An assesssment of Travis Wetland water quality

Abstract

This report documents the results of a water quality survey of Travis Wetland, undertaken by two Lincoln University third-year students. Field sampling was undertaken in five different areas of the swamp to ensure representability, while data was collected over four occasions between April 14 and September 23, 1999 to examine variations in water quality over time. The four areas examined included the upper unmodified reaches, the willowshaded stretch and lower open reaches of Travis Stream, the central ponding area, and Angela Stream. Because of its unmodified nature, the upper Travis was used as a control from which the water quality of modified areas was compared. Standard water quality parameters were examined in order to provide a set of baseline information to the Christchurch City Council. Field observations including bird counts, a riparian assessment and an evaluation of the bank and channel conditions, whilst rainfall data was collected for analysis from the Burwood Hospital gauge. From this data, two simple hypotheses were tested- (i) that water quality would improve over time primarily as a result of the cessation of works; and (ii) that areas that had experienced the longest period since renovations would have the highest water quality. The first hypothesis was not conclusively supported by the results of the study. Although some parameters (including nitrate, turbidity and conductivity) are showing improvements, others (most notably reactive phosphates) depict either worsening or at best stable water quality over time. The second hypothesis was more favourably supported by the results. Highest overall water quality is found in the weir, which has had the longest period to recover. However, the lake, which had only just been completed prior to the beginning of fieldwork, showed surprisingly low nutrient levels, while the control exhibited the worst clarity despite remaining in its unmodified state throughout renovations. The major factors that may have upset the aforementioned hypotheses were identified as substrate type, riparian conditions (especially whether open or sheltered) and rainfall. The interrelatedness of these factors complicates the future management of water quality in the swamp. Therefore, further studies identifying and isolating the effects of such factors are required.