Conversion from Flood to Sprinkler

Water Supply Impacts

Mike Roberts, Hydrologist

Department of Natural Resources and Conservation

Water Management Bureau March 2012

Flood Irrigation

Center Pivot Irrigation

wild flood

contour ditch

wheel line

center pivot

What is Consumptive Use?

The volume of water used for a beneficial purpose, such as

water transpired by growing vegetation, evaporated from soils

or water surfaces, or incorporated into products that does not

return to ground or surface water (ARM 36.12.101(15))

Evapotranspiration (ET)

Irrecoverable losses (do not return to the source)

Surface and Groundwater are Connected

Flint Creek Return Flow

Study (DNRC 1997)

NF Blackfoot River

Hydrologic Study (DNRC

2001)

Stream and Fluvial Plain

Ground Water Interactions

(Woessner 2000)

Surface and Groundwater are Connected

Increase in yield = increase in Consumptive Use (ET)

From: Agronomy News, Colorado State University Extension, April 2007, Volume 26

0

0.5

1

1.5

2

2.5

3

3.5

4

1929 1934 1939 1944 1949 1954 1959 1964 1969 1974 1979 1984 1989 1994 1999 2004

Ton

s/A

cre

Year

Montana State Yields (Alfalfa)

Irrigated

Non Irrigated

Pre-Center Pivot Era Center Pivot Era (1955-Present)

USDA, National Agriculture Statistics Service

Montana Field Office

Production in Montana

Note: Better management practices

Fertilizers

1997

Photos courtesy of Scott Irvin

What typically happens when a flooded field is converted to sprinkler?

1997 2005

Photos courtesy of Scott Irvin

What typically happens when a flooded field is converted to sprinkler?

1997 2005

Photos courtesy of Scott Irvin

What typically happens when a flooded field is converted to sprinkler?

river flow

Flood irrigation = 15 to 60% efficient

Need to divert more water

Requires higher stream flows

Increases groundwater storage and

results in more return flow

System Efficiencies (% diverted that is used by the crop)

river flow

Flood irrigation = 15 to 60% efficient

Sprinkler irrigation = 60 to 85% efficient

Need to divert less water

Less instream flow needed to divert

Less groundwater storage and

return flow

System Efficiencies (% diverted that is used by the crop)

Need to divert more water

Requires higher stream flows

Increases groundwater storage and

results in more return flow

How does consumptive use increase with conversion from flood

irrigation to sprinkler irrigation?

Increases Production (yield)

Water Distribution

Irrigated Acres

Irrigation Season

Crop Type

Change to more

productive location

Typical Flood Irrigation (percentages relative to diverted amount)

Crop Consumptive Use = 25%

Conveyance

loss = 20% Additional irrecoverable

losses = 10%

Surface and groundwater

returns = 45%

Typical Sprinkler Irrigation (percentages relative to diverted amount)

Crop Consumptive Use = 75%

Conveyance

loss = negl. Additional irrecoverable

losses = 10%

Surface and groundwater

returns = 15%

Case Studies

0

4,000

8,000

12,000

16,000

0

100

200

300

400

Jan. Feb. Mar. Apr. May Jun. Jul. Aug. Sep. Oct. Nov. Dec.

Inc

hes

CF

S

Modeled Average Flows for the Smith River below Sheep Creek

100 % Flood

33% Sprinkler

66% Sprinkler

(Source: DNRC Smith River Basin Permit and Change Applications Supplemental Environmental Assessment, 2002)

Center Pivot Sprinkler

replaced flood field, diversion reduced from

12 cfs to 2 cfs.

Potential Advantages

Increases production (especially on

non-level field)

Decrease labor costs

Decrease Ag chemical application

Water quality improvements (saline seep)

Fisheries (spring spawning)

Instream water quantity increases (early season)

- channel maintenance

Potential Disadvantages

Instream water quantity reductions

Downstream producers and well users

water availability reduced or

eliminated.

Fisheries (fall spawning, WQ, etc.)

Water Quality (increased temperatures)

Increase power costs

Management Objective

NF Blackfoot River

Potential Advantages

Increases production (especially on

non-level field)

Decrease labor costs

Decrease Ag chemical application

Water quality improvements (saline seep)

Fisheries (spring spawning)

Water quantity increases (early season)

- channel maintenance

Potential Disadvantages

Less Groundwater Storage

Decreased late season flows

Fisheries (fall spawning, WQ)

Water Quality (increased temperatures)

Increased power costs

Management Objective

NF Blackfoot River

Potential Advantages

Increases production (especially on

non-level field)

Decrease labor costs

Decrease Ag chemical application

Water quality improvements (saline seep)

Fisheries (spring spawning)

Water quantity increases (early season)

- channel maintenance

Potential Disadvantages

Water quantity reductions

Downstream producers and well users

water availability reduced or

eliminated.

Fisheries (fall spawning, WQ, etc.)

Water Quality (increased temperatures)

Increase power costs

Depends on

Management Objective

NF Blackfoot River

Key Points on Water Supply

• Increased efficiency does not always equate to increase water savings

Key Points on Water Supply

• Increased efficiency does not always equate to increase water savings

• Typical conversion from flood to sprinkler in Montana can result in

increased consumption of water (acre for acre and from expansion).

Key Points on Water Supply

• Increased efficiency does not always equate to increase water savings

• Typical conversion from flood to sprinkler in Montana can result in

increased consumption of water (acre for acre and from expansion).

• Increased consumption of water and decreased return flows can lead to

streamflow depletions late in the irrigation season.

Key Points on Water Supply

• Increased efficiency does not always equate to increased water savings

• Typical conversion from flood to sprinkler in Montana can result in

increased consumption of water (acre for acre and from expansion).

• Increased consumption of water and decreased return flows can lead to

streamflow depletions late in the irrigation season.

• Many basins in Montana experience shortages. On any given day,

irrigators are being shut-off by water commissioners

ex. Musselshell R.

Key Points on Water Supply

• Increased efficiency does not always equate to increase water savings.

• Typical conversion from flood to sprinkler in Montana can result in

increased consumption of water (acre for acre and from expansion).

• Increased consumption of water and decreased return flows can lead to

streamflow depletions late in the irrigation season.

• Many basins in Montana experiences shortages. On any given day,

irrigators are being shut-off by water commissioners

ex. Musselshell R.

• Benefits of flood to sprinkler conversions depend on management

objective.

Key Points on Water Supply

• Increased efficiency does not always equate to increase water savings.

• Typical conversion from flood to sprinkler in Montana can result in

increased consumption of water (acre for acre and from expansion).

• Increased consumption of water and decreased return flows can lead to

streamflow depletions late in the irrigation season.

• Many basins in Montana experiences shortages. On any given day,

irrigators are being shut-off by water commissioners

ex. Musselshell R.

• Benefits of flood to sprinkler conversions depend on management

objective.

• Can be site-specific, it’s not simple, lots of variables