Evaluation of a Small, In-field Runoff Collector

Proceedings of the 1999 Georgia Water Resources Conference, March 30 and 31, Athens, Georgia.Increased environmental concern about surface water pollution has heightened the need for small, in-field runoff collectors to assess the impact of land management practices without altering the landscape. We modified a surface flow sampler designed for sheet flow in Coastal Plain soils. Modifications were made to accommodate steep slopes (3 to 15% ), large flow rates, and channelized flow which are common in the Southern Piedmont. The runoff collector consists of two sample splitters (10x and 100x) and two sample collectors. Runoff collector performance was evaluated in the laboratory to determine percent flow captured by 10x and 100x splitters relative to flow rate and slope. Average flow captured on a 5% slope was 10.3% for 10x and 1.8% for the l00x. When the slope was increased to 12% the percent flow capture also increased slightly, 10.4% for l0x and 2.3% for l00x. It was determined that the small, in-field runoff collector captures runoff volumes at specific rates at fairly consistent ratios.Sponsored and Organized by: U.S. Geological Survey, Georgia Department of Natural Resources, The University of Georgia, Georgia State University, Georgia Institute of TechnologyThis book was published by the Institute of Ecology, The University of Georgia, Athens, Georgia 30602-2202 with partial funding provided by the U.S. Department of Interior, geological Survey, through the Georgia Water Research Insttitute as authorized by the Water Research Institutes Authorization Act of 1990 (P.L. 101-397). The views and statements advanced in this publication are solely those of the authors and do not represent official views or policies of the University of Georgia or the U.S. Geological Survey or the conference sponsors

Water Quantity and Quality from a Small Georgia Pasture During 1998-2009: Impact of Drought

Proceedings of the 2011 Georgia Water Resources Conference, April 11, 12, and 13, 2011, Athens, Georgia.The water quality impact of pasture grazing in the Piedmont, which generally occurs under low-input management, is not well studied. Cattle, hydrologic and water quality data were collected from 1999 to 2009 from a rotationally grazed 7.8-ha pasture near Watkinsville Georgia. Grazing occurred during 69 time periods, with 20 to 225 head of cattle grazing 1 to 71 days each period. Mean cattle days (head of cattle x days spent) was 182.4 ha⁻¹ grazing-period⁻¹. Drought occurred with 7 of the 11 years having below average annual rainfall. Runoff events were limited to 20 during 86 months of below average rainfall (deficit period) compared with 54 during 46 months of the non-deficit period. Instrument problems limited sample collection to 43-47 out of possible 67 events from 2000-2009. Across all data, mean event flow weighted concentration (FWC) in mg L⁻¹ was < 1.0 for nitrate-nitrogen (NO₃-N) and ammonium-nitrogen (NH₄- N), 3.7 for total nitrogen (TN), 9.1 for total organic carbon (TOC), 2.0 for ortho-P (PO₄4-P), 2.4 for total P (TP), 0.23 for iron (Fe), and 0.06 for aluminum (Al). Nutrient loads in kg ha⁻¹ event⁻¹ averaged 0.04 for NO₃-N, 0.03 for NH₄-N, 0.19 for TN, 0.54 for TOC, 0.11 for (PO₄4-P, and TP, 0.02 for Fe, and 0.01 for Al. Peak nutrient concentrations and loads occurred during calving season and/or when monthly rainfall was above average. Total load was 3 to 6 times greater from non-deficit than deficit periods. Concentrations of N were well below drinking water standards. Nevertheless observed N and P losses could pose risk of eutrophication because it can be stimulated at low concentrations. Such long-term data are needed to help states set or refine water quality standards.Sponsored by: Georgia Environmental Protection Division U.S. Geological Survey, Georgia Water Science Center U.S. Department of Agriculture, Natural Resources Conservation Service Georgia Institute of Technology, Georgia Water Resources Institute The University of Georgia, Water Resources FacultyThis book was published by Warnell School of Forestry and Natural Resources, The University of Georgia, Athens, Georgia 30602-2152. The views and statements advanced in this publication are solely those of the authors and do not represent official views or policies of The University of Georgia, the U.S. Geological Survey, the Georgia Water Research Institute as authorized by the Water Research Institutes Authorization Act of 1990 (P.L. 101-307) or the other conference sponsors

