Stuart W. Styles

Strawberries: Effects of Modifying Irrigation Methods for Transplant Establishment

In 2009, the Cal Poly Irrigation Training and Research Center began a multi-year analysis of the current irrigation practices of strawberry growers on the Central Coast of California. Specifically, the project examines the impacts of salinity on young strawberry transplants and the current practice of sprinkler use during the establishment of transplants for salinity control in areas where drip irrigation is available. The overall goal of the project is to study current practices and determine any conditions where growers can minimize or eliminate sprinkler use on strawberries, thereby conserving water, saving pumping costs, and reducing runoff. Results from the first year of the study have suggested that, contrary to previous belief, using reduced sprinkler or only drip irrigation results in higher yields than conventional methods.

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.

Pressure Recorders: Low-Cost, Robust, Low-Battery-Use Field Measurement Techniques for Trending Water Pressure

Water users across California need robust, low-cost water level/pressure sensors with integrated data loggers for a high level of precision and accuracy. The Cal Poly Irrigation Training and Research Center (ITRC) has installed Telog Instruments devices in California and Nevada over the last 12 years to provide a performance review of the devices. The two devices focused on were the Telog Instruments WLS-31 Level Tracker and LPR-31i Line Pressure Recorder. Over the study period, ITRC has collected several sets of data in varying situations. After 11 years of use on a reservoir, the two Telog WLS-31 units had a 1% difference in readings. After intensive testing, the LPR-31i has proved to be an accurate, pipeline pressure surge recorder for pressures up to 2,100 kPa. This paper discusses the capabilities of the Telog Instruments devices along with ITRC’s research experience and evaluation of the two units. INTRODUCTION For water districts and other entities throughout the United States, it is a necessity to know the status of the operating water system(s). Countless tools and methods of obtaining data from water systems have been developed over the past decades. It is essential to be able to single out the best methods to determine the pressures for the entity as a whole. In these decisions, cost, accuracy, and durability are the main factors. This is why Telog Instruments data loggers have been commonly used to record water levels in the agricultural sector over the past 20 years. This is due to the durability and long battery life of the Telog WLS-31 Level Tracker. The ITRC uses both the Telog WLS-31 and LPR-31i units in research. The WLS-31 is simple, compact, and has a robust system designed to measure water level. Telog’s LPR-31i is installed in a water or gas line to record pressure. These devices’ long battery life and large storage capacity provide for minimal field maintenance without concern of data overload. This paper builds upon ITRC Report No. R 03-007, Telog PR-31 Water Level Tracker. Presented at the June 1-5, 2014, World Environmental and Water Resources Congress in Portland, Oregon. http://www.itrc.org/papers/telog14.htm ITRC Paper No. P 14-007 GENERAL OVERVIEW OF TELOG WLS-31 AND LPR-31 The ITRC has extensive experience with data recording using the Telog Instruments WLS-31 and the LPR-31i devices. Both devices have been instrumental in ITRC research. Among the devices’ positive attributes are long battery life, accuracy and data storage capabilities. WLS-31 Level Tracker. The purpose of the WLS-31 is to measure water level. For water level measurement, the ITRC collaborated with Telog to incorporate the General Electric (GE) Druck UNIK Series 5000 differential pressure transducer. The unit comes with a submersible pressure sensor and pressure sensor cable. The differential pressure transducer factors out the influence of atmospheric pressure, so the unit can be transported to a different location without recalibration. This device measures the pressure exerted on a strain gauge by the water above the gauge. WLS-31 Level Trackers are available to read pressures up to 103 kPa (Telog 2008b). The two WLS-31 units discussed are 17.2-kPa pressure sensors and have a maximum reading of 1.76 meters (George Mayoue, personal communication, November 5, 2012). LPR-31i Line Pressure Recorder. Telog’s LPR-31i is used for measuring pressure in a water line. The LPR-31 Pressure Monitor can be installed in either water or gas lines with a 1⁄4 inch tap fitting as the access point. LPR-31 Pressure Recorders are able to record pressure up to 2068 kPa and burst pressure up to 6895 kPa. Strain Gauge Pressure Sensor. The pressure is monitored with an internal strain gauge pressure sensor. Telog uses an internal strain gauge pressure transducer that is a conductor that stretches or shrinks with changes in pressure. At higher pressures, the conductor is stretched and the resistance in the wire goes up. Conversely, if the pressure decreases, the conductor shrinks and the