Drip Irrigation Efficiency. Fact or Fiction?

Transcription

1 Drip Irrigation Efficiency Fact or Fiction?

2 Why do We use Drip? It saves water! How does it save water? Because it s very efficient Is it? Sadly in the real world it often has very poor efficiency

3 What Makes it Efficient? Proper design Hydraulics

4 What Makes it Efficient? Proper components Pressure Compensating emitters Pressure management Maximum Allowable pressure loss Through a zone? 10%

5 Measuring Efficiency Low Quarter Emission Uniformity Average of lowest quarter Average of all measured

6 Testing the Efficiency

7 Testing the Efficiency Do you measure all of the emitters? No one would ever do that Measure some at the beginning Measure some in the middle Measure some at the end Make sure it s divisible by four

8 A Poor Efficiency Zone 214 shrubs (all 1 1gph emitter) LQEU = 53% Precipitation rate = 0.34 /Hr GPM = 9.3 (558GPH) annual Eto (.3 K c ) 18 root depth Clay loam soil 69,412 gallons per year

9 Efficiency Corrected 214 shrubs (all 1 1gph emitter) LQEU = 94% Precipitation rate = 0.20 /Hr GPM = 3.9 (234GPH) annual Eto (.3 K c ) 18 root depth Clay loam soil 27,947 gallons per year

10 Now it s Very Efficient Or is it? Every shrub one 1GPH emitter That s very inefficient Or is it?

11 Balancing the Delivery A philosophical question: Where did this math come from?

12 Balancing the Delivery What is the goal of agricultural irrigation? Yield!

13 Balancing the Delivery If we irrigate urban landscapes for yield, where does it go?

14 Now it s Very Efficient Or is it? Emitter placement Water roots, not plants

15 Now it s Very Efficient Or is it? Who s programming the controller?

16 Inefficient Scheduling Shrubs in June 2 hour run times Monday, Wednesday, Friday At 3.9 GPM =5,616 gallons That s controlling an efficient drip system inefficiently

17 Efficient Scheduling Monday is not a reason to water! ETo Wind Sun Humidity Temperature

18 Efficient Scheduling Here comes the math!!!!!!

19 Efficient Scheduling Reference ET (Eto) in June Plant species Crop/landscape coefficients Desert adapted on average around 30% (.3) Plant water requirement 10.19*.3 =3.06 for the month

20 Efficient Scheduling Soil type Available Water Holding Capacity (AWHC) Clay soil is 0.18 /inch of soil Root depth 18 for shrubs Root Zone Available Water (RZAW).18*18=3.24

21 Efficient Scheduling How much water to use before watering again? Management Allowable Depletion (MAD) 50% for our soils and desert plants Working Storage (WS) RZAW 3.24 * MAD.5 = WS 1.62

22 Efficient Scheduling Zone efficiency LQEU = 94% (.94) Precip rate = 0.20 /Hr

23 Putting it Together Irrigation requirement Plant water requirement/lqeu 3.06 /.94=3.25 Run hours per month Irrigation requirement/precip rate 3.25 /0.2(inches/Hr)=16.29 ~16 hours

24 Putting it Together Irrigation days per month Irrigation requirement/ws 3.25 /1.62 =2 times per month Runtime per irrigation day Run hours per month/days 16/2=8

25 Putting it Together 8 hour runtime 2 times per month At 3.9 GPM=3,881 gallons 1,735 gallons savings On one zone In one month

26 Now We re Very Efficient Or are we? How are the schedules managed? Winter schedule (Nov-March) 2Hrs 1X/week =4Hrs/month Summer schedule (Apr-Oct) 2Hrs 3X/week =24Hrs/month 48,672 annual gallons

27 Now We re Very Efficient Does the weather act that way? 6000 Gallons Gallons Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

28 Now We re Very Efficient Do it based on ET, Precip, LQEU For each month of the year A spreadsheet can do the math for you PR 0.2 EU 0.94 GPM 3.9 RZAW 3.24 WS 1.62 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Total Eto Kc Irrig Requirement Month run time (hr) Minutes/month ,166 Gallons/month 960 1,260 2,162 2,880 3,542 3,811 3,579 3,172 2,641 1,945 1, ,946 Days/month Runtime/day

29 Now We re Very Efficient What a difference! X Monthly Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

30 Now We re Very Efficient So what is the difference? Summer/winter schedule 48,672 gallons Proper monthly schedule 27,946 gallons On one zone

31 Drip Precipitation Rates The mystery of drip irrigation Turf is easy

32 Drip Precipitation Rates Drip is a little hinky

33 Drip Precipitation Rates By flow and area Contained areas Densely planted 96.3 X GPM Area

34 Drip Precipitation Rates This has been applied based on the square footage of the plant 1GPH emitter on a 1 diameter plant 96.3*(1/60)/.79=2.03 /Hr 1GPH emitter on a 6 diameter plant 96.3*(1/60)/28.3=0.06 /Hr

35 Drip Precipitation Rates 1GPH emitter on a 1 diameter plant 96.3*(1/60)/.79=2.03 /Hr 1GPH emitter on a 6 diameter plant 96.3*(1/60)/28.3=0.06 /Hr How did the difference in plant size change the precipitation rate? IT DIDN T!!!!!!!!!!!!!

36 Drip Precipitation Rates What is this telling you? The system is not balanced. 2 foot canopy 10 foot canopy

37 Drip Precipitation Rates By flow, emitter, and row spacing For inline grid drip zones X GPH E X R X.6 12 X 12 = 0.97 /Hr

38 Drip Precipitation Rates How many inline grid systems do you have? Point source drip is more common here Precipitation rate is a relationship between the emitter and the soil All soils are not created equal

39 Drip Precipitation Rates Calculated by the radius of the wetted area around the emitter This maintains the relationship between the emitter and the soil it s wetting We want inches per hour So how long do we run it? One hour!

40 Drip Precipitation Rates Capillary radius is added in This accounts for the lateral movement of the water beneath the soil surface If the wetted radius is.6 1 how much do we add for a clay soil? Soil Type Cr (ft) Clay 1 Clay Loam 1 Coarse Sand 0.2 Fine Sand 0.3 Loam 0.7 Loamy Sand 0.4 Sandy Loam 0.6 Silt Loam 0.9

41 Drip Precipitation Rates By zone and emitter count.6 (wetted radius)+1 capillary =1.6 Area of a circle? p*r *1.6 2 *number of emitters 3.14*1.6 2 *214=1720 (TWA) PR=96.3*((1*214)/60)/TWA 96.3*((1*214)/60)/1720=0.2 /Hr

42 Drip Precipitation Rates Do you need to do this math again? Only if the soil changes Only if the emitter output changes

43 Total Efficiency Pressure compensating emitters Pressure management Balancing the system Emitter placement Efficient scheduling Controller management Proper drip precip calculations

44 Questions?