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

Improving spreadsheet model estimates of water balance components and groundwater dynamics using remote sensing and groundwater levels data

Albuhaisi Y.A.

Titre : Improving spreadsheet model estimates of water balance components and groundwater dynamics using remote sensing and groundwater levels data

Auteur : Albuhaisi Y.A.

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

Grade : Master of Science (MS) 2016

Hydrological models have become more and more important tools for the management of the water resources. They are used for managements, decision support, forecasting and protection and for many other purposes. Recently hydrological models have found a new role in studies of climate change impacts on water resources. The Dutch Water Board of Utrecht Province management area HDSR (Hoogheemraadschap de Stichtse Rijnlanden) is using several hydrological models for water resources management purposes, subsidence observation and analysing flow system for the entire region. One of these models is a spreadsheet model (black- box model principle) that calculates water balance and mass balance for few chemical components for the polder of Zegveld, which is the study area for this research. The main inputs for the spreadsheet model, like other models, is the meteorological data such as precipitation, evapotranspiration and temperature. Moreover, the area characteristics and the vegetation activities are also part of the inputs parameters. Furthermore, soil physical parameters for the area (dominantly peaty clay) based on the field work lab investigation are used like a basic requirement for any hydrological model. In addition, daily groundwater levels (for shallow and deep aquifers) and discharge are used as indicators of the quality of the simulation results. The results of the spreadsheet model were not satisfactory, and the simulated groundwater level is far away from the observed values. In addition, the simulated discharge values are entirely different from the observed values for the year of 2012. However, the discharge values are doubted by the HDSR and, therefore, they are not used as indications for the simulation results. The data of precipitation and evapotranspiration are calculated using classical methods ; such as rain gauges for the precipitation and evaporation pan for the evapotranspiration. From the literature it was found that these methods are not accurate enough as an input data for such a hydrological model due to its over or underestimations. Thus, they affected the output results. Therefore, an attempt to improve the results of the spreadsheet model is the use of new advanced meteorological data based on radar recipitation techniques and satellite data images for evapotranspiration calculated by using the ETLook algorithm. The spreadsheet model is executed for two simulations year of 2011 and 2012 and validated for the years of 2010 and 2013. The spreadsheet model is show comparatively good results regarding the simulated groundwater level. However, the ambition to have more accurate results drive the research a way to think about other parameters that might be included in the improvement process. The implementation of the transient groundwater level instead of assuming constant hydraulic head for the deep aquifer is helped for better-simulated outputs when it is combined with new meteorological data. Furthermore, the lateral resistances (Drainage and Infiltration) are found the most sensitive parameters after conducting a sensitivity analysis of the spreadsheet model. The default input value for this parameters is constant for the whole year ; disregard the soil moisture ii content of the soil and the climate conditions. The calibration of lateral resistances shows that it varies seasonally and when to apply this finding to the spreadsheet model the simulated groundwater level become more realistic. In conclusion, the use of advanced meteorological data is found useful to improve the results of the spreadsheet model. However, to reach more representative results ; the transient groundwater level is necessary to be included beside the lateral resistances values which found not constant but varies over time. Development of the discharge measurements techniques is recommended in addition to an important study about the ditch-soil interaction. This study will allow understanding the influence of extended ditch storage volume in the soil. Moreover, the lateral resistance should be tested to know the approximate seasonal value instead of the fixed value used for the whole year.

Sujets  : hydrological modelling ; groundwater levels ; remote sensing ; water resources management

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Page publiée le 31 décembre 2016, mise à jour le 11 novembre 2019