Irrigation Association Anaheim Revisiting Farm Ponds for Irrigation Water Supply in the Southeast US

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Irrigation AssociationAnaheimRevisiting Farm
Ponds for Irrigation Water Supply in the
Southeast US

• presented by
• Jim Hook, Shane Conger, and Kerry Harrison
• National Environmentally Sound Production
  Agriculture Laboratory
• The University of Georgia, Tifton Campus
• http//www.nespal.org/SIRP

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Assessment of man-made ponds

• As State and Federal Governments begin to look
  stream flow for withdrawal and discharge
  permitting
• As they examine threatened habitats and species
• As ground water level decline
• Agricultural Irrigation
• Ponds as
• As alternative to direct stream withdrawals
  during dry periods that trigger irrigation
• As alternative to GW withdrawals from aquifers
  that sustain base flow
• As alternative to GW withdrawals that lower heads
  in areas with long term decline (confined
  aquifers)

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Ponds supply water for irrigationon Coastal
Plain Farms

• Early irrigation in Georgia
• Tobacco, vegetables, and various supplemental
  irrigation
• Mostly applied by portable and temporary
  irrigation
• Water supplies from the streams flowing through
  and along their property, but because many of
  these streams dried during growing season they
  turned to ponds
• Ponds among earliest irrigation water sources.

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Man-made Ponds on Georgia Farms

• For more than 75 years, farm ponds promoted by
  USDA Natural Resources Conservation Service
  (formerly SCS)
• Integral part of farm conservation plans
• Livestock water security
• Recreation, fish production, fire protection
• Approval engineering design by SCS/NRCS
• construction supervision and approval
• Often cost shared (ASCS/FSA)

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Irrigated Area CES Irrigation Surveys 1970 to
2004
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Location of agricultural withdrawal permits. The
majority of agricultural irrigation areas.
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Assessment of Farm Ponds Quantity and their
hydrologic significance
The Study Area South Georgia HUC08
(Sub-basins)
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Irrigation Water Sources CES Irrigation Surveys
1970 to 2004
Despite growth in irrigation, numbers fed by
surface water sources remained constant. Much
of growth come from groundwater
sources. Surface water includes ponds and
streams.
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The Floridan aquifer underlies most of the SE
Coastal Plains in Georgia and Florida and is
their most important source of water.
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Agriculture is biggest user of Floridan aquifer
water. Growing pressure on ag to reduce
withdrawals
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In recharge areas the aquifer is resilient and
rebounds every year from pumping and natural
drainage.
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USGS NHD 2006 Waterbodies
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Ga DOT 2003 Waterbodies
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Water Bodies in the Coastal Plain Landscape

• Man-made ponds and reservoirs
• Lake/Ponds 81,000
• Range lt 1 to 800 ac
• Median 1.2 ac mean - 2.8 ac
• Total area lake/ponds 225,000 ac
• GA DOT 2003 Waterbodies So. Ga. HUC08s

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Candler Co DOT mapped ponds
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Transects to characterize a sample of study area
ponds
Random vectors 140 transects 10-25 mi long 1000
ft wide
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Assessment of man-made ponds

• Transect Results
• Data results Ponds size 0.25 to 220 ac
• Average size of all visible ponds was 11 ac
  median 5 ac

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Assessment of man-made ponds

• Transects
• Pond Clusters distance to upstream and
  downstream ponds
• 30 had nearby upstream pond
• Half within 0.25 mi
• 50 had nearby downstream pond
• Half within 0.25 mi

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Assessment of man-made ponds

• Catchment areas small to medium
• Mean 350 ac
• Median 200 ac
• Range 160 ac to 16,000 ac
• With the average size pond and average size
  catchment area, it requires 2.0 in runoff to fill
  if empty
• Range 0.1 in to 10 in

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Assessment of man-made ponds

• Proximity and Use for irrigation
• 83 within 0.25 mi of farm field
• 64 adjacent to farm field
• 25 had existing pump or permitted withdrawal
  present
• Within Ga, 12,700 permits for ag water withdrawal
  from ponds

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Study area with existing Surface Water Permits
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Reliability of Farm Water Supply

• Quantity of stored water
• Assume ratio of mapped to unmapped NHD and
  relative sizes, there are
• 9,500 farm ponds in South Georgia having average
  area of 11 ac
• At average depth of only 5 ft these store 530,000
  ac-ft
• Relative to irrigation in Georgia
• With a typical to high annual consumption of 1
  ac-ft/ac, this would supply 1/3 to ½ of all
  irrigated acreage in Georgia without in-season
  resupply

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Reliability of Farm Water Supply

• Capability of average sized ponds for center
  pivots
• An average sized center pivot in Georgia is 100
  ac
• To supply 1 acre-ft/year, a pond would have to
  provide 100 acre-ft.
• Without in-season refill this is a 10 acre pond
  with and average depth of 10 ft
• This is more than twice the capacity of average
  ponds measured thus far
• Considerable cleanout and expansion needed for
  more dependable pivot supplies

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Irrigation Density
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Pond Density
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For existing ponds and irrigationCapability to
meet irrigation demand
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Reliability of Farm Water Supply

• Conclusions
• Existing and refined GIS data show that man-made
  ponds are numerous and widespread.
• Many are too small or too remote from farm fields
  to serve as reliable irrigation supplies. Still
  there are at least 10 thousand suitable for
  irrigation supply.
• Expansion and cleanout efforts on existing ponds
  could substantially increase water security for
  irrigated farmers and lower dependence on
  groundwater

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