Fisheries Resource Management, Central Institute of Fisheries Education, Indian Council of Agriculture Research, Panch Marg, Off-yari Road, Versova, Mumbai, 400 061, India.
Centre of Studies in Resources Engineering, Indian Institute of Technology (IIT), Bombay, Powai, Mumbai, 400 076, India.
Environ Monit Assess. 2019 Aug 22;191(9):586. doi: 10.1007/s10661-019-7740-5.
Lakes and reservoirs around the world are facing a substantial water quality degradation problem that poses significant environmental, social, and economic impacts. Reservoir productivity is influenced primarily by the climatic, morphometric, and hydro-edaphic features. High nutrient loadings in the reservoir from agriculture runoff often provide ideal conditions for algal blooms, leading to eutrophication. Reservoir and lake management to prevent or reduce eutrophication, therefore, has become the need of the hour. The traditional approach of trophic state monitoring by rigorous field surveys and eutrophication modeling has been revised in the present study by developing a new trophic state index (TSI)-based model for tropical shallow freshwater reservoirs. The new model has been constructed based on Carlson's Limnology and Oceanography, 22, 361-369, (1977) guidelines by establishing an empirical relationship between trophic parameters including total phosphorus (TP), Secchi disk depth (SDD), and chlorophyll (Chl-a). After comparing the new model with various earlier models for its applicability and validation with actual field conditions, it was found to be most precise over previous TSI models. Temporal and spatial fluctuations in the water quality of the Tiru reservoir were primarily attributed to the changing climatic conditions during the study period. Seasonal monsoon with less frequency, heavy nutrient loading from agriculture runoff, and increased turbidity due to a high level of sediment inflow during monsoon raised the TSI (SDD) values of the Tiru reservoir to place it in the hyper-eutrophic class. Average TSI values during winter for SDD, Chl-a, and TP were indicative of the meso-eutrophic to eutrophic state. Saturation of nutrients due to low water level during summer season caused the poly-eutrophic condition for TSI (SDD)- and TSI (TP)-based estimates and eutrophic condition as per TSI (Chl-a) estimates. However, seasonal deviations of the TSI values based on the relationship between TSI (Chl-a) and TSI (SD) indicated a predominance of smaller particles (non-algal turbidity) during all seasons. Even though TP present in the Tiru reservoir is controlling the algal production, it is also affected by low-light conditions due to non-algal turbidity. The recommendation from this study is that the TSI method for estimating the health of the water bodies is the efficient, cost-effective, and time-saving approach. The model developed during the study would help managers and policy makers to take necessary steps to reduce eutrophication levels in the reservoir and would be helpful for researchers in developing new concepts and protocols, mainly focusing on shallow freshwater reservoirs.
世界各地的湖泊和水库正面临着严重的水质恶化问题，这对环境、社会和经济都产生了重大影响。水库的生产力主要受气候、形态和水文土壤特征的影响。农业径流中的高养分负荷通常为藻类大量繁殖提供了理想的条件，导致富营养化。因此，对水库和湖泊进行管理以防止或减少富营养化已成为当务之急。目前，本研究通过开发一种新的基于营养状态指数（TSI）的热带浅层淡水水库模型，对传统的通过严格的野外调查和富营养化模型进行营养状态监测的方法进行了修订。该模型是根据 Carlson 的《湖泊学和海洋学》（Limnology and Oceanography，22，361-369，1977）中的准则，通过建立包括总磷（TP）、透明度（SDD）和叶绿素（Chl-a）在内的营养参数之间的经验关系来构建的。在对新模型的适用性进行比较，并根据实际现场条件对其进行验证后，发现该模型比以前的 TSI 模型更精确。Tiru 水库水质的时空波动主要归因于研究期间气候条件的变化。季节性季风的频率降低、农业径流带来的大量养分负荷以及季风期间由于高泥沙流入导致的浊度增加，使得 Tiru 水库的 TSI（SDD）值升高，使其处于超富营养级。冬季 SDD、Chl-a 和 TP 的平均 TSI 值表明其处于中营养到富营养状态。夏季由于水位低导致养分饱和，使得 TSI（SDD）和 TSI（TP）基于估计的多富营养条件和 TSI（Chl-a）基于估计的富营养条件。然而，基于 TSI（Chl-a）和 TSI（SD）之间关系的 TSI 值的季节性偏差表明，所有季节都存在较小颗粒（非藻类浊度）的优势。尽管 Tiru 水库中的 TP 控制着藻类的生长，但它也受到非藻类浊度导致的低光照条件的影响。本研究的建议是，TSI 方法是一种高效、经济、省时的评估水体健康的方法。研究中开发的模型将帮助管理者和决策者采取必要措施来降低水库的富营养化水平，并有助于研究人员开发新概念和协议，主要侧重于浅层淡水水库。
