Changes in the quality of river water before, during and after a major flood event associated with a La Niña cycle and treatment for drinking purposes

Abstract

a major flood period was investigated. The flood period (over 6 months) occurred during an intense La Niña cycle, leading to rapid and high increases in river flows and organic loads in the river water. Dissolved organic carbon (DOC) increased (2-3 times) to high concentrations (up to 16 mg/L) and was found to correlate with river flow rates. The treatability of organics was studied using conventional jar tests with alum and an enhanced coagulation model (mEnCo©). Predicted mean alum dose rates (per mg DOC) were higher before (9.1 mg alum/mg DOC) and after (8.5 mg alum/mg DOC) than during the flood event (8.0 mg alum/mg DOC), indicating differences in the character of the organics in raw waters. To assess the character of natural organic matter present in raw and treated waters, high performance size exclusion chromatography with UV and fluorescence detectors were used. During the flood period, high molecular weight UV absorbing compounds (>2 kDa) were mostly detected in waters collected, but were not evident in waters collected before and afterwards. The relative abundances of humic-like and protein-like compounds during and following the flood period were also investigated and found to be of a higher molecular weight during the flood period. The treatability of the organics was found to vary over the three climate conditions investigated.

Long-Term Changes in Water Clarity in Lake Liangzi Determined by Remote Sensing

“…In addition, flood events and heavy rainfall may have great impacts on water quality and aquatic ecosystems [20,21]. The mean SDD during the flood years (2010 and 2016) was significantly decreased compared to that of the previous year.…”

“…However, the SDD was significantly negatively correlated with water levels in Lake Liangzi (Figure 10a). High water levels could introduce terrestrial phosphorus and nitrogen from flood land areas, which could fuel algal populations [21]. Furthermore, high water levels could also cause light limitations to submerged macrophytes and reduce their effects in maintaining the water's clarity [38].…”

“…Alternatively, some extreme weather events, such as floods and heavy rainfall, may also strongly influence water quality. The immediate and short-term effects of floods and heavy rainfall on water quality are usually associated with elevated turbidity, total suspended matter and nutrient matter by inputting a large amount of domestic, industrial, and agricultural effluents into the lake [19][20][21][22]. However, little attention has been given to the effects of the relationship between anthropogenic activities and climate change on water clarity.…”

Microbiological Assessment of Tap Water Following the 2016 Louisiana Flooding

“…Additionally, flooded homes might be hotspots for the proliferation of pathogens and antibiotic resistant bacteria [7]. However, there is lack of data on the dynamics of harmful pathogens and fecal indicator bacteria in urban floodwaters, particularly due to difficulty in sampling following the aftermath of such a disaster [8,9]. According to Paterson et al [10], floods (excluding landslides) affected >74 million persons globally, resulted in 4720 deaths and had an economic cost of >$57 billion in 2016 alone.…”

Flood impacts on a water distribution network

“…The assessment of flood risk requires the evaluation of the three risk components -i.e. hazard, vulnerability and exposure -for each subsystem and the assessment of functional dependencies (Serre et al, 2011). In particular, flood hazard of a component relates to the likelihood of being flooded, which can be evaluated through flood maps; exposure is the position with respect to inundation extent and vulnerability is the proneness to being harmed (Meyer and Messner, 2005).…”