resistance goes up. Battery Life of WLS-31 and LPR-31i. The WLS-31 and LPR-31 require AA Lithium batteries. A new battery is rated at 3.6 VDC. The battery should be replaced at 3 VDC. Based on a 10-second sample rate, the battery should last about 5-7 years. Battery voltages have been monitored on two WLS-31 data collectors: ITRC0001 and ITRC0002, for ten years. The batteries in ITRC0001 were replaced once in ten years. The batteries in ITRC0002 have lasted ten years and have yet to be replaced. Figure 1 shows level of Drumm Reservoir at the ITRC’s Water Resources Facility over a decade. These recorders are set at a fifteen minute sample rate. The battery voltage on the LPR-31i has only been monitored by the ITRC for one year. This recorder’s batteries are estimated to last 5-7 years. Presented at the June 1-5, 2014, World Environmental and Water Resources Congress in Portland, Oregon. http://www.itrc.org/papers/telog14.htm ITRC Paper No. P 14-007 Figure 1. Recording of Drumm Reservoir Level over a decade APPLICATIONS OF TELOG Overview of Telog Units. The Water Level Tracker is used mainly for water level monitoring. Depths of water are needed for reservoir levels, stream levels, well and groundwater monitoring, and canal levels (Telog 2008b). One of ITRC’s applications of the WLS-31 is the monitoring of the Drumm Reservoir. The LPR-31i, in which the “i” stands for “impulse”, can be configured to record 20 readings per second. Impulse recordings are very useful for observing pressure surges and water hammer in lines. On top of routine pressure readings, the LPR-31i has the ability to capture water hammer events or negative pressures, and investigate pressure complaints (Telog 2008a). The ITRC has impulses that cause water hammer with the LPR-31i. Reservoir monitoring at Drumm Reservoir with the WLS-31. Drumm Reservoir has been monitored by the ITRC since November 2002. Two WLS-31 Telogs were installed at set heights on the reservoir. Figure 2 shows the tracking of the reservoir in Excel over 2012. Presented at the June 1-5, 2014, World Environmental and Water Resources Congress in Portland, Oregon. http://www.itrc.org/papers/telog14.htm ITRC Paper No. P 14-007 Figure 2. Reservoir level recording with the WLS-31 On the graph, two Telog units (ITRC0001 and ITRC 0002) are shown to trend in proximity to each other. This shows the precision of the WLS-31 units. Precise tracking is essential in various applications such as a delivery canal in an irrigation or water district or stream monitoring. Telog WLS-31 Pressure Limit Setting. When using the Telog WLS-31 for water level monitoring, the user must select a pressure measurement limit of either 17.2 or 34.4 kPa. This decision is based on the amount of precision needed. Using the 12 bit resolution of the unit, the ITRC determined that the water depth precision at 17.2 kPa is 0.43 mm and at 34.4 kPa is 0.86 mm. It is recommended that if the sensor is used purely for measuring the water depth, the 0.86 mm precision of the 34.4 kPa setting is adequate for the application. If the sensor is used for calculating the flow rate over the weir, or other flow measurement structure, the normal range of the head over the weir must be considered. If the head over the weir normally ranges from 12.3-30.5 cm, then the 0.43 precision of the 17.2 kPa setting would be essential to assure flow rate accuracy less than 5%. If the head over the weir is normally above 30.5 cm, then either setting can be selected. Water hammer with the LPR-31i. As mentioned before, the LPR-31i has the ability to record 20 impulses per second. Recording of water hammer is essential to determining what is happening in pipelines. Figure 3 shows one of the water hammer events that the ITRC has captured. Presented at the June 1-5, 2014, World Environmental and Water Resources Congress in Portland, Oregon. http://www.itrc.org/papers/telog14.htm ITRC Paper No. P 14-007 Figure 3 Figure 3. Recording of water hammer with the LPR-31i The water hammer recorded in Figure 3 shows that the pressure goes from 1,503 kPa to -96 kPa. A pressure change of 1,600 kPa in 0.45 seconds can be very detrimental to pipelines. For large water districts, the timing, cause and damage of the event can be difficult to determine. The Telog LPR-31i can help solve these problems and further inform the operator of the state of the system. Having a tool that can easily measure events like this is useful to detect water hammer instead of blaming pipe failures on other causes. ATMOSPHERIC PRESSURE IMPACT ON DEVICE Detecting Atmospheric Influence of Measurements. The pressure recorder has a built-in, 0.02 micron Gore-Tex filter (see Figure 4). This filter is instrumental in keeping the atmospheric pressure from having an impact on the pressure reading output. In the ten years that the ITRC has monitored the two recorders, only one filter has worn out. It was evident that the filter needed to be replaced by looking at the output pressure reading compared to the atmospheric pressure. Figure 4. 0.02 micron Gore-Tex filter in the Telog WLS-31 and removed from the device ‐100 50 200 350 500 650 800 95

