IRRIGATION TECH SEMINAR SERIES

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1 AGENDA: Irrigation Performance - Tips & Tools December 11, 2008 Presented by Bill Green, CIT Work Shop Registration Welcome Effective vs. Efficient Irrigations Distribution Uniformity vs. Irrigation Efficiency (DU vs. IE) Factors in Obtaining High DU in All Systems Irrigation System Evaluations Irrigation Management for Conserving Water and Obtaining High IE Irrigation Performance and Fertilizer/Chemicals/Yield/Water Quality/Conservation CIT Pump and Sprinkler Demonstration Irrigation Tech Seminar Series California State University, Fresno

2 IRRIGATION PERFORMANCE TIPS & TOOLS Irrigation System Performance - Tips and Tools Bill Green - Education Manager Center for Irrigation Technology, California State University, Fresno Agenda 1. Effective vs. Efficient Irrigations 2. Distribution Uniformity vs. Irrigation Efficiency (DU vs. IE) 3. Factors in obtaining high DU in all systems 4. Irrigation system evaluations 5. Irrigation management for conserving water and obtaining high IE 6. Irrigation performance and fertilizer/chemicals/ yield/water quality/conservation 7. CIT pump and sprinkler demonstration Effective and Efficient Irrigations When to irrigate Agronomic decision How much to irrigate Soil moisture depletion (SMD) in root zone How to irrigate Applying water evenly across a field Controlling total amount of water applied 2

3 CENTER FOR IRRIGATION TECHNOLOGY Irrigation Efficiency (IE) is Only as Good as the Management IE is the % of water is effectively used by the target The best irrigation system in the world Will not be efficient If you run it twice as long as you need to (or half as long as you need to) How to Determine Irrigation Efficiency How much of pumped water goes where you want it? Losses due to deep percolation (beyond leaching) Losses delivering water to the field Losses due to surface runoff Losses due to surface evaporation All may change with each irrigation- monitor the plan Distribution Uniformity DU is a measure of how evenly water is applied across the field or to the target area DU is upper limit of IE Need good DU before good IE (if entire field to be watered sufficiently) Good DU is no guarantee of good IE (e.g. drip system run twice as long as needed) 3

4 Audit To Determine The UNIFORMITY of COVERAGE (DU) All Types of Irrigation Systems can be Audited to Determine DU Distribution Uniformity (DU) DUlq = 80% High Qtr 2nd Qtr 3rd Qtr Low Qtr 4

5 CENTER FOR IRRIGATION TECHNOLOGY Poor DU Good DU with Drip Irrigation on Grapes Distribution Uniformity: What Does it Mean? 100 % is perfect DU meaning a totally uniform distribution of the water applied Most irrigation systems, when new, range between 70% and 95% DU Most growers systems are fairly close to average for the system type System maintenance is the key to maintaining good DU 5

6 What Causes Low DU Averages? For Drip and Micro systems, it is very important to keep the system clean. That means flush often. For Hand-move sprinklers, maintenance of the nozzles and gaskets is the key to a good system. Many growers overlook this and pay in the long run. For Furrow irrigation it is all about timing and infiltration. How Can Your Irrigation System Affect Your Pumping Plant Performance or Vice Versa? Was the pumping plant designed to run the system or was it just laying around? Was your system designed to provide you with a very high Distribution Uniformity? Did you change your system in any way after design? Do you maintain your irrigation system on a regular basis? Case Study: Under Tree Sprinkler with Canal Vertical Turbine Boosters Two almond orchards. Water is very dirty, and both systems were loosing pressure. Both growers had pumps repaired and it didn t correct pressures. One grower installed larger pump to provide more pressure. Cost about $16,000. 6

7 CENTER FOR IRRIGATION TECHNOLOGY Case Study (Continued) Grower # 2 repaired pump and when it didn t correct the pressure problem he asked us to look at the system. He had already spent about $5,000 on repair. We found the the main problem was worn nozzles. Larger nozzles caused lower pressures and water application rates that exceeded the soils intake capabilities. Poor DU and Excessive Deep Percolation Poor DU and Under-watering the Field 7

8 Good Uniformity but Excessive Deep Percolation Efficiently Watered Field with Good Uniformity and Irrigation Efficiency Have a Plan for Each Irrigation Goal What do I want to achieve? Pre-irrigation Fill the soil profile Early season Refill a shallow root zone Mid season Try to keep up with ET Late season Supply just enough to finish the crop 8

