A thesis submitted in partial fulfilment of the requirements for the degree of Master of Engineering, School of Engineering and Technology

Thesis (M.Eng.) - Asian Institute of Technology, 1991

Groundwater recharge is an "unseen" element of the hydrological cycle. As it is out of sight, it is frequently out of mind, especially to the layman. However, its occurrence . and hydrological significance cannot be ignored by hydrologists and water resources planners. The main purpose of this study is to investigate the groundwater recharge estimation capacity of the NAM (a conceptual, deterministic, rainfall runoff model) by simulating rainfall, runoff and groundwater level values for two typical river basins of Nepal. Concurrent data of daily rainfall and runoff and monthly evaporation and groundwater level values are used for rainfall runoff and groundwater recharge analyses. Final values of the NAM model parameters are optimized by trial and error technique using the observed and simulated runoff and groundwater level hydrographs, including the statistical criteria of fitness. In the case of the Bagmati river basin, the model is calibrated both with runoff and groundwater level and the performance of the model is found to be very good. In the Kankai river basin, however, due to lack of groundwater level data, model is calibrated with runoff only and the model performance can be said to be satisfactory. The groundwater recharge simulated by the NAM is verified with the recharge obtained from the Water Balance Model . It is found that the prospects of the applicability of the NAM Model to estimate groundwater recharge is promising and the model, inevitably, serves as a good engineering tool for water resources investigations in small catchments.