Assessment of the influence of water quality on the primary productivity of the mtera dam, Tanzania

Abstract

Mtera Dam, the largest dam in Tanzania, was built primarily for hydroelectric power generation. It also serves other potential purposes, including fishing, irrigation, and community water supply. Despite government efforts, fish production in the dam has decreased, and pollution levels have increased due to disturbances caused by anthropogenic activities. This study investigated the influence of physical and chemical water quality parameters on Mtera Dam's primary productivity. Water samples were collected from three fish landing sites and each site was divided into strata I (shallower part) and strata II (Deeper part). Temperature (temp), dissolved oxygen (DO), pH, total dissolved solids (TDS), electrical conductivity (EC), turbidity (Turb), phosphate (PO43-), nitrate (NO3-), nitrite (NO2-), silicate (SiO2), and chlorophyll a (Chl-a) were measured. Most parameters fell within allowable limits, except for temperature, which exceeded them, and pH levels, which approached maximum standards (8.48±1.01) in the dry season. Measurements were as follows: pH (7.71±1.07), temp (30.64±4.17°C), DO (7.72±1.22 mg/L), TDS (120.23±11.10 mg/L), EC (239.68±22.87 µS/cm), Turb (165.37±22.59 NTU), PO43- (3.25±3.85 mg/L), NO3- (11.88±6.75 mg/L), NO2- (9.27±6.49 mg/L), SiO2 (7.72±4.09 mg/L), and Chl-a (8.08±7.03 mg/L). Physicochemical parameters exhibited significant variations across seasons and stations (p < 0.01) and showed a significant correlation with primary productivity (p < 0.01). Linear regression results indicated that physicochemical parameters positively influenced primary productivity (p < 0.01). Chl-a significantly varied between strata I and strata II in dry (4.34 ± 3.04 mg/L) and wet seasons (11.82 ± 5.04 mg/L) within a range of 1.4 mg/L to 24.42 mg/L. The study observed changes in primary productivity as water quality variables fluctuated. Therefore, implementing a more comprehensive and adaptive management approach that includes long-term, improved water quality monitoring programs is necessary.