Implementation of New Irrigation Protocols on Strawberry Transplants on the California Central Coast

For the past five growing seasons, the Cal Poly Irrigation Training and Research Center (ITRC) has conducted research on water use, salinity levels and various other factors related to strawberry transplant establishment. This report summarizes research that can be found online: www.itrc.org/projects.htm. The project’s goal was to develop an analysis of irrigation practices of the strawberry growers on the central coast of California, primarily during the establishment of transplants. From the analysis, sprinkler use reduction methods were developed. These methods conserve water, save pumping costs, and reduce the runoff that can potentially contaminate local waterways. California growers contributed control and research plots to thoroughly represent the production areas and this project was a great success due to their input. This project had a major impact on the strawberry industry and modified the methodology for irrigating a high value crop. This new methodology has been adopted by the innovative growers in California. After the developed irrigation methodology was in practice, growers reported up to a 15-percent yield increase, a 10-percent decrease in water usage and a peak production of strawberries earlier in the season. The key determinant in the transition to new irrigation management is the impact of salinity, which must be effectively managed.

Implementation of Magnetic Meters for Irrigation Volumetric Measurement

The irrigation industry is experiencing a growth in the use of magnetic meters for measuring the flow rate and volume in irrigation pipelines. Historically, propeller meters have been the device selected by users. New legislation in California (SB7x7) will require measurement devices at key locations for irrigation water delivery. Some users are very interested in the magnetic meter for making the measurement at the turnout or farm gate. The key feature of the new meter is the ability for the device to work in less than ideal flow conditions. Electromagnetic meters have been tested by the Irrigation Training and Research Center in lab and field pipelines located less than the 10 diameters upstream of disturbances with good results. There are several manufacturers that are selling units to the irrigation market as well as several types of magnetic meter designs. This paper discusses how a magnetic flow meter works, advantages/disadvantages of this type of meter, test results, and new guidelines for field applications.

Implementation and Field Calibration Pipeline Doppler Meters in Northern California

The Tehama-Colusa Canal Authority (TCCA) has been using SonTek Doppler flow meters at approximately 30 installations for about 3 years. TCCA is located in northern California with its headquarters in Willows. The Cal Poly ITRC compared the accuracy of the flow measurement readings from the new Doppler flow meters to the venturi meters that were installed by the US Bureau of Reclamation (USBR). The venturis were used as the historical standard for flow measurement for TCCA. TCCA has opted to move away from the existing technology for a variety of reasons, especially due to the issue concerning access requirements for an enclosed space. TCCA has opted to use the Doppler meter as the replacement. In past studies, ITRC has used the R-Squared statistic to set the minimum number of data points for calibration. This paper evaluates the technique used by USGS to report the calibration of a meter.

