ASSIGNMENT OF THE HUMAN ACTIVITIES ON WATER QUALITY IN NASOLO RIVER

Rivers provide several ecosystem services that support human beings as well as a variety of plants and animal species from all sources, including terrestrial, marine, and other aquatic ecosystems. However, poor water quality as a result of increasing human activities leads to biodiversity losses and high rates of waterborne disease. This study focused on assessing the influence of human activities on water quality in relation to physico-chemical and microbiological water quality analysis and the species abundance of macroinvertebrates in Nasolo River. Firstly, the study employed laboratory and in-situ measurements of physico-chemical and microbiological water quality variables at four sampling sites that were interpreted by developing a National Sanitation Foundation Water Quality Index (NSFWQI) to depict the overall water quality status. Secondly, this study also employed South Africa Scoring System Version 5 (SASS5) biomonitoring techniques to collect and identify suitable biological indicators whose presence or absence, abundance and diversity reflect environmental conditions. The macroinvertebrates data was interpreted by calculating average scores per taxon (ASPT) values to also depict the overall water quality status. A total of six orders of macroinvertebrates were identified including the Ephemeroptera, Diptera, Trichoptera, Annelida, Coleoptera and Turbellaria. Water samples were collected by grab sampling technique. A multi-probe Aqua meter was used to obtain values of pH that ranged from 6.4 to 7.7, conductivity and temperature ranged from 71.7 to 1896.7μs/cm and 19.47 to 23.80C respectively, salinity and Total Dissolved Solids (TDS) ranged from 0.03 to 1 ppt and 53 to 1234mg/L respectively, dissolved oxygen and oxidation-reduction potential ranged from 2.1 to 5.2 mg/L and -11.6 to 6.27 millivolts respectively. A membrane filtration method was used to determine faecal coliforms that ranged from 10 to 1966 Colony Forming unit/100mL and total coliform that ranged from 126 to 2313 CFU/100Ml. In addition, a hydrotest photometer (HT 1000) was also used to analyze turbidity and total suspended solids that ranged from 10 to 51 NTU and 14 to 52mg/L respectively without the use of coloring reagents. The photometer also helped to analyze nitrates and ammonia that ranged from 20 to 68.9 mg/l and 2.27 to 5.6mg/L respectively with the use of coloring tablets and powdered reagents. Lastly, a correlation analysis between the NSF water quality index and ASPT (biotic index) was carried out to quantify the degree to which the two indices are related. The results revealed that both the water quality and biotic indices were strongly correlated. Both indices indicated that sampling site 1 at the upstream of Nasolo River was moderately polluted. For the other sampling sites 2,3 and 4, both indices indicated that those sites were seriously polluted. Overall, the outcome of this study showed that human activities led to poor water quality in Nasolo River that poses an ecological risk to aquatic biota. Therefore, biomonitoring techniques have to be employed for surface water resources in Malawi in conjunction with physico-chemical and microbiological water quality assessments to obtain a more comprehensive studies of ecological health of watersheds.