Informations et ressources scientifiques
sur le développement des zones arides et semi-arides

Titre : Partitioning subsurface water fluxes using coupled hydrus - modflow model : case study of La Mata catchment,

Auteur : Deme, G. (Gezahegn)

Etablissement de soutenance : University of Twente International Institute for Geo-Information Science and Earth Observation (ITC)

Grade : Master of Science in Geo-Information Science and Earth Observation 2011

Résumé
Spatial and temporal variation of dry season subsurface water fluxes in granitic La Mata catchment in Spain, 5km 2 has been assessed using a coupled HYDRUS-MODFLOW model. The data sources used were from field measurements, remote sensing, laboratory analysis of soil samples, meteorological measurements and groundwater level monitoring, recession curve analysis, slug and pumping tests and geophysical measurements. This study is mainly aimed to obtain dry season quantities of different subsurface fluxes such as water that leaves aquifer vertically upward i.e bottom flux (BF), evaporation from groundwater (Eg), change in the storage of unsaturated zone (Eu if negative), transpiration from groundwater (Tg), transpiration from unsaturated zone (Tu) and out flow in the catchment through drains. The study was carried out comparing dry season fluxes of September 2009 and September 2010. The vadose zone flow complexity was analyzed through unsaturated zone model HYDRUS 1D, transpiration using sap flow measurements partitioned aplying isotope tracing and transient groundwater modelling with MODFLOW for spatio-temporal groundwater balance. The calibration of the coupled HYDRUS MODFLOW model resulted in maps showing spatial and temporal variability of the subsurface fluxes in the catchment. All the subsurface fluxes showed a tendency of decline from the beginning to the end of September 2009 and 2010. In September 2009 the average BF for the entire catchment decreased from 0.984 mmd-1 to 0.889 mmd-1 , Eg decreased from 0.064 mmd-1 to 1.914 mmd-1 , no evaporation from unsaturated zone (Eu) throughout the month, Tg decreased from 0.13 mmd-1 to 0.06 mmd-1, Tu from 0.092 mmd-1 to 0.078 mmd-1 , and out flow to Sardon River coinciding with the fault zone from 31.5 m3d-1 to 0.00m3d-1 in 2009. In September 2010 the average BF decreased from 1.46 mmd-1 to 1.118 mmd-1 , Eg from 1.703 mmd-1 to 0.069 mmd-1 , no evaporation from unsaturated zone (Eu) throughout the month, Tg decreased from 0.109 mmd-1 to 0.084 mmd-1 and Tu from 0.15mmd-1 to 0.12 mmd-1 and groundwater out flow to Sardon River coinciding with the fault zone from 0.085 m3d-1 to 0.064 m3d-1 . The total amount of water that leaves the catchment because of all the subsurface fluxes is 0.302 mmd-1 in September 2009 and 0.311 mmd-1 in September 2010, which is significant as compared to the annual mean value of precipitation (about 500 mmy-1 ) or estimated recharge (about 10-100 mmy-1 ).

Version intégrale (ITC)