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COMPLETEING A PRELIMAINRY ASSESSMENT FOR AG. WATER SUPPLY PONDS
Water Quantity and Conservation #1
Use land according to its capability and treat it according to its needs
Use management to gain the most agricultural benefit from precipitation and shallow groundwater
Improve water use efficiency
Keep runoff clean
Capture runoff and use it on the farm
Farmers, Consultants and Partners #1
NRCS wants the opportunity to assist you in development of a conservation plan that adds value to your land.
Why is NRCS ability to assist you with pond development limited to a preliminary site assessment?
Time- people w/ pond experience, broader mission
Money- program funds targeted, demand v. supply
Red tape- the federal compliance burden
Farmers, Consultants and Partners #2
This process is for ag. water supply ponds- irrigation, stock watering, wash water and cooling water.
Do you need to use this process? NRCS workload priorities might be
directed elsewhere when you request assistance.“ I won’t be able to assist you right now, but I’d like
to get some information about your needs and if time becomes available we’ll get in contact with you.”
NRCS and District folks- #1
Are we getting back into the pond business?
Is this the only training I’m going to get? Please don’t over-think this assessment
Off-site evaluationNo lay-outNo design
NRCS and District folks- #2
Use pond interest to engage in on-farm planning.“Can I get you to go on site to look at my place?”
Prelim. Site Assessment “pre-planning service” evaluate candidate site’s natural resources for
capability of land to support pond development
explain potential regulatory issues
enable early identification of problems with a proposed site that can be changed or solved because the idea is still being developed
help farmer’s develop ponds they need
will save farmer’s time in the overall process by ensuring practical alternatives, site limitations and regulatory issues are considered before large investments of time or money are made
Not all sites are good candidates: Soils and geology can cause limitations
Size of drainage area
Flood hazards
Unique cultural or environmental features
Ratio of drainage area to pond surface area affects water level At least 10:1. Not more than 30:1. Mid-range is ideal.
Good soil conservation in the drainage area is important
Rules of Thumb #1
Rules of Thumb #2
Irrigation storage: at least 1.3 to 1.5 acre-feet of storage per acre irrigated
Evaporation and seepage losses: 2.5 to 4 ft. per irrigation season
Beef cattle require at least 15-20 gallons per animal per day.
Pond may not be best alternative for livestock water supply.
NRCS has published technical references that can be used to support planning and design:
National Eng. Handbook, Ponds and Reservoirs
NC Irrigation Guide
Conservation Practice Standard: Pond (378)
Use ArcMapNavigate toArea of Potential Pond Site
Define Area of Interest
Bare Earth Data Converted to Tin
Tin Converted to 5ft Contours
Site Characteristics Question 1:Estimated
Drainage Area
For THIS Example - 10:1 Ratio of Drainage Area to Surface Area of Pond Needed
IDEAL = 20:1 Ratio
ASSUMPTION:
68 Acre Drainage Area=
6.8 Acre Pond
Site Characteristics Question 2:
Estimated Pool Area
Site Characteristics Question 3:Estimated Depth of Water
Elevation Difference - Lowest Point to Top of Pool Area
955’
931’
Site Characteristics Question 4:Estimated Embankment Height
Add 5ft to Embnakment Height for Freeboard and Spillway
960’
931’
Site Characteristics Question 5: Estimated Length of Dam
Look Downstream
What Hazards are Observed?
• Measure the Distance to Any Downstream Hazards • Create .pdfs to Attach to Assessment Showing Potential Hazards
Following General Guidelines Referenced in USDA: Ponds – Planning, Design, and Construction
Based on Embankment Height of 29ft =
Dam Width of 14ft
Ass
ume
3:1
– O
utsi
de T
oe
Assum
e 3:1 – Inside Toe
94 ft 94 ft
Estimated 188 ft of the Stream Filled by Embankment
Using Soil Data Viewer
ArcMap or Toolkit Environment
Use the NC Floodplain Mapping Program Stream
Data to Determine if a Blue Line Stream Exists
Calculate Feet of Stream Inundated by Pond
Length of NCFPMP Stream Inside Pond
MINUS
Length of Inside Toe
631 ft – 94 ft= 537 ft
Does the potential pond area fall within the boundaries of the property owned by the person?