Estimation of natural groundwater recharge in Chennai River basin using multiple approaches

Groundwater is vital in Chennai Metropolitan Area, and thus its sustainable management is essential. This study aims to estimate groundwater recharge in the Chennai River basin (CRB) using an empirical method, a rainfall infiltration factor (RIF) method, a geographical information system (GIS)-distributed model, and the water table fluctuation (WTF) method. The average recharge estimates were 196 mm/year (empirical), 127 mm/year (WTF), and 122 mm/year (RIF). These results agree with the estimate of the GIS-distribution model, where 59% of the area has high recharge (>100 mm/year). The effective recharge from rainfall was around 10% with the RIF and WTF methods and 16% using the empirical method. All the estimates were statistically significant with confidence levels of over 98%, using a 95% confidence interval. The WTF method (with a 99.9% confidence level) was the most reliable of the four approaches. However, we suggest using multiple methods to cross-check the results and that measuring rainfall and water level is necessary for accurate recharge estimates in the future.