|Copyright Michael R. Martin|
Researchers in Australia examined the effect of prolonged draught on water quality in freshwater systems.
Effects of drought varied depending on the characteristics of a water body and its catchment. Water flow and volume decreases during drought tended to lead to increased salinity due to reduced dilution. And when air temperatures increased in some systems, water temperatures rose along with stratification.
“This also enhanced algal production, promoted toxic cyanobacterial blooms and lowered dissolved oxygen concentrations,” said Luke Mosley, senior research fellow at U. Adelaide and author of a drought-impact study published in Earth-Science Reviews. “Nutrient, turbidity and algal levels also often increased in lake systems due to reduced flushing and enhanced productivity.”
In contrast, Mosley found that nutrients and turbidity levels often went down during droughts in rivers that didn’t have significant loads coming in from point and non-point sources of agricultural runoff. This, he says, was due to drought’s disruption on catchment inputs and its influence on processes like biological uptake, denitrification and settling. Drought also caused a buildup of materials in these systems that resulted in large post-drought flood loadings of pH, major ions, nutrients and carbon.