Total Coliform, E. Coli, and Enterococci Bacteria in Grazed and Wooded Watersheds of the Southern Piedmont

Proceedings of the 1999 Georgia Water Resources Conference, March 30 and 31, Athens, Georgia.Contamination of surface waters with fecal bacteria from grazinglands is a component of nonpoint source agricultural pollution. Methods are needed to limit the movement of fecal bacteria from grazinglands into surface water. We used two experimental watersheds to test for impact of cattle on total coliform, E. coli, and enterococci bacteria numbers. Grazing cattle elevated these microbe numbers but we found that positioning animals above a pond in the landscape was an effective means of reducing total coliform, E. coli, and enterococci bacteria in surface water leaving the grazed watershed. Microbe numbers in the pond outflow were similar to those in surface water from wooded watershed.Sponsored and Organized by: U.S. Geological Survey, Georgia Department of Natural Resources, The University of Georgia, Georgia State University, Georgia Institute of TechnologyThis book was published by the Institute of Ecology, The University of Georgia, Athens, Georgia 30602-2202 with partial funding provided by the U.S. Department of Interior, geological Survey, through the Georgia Water Research Insttitute as authorized by the Water Research Institutes Authorization Act of 1990 (P.L. 101-397). The views and statements advanced in this publication are solely those of the authors and do not represent official views or policies of the University of Georgia or the U.S. Geological Survey or the conference sponsors

Role of Iron-Rich Georgia Soils in Controlling Nitrate Contamination of Ground Water

Proceedings of the 2003 Georgia Water Resources Conference, held April 23-24, 2003, at the University of Georgia.Nitrate contamination of ground water is widespread in the USA, and is often associated with nutrient losses from grazing and row-crop agriculture. Studies in Georgia find, however, generally lower levels of nitrate in ground water than in many other parts of the country. The mechanisms controlling the fate of nitrate and related N compounds in groundwater are poorly understood, but the commonality of iron minerals in Georgia soils suggests iron may play a role. We monitored ground water for several solutes for a year and examined the data thermodynamically. The redox states quantified as electron activity pE between couples of N-species (NO₃⁻, NO₂⁻, NH₄+) were found to lie on the intersection of the stability field of freshly precipitated Fe(OH) ₃ with Fe²⁺ on a Pourbaix (pE-pH)diagram. Moreover, the evident redox potential relationship between these couples seems stable through time as well. This strongly suggests that the energy generating nitrification and denitrification reactions are being drawn toward equilibrium with Fe(OH) ₃/Fe²⁺₊redox couple. These observations support the hypothesis that nitrate reduction proceeds largely by oxidation of Fe²+ to an amorphous solid that subsequently recrystallizes to a meta-stable ferric hydroxide. An inverse relationship between [Fe²⁺] and [NO₃-] in GA waters noted in other studies, suggests that this phenomenon might exercise a regional control on [NO₃-] in ground waters of the southeastern USA

A Modeling Approach to Assess the Water Balance of a Typical Southern Piedmont Catchment under Long-Term No-Till Usage

Proceedings of the 2003 Georgia Water Resources Conference, held April 23-24, 2003, at the University of Georgia.We used the Root Zone Water Quality Model to simulate runoff and seepage below the root zone from a 2.7 hectare watershed to look at rates of ground water recharge under long-term, no-till crop production systems in the Piedmont of Georgia. The watershed is located at the USDA-ARS-JPCNRCC (J. Phil Campbell Sr., Natural Resource Conservation Center) in Watkinsville, Georgia. It has been in crop production under no-till and winter cover cropping management practices since 1974. The model over predicted soil moisture and slightly over predicted runoff, however, the pattern of deep seepage to ground water was distinctly different for rainfall patterns that were small and consecutive versus large rain events. Ground water depth immediately responded when root zone soil moisture was at field capacity or greater. This indicates that under saturated or field capacity soil moisture conditions, larger rain events of short duration (> 15 cm and < 30 hours in this case) are recharging ground water rather than creating significant runoff. Simulations of watershed management practices such as long-term no-till and cover cropping can serve as a useful tool to show the effects of long-term management on potential surface water contamination

