Groundwater Flow Modeling in Chitwan Dun Valley (Between Narayani River and Lothar Khola), Nepal

Models are simplification of reality to investigate certain phenomena or to predict future behavior and always tries to generate scenario that is close to the real condition. Groundwater flow models are computer models generated through using established flow equations that simulate and predict aquifer conditions. The result of groundwater modeling is used for groundwater management and remediation. In the present study, hydrostratigraphic units were identified through interpreting the lithological logs of the drilled wells then fence diagram was prepared with three major aquifer horizons, namely unconfined, shallow confined and deep confined aquifers. In addition, hydrogeologic data were integrated to develop a conceptual hydrogeologic model of the aquifer system of the Chitwan Dun valley, which was the basis for the development of the numerical model. The aquifer system was modeled numerically using MODFLOW-2005 numerical modeling, which was further calibrated and an acceptable numerical model was obtained which showed different flow direction in each aquifer layer. The model was validated by comparing the observed and simulated heads. The result shows that in each of the aquifer layers, the general flow direction is towards west and south-west.

Groundwater flow modeling in an intermontane basin

Groundwater model has become a commonly used tool to perform various tasks. Geological, hydrogeological and geophysical data is required for constructing 3D hydrogeological framework models. Most of the time, it is realised that there is lack of sufficient data to build a groundwater model. The present work has been achieved after systematic data collection and hydrogeological study of Nara Basin, west Japan. Groundwater has been widely exploited for drinking water supply as well as for recreation purpose as Thermal Springs in the Nara Basin. There are hundreds of wells drilled in unconsolidated sediments and some tens of deep wells encountering the fractured basement. When water is exploited from a groundwater basin, it is necessary to understand properly the groundwater flow in different aquifer zones in the basin. Hydrostratigraphic units in the unconsolidated sediments overlying the basement rocks were established by using the borehole log data. In order to have understanding of the three dimensional configuration of these units, fence diagram was constructed. The geological and hydrogeological information were used to develop a conceptual model which was further calibrated and an acceptable model was obtained. The model was validated by comparing the observed and simulated heads and discharge.