Evaluation of Magnetic Meters for Irrigation Pipeline Measurement

Magnetic flow meters are used to measure the flow rate of a liquid in a closed pipeline. This type of meter is becoming increasingly popular for measurement with agriculture applications. Electromagnetic meters were tested by the Irrigation Training and Research Center in pipelines located less than the 10 diameters upstream of disturbances with good results. Results show that location guidelines for placing a magnetic meter can be decreased even for turbulent conditions. This paper will discuss how a magnetic flow meter works, advantages and disadvantages of this type of meter, test results, and new guidelines for field applications. INTRODUCTION The accuracy and long-term success of any flow measurement program depends on many factors. Magnetic flow measurement is rapidly becoming the technique of choice in pipelines because of its simplicity and accuracy. However, the application of this technology has been limited in the past because of standard practice guidelines for magnetic flow meters, which have required installing the meters in a straight section of pipe at least 8-10 pipe diameters from any source of turbulence. In addition, standard practice recommends having at least two pipe diameters of straight unobstructed pipe downstream from the meter. However, in the case of many irrigation pumping plants, turnouts, and deliveries, these conditions can rarely be met without extensive and expensive modifications. Therefore, the Irrigation Training and Research Center (ITRC) at Cal Poly State University San Luis Obispo is currently investigating electromagnetic flow meters for potential applications under non-standard conditions. Several current manufacturers claim that their magnetic meters can perform well even in locations where only two diameter lengths of straight pipe are available. Testing was done by the ITRC on several magnetic meters at the Cal Poly Water Resources Facility to evaluate comments by the manufacturers and to make recommendations to irrigation districts and growers interested in this new technology. This research was conducted to determine: The accuracy of the magnetic meters in locations that are less than optimal The sensitivity of meters to increasing amounts of turbulence Since this research was conducted, there have been numerous field installations of magnetic meters in various irrigation applications in California. The general consensus is that they are working well. Presented at the May 17-21, 2009, World Environmental and Water Resources Congress in Kansas City, Missouri. http://www.itrc.org/papers/magmeter09.htm ITRC Paper No. P 09-002 Magnetic Meters According to Faraday’s Law, a voltage will be induced proportional to the velocity of a conductor as it moves at right angles through a magnetic field. The water in the pipe is the conductor. By simply measuring the voltage, a magnetic meter is able to calculate the volume of the liquid passing through a controlled section. Faradays Formula: E is proportional to V x B x D E = The voltage generated in a conductor V = The velocity of the conductor B = The magnetic field strength D = The length of the conductor This principle works for irrigation water passing through the magnetic field generated by the magnetic meter since the water acts as the conductor. The basic operating principle for magnetic meters is illustrated in Figure 1. Note that this discussion is limited to full-bore or in-line magnetic meters. There are several other types of meters on the market but this type is the one that was evaluated. Figure 1. Operating principle for full-bore magnetic meter (Omega 2009) As seen in Figure 2, there are two electrodes located inside the magnetic meter to measure the induced voltage. The flow rate/totalizer indicator is located on the top of the unit. These units can be placed at any angle. It is recommended that they be rotated so that one of the electrodes does not sit on the bottom of the pipe. This helps prevent problems from sediment covering the electrode. Note that on the unit in Figure 2, the magnetic field is generated by an insert unit into the pipeline. Some manufacturers install the coils to generate the magnetic field outside of the spool piece. Presented at the May 17-21, 2009, World Environmental and Water Resources Congress in Kansas City, Missouri. http://www.itrc.org/papers/magmeter09.htm ITRC Paper No. P 09-002 Figure 2. View of typical magnetic meter (SeaMetrics 2009) Advantages of Magnetic Meters Highly accurate even with some flow disturbance. No headloss caused by meter. Is not impacted by trash, sediment, or sand. Can measure a wide range of velocity. This is a key criterion in areas that have seasonal high flows combined with very low flows. Has instantaneous and volumetric totalizing capability. Measurement accuracy is NOT affected by varying canal water levels. Minimal maintenance required. Temperature of the liquid has no effect on accuracy. Disadvantages of Magnetic Meters Cost is a major constraint. Recently the cost has dropped dramatically, but this is still the most expensive option in some cases. Pipe must be full (as is the case in most agricultural applications). Installation into existing sites is often difficult and expensive. Sensitivity to turbulence. Turbulence and Magnetic Meters Magnetic meters have been considered particularly tricky for pumping plants and turnouts, because of the meter’s sensitivity to turbulence. For example, one of the main problems associated with turnouts is the turbulence that occurs just downstream of the gate. Figure 3 shows a typical turnout application with a magnetic meter. Presented at the May 17-21, 2009, World Environmental and Water Resources Congress in Kansas City, Missouri. http://www.itrc.org/papers/magmeter09.htm ITRC Paper No. P 09-002 Figure 3. Conceptual sketch of magnetic meter installation for turnouts (not to scale) In 1998, Hanson and Schwankl published results from non-optimal flow meter testing in their paper Error Analysis of Flowmeter Measurements. Pipeline measurements were taken with different types of flow meters to determine the effects on error resulting from different degrees of turbulence caused by elbows, check valves, and a partially opened check valve. Measurements were made at 2, 5, 10, and 15 pipe diameters downstream from the source of turbulence. The results from Hanson and Schwankl (1998) indicated that for generally acceptable accuracy with propeller meters, pitot meters, and Doppler meters, measurements should be taken upstream of valves. The tests found that in some circumstances even with as little as 2 or 5 pipe diameters upstream of a flow meter, there were still large errors with all meters under conditions of severe turbulence. Since most applications require the flow measurement downstream of a valve or turnout gate, manufacturers have recently claimed that their magnetic flow meter technology is now able to work effectively in situations where there is as little as two diameters of pipe length available. ITRC tested several magnetic meters at the Cal Poly Water Resources Facility to investigate these claims.