Challenges for contact recreation in a tropical urban lake: assessment by a water quality index

Abstract

Water pollution control is challenging in catchments affected by ‘informal’ urban development. Lake Pampulha, an impoundment that is a major tourist focus within the municipality of Belo Horizonte, Minas Gerais state, Brazil, provides an example of degradation of aquatic environments by disorganised urbanization. We evaluated the current recreational suitability of the lake using state government monitoring data (2012-2017) with reference to Brazilian legislation and a water quality index for contact recreation in Brazilian freshwaters, considering E. coli (indicating faecal pollution and microbial hazards), cyanobacterial density (health risks and aesthetic quality), turbidity (aesthetics and safety associated with visual clarity), and pH (safety and eye-comfort). Our results show that, despite investments in pollution control, the recreational water quality of Lake Pampulha remains very poor. Contact recreation was most limited by persistent cyanobacterial blooms, but also faecal contamination and low visual water clarity. The effects of high phosphorus loading and faecal contamination from unsewered domestic wastewater is exacerbated by a tropical climate, promoting stable thermal stratification (favouring cyanobacterial dominance) and turbid wet-season runoff. Water quality indexing is a powerful tool not just for interpreting and communicating multiple metrics affecting water resources, but also for guiding rehabilitation efforts and tracking progress.