficiency (OPPE) values, but high flow rates and input power are typically associated with better OPPE values. According to this analysis, energy savings of more than 100,000  MWh/year could be achieved for well pumps, with a per-pump average of 50  MWh/year. For non-well pumps, the total potential savings are 16,500  MWh/year, and the average per pump is 34  MWh/year.

Hierarchical Operation of Water Level Controllers: Formal Analysis and Application on a Large Scale Irrigation Canal

We introduce a hierachical controller, the purpose of which is to speed up the water delivery process as compared to the standard method applied currently in the field. The lower layer of the hierarchical control consists of local proportional integral filter controllers (PIF controllers) for upstream control at each gate; specifically they are proportional integral controllers with a low-pass filter. In contrast, the higher layer is composed of a centralized model-based predictive controller, which acts by controlling the head gate and by coordinating the local PIF controllers by modifying their setpoints when needed. The centralized controller is event-driven and is invoked only when there is a need for it (a water delivery request) and as such it contributes scarcely to the communication burden. The scheme is robust to temporary communication losses as the local PIF controllers are fully able to control the canal in their normal independent automatic upstream control mode until the communication links are restored. We discuss the application of the hierarchical controller to a precise numerical model of the Central California Irrigation District Main Canal. This shows the improved performance of the new hierarchical controller over the standard control method.

Subcritical Contraction for Improved Open-Channel Flow Measurement Accuracy with an Upward-Looking ADVM

Acoustic Doppler velocity meters (ADVMs) provide an alternative to more traditional flow measurement devices and procedures such as flumes, weirs, and stage rating for irrigation and drainage canals. However, the requirements for correct calibration are extensive and complex. A three-dimensional computational fluid dynamics (CFD) model was used to design a subcritical rapidly varied flow contraction that provides a consistent linear relationship between the upward-looking ADVM sample velocity and the cross-sectional average velocity in order to improve ADVM accuracy without the need for in situ calibration. CFD simulations validated the subcritical contraction in a rectangular and trapezoidal cross section by showing errors within +1.8 and −2.2%. Physical testing of the subcritical contraction coupled with an upward-looking ADVM in a large rectangular flume provided laboratory validation with measurement errors within ±4% without calibration.

Responses to Gleick et al. (2011), which was itself a response to Frederiksen and Allen (2011)

The response by Peter Gleick and his colleagues at the Pacific Institute to Frederiksen and Allen (2011), published in Water International, is very helpful for understanding their application of hydrological principles and references in their analyses of water uses. It had been hoped that a more productive exchange within the journal would have resulted. A summary of the principles and their application in our article will be set out here to allow water resources managers, legislators, and others active in the water resources field to compare the two approaches when choosing the methodology to apply in assessing water uses. Greater detail can be obtained from our paper. Our objective was to introduce a common basis for the analysis and comparison of all “offstream” uses of water resources. This was followed by an example of flawed analysis. Other misleading methods of evaluating water resources were cited in our article, but not addressed in detail. Categories of water use – offstream and instream. The U.S. Geological Survey (USGS) categorizes “offstream” water uses in the USA as water diversions from a fresh-water body, all of which consume water to a varying extent (USGS 1988). Examples include municipal, domestic, manufacturing, agricultural, mining, and cooling uses. The USGS describes “offstream” uses in terms of the source and quantity of diversion (groundwater or surface water) and its disposition (water consumed or returned and available as supply to other users; the unconsumed unusable quantity is negligible relative to the total volume of fresh water diverted in the US). Figure 21 (p. 55) in the USGS circular presents an application reporting total US water use. Of the total quantity diverted in the US, 28% was consumed and 72% was return flows. The quantity of return flow reflects the repeated reuse of water in the course of most offstream uses. “Instream” uses include fisheries, shipping, recreation and hydroelectric; all are nonconsumptive uses. However, any water discharged directly to the ocean that otherwise could have been used by “offstream” uses would be classified as consumptive use within the context of a state or country’s total resources. Such situations arise when the ocean discharge is authorized by legislation or court orders as having superior water rights, whether for reasons of instream water quality or quantity. Some references and background work reflected in Frederiksen and Allen (2011). An early application of the USGS (1988) hydrological definitions and principles to the evaluation of water uses was made in World Bank Technical Paper 185 (Frederiksen 1992), which was later referenced in Willardson et al. (1994). The document presented a universal relationship in terms of efficiencies for evaluating all offstream water uses. At that

Canal Seepage Reduction by Soil Compaction

Simple in situ vibratory soil compaction of earth lined canals was tested to determine the impact on seepage losses. Commercial equipment was used for vibratory compaction of long sections of five irrigation district earthen canals. Ponding tests were conducted before and after compaction. When the sides and bottoms of the canals were compacted, seepage reductions of about 90% were obtained; reductions of 16–31% were obtained when only sides were compacted.

