Woldeab Bizuneh, Ambelu Argaw, Efrem Zewdu, Deribe Siyoum, Megersa Moa, Alemu Tibebu, Mereta Seid Tiku
Department of Biodiversity Conservation and Ecotourism, College of Agriculture and Natural Resource Madda Walabu University, P.O. Box 247, Robe, Ethiopia.
Division of Water and Health, Ethiopian Institute of Water Resources, Addis Ababa University, Ethiopia.
Heliyon. 2023 Jun 24;9(7):e17474. doi: 10.1016/j.heliyon.2023.e17474. eCollection 2023 Jul.
The objective of this research was to investigate the variation of water quality parameters at different depths of the Gilgel Gibe I reservoir in Oromia Jimma zone during wet seasons. Five stations within the reservoir were selected, and water quality parameters were determined at four different depths (surface, 5 m, 10 m, and 15 m). Water quality parameters were analyzed on-site using a HACH, HQ40d portable multi-meter, and turbidity was measured using Wag tech turbidity meter and in the laboratory using the standard method. Comparison of water quality parameters among depths were conducted using one-way ANOVA and Tukey's pairwise comparisons with 5% significance level. The probable contributing source of the investigated physicochemical water quality parameters at different depth was identified using Principal components analysis. The results show that depth wise except for total suspended solids (TSS), total dissolved solids (TDS), total phosphorus (TP) and soluble reactive phosphorus (SRP) the rest showed statistically significant difference at p < 0.05 level. Negative correlations were found between depth and dissolved oxygen (DO), water temperature, pH, nitrate (N0) and chlorophyll (Chl.a) while positive correlations were found between electrical conductivity (EC), biochemical oxygen demand (BOD), turbidity and N0. The study revealed that the release of nutrients associated with increased concentration of BOD5 at the bottom depth caused low concentration of dissolved oxygen due to oxygen consumption. This was further aggravated through the decomposition of organic matter, indicating organic pollution resulting from runoff from the catchment. The presence of dense masses of blue-green algae in the pelagic zone of Gilgel Gibe I reservoir suggested the presence of ample nutrients for its blooming and significant reduction of water quality, indicating possible eutrophic conditions. Therefore, catchment management is required to protect aquatic life and the reservoir function as a whole from reservoir water quality degradation.
本研究的目的是调查雨季期间奥罗米亚吉马地区吉尔格尔吉贝一号水库不同深度的水质参数变化。在水库内选择了五个站点，并在四个不同深度（水面、5米、10米和15米）测定水质参数。使用哈希HQ40d便携式多参数水质分析仪在现场分析水质参数，使用瓦格科技浊度仪测量浊度，并在实验室采用标准方法进行测量。使用单因素方差分析和5%显著性水平的Tukey成对比较法对不同深度的水质参数进行比较。利用主成分分析法确定了不同深度所调查的理化水质参数的可能贡献源。结果表明，除总悬浮固体（TSS）、总溶解固体（TDS）、总磷（TP）和可溶性活性磷（SRP）外，其他参数在深度方向上在p<0.05水平上存在统计学显著差异。深度与溶解氧（DO）、水温、pH值、硝酸盐（NO）和叶绿素a（Chl.a）之间呈负相关，而电导率（EC）、生化需氧量（BOD）、浊度和NO之间呈正相关。研究表明，底部深度与BOD5浓度增加相关的营养物质释放导致溶解氧浓度降低，这是由于氧气消耗所致。通过有机物分解，这种情况进一步加剧，表明集水区径流造成了有机污染。吉尔格尔吉贝一号水库中上层水域存在大量蓝绿藻，表明有充足的营养物质使其大量繁殖，水质显著下降，表明可能存在富营养化状况。因此，需要进行集水区管理，以保护水生生物和整个水库功能，防止水库水质恶化。
