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Technische Universität Bergakademie Freiberg (2012)

Groundwater investigation and modeling - western desert of Iraq

Al-Muqdadi Sameh Wisam

Titre : Groundwater investigation and modeling - western desert of Iraq

Auteur : Al-Muqdadi Sameh Wisam

Université de soutenance : Technische Universität Bergakademie Freiberg

Grade : Doctor rerum naturalium Dr. rer. Nat. (PhD) 2012

Mots Clés : hydrogeology, groundwater, modelling, Iraq

The region of interest is part from Iraqi western desert covering an area about 100,000 km². Several of the large wadis such as Hauran, Amij, Ghadaf, Tubal and Ubaiydh traverse the entire region and discharge into the Euphrates River. The present study included the following hydrogeological investigations : Lineaments interpretation was done by using different data sets (SRTM 30 m and Landsat ETM 15m), within different algorithms. Some faults recognized by field survey match rather well with the automatically extracted lineaments with only a small difference between field data and remote sensed data. The groundwater flow directions (west to east) for three aquifers were determined by using different spatial interpolation algorithms. Due to the faults impact, the flow direction gets a slightly other direction when reaching the fault’s zone. Two pumping test were performed close to fault 2 in the unconfined aquifer Dammam using well no. 9 and 17. Results of pumping test and recovery were evaluated with the analytical model MLU for Windows. Well 17 shows a slightly higher transmissivity (0.1048 m²/min) in comparison to well 9 (T= 0.0832 m²/min). This supports the assumption of a zone of unique elevated permeability between fault 1 and fault 2 because of the tectonic stress and the anticline structure. The catchment and watershed delineation was performed by means of four GIS packages utilizing three DTM´s : 90 m and 30 m SRTM (Shuttle Radar Topography Mission) and the ASTER 30 m. A thorough field survey and manual catchment delineation of the same area was available from Division 1944. Software used was Arc Hydrotools, TNTmips, River Tools and TecDEM. Ten 90 m SRTM and twelve 30 m ASTER files were merged by means of ArcGIS. The 30 m SRTM dataset of Iraq was supplied by courtesy of the US Army and the region of interest (ROI) was clipped from this DTM using ArcGIS. No additional steps were performed with both DTM data sets before using the mentioned software products to perform the catchment analysis. As a result the catchment calculations were significantly different for both 30 m and 90 m data and the different software products. The groundwater model implemented in Visual Modflow V.4.2 was built by 5 main layers representing Dammam aquifer, first aquiclude, UmEr Duhmma aquifer, second aquiclude and the Tayarat aquifer. Averaged readings of groundwater head from 102 observation wells were used to calibrate the model. Calculated recharge average was 17.5 mm/year based on the water balance for 30 years (1980- 2008). A sensitivity analysis was performed by using different permeability and recharge valuesHowever, the model showed a rather low sensitivity because the values of the standard error of the estimation were between 2.27 m and 3.56 m. Models with recharge less than 11.85 mm/year or more than 60 mm/year did not converge and thus failed to produce a result. Models with Kf values from 1.1-3 to 1.1-4 m/s for aquifers and from 1.1-7 to 1.1-8 m/s for aquicludes converged. Water budget is about 2.17*10¹⁰ m³/year ; by irrigating the greenhouses this budget will cover only 1.75% of the total area. However, this value could be upgraded up to 8 – 9 % by utilizing the groundwater inflow from Saudi Arabia.

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Page publiée le 15 septembre 2012, mise à jour le 2 décembre 2018