Ag Water Energy Center at Fresno State

Transcription

1 Water Use Efficiency for Grapes and Almonds Presented by the (CIT) California State University, Fresno Ag Water Energy Center at Fresno State

2 The Designers and Managers of the Program: Water and Energy Technology (WET) Lab- Pump Certification Facility Hydraulic Laboratory Testing (Flowmeters, Filters, Valves, Sprinklers, Irrigation equipment, etc.) Applied Research, Analytical Studies and Special Projects Education Grants Program Design and Management A part of the: Jordan College of Agricultural Sciences and Technology (JCAST) California State University Fresno (Fresno State) 2

3 The Operating Condition of a pump Every irrigation system has a flow and pressure requirement. The pump output must match this. The combination of flow and pressure supplied by the pump is termed the Operating Condition. Every pump has a combination of flow and pressure as it operates 3

4 What is Flow? 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 4

5 How do we get flow rates? From flowmeters WHY? You need to measure water in order to manage water! On every list of best management practices. Cannot plan, monitor, or improve without knowing how much water is flowing or was applied. Provides the benchmark for management and improvement of pumping systems. 5

6 Doesn t a Pump Test Give Me Flow?... The pump test is a snapshot, at the conditions tested. Especially with wells, flow rates may be significantly different throughout a season. Won t help if something starts to go wrong during a season. 6

7 Water Flow Meters Do What?... May measure the flow rate - volume of water passing the measurement point per unit time Gallons per minute (gpm) Cubic feet per second (cfs) second feet May measure total volume of water passing the measurement point Acre-feet Gallons (325,900 gallons per acre-foot) Many do both 7

8 What is Total Dynamic Head- Diagram showing TDH components 8

9 TDH example- Total Lift from the water source level (PWL) to the field level + the pressure to operate the irrigation system 9

10 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 10

11 Efficiency Numbers on the curve 11

12 Input Horsepower and Pumping Costs 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 (%) 12

13 Pumping Energy Calculator 13

14 Your Role in Specifying a Pump If the required operating condition(s) is/are known then the pumping specialist can pick an efficient pump or pumping system. You need to help him/her identify the required operating condition(s) what flow rate(s) and pressure(s) are you going to need to operate your system correctly? 14

15 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 15

16 Stable Condition 16

17 Flood pump used for drip Good pump what condition? Summer 68 /stg Winter 45 /stg Worn Pump How worn? 17

18 Our Focus at the APEP is Bowl Efficiency (Impeller Efficiency) The pump itself 18

19 Impellers There are different impellers engineered to create almost any operating condition required for pumping water. The sizes range from impeller trims of a few inches to many feet in width. 19

20 Impellers Radial flow or closed impeller High pressure or lift situations Commonly used for high pressure Adjustments can increase efficiency 1 to 4% 20

21 Impellers Semi-open or mixed flow impeller Adjustable for clearance between the impeller and the bowl Mixed flow- high pressure/low flow or high flow/low pressure Limitations with high TDH situations 21

22 Impellers Axial or open flow Similar to a boat propeller High Flow (GPM) Low Pressure (TDH) Used to move water from a canal or pond to a flood irrigation system 22

23 Major Types of Pumps Vertical Turbine.... Submersible..... End Suction Centrifugal... 23

24 Pump Stages Multi-stage Vertical Turbine Pump, common in deep well and reservoir applications Each staged impeller creates additional TDH or pressure while maintaining flow 1 impeller = 20 TDH 2 impellers = 40 TDH 3 impellers = 60 TDH 24

25 Pumps in a series (booster pump) Deep Well Pump brings water to the surface Booster pump creates additional pressure (TDH) required for drip or sprinkler irrigation system 25

26 Pumps in parallel Very common in municipal water systems but also used in agriculture Maintain pressure in the delivery system under different flow rates. Can use pumps of different sizes but recognize each operating pump will see the same discharge pressure. Different combinations of flow and pressure from different combinations of pumps. The alternative VFDs on one or more pumps. 26

