Tifton

1. Georgia Athens Atlanta Tifton Florida Gulf of Mexico SE Environmental Flows ConferenceRoles of Farm Ponds and Potential Impacts on Streams in the Coastal Plain of GA presented by: Jim Hook & Shane Conger National Environmentally Sound Production Agriculture Laboratory The University of Georgia, Tifton Campus http://www.nespal.org/SIRP

2. Assessment of Farm Ponds • Rationale: • Recognizing its importance for current and its potential for future water supply for irrigation, we began a study of on-farm ponds. • That has proven to be good start on the State Plan’s Assessment of surface water supply stored in its numerous small constructed and natural ponds. • Objectives: • Determine quantity and their hydrologic significance • Determine their use and utility for irrigation supply • Influence on stream flow • Explore the potential for regional reservoirs

3. Assessment of Farm PondsQuantity and their hydrologic significance The Study Area: South Georgia HUC08 (Sub-basins)

4. USGS NHD+ 2006 Waterbodies

5. Ga DOT 2003 Waterbodies

7. Natural Ponds in the Coastal Plain Landscape • Natural ponds and marshes • USGS NHD+ 2006 Waterbodies So. Ga. HUC08’s • Swamps/Marshes – 3676 – excluding mapped wetland areas • Range (1 ha to 1480 km2) • Median – 38 ha; mean - 225 ha • Total area swamps/marshes – 8,223 km2 • GA DOT 2003 Waterbodies So. Ga. HUC08’s • Swamps/Marshes – 89,059; • Range 0.001 to 456 km2) • Median – 1.3 ha; mean - 12.3 ha • Total area swamps/marshes – 10,900 km2 • Note Swamps/marshes are often mapped in several smaller segments even when they are connected during high water periods. Includes Lake/Pond waterbodies relabeled as Swamp/Marsh after examination of aerial images and Swamps/Marshes already so labeled by USGS or DOT.

9. Assessment of Farm PondsQuantity and their hydrologic significance Study area: South Georgia HUC08 Sub-basins

10. Man-made Ponds in the Coastal Plain Landscape • Man-made ponds and reservoirs • USGS NHD+ 2006 Waterbodies So. Ga. HUC08’s • Lake/Ponds – 8000 • Range (0.1 ha to 2,600 ha) • Median – 3.3 ha; mean - 7.3 ha • Total area lake/ponds – 586 km2 • GA DOT 2003 Waterbodies So. Ga. HUC08’s • Lake/Ponds – 81,500; • Range 0.001 to 3,400 ha • Median – 0.5 ha; mean - 1.4 ha • Total area lake/ponds – 1132 km2 • Note Lakes are often mapped in several smaller segments even when they are connected during high water periods.

11. Candler Co NHD/DOT Ponds

12. Transects to characterize a sample of study area ponds Random vectors 140 transects 25-60 km long 0.33 km wide

13. Transects to characterize a sample of study area ponds Any pond w/in or touched by buffered line USGS mapped DOT mapped Visible unmapped

14. Assessment of man-made ponds • Transects • Currently completed 100 transects intersecting 190 ponds (02/01/08) • Data results: Ponds size 0.09 to 90 ha • Average size of all visible ponds was 4.5 ha; median 2 ha • Average visible area mapped was 8.3 ac vs 10.6 acres for same ponds – NHD+ ponds drawn larger than current

15. Assessment of man-made ponds • Transects • Character of location re stream order • 46% on upland or unmapped ephemeral streams • 0% on mapped ephemeral • 42% on 1st order streams • 11% of 2nd order streams • 1% on 3rd or higher order

16. Assessment of man-made ponds • String of beads

20. Assessment of man-made ponds • Transects • Pond Clusters: distance to upstream and downstream ponds • 30% had nearby upstream pond • Half within 0.41 km • 50% had nearby downstream pond • Half within 0.33 km

21. Assessment of man-made ponds • Catchment areas – small to medium • Mean 143 ha; • Median 78 ha • Range 69 ha to 6800 ha • With the average size pond and average size catchment area, it requires 60 mm runoff to fill if empty • Range 2.5 mm to 250 mm

22. Assessment of man-made ponds • Proximity and Use for irrigation • 83% within 0.6 km 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

25. Assessment of man-made ponds • Begin to look at how ponds impact stream flow • When full most of the water is passed through during rain events • Acts by shaving peak flows (even small ponds designed to store 1-yr floods) moving some to base. • Seepage adds to base flow – but only from lowest in string

26. Assessment of man-made ponds • Begin to look at how ponds impact stream flow • During rainless periods ET loses; • If ponds remain full, in effect portion of channel flow or seepage lost to ET • That direct pond evaporation must be compared with ET from wetlands and forests that would otherwise occupy these pond spaces.

27. Assessment of man-made ponds • Begin to look at how ponds impact stream flow • During irrigation season, first or all of runoff will be used in refilling pond, further shaving peak and also base flow. • Act similarly to storm water retention facilities counter balancing effects of enhanced runoff from bare soils and hard surfaces.

28. Assessment of man-made ponds • Begin to look at how ponds impact stream flow • As irrigation supplies: • 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)

29. Assessment of man-made ponds • Plea for inclusion of ponds in models of behavior of watersheds • Incorrect to assume that this is a stream dominant flow system. Ponds are so ubiquitous in Georgia Coastal Plains that they must be considered in runoff - stream discharge models used water planning as well as water resources

30. Assessment of man-made ponds • Recommendations • Multi-agency and farmer assessment of pond data and pond design to address ways to improve existing pond sites for irrigation water supplies. • Assessment of pond location and pond use on flows downstream in the region’s watersheds. • Assessment of farm ponds on species and habitats in South Georgia