The variations in water quality parameters and trophic status of a multipurpose reservoir in response to changing intensity of monsoon rain was investigated by applying a trophic state index deviation (TSID) analysis and an empirical regression model to the data collected in two periods from 2014 to 2017. The reservoir in general maintained mesotrophic conditions, and Carlson’s trophic state index (TSIc) was affected most by TSI_TP. Nutrient concentrations, particularly phosphorus, did not show strong correlations with precipitation, particularly in the period with weak monsoon, and a significant increase in total phosphorus (TP) was observed in Spring 2015, indicating the possibility of internal phosphorus loading under decreased depth and stability of water body due to a lack of precipitation. TSI_Chl was higher than TSI_SD in most data in period 1 when a negligible increase in precipitation was observed in the monsoon season while a significant fraction in period 2 showed the opposite trend. Phytoplankton growth was not limited by nutrient limitation although nutrient ratios (N/P) of most samples were significantly higher than 20, indicating phosphorus-limited condition. TSID and regression analysis indicated that phytoplankton growth was limited by zooplankton grazing in the Spring, and that cell concentrations and community structure in the monsoon and post-monsoon season were controlled by the changing intensity of the monsoon, as evidenced by the positive and negative relationships between community size and cyanobacterial population with the amount of precipitation in the Summer, respectively. The possibility of contribution from internal loading and an increase in cyanobacterial population associated with weak monsoon, in addition to potential for nutrient enrichment in the post-monsoon season, implies a need for the application of more stringent water quality management in the reservoir that can handle all potential scenarios of eutrophication.

中文翻译：

---

水库对季风季节和年度变化的营养响应评估

通过对2014年至2017年两个时期收集的数据应用营养状态指数偏差（TSID）分析和经验回归模型，研究了多功能水库水质参数和营养状态随季风降雨强度变化的变化. 水库总体保持中营养状态，卡尔森营养状态指数（TSIc）受TSI _TP影响最大。养分浓度，特别是磷，与降水没有很强的相关性，特别是在弱季风时期，2015年春季观察到总磷（TP）显着增加，表明在深度和稳定性降低的情况下内部磷负荷的可能性因降水不足而导致水体减少。TSI_Chl高于TSI _SD在第 1 期的大多数数据中，在季风季节观察到降水量的增加可以忽略不计，而第 2 期的大部分数据显示出相反的趋势。浮游植物的生长不受养分限制，尽管大多数样品的养分比（N/P）显着高于 20，表明磷限制条件。TSID和回归分析表明浮游植物生长受到春季浮游动物放牧的限制，季风和季风后季节的细胞浓度和群落结构受季风强度变化的控制，正负关系证明了这一点群落大小和蓝藻种群与夏季降水量之间的关系。