Mungonya River is subjected to anthropogenic activities impacts from upstream to
downstream, because of rapid population increases in the basin. The main pollution
sources include irrigation, washing, bathing, brick making, sand mining and grazing.
This study was conducted from December 2015 to March 2016 at six selected sampling
points from the upper reaches of the river. The main aim was to assess water quality for
river health using selected physico-chemical, biological parameters and
macroinvertebrates using the TARISS scoring system in relation to land use and land
cover changes. The National Sanitation Foundation Water Quality Index (NSFWQI) and
TARISS scoring system methods were used to assess the water quality of the river.
Eleven water quality parameters were analyzed and only two were tested in-situ,
namely temperature and DO, and four were tested on-site namely, pH, EC, TDS and
turbidity, while five were tested in the laboratory (BOD5, PO4
-3, NO3
-
, TSS and FC). The
physico-chemical and biological results were within acceptable standards, except for
turbidity (202.5-413.2 NTU) and FC (270.0-616.5 cfu/100ml). It was concluded that the
significant increases in irrigation and settlements Land Use Land Cover from 2013 to
2016 were correlated to changes in water quality parameters. The current water quality
status of the river was within acceptable standards, except for turbidity and faecal
coliforms, with the NSFWQI confirming that the water quality status was medium or
average. The TARISS rapid bioassessment method also showed that the river health
was fair and there was a weak significant correlation between NSFWQI and TARISS,
suggesting complimentarity of the two indices. It was recommended that there should
be means of control and mitigation of further pollution of the river and that further
studies should be carried out along the river, covering different seasons, in order to
establish the status of water quality of the entire river and to establish proper means of
managing the river as proposed in the Integrated Water Resources Management and
Development Plan (2015) for LTBWB. It is also recommended that the LTBWB should
develop a water quality database in order to facilitate improved water quality
monitoring.