27 Varying Speed of Pump Varying the rotational speed of a pump changes the performance curve, just as trimming an impeller. This may help you meet variable operating conditions in real time (i.e. you can t install different diameter impellers on the fly ). You can do this with Internal Combustion engines or Variable Frequency Drives (VFD s) 27

28 Variable Frequency Drives Allow you to (automatically) throttle an electric motor just as you would a diesel or natural gas engine Can save energy, which equals money Easier on machinery (soft-starts) HOWEVER, there are always tradeoffs Cost Power quality considerations Physical restrictions 28

29 Pump Curves at different speeds same pump in field, different speed 29

30 Knowing How Much Water to Apply and When- Water Use Efficiency Focus is on an individual irrigation or time frame on a single field or irrigation set Each irrigation should have a purpose: Put a specific amount of water, in a specific volume of soil, as uniformly as possible

31 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

32 Irrigation Efficiency is Only as Good as the Management The best irrigation system in the world Will not be efficient If you run it twice as long as you need to.

33 How to Determine Irrigation or Water Use 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

34 Distribution Uniformity DU is a measure of how evenly water is applied across the field DU is upper limit of IE Need good DU before good IE and potentially good Water Use Efficiency (WUE) (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)

35 Poor DU and excessive deep percolation

36 Poor DU and under watering the field

37 Efficiently watered field with good uniformity and irrigation efficiency

38 Good uniformity but excessive deep percolation

39 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

40 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?

41 Available water in soils- approximate Coarse Sand/ Gravel-.45 Sand-.80 Loamy Sand Sandy Loam Fine Sandy Loam Loams/ Silt Loams Clay Loams Silty Clay/ Clays

42 What do I need to know about my grape crop? 1. Effective root depth for water penetration- for grapes, could use 3-6 feet. 2. Soil Type- water holding capacity and availability 3. Depletion of water Example- 4 root zone, Loamy Sand soil / ft.= 4.2 water, depleted 50% = 2.1 of net water to apply 42

43 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

44 Calculating The Gross Depth of Water to Apply Set the NET DEPTH OF WATER REQUIRED = 2.1 inches at IRRIGATION EFFICIENCY =70% for flood irrigation (average)

45 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).

46 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

47 Grape example for flood irrigation Scenario 1- How many hours do I need to run the pump to achieve good Water Use Efficiency with this flood irrigation system? 50 acre block of raisin grapes Sandy Loam soil- 1.6 of water per foot Effective root zone- 4 feet- 6.4 total water Pump flow rate- 1,000 GPM 47

48 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 - approximately 50% depletion for Sandy Loam soil Acres = acres irrigated = 50 acres = constant Pump flow = 1,000 gpm

49 Furrow, Flood and Low Frequency Field Sprinklers Set GROSS DEPTH OF WATER TO APPLY = 3 inches under PUMP FLOW RATE = 1,000 gpm

50 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

51 Conclusion If I can irrigate as evenly as possible, attaining a 70% uniformity and efficiency- the pump would run for 70 hours. If the pump runs for longer than 70 hours or if the irrigation sets are not run evenly, the Water Use efficiency will be lower than 70%

52 Almond drip irrigation example How long do I need to run the pump to irrigate the almonds today? Row spacing 18 x 20 Need to apply.5 of water today Usually figure drip irrigation scheduling for the week to set the timer on the sytem

53 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

54 Standard Micro Irrigation Set the GROSS DEPTH OF WATER TO APPLY =.5 inches under GALLONS PER HOUR PER TREE/VINE = 8 gph

55 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

56 Conclusion To deliver a.5 to the almonds, the pump will run for 14 hrs. Usually drip schedulers set the timer for the week. If 2 of water needs applied for the week, the pump would run: 2 /.5 = 4 x 14 hrs = 56 hrs.

57 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

58 Good Irrigation Planning & Management Means a Profitable Crop