Hierarchical MPC-Based Control of an Irrigation Canal

We discuss the problem of controlling an irrigation canal to accommodate fast changes in the canal state in response to events such as offtakes announced with no time lag or sudden weather changes. Our proposed approach comprises a hierarchical controller consisting of two layers with decentralized PI controllers in the lower layer and a centralized MPC-based event-driven controller in the higher layer. By incorporating the hierarchical controller structure we achieve a better performance than with the PI controllers only as currently in use in the real world, while barely increasing the communication requirements and remaining robust to temporary communication link breakdowns as the lower layer can work independently of the higher layer when the links are being restored. The operation of the higher-layer controller relies on controlling the head gate and modifying the settings of the local controllers. This way, an acceleration of water transporting is attained as the controller allows for rapid reactions to the need for more water or less water at a location. Specifically, when there is a sudden need for water, the storage in some of the pools is used to temporarily borrow water. Alternatively, when there is too much water at a location, it can be stored for some time in upstream or downstream pools before the PI controllers manage to remove the water.

Case Study: West Stanislaus Irrigation District Modernization

West Stanislaus Irrigation District (WSID) provides agricultural irrigation water to about 22,000 acres in the San Joaquin Valley. The majority of WSID’s water is diverted directly from the San Joaquin River, with supplemental water obtained from the Delta-Mendota Canal (DMC), groundwater wells, and a variety of other sources. WSID operates a series of pumping plants that lift water from the San Joaquin River sequentially into six short canal reaches. Each main canal pool supplies one or two laterals along the valley contour. Water from the DMC enters the district via a gravity pipeline at the tail end of the main canal. Water supply curtailments, regulatory changes, and significant increases in drip/micro irrigated acreage have steered the district and its board members towards modernization of its original 1920’s-era infrastructure. To that end, the Cal Poly Irrigation Training and Research Center (ITRC) has worked in cooperation with WSID since the early 2000’s on a phased modernization planning and implementation process. Following a Main Canal Modernization Study, significant improvements have been executed along the main canal including the automation of all original pumping plants and lateral headings as well as the construction of two new, automated pumping plants. An industrial-grade Supervisory Control and Data Acquisition (SCADA) system has also been commissioned. Further project planning is underway at the San Joaquin River diversion and throughout the lateral canal system. This paper describes the modernization process and results. Lessons learned throughout the various projects are also discussed.

Improving Flow Measurement Accuracy Using a Portable Irrigation Turnout Calibration Unit

Relatively accurate flow measurement at irrigation district water delivery points is an important component of volumetric billing and equitable service. In California, this has often occurred with conversions to pressurized irrigation systems which commonly include the installation of pipeline flow meters as part of the on-farm system. However, a large portion of irrigation turnouts in the western US continue to operate via gravity and fall into one of the following categories: (a) a metergate, or similar structure was installed without adherence to standard construction requirements or (b) the structure was never intended for flow measurement. For these and other scenarios, there is a need to efficiently calibrate turnouts in the field. While some in-situ calibration methods exist for open channel turnouts, they are rarely applied in the field for a variety of practical reasons. After identifying this gap in field-practice, a special pump, or portable irrigation turnout Calibration Unit (Calibration Unit) was designed and constructed at the Cal Poly Irrigation Training and Research Center (ITRC). Within six weeks, thirty-two field turnout calibrations were performed using the Calibration Unit throughout seven California irrigation districts. Field testing protocol followed new guidelines developed by the USBR Mid Pacific Region and the California Department of Water Resources (DWR). The results and analyses of these calibrations are presented in this paper. Practical applications, such as compliance with California regulations developed out of The Water Conservation Act of 2009 (SB X7-7) and constraints of this new calibration method are also discussed.