Accepted 2nd August, 2020.
The study was aimed at examining the impact of nonpoint source pollutant loadings from irrigation sites on the physico – chemical water quality and biodiversity of river Ngadda, Maiduguri, Borno State, Nigeria. Water samples was collected biweekly for the period of six months from four sampling stations. The physico – chemical qualities (total nitrogen (TN), ammonium (NH4+), total phosphorus (TP), total organic carbon (TOC), total dissolved solids (TDS), turbidity (Tur) and total suspended solids (TSS)) were determined using standard methods described by APHA, (2005); Gwamna et al, (2017) with slight modification. A 40µm mesh size standard plankton net was used to filter 20l (4L x 5) of kicked and grabbed sample of water for phytoplankton examination which was preserved with 4% formalin and transported to the laboratory for determination of phytoplankton using drop and count method with the aid of key. Capture and recapture method was employed to determined the relative abundance of fish species using Lincoln index. Total Nitrogen (TN) ranges from 5.02 mg/L – 8.31mg/L, ammonium (NH4+) ranges from 0.93mg/L – 2.01, Total phosphorous (TP) ranges from 0.07mg/L – 1.81mg/L. Total Organic Carbon (TOC) ranges 5.87mg/L – 7.45mg/L, Turbidity (Tur) ranges from 27mg/L – 31mg/L, Total Dissolved Solids (TDS) ranges 198NTU – 298NTU, Total Suspended Solids ranges from 34mg/L – 47mg/L and Temperature ranges from 260C – 280C. A total of seven (7) classes and sixteen (16) species of phytoplankton were identified in all the four (4) different sampling stations. A total of four (4) families and ten (10) species of fishes were identified in the sampling stations. The study revealed that irrigation runoff adversely impact fish community of river Ngadda, hence the need for period monitoring to ensure the safety and health standard of this aquatic ecosystem.
Keywords: Non-Point Pollution, Irrigation, River Ngadda