Low Flow Testing

In arid environments, streamflow enhancement in low flow channels is common. It is challenging to assess enhancement project effectiveness in these channels because of uncertainties in metering (regarding both meters and procedures). The basic equation for flow is: Q = VA (Eq. 1) Where, Q = channel flow rate (e.g., cubic feet per second, CFS) V = cross sectional average velocity (e.g., feet per second, fps) A = cross sectional area (e.g., square feet, ft2) There are three main factors that impact flow measurement uncertainty in natural channels: 1. Flow meter velocity measurements (V) 2. Depth and area measurements (A) 3. Lack of continuous measurements over time Items 1 and 2 above are directly shown in Eq. 1. However, the third point is important to also understand because point flow measurements are difficult to utilize, since flow changes over time. The work outlined in this report only focuses on the first two factors (V and D). The last factor is typically overcome by somehow continuously measuring the flow or relating point flow measurements to water depth (stage discharge relationship). The objectives of this study were to evaluate several meters under laboratory and semi-laboratory conditions in order to: 1. Determine the most effective meter to use under low flow conditions 2. Identify constraints in the metering process or with meters themselves 3. Utilize the results to identify improved methods or recommendations for improving low flow measurement accurac

Grass Referenced Based Vegetation Coefficients for Estimating Evapostranspiration for a Variery of Natural Vegetation

In arid and semi-arid regions, evapotranspiration from vegetation results in the significant utilization of available water. Accurate estimates of evapotranspiration are required for surface and subsurface hydrologic evaluations as well as irrigation district water balance studies. A significant amount of transferable information exists for irrigated agricultural crops through past and current research in the form of grass or alfalfa reference based crop coefficients (Kc) and basal crop coefficients (Kcb). However, transferable evapotranspiration information on natural vegetation is limited. Much of the work was conducted in the early to mid-1900’s and is presented as actual evapotranspiration from the vegetation at the research site either as annual or monthly values. In some cases, the data may have been referenced to evaporation pan measurements (typically Class A type pans) with unknown site conditions. An intensive literature review was conducted to extract monthly measured evapotranspiration information for natural vegetation types under various conditions. Monthly vegetation coefficients (Kv) for standardized grass reference based evapotranspiration (ETo) were computed using long-term average grass reference evapotranspiration information computed with data from nearby weather stations. Comparisons of the Kv values for similar vegetation indicate higher variability during the non-summer months but results from most of the studies examined are in good agreement. These Kv values provide some level of transferability so that it is possible to compute an accurate estimate of vegetative evapotranspiration with daily or monthly standardized grass reference evapotranspiration values in areas away from the original study

California Energy Commission Agricultural Peak Load Reduction Program Case Study: North Kern WSD

The North Kern Water Storage District (NKWSD) is located just north of Bakersfield in Kern County and encompasses nearly 60,000 acres. The district receives water from the Kern River as well as groundwater pumping to supply its users

Infrared Inspection

Infrared thermography is the use of infrared radiation to qualitatively and quantitatively express heat signatures and heat differences. Infrared inspection can help identify weak connections in an electrical box, uneven heating of pump windings, overheating of bearings, and many other possibly devastating problems well before any failure occurs. The use of thermography as a preventative tool can increase system reliability and efficiency

Accuracy of Round Meter Gates for On-Farm Deliveries

Recent California legislation requires irrigation water agencies larger than 25,000 acres to measure volumetric water deliveries within specified levels of relative uncertainty. Although the meter gate is one of the most widely used flow measurement devices in California, little investigation has been conducted into the accuracy, limitations, and uncertainties of the rating tables developed over 60 years ago. A meter gate testing facility was constructed at the Cal Poly Irrigation Training and Research Center’s Water Resources Facility capable of testing gates up to 0.76 m (30 in.). The facility was constructed with gates oriented perpendicular to the supply channel flow to match actual field conditions. Three commonly used gate sizes of 0.30 m (12 in.), 0.46 m (18 in.), and 0.61 m (24 in.) were examined under a variety of upstream head, head loss, and gate opening conditions. Based on the limitations, guidelines are included to assist users and lower the uncertainty of these devices. It was found that meter gates can be an accurate flow measurement device if installed and operated correctly according to guidelines provided. Limitations were found: upstream head above the top of the turnout pipe must be maintained equivalent to at least half the pipe diameter, and gate openings less than 25% open can lead to large uncertainties. Using the new rating tables for the three gates examined, the relative uncertainty is less than ±5to ±7%at the 95% confidence level with the new rating tables, as compared with less than ±10%at a 95% confidence level using common published tables. Uncertainties are lower than the required estimated 10.7% instantaneous flow rate uncertainty that will be needed to meet current SB X7-7 requirements

California Energy Commission Agricultural Peak Load Reduction Program Case Study: Berrenda Mesa WSD

Berrenda Mesa Water Storage District (BMWSD) is located in the southern part of the San Joaquin Valley near Bakersfield. The district receives water from the State Water Project – California Aqueduct

Rating Rectangular Farm Delivery Meter Gates for Flow Measurement

Traditional meter gates for farm delivery flow measurement from an open channel conveyance have traditionally incorporated round canal gates (Armco type) for control. In recent years, some irrigation water agencies (i.e., irrigation districts) have replaced deteriorating round gates with lower-cost rectangular gates that cover round holes. Similar to the situation described in a companion paper, where round gates were examined, there have been no investigations into flow measurement uncertainty using the existing rating tables for these gates. In this study, two commonly used rectangular gate sizes, 0.46 m (18-in.) and 0.61 m (24-in.), were tested under scenarios of various gate openings, upstream heads, and head differences. Coefficient of discharge (Cd) values were computed based on actual gate open areas. These improved Cdvalues were used to generate new discharge rating tables for 0.46 m (18-in.) and 0.61 m (24-in.) rectangular meter gates. Limitations for these rectangular gates are discussed. If guidelines presented in this paper and in the companion paper are followed, the average instantaneous flow measurement uncertainty that could be expected is better than ±5%. However, uncertainty is higher (up to approximately ±9.5%) at the lower end of the recommended gate openings [0.10 m (4 in.)] for these rectangular gates

California Energy Commission Agricultural Peak Load Reduction Program Case Study: Orange Cove ID

The Orange Cove Irrigation District is located in Fresno and Tulare Counties, approximately 30 miles southeast of Fresno and 20 miles north of the City of Visalia. The Friant-Kern Canal is the district’s main source of water to supply 28,000 acres of farmland

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

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