Transcript Nutrient Concentrations in the Soil Solution and Shallow

Georgia
Athens
Irrigation Association
Anaheim
Atlanta
Tifton
Gulf of Mexico
Florida
Revisiting 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
Assessment of man-made ponds

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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)
Ponds supply water for irrigation
on 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.
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)
Irrigated Area
CES Irrigation Surveys 1970 to 2004
1.80
1.60
Area (million ac)
1.40
1.20
1.00
0.80
0.60
0.40
Area of irrigation systems
Area of Irrigated Crops
0.20
0.00
1970 1975 1977 1980 1982 1986 1989 1992 1995 1998 2000 2004
Location of
agricultural
withdrawal permits.
The majority of
agricultural
irrigation areas.
Assessment of Farm Ponds
Quantity and their hydrologic significance
The Study Area:
South Georgia
HUC08 (Sub-basins)
Irrigation Water Sources
CES Irrigation Surveys 1970 to 2004
Despite growth in
irrigation,
numbers fed by
surface water
sources remained
constant.
12,000
No. of Systems
10,000
8,000
6,000
Much of growth
come from
groundwater
sources.
4,000
2,000
0
1970 1975 1977 1980 1982 1986 1989 1992 1995 1998 2000 2004
Ground Water
Surface Water
Waste Water
Surface water
includes ponds and
streams.
The Floridan aquifer
underlies most of the
SE Coastal Plains in
Georgia and Florida
and is their most
important source of
water.
Agriculture is
biggest user of
Floridan aquifer
water. Growing
pressure on ag to
reduce withdrawals
In recharge areas
the aquifer is
resilient and
rebounds every year
from pumping and
natural drainage.
USGS NHD+ 2006 Waterbodies
Ga DOT 2003 Waterbodies
Water Bodies in the Coastal Plain
Landscape

Man-made ponds and reservoirs
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
Lake/Ponds – 81,000;
Range < 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. HUC08’s
Candler Co
DOT mapped ponds
Transects to characterize a sample
of study area ponds
Random vectors
140 transects
10-25 mi long
1000 ft wide
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

Assessment of man-made ponds

Transects
Pond Clusters: distance to upstream and
downstream ponds

30% had nearby upstream pond

50% had nearby downstream pond
– Half within 0.25 mi
– Half within 0.25 mi
Assessment of man-made ponds
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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
Assessment of man-made ponds
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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
Study area with existing Surface
Water Permits
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
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
Irrigation
Density
Pond Density
For existing ponds
and irrigation
Capability to meet
irrigation demand
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