Ground Water Quality Dynamics During Wet and Dry Episodes in Urban West Region of Zanzibar Island
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Date
2019-12
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Publisher
THE STATE UNIVERSITY OF ZANZIBAR
Abstract
Groundwater is the major source of water by inhabitants of Zanzibar communities without any treatment. However, the quality of this water source during both dry and wet season is not closely known, therefore, there is a question of its safety. In this study, twenty-one water sources from three districts of Urban West Region of Unguja Island were studied, from 23/05/2019 – 10/06/2019 (during wet season) and from 09/07/2019 - 26/07/2019 (dry cold season). INSITU measurement of Temperature, pH, Dissolved Oxygen (DO) and Electrical Conductivity (EC) in groundwater sources were conducted using electronic equipment known as Professional Digital Sampling System (ProDSS). The analyzed data revealed that measured parameters in groundwater are not stable rather dynamics (spatial and temporal). Temperature, pH, DO and EC range were (27.17° C - 28.88° C), (4.98 – 7.50), (3.51 mg/L – 7.51 mg/L), and (156.2 μS/cm – 2047.6 μS/cm) respectively during the wet period, while the range were (26.74° C - 28.83° C), (5.14 – 7.41), (2.71 mg/L – 7.20 mg/L), and (223.1 μS/cm – 1936.8 μS/cm) respectively during the dry period. The values of temperature and DO showed an inverse relationship between each other, and those of temperature and EC revealed a direct relationship between each other. The results revealed that a small changes in temperature within the water system led to some changes in DO and EC level in water system, and EC changes led to changes of salinity level in the water system. The analyzed data retrieved a very strong correlation between EC and salinity, where R2 linear = 0.999. Also data showed a strong correlation between data taken during the dry period and the wet period. For example between values of DO of dry period and that of wet period showed R2 linear = 0.734, and values of EC recorded during the dry period and those of the wet period showed R2 linear = 0.896. The mean values recorded for all studied parameters during wet period were 27.87° C, 6.92, 782.85 μS/cm, and 5.44 mg/L for temperature, pH, EC, and DO, respectively. While during dry period were 27.83° C, 6.97, 743.80 μS/cm, and 5.12 mg/L for temperature, pH, EC, and DO, respectively. These suggest that the groundwater in the study area is of rather good quality with values quite below and within the guideline values of WHO, MRCCC, and Washington State Department of Ecology standards although its safety is a factor affected by several parameters.
Description
Groundwater is the major source of water by inhabitants of Zanzibar communities without any treatment.
Keywords
CLIMATE CHANGE, WATER QUALITY