Thesis (M.Sc.) - Asian Institute of Technology - UNESCO-IHE, 2015

A thesis submitted in partial fulfillment of the requirements for the Degree of Master of Science in Urban Water Engineering and Management jointly offered by the Asian Institute of Technology, Thailand and UNESCO-IHE, The Netherlands

Groundwater in Kathmandu Valley is under stress due to uncontrolled abstraction, limited recharge, and inadequate management. Consequences of groundwater over - exploitation are already observed in the form groundwater level depletion. Understanding dynamics of groundwater flow and recharge rates and processes is the very first step to develop strategies for groundwater management, protection and sustainable usage. This study develops hydrological and groundwater models of the valley and recommends management interventions based on analysis of a set of scenarios. A hydrological model developed using Soil and Water Assessment Tool (SWAT) based on daily hydro - meteorological data from 1999 to 2009 suggested that recharge to the valley{u2019}s aquifers varies from 93.40 to 187.5 mm/year with an average value of 149.65 mm/yea r. The recharge map was then fed with MODFLOW, the groundwater model used in this study with ModelMuse interface for data preparation, model running, and analyzing outputs. The MODFLOW model developed for 2001 and 2009 using a three - layer conceptual model revealed that simulated ground water levels has decreased in a range of 0.27m to 3.8m for shallow and 1.49 to 3.78m throughout the valley. The reasonably calibrated MODFLOW was then used for analyzing two scenarios focused mainly on augmenting recharge: i ) Fourteen types of land use scenarios, and ii) Installing a set of injection wells. The analysis suggested that changing land cover have potential to increase recharge rate of 9.55 mm/year at maximum i.e. from 149.65 to 159.2 mm/year, whereas use of a set of nine injection wells results in - 0.01 to 10.79m increase for shallow aquifer and in 2.40 to 10.03m increase for deep aquifer in groundwater table. Based on the findings it also provides a set of recommendations for further research as well as groundwat er management in the valley.