Tifton Georgia Florida Gulf of Mexico Atlanta Athens SE Environmental Flows Conference Roles 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

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

Assessment of Farm Ponds Quantity and their hydrologic significance The Study Area: South Georgia HUC08 (Sub-basins)

USGS NHD Waterbodies

Ga DOT 2003 Waterbodies

Natural Ponds in the Coastal Plain Landscape  Natural ponds and marshes <USGS NHD Waterbodies So. Ga. HUC08’s 6 Swamps/Marshes – 3676 – excluding mapped wetland areas 6 Range (1 ha to 1480 km2) 6 Median – 38 ha; mean ha 6 Total area swamps/marshes – 8,223 km2 <GA DOT 2003 Waterbodies So. Ga. HUC08’s 6 Swamps/Marshes – 89,059; 6 Range to 456 km2) 6 Median – 1.3 ha; mean ha 6 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.

Assessment of Farm Ponds Quantity and their hydrologic significance Study area: South Georgia HUC08 Sub-basins

Man-made Ponds in the Coastal Plain Landscape  Man-made ponds and reservoirs <USGS NHD Waterbodies So. Ga. HUC08’s 6 Lake/Ponds – Range (0.1 ha to 2,600 ha) 6 Median – 3.3 ha; mean ha 6 Total area lake/ponds – 586 km2 <GA DOT 2003 Waterbodies So. Ga. HUC08’s 6 Lake/Ponds – 81,500; 6 Range to 3,400 ha 6 Median – 0.5 ha; mean ha 6 Total area lake/ponds – 1132 km2 <Note Lakes are often mapped in several smaller segments even when they are connected during high water periods.

Candler Co NHD/DOT Ponds

Transects to characterize a sample of study area ponds Random vectors 140 transects km long 0.33 km wide

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

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

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 1 st order streams <11% of 2 nd order streams <1% on 3 rd or higher order

Assessment of man-made ponds  String of beads

Assessment of man-made ponds  Transects <Pond Clusters: distance to upstream and downstream ponds 6 30% had nearby upstream pond –Half within 0.41 km 6 50% had nearby downstream pond –Half within 0.33 km

Assessment of man-made ponds  Catchment areas – small to medium <Mean 143 ha; <Median 78 ha 6 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 6 Range 2.5 mm to 250 mm

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

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

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.

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.

Assessment of man-made ponds  Begin to look at how ponds impact stream flow <As irrigation supplies: 6 As alternative to direct stream withdrawals during dry periods that trigger irrigation 6 As alternative to GW withdrawals from aquifers that sustain base flow 6 As alternative to GW withdrawals that lower heads in areas with long term decline (confined aquifers)

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

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