9 CENTER FOR IRRIGATION TECHNOLOGY How to Determine SMD... Low tech - Feeling the soil is fast, flexible, and inexpensive but accurate? High tech Tensiometer, gypsum block, neutron or electronic probe (higher technology) is fast, restricted to the sampling site, more expensive more accurate (with proper calibration) Questions: Is the sampling site representative? Do you know the effective root zone? Calculating The Gross Depth of Water to Apply Gross = NET/IRREFF Where: Gross = gross water application required Net = water required by the irrigation IRREFF = irrigation efficiency as a decimal (0-1.0) Note: This is based on individual field irrigation efficiency Calculating The Gross Depth of Water to Apply Set the NET DEPTH OF WATER REQUIRED = 2.1 inches at IRRIGATION EFFICIENCY =70% 9

10 Calculating The Gross Depth of Water to Apply Set the NET DEPTH OF WATER REQUIRED = 2.1 inches at IRRIGATION EFFICIENCY =70% Read GROSS DEPTH OF WATER TO APPLY at the arrow (3 inches) Calculating Required Hours of Irrigation System Operation Estimates of required irrigation hours knowing: Gross depth of water to apply in inches An irrigated area in acres The irrigation system flow rate in GPM Furrow, Flood and Low Frequency Field Sprinklers Hours = Gross x Acres x 452.5/Pump flow Where: Hours = required hours of pumping for the irrigation Gross = gross depth of water to apply = 3 Acres = acres irrigated = 50 acres = constant Pump flow = 1,000 GPM 10

11 CENTER FOR IRRIGATION TECHNOLOGY Furrow, Flood and Low Frequency Field Sprinklers Set GROSS DEPTH OF WATER TO APPLY = 3 inches under PUMP FLOW RATE = 1,000 GPM Furrow, Flood and Low Frequency Field Sprinklers Set GROSS DEPTH OF WATER TO APPLY = 3 inches under PUMP FLOW RATE = 1,000 GPM Read the REQUIRED HOURS OF PUMP OPERATION (~70 hours) for entire irrigation above the ACRES IN THE FIELD = 50 acres Standard Micro Irrigation Hours = Gross x Area x.623/gph Where: Hours = required hours of pumping/set Gross = depth of water to apply =.5 Area = square foot of field per tree or vine = 18x20 = 360 sq ft.623 = constant GPH = total gallons/hour supplied to each tree or vine = 8 GPH 11

12 Standard Micro Irrigation Set the GROSS DEPTH OF WATER TO APPLY =.5 inches under GALLONS PER HOUR PER TREE/VINE = 8 GPH Standard Micro Irrigation Set the GROSS DEPTH OF WATER TO APPLY =.5 inches under GALLONS PER HOUR PER TREE/VINE = 8 GPH Read the REQUIRED HOURS OF PUMP OPERATION PER SET (14 hours) above the AREA PER TREE/VINE = 360 sq ft per tree/vine Row Crop Drip Irrigation Hours = Gross x Spacing x.0866/gpm100 Where: Hours = required hours of pumping/set Gross = depth of water to apply =.5 Spacing = spacing of drip tape in the field (inches) = = constant GPM100 = flow rating of the drip tape (GPM/100 feet of tape) =.33 GPM/100 12

13 CENTER FOR IRRIGATION TECHNOLOGY Row Crop Drip Irrigation Set the GROSS DEPTH OF WATER TO APPLY =.5 inches is under the GALLONS PER MINUTE PER 100 of TAPE =.33 GPM/100 Read the REQUIRED HOURS OF PUMP OPERATION PER SET (5.25 hours/set) above the DRIP TAPE SPACING = 40 inches Row Crop Drip Irrigation Set the GROSS DEPTH OF WATER TO APPLY =.5 inches is under the GALLONS PER MINUTE PER 100 of TAPE =.33 GPM/100 Read the REQUIRED HOURS OF PUMP OPERATION PER SET (5.25 hours/set) above the DRIP TAPE SPACING = 40 inches Review Plan each irrigation objectively. Use the slide rule to develop a plan Monitor the plan during the irrigation. Manage system to assumed IrrEff (the key) Evaluate the plan after the irrigation and learn from your mistakes. Uniformity of application Minimize losses to deep percolation Control or manage surface runoff 13

14 Good Irrigation Planning & Management Means a Profitable Crop Is a volume of water per time, typically expressed as gallons per minute or GPM Flow Rate The Required Flow Rate is Determined by the system and its components, such as sprinklers in an orchard. These sprinklers are rated at 0.2 GPM at 20 psi. 14

