Changes in environment as land-use and population growth cause significant change in recharge in the City of Jeddah in Saudi Arabia

Angela Prein1
1 Hessisches Landesamt für Umwelt und Geologie

O 10.4 in Hydrogeologie arider Gebiete

30.05.2014, 18:20-18:40, H17, NW II

Changes in land-use and population do not necessarily lead to groundwater depletion, but could instead result in rising groundwater levels, which can cause severe problems. In the course of the refurbishment and expansion programme for the Holy City of Mecca (KSA), Jeddah Airport is being expanded to a greater capacity; in this context, rapid development of residential areas of Jeddah is underway. During the last decade, several flash floods and rising groundwater levels have been observed. The latter are affecting the foundations of buildings due to uplift and corrosion by highly mineralized water.

One of the objectives of the study is to investigate the causes of the measured groundwater rise. Groundwater hydrographs clearly show impacts of natural climatic and hydrologic changes over the last 30 years. Possibly, anthropogenic impacts might arise from leakages from water supply and waste water systems. In addition, reasons for groundwater rise in this arid area are climatic impacts by increased precipitation or from an enhanced recharge via wadi leakage or flood control reservoirs.

To quantify the problem informations about the development of population and land-use, the location of wastewater dumping and of large pipelines and wastewater treatment plants were collected. In addition, tools like analysis of catchment areas and groundwater model were used. Assumptions have been made regarding the water loss from networks, the indirect recharge in wadi areas, the future Sea level rise and the extinction depth of evaporation.

In order to identify and quantify possible contributions to groundwater recharge, a numerical groundwater model has been developed comprising an investigation of the local water balance. Information from many shallow boreholes and few deep boreholes comprising stratigraphy and hydraulic parameters were incorporated. The spatial distribution of recharge were taken from the analysis of existing and planned water supply and wastewater networks. The knowledge from geophysical investigations about the aquifer thickness and the permeability was used for the transient calibration of the groundwater flow model.

The modelling results show that indeed the anthropogenic recharge caused by leakage from water infrastructure is the most important source of the groundwater level rise. Thus, to improve the model accuracy a methodology is needed to cope with limited data availability regarding the leakage from networks.

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Letzte Änderung 03.04.2014