Assessment of the State of the Water Quality of The Lusushwana River, Swaziland, using selected Water Quality Indices

Abstract

Water quality indices are one of the major developments that have taken place in water quality monitoring. Since the development of the first water quality index various other water quality indices have been developed, utilised, modified and infused into policies by various environmental monitoring agencies. The Aquatic Toxicity Index (ATI), National Sanitation Foundation Water Quality Index (NSFWQI), Idaho Water Quality Index and the South African Scoring System (SASS) were used to evaluate the quality of the water of the Lusushwana River in Swaziland. Bimonthly samples of water and macro invertebrates were collected over a period of two months (February and March, 2010). The data was collected from five sampling points (T1 to T5) along the Lusushwna River, covering points upstream and downstream of the Matsapha Industrial Complex. The physico chemical water quality data was used to derive the physico chemical water quality indices’ scores and for comparing their concentration with the Swaziland Water Quality Objectives (SWQO) for surface water and the South African Aquatic Ecosytem Water Quality Guidelines (SAAEWQG). Aquatic macro-invertebrates were sampled and identified for the South African Scoring System version 5, devised by Chutter (1998). The ATI was calculated using the RAUWATER 2 Software, the NSFWQI was calculated using the Wilkes University online calculator for the index and the Idaho WQI was calculated using a logarithmic equation developed by Said et al. (2004). After deriving scores for these indices their values were further correlated to establish possible relationships amongst them. From this study it was concluded that the water quality of the Lusushwana River was polluted due to faecal contamination, turbidity and iron with respect to the SWQO, whilst DO (% saturation) was below the SAAEWQG stipulated range. The indices on the other hand indicated decline in water quality from site T3 to site T5. With respect to correlations between the indices it was concluded that they were all positively correlated. The correlations were, however, significant for the relationships between all physico chemical water quality indices (p < 0.05). For relationships with the indices of the SASS 5 Biotic Index the correlations were only significant between the NSFWQI and the SASS score and between the Idaho WQI and the ASPT. The other correlations (between the NSFWQI and the ASPT, the ATI and the ASPT, ATI and SASS score, Idaho WQI and SASS score) were not significant (p < 0.05). It was recommended that the study be carried out covering more sampling sessions and sampling points, covering both the rainy and dry seasons and to monitor effluent and waste water effluent downstream of the Matsapha Industrial Complex.