The seasonal and interannual variations of total coliforms (TC) and Escherichia coli (EC) were investigated in an urban tropical lake. Precipitation and flow rate were the controlling parameters influencing coliform dynamics. Correlations were obtained to describe the lake inlet conditions of flow rate, TC and EC. While TC increased with flow rate, EC slightly decreased. This unexpected behaviour for EC was attributed to the counterbalancing impact of coliform loading and surface runoff dilution. Correlations were computed to obtain first-order decay rates of TC and EC as functions of the Reynolds number, assuming the plug-flow model. A general mechanistic-empirical model was proposed to simulate coliform dynamics. The results indicated that seasonal coliform variations are more pronounced than interannual variations. Considering both the plug-flow and complete-mix models, it was shown that eliminating dry weather load reduces TC and EC but still leads to exceedances of the mandatory standards during the rainy season.

大肠菌群（TC）和大肠杆菌的季节性和年度变化（EC）在城市热带湖泊中进行了调查。降水和流速是影响大肠菌群动力学的控制参数。获得相关性来描述流量，TC和EC的湖泊入口条件。TC随着流量增加而增加，EC略有下降。EC的这种意外行为归因于大肠菌负荷和表面径流稀释的平衡作用。假设塞流模型，计算相关性以获得TC和EC的一阶衰减率作为雷诺数的函数。提出了一个一般的机械-经验模型来模拟大肠菌的动力学。结果表明季节性大肠菌群变异比年际变异更为明显。考虑到塞流模型和完全混合模型，