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Georgia Water Resources Conference

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Author: Golladay, Stephen W. × Author: Hicks, David W. ×

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    Indicators of Long Term Hydrologic Change in the Flint River
    (Georgia Institute of Technology, 2013-04) Golladay, Stephen W. ; Hicks, David W.
    The occurrence of three substantial climatic and hydrologic droughts since 1998 has raised concerns about water supply and stream flow throughout Georgia. This concern is acute in the Flint River Basin where low flows of unusual duration and magnitude were observed. The Flint River is essentially unregulated, originating just south of Atlanta and joining the Chattahoochee River to form Lake Seminole in southwestern Georgia. In addition to being an important water supply, the Flint River is noted for its biological and habitat diversity. For our analyses we used long term daily flow records from four stations (USGS: 02344478 – Griffin, 02347500 – Carsonville, 0234750 – Montezuma, 02353000 – Newton) to examine potential changes in hydrologic characteristics. We compared the period of 1940-1974 to 1975-2010, with the later period representing extensive development and population growth in the upper basin, and expansion of irrigated agriculture in the lower basin. Trends in rainfall were compared over the same intervals. No long term changes in annual rainfall were observed. Cycles of above and below average rainfall were observed as were periodic multi-year droughts. Annual water yields (annual CFS/watershed area at the station) ranged from 1.0 to 1.6 CFS/mi2 at all stations during most years. A declining tendency was observed at each station during the 1975-2010 interval, but was only significant at the Montezuma Station (p = 0.04). Winter yields showed similar declines only being significantly lower at the Griffin Station (p = 0.05). Summer yields were lower at all sites and significant declines were observed at Griffin, Carsonville, and Newton (p < 0.05). Calculation of 32 hydrologic indicators showed that the frequencies of low June-September median monthly flows, 1-day, 3-day, 7-day, and 30-day low flows were more common in the 1975-2010 interval at all stations. Our results indicate that human water use is causing increased severity and duration of low flows during the spring and summer seasons throughout the Flint River. These tendencies are pronounced during seasonal and extended droughts. Increased demand is the result of population expansion in the upper basin and irrigation expansion in the lower basin. Current rates of water use are likely unsustainable and pose a significant threat to stream health and the unique biological diversity characteristic of the Flint River.
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    Stream Flow Changes Associated With Water Use and Climatic Variation in the Lower Flint River Basin, Southwest Georgia
    (Georgia Institute of Technology, 2007-03) Golladay, Stephen W. ; Hicks, David W. ; Muenz, Tara K.
    In the 1970’s agricultural water use expanded rapidly in the lower Flint River Basin resulting from the introduction of center pivot irrigation technology. The rapid expansion has raised concerns about impacts on regional stream flows essential to support aquatic fauna. Using long-term stream gage records from the USGS and climate data, we analyzed trends in stream flow in two major sub-watersheds and regional patterns of rainfall from 1940 through 2004. We observed no change in annual rainfall but seasonality changed with winters being slightly wetter. Minimum flows showed substantial declines since the development of irrigation. We attribute altered stream flows to increased regional water demand however; the demand for water is also exacerbated by long-term variations in climate and rainfall distribution.
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    The Effects of the 2000 Drought on Freshwater Mussels in the Lower Flint River Basin
    (Georgia Institute of Technology, 2003-04) Golladay, Stephen W. ; Gagnon, Paula ; Kearns, Margaret ; Battle, Juliann ; Hicks, David W.
    A drought during the summer of 2000 caused record low flows in the lower Flint River Basin (FRB) and many perennial streams dried or became intermittent. Pre-drought surveys conducted in 1999 allowed an assessment of the impact of the drought on mussel assemblages. During 2001, 21 stream reaches which had abundant or diverse mussel assemblages were resurveyed. Where possible, study sites were classified as flowing or non-flowing during the drought. Mussel abundance at sites classified as non-flowing showed significant declines (median value 80% decrease) compared to flowing sites (median value 5% increase). Generally, greatest declines in mussel abundance occurred in the mid-reaches of the major tributaries of the lower Flint River. Declines in mussel populations appear to be associated with unusual climatic conditions and increasing demand on the area streams and the regional aquifer system for irrigation water supply.