Effects of drought on the physicochemical, nutrient and carbon metrics
of flows in the Savannah River, Georgia, USA.
Abstract
Hydrological drought has wide-ranging impacts on water quality, nutrient
and carbon metrics that are critical to investigate with the increased
drought frequency predicted with climate change. This study compared
physicochemical parameters (temperature, conductivity, pH and DO),
nutrients (TN, NO X, NH 3, TP) and
carbon (TOC and DOC) between hydrological drought conditions
(2006–2009) and hydrological normal conditions (2016–2019) at five
sites along the lower Savannah River (Georgia, USA). We unexpectedly
found temperature (F 1,220=4.27, p=0.04) was
significantly lower during drought conditions. Levels of pH (F
1,220=11.99, p<0.01) and DO (% saturation; F
1,220=9.17, p=0.01; and mg L –1; F
1,220=4.04, p<0.01) were significantly higher
during drought. We found TN (F 1,220=5.23, p=0.02), TOC
(F 1,220=30.22, p<0.01) and DOC concentrations
(F 1,220=30.22, p<0.01) were significantly
lower during drought, but NO X concentrations (F
1,219=4.04, p=0.05) were significantly higher during
drought. Conductivity only varied at the lower river sites, being
significantly higher during drought at Sites 3 (F
1,47=12.56, p<0.01), 4 (F
1,47=12.96, p<0.01) and 5 (F
1,34=17.60, p<0.01). These complex changes
could be attributed to volume reductions coupled with an increase in the
percentage of total flow originating from groundwater and limnetic
reservoir inputs, persistent point source pollution, reduced natural
catchment inputs and/or reduced floodplain interactions. The changes
that occurred during drought may be disruptive to aquatic life, not only
from reduced water quantity but also due to a scarcity of some
biologically essential materials and lower food resources, combined with
artificially high levels of some other potentially stressful materials.