Water quality degradation of coastal waterways in the Wet Tropics, Australia

The Wet Tropics region of north Queensland has outstanding environmental values, contains the highest biological diversity in Australia, and borders the Great Barrier Reef. Comparable to other tropical areas worldwide, increasing urban and agricultural development in the Wet Tropics has caused concerns with respect to ecosystem degradation due to poor water quality in freshwater reaches and marine environments. Key issues currently identified in the Wet Tropics include erosion and subsequent stream turbidity and sedimentation, nutrients from erosion and fertiliser use and pesticide residue contamination. Issues such as reduced dissolved oxygen, acid sulfate soil runoff, and biological factors such as weed infestation, reduced and degraded riparian vegetation condition, and flow modification have also been identified. These issues mainly arise from agricultural activities with lesser effects from urban development. Management of pollution to improve in-stream water quality requires a long-term monitoring program to characterize water quality conditions over different flows and seasons. This type of monitoring program is underway; however, the focus is on the Great Barrier Reef and does not fully consider freshwater ecosystem health. Another major issue is the lack of a fully developed conceptual framework that links changed land use to water quality and subsequently to aquatic ecosystem health. In this paper, we establish the current level of water quality knowledge in the Wet Tropics while outlining a conceptual framework connecting changing land management practices and their effects to water quality and to ecosystem health

Fine-suspended sediment and water budgets for a large, seasonally dry tropical catchment: Burdekin River catchment, Queensland, Australia

The Burdekin River catchment (~130,400 km2) is a seasonally dry tropical catchment located in north-east Queensland, Australia. It is the single largest source of suspended sediment to the Great Barrier Reef (GBR). Fine sediments are a threat to ecosystems on the GBR where they contribute to elevated turbidity (reduced light), sedimentation stress, and potential impacts from the associated nutrients. Suspended sediment data collected over a 5 year period were used to construct a catchment-wide sediment source and transport budget. The Bowen River tributary was identified as the major source of end-of-river suspended sediment export, yielding an average of 530 t km−2 yr−1 during the study period. Sediment trapping within a large reservoir (1.86 million ML) and the preferential transport of clays and fine silts downstream of the structure were also examined. The data reveal that the highest clay and fine silt loads—which are of most interest to environmental managers of the GBR—are not always sourced from areas that yield the largest total suspended sediment load (i.e., all size fractions). Our results demonstrate the importance of incorporating particle size into catchment sediment budget studies undertaken to inform management decisions to reduce downstream turbidity and sedimentation. Our data on sediment source, reservoir influence, and subcatchment and catchment yields will improve understandings of sediment dynamics in other tropical catchments, particularly those located in seasonally wet-dry tropical savannah/semiarid climates. The influence of climatic variability (e.g., drought/wetter periods) on annual sediment loads within large seasonally dry tropical catchments is also demonstrated by our data

Effects of Stock Use and Backpackers on Water Quality in Wilderness in Sequoia and Kings Canyon National Parks, USA

During 2010-2011, a study was conducted in Sequoia and Kings Canyon National Parks (SEKI) to evaluate the influence of pack animals (stock) and backpackers on water quality in wilderness lakes and streams. The study had three main components: (1) a synoptic survey of water quality in wilderness areas of the parks, (2) paired water quality sampling above and below several areas with differing types and amounts of visitor use, and (3) intensive monitoring at six sites to document temporal variations in water quality. Data from the synoptic water quality survey indicated that wilderness lakes and streams are dilute and have low nutrient and Escherichia coli concentrations. The synoptic survey sites were categorized as minimal use, backpacker-use, or mixed use (stock and backpackers), depending on the most prevalent type of use upstream from the sampling locations. Sites with mixed use tended to have higher concentrations of most constituents (including E. coli) than those categorized as minimal-use (P ≤ 0.05); concentrations at backpacker-use sites were intermediate. Data from paired-site sampling indicated that E. coli, total coliform, and particulate phosphorus concentrations were greater in streams downstream from mixed-use areas than upstream from those areas (P ≤ 0.05). Paired-site data also indicated few statistically significant differences in nutrient, E. coli, or total coliform concentrations in streams upstream and downstream from backpacker-use areas. The intensive-monitoring data indicated that nutrient and E. coli concentrations normally were low, except during storms, when notable increases in concentrations of E. coli, nutrients, dissolved organic carbon, and turbidity occurred. In summary, results from this study indicate that water quality in SEKI wilderness generally is good, except during storms; and visitor use appears to have a small, but statistically significant influence on stream water quality