Elucidating Differences in Limnological Parameters of Three Ghanaian Reservoirs (Tono, Bontanga and Golinga)

Abstract

Reservoirs play a crucial role in sustaining fisheries and local livelihoods; however, their ecological dynamics in dryland environments remain understudied. This study examines the spatial and seasonal variations in key physicochemical parameters, including chlorophyll a, temperature, electrical conductivity, dissolved oxygen, pH, and turbidity, across three reservoirs (Tono, Bontanga, and Golinga) in Ghana. Understanding these variations is essential for sustainable reservoir management, particularly in the context of increasing anthropogenic pressures. Water quality parameters were monitored in situ using an OTT Hydrolab DS5X multi-parameter water quality probe, while nutrient concentrations were analysed using a TECAN-plate reader and a combustion analyzer (TOC-V, Shimadzu). Data were collected over one year, covering dry, pre-wet, wet, and post-wet seasons. Linear models with Gaussian error terms were used to assess variability, with degrees of freedom and sample sizes explicitly stated for statistical robustness. Results revealed significant spatial variation in o-SiO₄⁴⁻ concentrations (F₂,29 = 7.252, p = 0.0028), with the largest and deepest reservoir, Tono, exhibiting the highest concentration (0.762 mg L⁻¹), likely due to geological inputs or hydrodynamic factors. Dissolved organic carbon (DOC) concentrations also varied significantly among reservoirs (F₂,27 = 6.798, p = 0.0041), with the smallest and shallowest reservoir, Golinga, recording the highest levels (533.63 μM), significantly exceeding Tono (350.02 μM, p = 0.0098) and Bontanga (359.40 μM, p = 0.0108). Similarly, Golinga had significantly higher total dissolved nitrogen (TDNb) concentrations (F₂,27 = 6.798, p = 0.0041), reaching 80.22 μM compared to Tono (31.98 μM, p = 0.0011) and Bontanga (44.40 μM, p = 0.0269). These findings suggest that Golinga is more impacted by anthropogenic activities, such as agricultural runoff and organic matter input, leading to greater nutrient accumulation and water turbidity. Despite seasonal variations, dissolved oxygen concentrations in all reservoirs remained within optimal ranges for sustaining aquatic life. The high nitrate-nitrogen levels stimulated photosynthetic activity, as evidenced by occasional algal blooms. Anthropogenic activities, such as agricultural runoff and domestic waste disposal, disproportionately impacted the Golinga reservoir, contributing to increased DOC, TDNb, NO2-N, and turbidity. These findings underscore the urgent need for improved regulatory enforcement to mitigate human-induced degradation. Future research should focus on long-term ecological monitoring to assess the resilience of reservoir ecosystems in dryland regions.