Water resources are increasingly impacted by growing human populations, land use, climate change, and complex interactions among biophysical processes. In the semi-arid Western U.S., in particular, variable snowpack levels due to a warming climate and unprecedented population growth in metropolitan areas is threatening to impact water quality. In addition, the effects of urbanization on water quality vary in time and are extremely hard to capture. To more fully understand the temporal impact of urbanization on water resources, we created a real-time observatory network spanning three watersheds in northern Utah which possess similar climates and a common water source, mountain winter-derived precipitation, but differ levels of urbanization. The aquatic monitoring stations in the GAMUT Network include sensors to measure chemical (dissolved oxygen, specific conductance, pH, nitrate, and fluorescent dissolved organic matter, (fDOM)), physical (stage, temperature, and turbidity), and biological components (chlorophyll content and phycocyanin) logging every 15 minutes.
Results/Conclusions
As fall transitioned to winter, our high frequency water quality data captured runoff events in urbanized areas carrying pulses of nutrients and organic matter to rivers. In Red Butte Creek, the most urbanized of the GAMUT watersheds, pulses of fDOM occurred 22 times over a three-month period, sometimes lasting up to 3 days. By comparison, levels of fDOM remained relatively constant around 30 quinine sulfate units (QSU) in the Provo River and 1.5 QSU in the Logan River over the same time period. Further, urbanization led to more blooms demonstrated by Red Butte Creek experiencing 236 cyanobacteria blooms, measured as changes in phycocyanin. Over the same time period, 75 green algal blooms occurred, which increased chlorophyll-a concentrations an average of 313% per day compared to days without elevated levels. Photosynthetic pigment spikes were also present in the Provo River from mid-November to the end of December but to a much lesser extent (33 algal and 11 cyanobacterial). Our findings suggest that the built infrastructure, high percentages of impervious surfaces, and multiple storm drain outfalls that often accompanies the urbanization of rivers may lead to the flashier changes in water quality.