Abstract:
The objective of this study is to evaluate the surface water quality of the Lunawa
Lagoon in terms of physio-chemical parameters. The water quality was surveyed
from October 2015 to March 2016 by using eight different sample points. A total of
six water quality parameters, namely, water temperature, pH, Electrical Conductivity
(EC), Dissolve Oxygen (DO), Salinity, and Turbidity, were measured in-situ, while
laboratory analysis included five chemical parameters namely, nitrate, phosphate,
Total Dissolve Solids (TDS), Biological chemical oxygen demand (BOD), and
Chemical oxygen demand (COD). To identify natural and human impacts, the study
deployed a questionnaire survey using 50 samples in accordance with the random
stratified sampling method; spatial variation was analysed using Invers Distance
Interpolation (IDW). Arc GIS 10.1 was performed to prepare spatial distribution
maps. Temporal variation was analysed and correlation calculated using MS Excel
2013. The study revealed that the pH level ranged between 7.1 and 7.7. Water
temperature had an average of 29.4°c to 29.6°c. DO average level was 1.4mg/l to
3.2mg/l across the sites, and the turbidity range was 27.4 to 7.3NTU. The salinity
average range was 10.4ppm to 28.4ppm. The nitrate concentration was high in the
southern part and the phosphate concentration was high in the northern part of the
lagoon. The BOD and COD averages in the lagoon were 281.81mg/l and 44.81mg/l
respectively. There were high negative correlations between pH and rainfall (r = -
0.81), EC / rainfall (r = -0.83) and high positive correlation between turbidity and
rainfall (r = 0.99), dissolve oxygen / rainfall (r = 0.92). According to the Water
Quality Index in the lagoon, this water is not suitable for drinking, bathing, aquatic,
and agricultural purposes.