A Mechanism for Storm Runoff Generation During Large Rainfall Events

Proceedings of the 2007 Georgia Water Resources Conference, March 27-29, 2007, Athens, Georgia.Flowpaths of stormwater from upland areas have long been the subject of major debate. A series of subsurface gutter experiments, situated on the mid- slope of a Piedmont catchment, were conducted to investigate a potential mechanism for the rapid mobilization of storm runoff from the unsaturated zone. Gutters were 1.45 m long and installed approximately 10 cm below the ground surface. Direct surface runoff was excluded from entering the gutters. Nearly a year of natural rainfall monitoring data showed a close relationship between rainfall intensity and the resulting runoff in the subsurface gutters. The gutter response closely followed the onset of intense rainfall and likewise “switched off” with the cessation of storm events. This behavior is not indicative of a saturated subsurface flow mechanism. Stable isotope analysis of runoff samples demonstrated that stormflow was comprised primarily of “old water,” which is water that was in the soil before the initiation of rainfall. Thus, the traditional explanations, macropore flow and overland flow, could not have been the dominant processes because they produce mainly “new water”. The data suggest that runoff from large storm events occurs when high intensity rainfall generates pressure waves that rapidly travel through the soil and induce pre-event water. Some hydrologists refer to this as a kinematic process. Research on this process at the field level will lead to understanding of stormflow pathways and the associated potential for transport of pollutants at the landscape scale.Sponsored and Organized by: U.S. Geological Survey, Georgia Department of Natural Resources, Natural Resources Conservation Service, The University of Georgia, Georgia State University, Georgia Institute of TechnologyThis book was published by the Institute of Ecology, The University of Georgia, Athens, Georgia 30602-2202. The views and statements advanced in this publication are solely those of the authors and do not represent official views or policies of The University of Georgia, the U.S. Geological Survey, the Georgia Water Research Institute as authorized by the Water Resources Research Act of 1990 (P.L. 101-397) or the other conference sponsors

No-till and Curve Numbers – A Closer Look

Proceedings of the 2011 Georgia Water Resources Conference, April 11, 12, and 13, 2011, Athens, Georgia.Since its inception in the 1950s, worldwide adoption and use of the Curve Number (CN) methodology for estimating runoff has highlighted some inconsistencies, limitations and problems. Analysis of curve numbers derived from 34 years of rainfall-runoff data, gathered from a 2.7 ha Georgia Piedmont catchment managed under no-till, showed that the average CN (57) that led to mean runoff estimate matching the mean measured runoff was 16 less than the average of the range of CN values (73) given in standard handbook tables for the catchment. The derived median value of the initial abstraction ratio (λ) was 0.04, compared to 0.2, the standard value. Many researchers recommend 0.05 for λ. Use of standard CN coefficients and values for fields managed in no-till, and possibly other conservation tillage systems, would likely lead to overestimation of runoff.Sponsored by: Georgia Environmental Protection Division U.S. Geological Survey, Georgia Water Science Center U.S. Department of Agriculture, Natural Resources Conservation Service Georgia Institute of Technology, Georgia Water Resources Institute The University of Georgia, Water Resources FacultyThis book was published by Warnell School of Forestry and Natural Resources, The University of Georgia, Athens, Georgia 30602-2152. The views and statements advanced in this publication are solely those of the authors and do not represent official views or policies of The University of Georgia, the U.S. Geological Survey, the Georgia Water Research Institute as authorized by the Water Research Institutes Authorization Act of 1990 (P.L. 101-307) or the other conference sponsors

