THE EFFECT OF SEASONAL RAINFALL VARIABILITY ON WATER QUALITY IN LAKE MUTANDA CATCHMENT, SOUTHWESTERN UGANDA

Abstract

Despite the vital importance of reliable data sets on the current effect of seasonal rainfall variability on water resources in Lake Mutanda catchment of southwestern Uganda, little is known about the status of this phenomenon. Lake Mutanda and its catchment provide water for domestic use, and irrigation. This study was aimed to assess the effects of seasonal rainfall variability on physicochemical and bacteriological water quality of Lake Mutanda and its catchments, and to suggest the water management strategies for local farmers in response to rainfall variability. Physicochemical quality parameter such as turbidity, temperature, calcium, electrical conductivity, pH, chemical oxygen demand, and nitrate was analyzed using standard method. A mixed research designs utilizing both qualitative and quantitative data collection methods was used regarding agricultural water management practices. A total of 397 respondents were selected to participate in the study using simple random and multistage sampling techniques. Survey questionnaires and key informant interview methods of data collection was also used. In terms of physicochemical quality, nitrates (7.50±0.71 mg/L), calcium (70.50±0.71 mg/L), pH (7.33±0.04), electrical conductivity (188.00±5.66 uS/cm), chemical oxygen demand (4.50±0.71 mg/L) were within the WHO guidelines during wet and dry seasons. However, turbidity (38.0±2.940 NTU), temperature was (19.20±0.14 °C), magnesium (138.5±6.36 mg/L), phosphates (9.00±0.00 mg/L), and dissolved oxygen (5.85±0.64 mg/L) were above the permissible limits (WHO, 2017) in both seasons. The study revealed that water samples from all the sampling sites contains high level of fecal coliforms (4.00±0.07 CFU/100 mL), total coliforms (16.00±1.41 CFU/100 mL), and total bacterial account (16.00±1.41 CFU/100 mL), and were not within the acceptable WHO permissible level (0/100 mL). The obtained results show poor lake water management but people use it untreated. However, there is moderate understanding of agricultural practices as reported by farmers: Mulching (38%), terracing (20%), and contour farming (15%) which would be imperative in the conservation of water quality in Lake Mutanda. Therefore, there is need for considering continuous public training, protection of water catchment areas, monitoring of water quality and treatment of water in Lake Mutanda by policy makers before the water is supplied to the public for domestic use