15 CENTER FOR IRRIGATION TECHNOLOGY The Required Flow Rate for This orchard with 4,250 sprinklers requires a pump that delivers 850 GPM The Total Head Required is a Sum of The pumping lift Elevation changes The friction losses And the pressure requirement of the equipment Head is usually expressed as feet Pumping Lift and Elevation Changes: 15

16 Pumping Lift and Elevation Changes: Pumping Lift and Elevation Changes: Friction is the Loss Due to All the Piping, Fittings, Valves, and Filters in the System 16

17 CENTER FOR IRRIGATION TECHNOLOGY The Operating Condition of a Pump HPin or energy in depends in part on the combination of flow and pressure or TDH (Total Dynamic Head) developed The combination of flow and pressure is termed the Operating Condition Every pump has a combination of flow and pressure as it operates Flow is the volume of water pumped measured in Gallons per Minute or GPM Flow can also be measured in cubic feet/second or CFS What is Flow? Main Components of TDH The main components for calculating Total Dynamic Head are: The lift in feet from the water source The pressure required to properly operate the irrigation system Accounting for friction losses (pressure losses) because of pipes, turns, valves, etc. 17

18 Diagram Showing TDH Components How is TDH Calculated Example for the previous diagram: Suction Lift - 10 ft. Elevation Lift ft. Friction Loss - 20 psi = 20 X 2.31 constant = 46 ft. Pressure at irrigation system 60 psi = 60 X 2.31 constant = 139 ft. TDH = = 385 feet TDH TDH example- Total Lift from the Water Source Level (PWL) to the Field Level + the Pressure to Operate the Irrigation System 18

19 CENTER FOR IRRIGATION TECHNOLOGY The Constant to Convert psi to Feet of Head Every 2.31 feet of water depth equals 1 psi. If you dive into a swimming pool you notice the pressure on your ears increases the deeper you go. Every 2.31 feet deeper you dive increases the pressure by 1 psi. Calculating Required Input Horsepower HPin = Flow x TDH (3960 x OPE) Where: HPin = required input horsepower Flow = pump flow rate (GPM) TDH = pressure in system (ft) OR (psi) 3960 = constant OPE = overall pump efficiency (%) Pumping Energy Calculator 19

20 Calculating Required Input Horsepower Set PUMP FLOW RATE = 1,000 GPM at the OPE = 50% Calculating Required Input Horsepower Set PUMP FLOW RATE = 1,000 GPM at the OPE = 50% Read REQUIRED INPUT HORSEPOWER (50Hp) at the TDH = 100 feet or 44 psi Calculating Energy Costs for Pumping Set the INPUT HORSEPOWER = 50 under the cost/kwh = $

21 CENTER FOR IRRIGATION TECHNOLOGY Calculating Energy Costs for Pumping Set the INPUT HORSEPOWER = 50 under the cost/kwh = $0.15 Read ENERGY COST PER HOUR PUMPING (~$5.50) Calculating Energy Costs for Pumping Set the INPUT HORSEPOWER = 50 under the cost/kwh = $0.15 Read ENERGY COST PER HOUR PUMPING (~$5.50) Read ENERGY COST PER ACRE-FOOT (~$30) pumped at FLOW RATE = 1,000 GPM The Pump Performance Curve A pump can operate over a range of operating conditions Pump manufacturers know this and produce Pump Performance Curves for each pump Performance curves show the different combinations of flow and pressure (TDH) that a particular pump will develop 21

22 Simple Pump Performance Curve Efficiency Isos Superimposed on the Curve Manufacturers Pump Curve Example 22

23 CENTER FOR IRRIGATION TECHNOLOGY Variable or Fluctuating Condition 1. Static or Standing Water Level (SWL)- varies as season progresses water table usually drops in summer 2. Drawdown 3. Pumping Water Level (PWL) varies in fluctuating situation Stable Condition PWL varies very little, so the pump lifts water from a consistent source Increasing elevations the water is delivered to can increase TDH and cause flows to decrease Elevation with a Stable Condition The PWL changes very little (not more than a few feet) however, greater elevation up the hill can still increase TDH 23

24 Operating Conditions Can Change Pump Water Level varies Different size planting blocks or sets Different emission devices in blocks Maturing crop adding emitters Poor filter selection or maintenance excessive (and variable) losses through filter Worn Pump Components Worn impellers Bearing Shaft out of alignment Worn Irrigation System Components Worn nozzles or emitters Leaks Plugging, poor maintenance Improper design 24