Tillage-Based Water Conservation on Farms in the Southeastern United States

Proceedings of the 2007 Georgia Water Resources Conference, March 27-29, 2007, Athens, Georgia.Conservation tillage, particularly no-till, has a significant role to play toward achieving agricultural water conservation goals envisaged in Georgia’s Comprehensive Statewide Water Management Planning Act of 2004. We base this on scientific evidence from across the country and our own research showing that conservation tillage allows substantially more of rain and/or irrigation water to infiltrate/percolate into the soil compared to conventional tillage methods, thus reducing much runoff waste. In one study spanning May 1, 1997 to May 5, 1998 near Watkinsville, GA, we found an extra 6.93 inches of rain water infiltrated into the soil profile in a no-till cotton/rye system compared to conventional tillage. This represents 14% of the average annual rainfall and is equivalent to more than 188 billion gallons of water from one million acres of cropland, which is about a third of Georgia’s harvested cropland. Annual irrigation use in Georgia fluctuates between 100 and 300 billion gallons. Additionally, conservation tillage reduces sediment that alters critical habitat and stream flow, and reduces non-point source contaminants that require additional assimilative capacity in those streams. While the current agricultural water conservation plan rightly targets potential waste in irrigated agriculture through retrofitting irrigation system components, conservation tillage offers water conservation both in irrigated and non-irrigated agriculture. For this potential to materialize, aggressive leadership that provides both political will and appropriate resources is needed across all government agencies and non-government organizations (NGOs) involved in natural resource policy formulation, research, education, extension, and outreachSponsored and Organized by: U.S. Geological Survey, Georgia Department of Natural Resources, Natural Resources Conservation Service, The University of Georgia, Georgia State University, Georgia Institute of TechnologyThis book was published by the Institute of Ecology, The University of Georgia, Athens, Georgia 30602-2202. The views and statements advanced in this publication are solely those of the authors and do not represent official views or policies of The University of Georgia, the U.S. Geological Survey, the Georgia Water Research Institute as authorized by the Water Resources Research Act of 1990 (P.L. 101-397) or the other conference sponsors

Nitrogen and Phosphorus Losses from No-till Cotton Fertilized with Poultry Litter in the Southern Piedmont

Proceedings of the 2001 Georgia Water Resources Conference, April 26 and 27, 2001, Athens, Georgia.Adoption of conservation tillage and use of poultry litter as fertilizer in major crops is increasing in the southeastern USA. The water quality impact of these alternative cropping methods needs investigation. In a study near Watkinsville, GA, nitrate loss through drainage was similar between no-till (NT) and conventional tillage (CT) cotton (mean 8.9 vs 8.2 kg ha⁻¹). Cotton fertilized with poultry litter (PL) had higher nitrate loss than that fertilized with ammonium nitrate as conventional fertilizer (CF) (10.3 vs 6.5 kg ha⁻¹). Peak nitrate concentrations reached 30 mg L⁻¹ from CT and 15 mg L⁻¹ from NT. Cotton under PL had about 5 mgL⁻¹ higher peak concentration than CF cotton. Losses of dissolved reactive phosphorus in runoff were: 0.24, 0.25, 0.45 and 0.72 kg ha⁻¹ respectively, for CTCF, CTPL, NTCF and NTPL. There was 48% more total runoff from CT than NT.Sponsored and Organized by: U.S. Geological Survey, Georgia Department of Natural Resources, Natural Resources Conservation Service, The University of Georgia, Georgia State University, Georgia Institute of TechnologyThis book was published by the Institute of Ecology, The University of Georgia, Athens, Georgia 30602-2202. The views and statements advanced in this publication are solely those of the authors and do not represent official views or policies of The University of Georgia, the U.S. Geological Survey, the Georgia Water Research Institute as authorized by the Water Resources Research Act of 1990 (P.L. 101-397) or the other conference sponsors