Impacts of buffer zone degradation on some water quality parameters in the northeastern part of Lake Tana, Ethiopia

Lake Tana, which contains nearly 50% of Ethiopia’s freshwater, is experiencing growing industrialization, urbanization, and agricultural expansion. These activities, especially in the northern part, threaten the lake’s ecosystem due to increasing human impact, such as resort development. To evaluate the effects of buffer zone degradation on water quality, data were collected from four sites twice a month between December 2020 and May 2021, with three replications. Key water quality parameters were analyzed across sites with varying degrees of anthropogenic disturbance. Most parameters exhibited significant spatial variability (p < 0.01), influenced by buffer zone integrity and human activities. Water temperatures (23.30–26.04 °C) remained within optimal ranges for aquatic life, though degraded littoral sites showed marginally higher temperatures linked to reduced vegetation and increased sediment heat absorption. DO levels (6.71–7.99 mg L−1) were consistent across sites, reflecting similar atmospheric interactions. pH varied spatially (6.89–8.30), with lower values at disturbed sites attributed to organic decomposition and agrochemical runoff. Secchi depth and turbidity differed significantly (p < 0.05), with clearer waters in vegetated littoral (Debresina: 39.6 cm) and pelagic zones (105.54 cm), contrasting sharply with degraded sites (Seraba: 13.33 cm) due to erosion and sediment resuspension. Conductivity and TDS peaked at disturbed sites (Seraba: 192 µS cm−1, 142 mg L−1), reflecting nutrient and pollutant influx. Nutrient loads (TN, TP) were elevated in littoral zones, driven by agricultural runoff and wastewater, signaling eutrophication risks. Strong correlations emerged between habitat degradation (HDA score) and reduced water clarity (r = −0.97) or increased turbidity (r = 0.86). The study highlights the importance of buffer zones in protecting Lake Tana’s water quality and ecosystem. It urges policymakers to implement integrated management strategies and establish a well-defined buffer zone along the lakeshore to mitigate human-induced impacts.