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UNESCO-IHE Institute for Water Education, Delft (2016)

Sensitivity of global recharge estimates to global precipitation estimates

Asri V.H.B.

Titre : Sensitivity of global recharge estimates to global precipitation estimates

Auteur : Asri V.H.B.

Etablissement de soutenance : UNESCO-IHE Institute for Water Education, Delft

Grade : Master of Science (MS) 2016

Résumé
Water is one of the most essential renewable natural resources for life on earth, but the increase of the human population has led to an increase to the stress on the available natural water resources, including groundwater. Understanding and quantification of groundwater recharge is essential to determine to what degree, and to which rates groundwater extractions are sustainable. To estimate groundwater recharge to important aquifers there is significant potential in the use of globally available datasets. The current study aims to explore the sensitivities and uncertainties of global recharge estimates using a simplified daily soil water balance model. The main research goal is to understand the sensitivity of the recharge estimates and the effects of intensification of precipitation rate on recharge for different aquifers under different climatic conditions. For this purpose four global precipitation datasets that are freely available and widely used, namely TRMM-3B42, CMORPH, CHIRPS and PERSIANN, and two sedimentary transboundary aquifers with different climate conditions, the Indus River Plain aquifer (arid climate) and the Cambodia Mekong River Delta aquifer (tropical climate), are evaluated for a temporal scale of 10 years (2000 2009). PERSIANN was found to highly overestimate precipitation in the two areas of interest, and this product was not considered for further analysis. For the purpose of sensitivity/uncertainty analysis, three types of variation are applied in the recharge assessment, namely : i) variation in precipitation dataset input ; ii) variation in root zone depth, and iii) variation in runoff characteristics as defined using the curve number method. Results for the Indus River Plain aquifer, which has a deep groundwater table and an arid climate, show that intensity of rainfall plays a major role on the recharge process. TRMM-3B42 product was found to be the suitable dataset for this aquifer. For the Cambodia Mekong River Delta Aquifer, recharge estimates show that the shallow groundwater table and constant recharge rate throughout the year gives a larger recharge as a percentage of rainfall. Intensity, precipitation amounts and spatial distribution of precipitation estimates have significant effect on recharge estimate results. Precipitation estimates input has the highest sensitivity on recharge estimates output compared to root zone depth and curve number parameters on both case study. Recharge estimates from the IGRAC - WHYMAP database and the PCR-GLOBWB global hydrological model are used to compare recharge estimates found. This shows that recharge estimates found compare well in the arid aquifer but are overestimated in the tropical aquifer, the reason could be the runoff value that is underestimated by the curve number method.

Sujets groundwater recharge ; soil water ; hydrological modelling ; precipitation ; global resources

Présentation

Page publiée le 28 décembre 2016, mise à jour le 11 novembre 2019