In order to fulfil the objectives of the project, a detailed investigation of all the available data was carried out by visual analysis to locate the most promising sites for groundwater search. This analysis was performed for the 30 priority areas selected by the FAO Field Team. The priority areas, spread over the whole study area, were ranked according to their level of importance as first, second and third priority.
Among the 30 priority areas, five were selected to illustrate in this paper the different occurrences of groundwater in the study area. Below, a discussion of the interpretation for each of these five zones is presented. For each zone, interpretation of Landsat images was performed as described in paragraph 2.8.
Priority area E2
Priority area E2 is located in the central part of the study area, inside the Governorate of Erbil. The area (Fig. 12) is located on the south-western flank of an anticline whose nucleus and flanks are constituted mainly of calcareous rocks and subordinately by other sedimentary rocks such as sandstones and marls. The area includes also a rather flat zone at the foothills of the anticline. Drainage on the SW flank of the fold is scarce, revealing karst phenomena in the zone. Moreover, some of the smallest creeks tend to disappear as soon as they reach the foot of the slope. The plain at the foot of the anticline is cultivated and some zones are also strongly vegetated.
Five promising sites were selected for this area. Sites 1 and 2 are suggested as favourable for potential deep groundwater, being at the crossing of two regional lineaments. The lineaments trending N35E are tensional, since they are perpendicular to the fold axis; thus they are open. They normally store and transmit groundwater. The other is compressive, but the fracture should have favoured solution of carbonatic rocks, thus also this lineament may be considered as draining uphill areas. The best place for drilling is near the crossing of the two fracture systems. At Sites 3 and 4 shallow aquifers are supposed to be present. These are lowlands filled by sediments bounded to the East by the slope of the anticline and to the West by a structural ridge made of a hard rock formation which should act as a natural dam for sediments (visible as a white line running NW-SE). Groundwater should be located in the sediments. Site 5 is located in a zone characterized by pediments and small alluvial fans. Groundwater is potentially present as shallow aquifers especially near the threshold between coarse and fine grained sediments.
Priority area E7
This zone is located in the south-eastern part of the Governorate of Erbil, at the border of the Sulaymaniyah Governorate (Fig. 13) A ridge, mainly constituted by limestone, white in colour in the Landsat image, crosses the area with an S shape. On the southern flank of the ridge, typical landforms called flat irons occur, showing the presence of a monocline plunging southwards (possibly an anticline flank). In the southern portion of the area, evaporite rocks outcrop (gypsum, anhydrite and salts) which can affect groundwater quality. For this reason, the search of promising sites in this area is restricted near the calcareous ridge.
Site 1 has been placed on a regional tensional lineament (perpendicular to the fold axis) on the southern flank of the anticline and at the foot of an outcrop of massive limestone (eastern part of the area). Site 2 is located on a regional tensional lineament crossing an area of karst limestone in the western side of the area. Site 3 is in a similar condition as site 1, since it is placed on a regional tensional lineament, and in a zone where dolomitic limestones outcrop.
Priority area D8
Located in the south-eastern part of the Dohuk Governorate, the area includes the southern flank of an anticline (Fig. 14). Hard rocks such as dolomitic limestone and limestone make up the flanks of the fold, where white "flat irons" are visible. At the core of the anticline, more erodible rocks outcrop, mainly shales. It is interesting to note that at the foot of the limestone slopes, a narrow flat zone occurs, bounded to the south by a small ridge of harder rock (possibly limestone, white in the satellite image). Inside this flat area two highly vegetated areas exist, crossed by streams. A possible interpretation of these vegetated zones is the presence of contact springs on the boundary between limestone and impervious rocks in the flat zone. The southern part of D8 area is characterized by rolling terrain constituted by clastic rocks (claystone, cyan in the Landsat image) and alluvial deposits, where some cultivated area is visible.
Site 1 is located at the crossing of two local lineaments, one of which tensional. Site 2 was chosen over a local tensional lineament at the foot of the slope where the boundary between limestone and shale occurs. Nearly the same situation is found in sites 3, 4 and 5 but with some differences: in these sites, thick vegetation shows the presence of springs as discussed above. Groundwater transmission should be more effective in these cases. Site 6 and 7 are found at the crossing of lineaments in the rolling terrain in the southern part of the area (site 6 is slightly outside). Although at site 6 one of the lineaments is a regional one, the setting for these two last sites is less promising than the previous (2, 3, 4 and 5).
Priority area S7
This area is located next to the eastern borders of the town of Sulaymaniyah (Fig. 15). The city is clearly recognizable in the Landsat image with its violet colour and its texture. A limestone and marly limestone ridge running NW-SE characterizes almost the entire area. This ridge constitutes a narrow anticline. The lithologic nature of this relief can be inferred by the thick drainage network (here with a pinnate pattern due to the structural control of folds) and by the white colour in the image. This ridge separates two zones, to the west and to the east, where clastic rocks outcrop.
Nine promising sites have been found. Site 1 is located in the central part of the area, west of Sulaymaniyah, over a regional lineament which is also tensional in this area, being orthogonal to the fold axis. The site is found in a topographic low (a small valley) and the lithology of bedrock could be limestone or marly limestone. Site 2 is in the northern part of the area, at the crossing of two lineaments: a regional tensional and a local. As a further favourable factor there is the position of the crossing, which occurs at the foot of the slope, thus in a topographic low. Sites 3 to 9 occur at the crossing of lineaments, in some cases regional ones (sites 5 and 9). Sites are located in topographic low areas inside the small valleys that cross the ridge. There are reasons to think that sites 6, 7, 8 and 9 should be really promising as there is a high correlation with thermal lineaments (orange in the figure).
Priority area S4
Priority area S4 occurs in the northern part of the Sulaymaniyah Governorate, near the Dukan lake, easily recognizable by its triangular shape (Fig. 16). The area is bounded to the south-east by a calcareous monocline ridge dipping NE. The calcareous nature of bedrock is clearly visible from the Landsat image since drainage network is almost completely absent. Although the monocline ridge is situated outside the priority area, it can be of interest to note that karst phenomena are likely to be expected in this zone. To the north, a big alluvial plain slopes towards this ridge and the result is that the ridge itself constitutes a natural dam for groundwater, which can be stored in the alluvial deposits near the ridge. Several sites are suggested here, but many more can be identified due to the particularly favourable conditions which exist in this area. An important note concerns water quality. All the groundwater extracted from the limestone ridge should be safe. On the other hand, care must be given to water extracted on the alluvial plain on the NE side of the area due to potential contamination by chemicals used in agriculture, which is well developed in the plains.
Eight sites have been identified. Sites 1 to 5 have their location in common which is near the foot of the SW ridge slope. They are all positioned on tensional lineaments or at the crossing of them (1 and 3 are at the crossing of regional lineaments). Moreover, a very important factor is that they are found in the topographically lowest area and at the boundary of the natural dam constituted by the calcareous ridge. Here there should be the highest concentration of groundwater. Sites 6, 7 and 8 are in a different condition: although they are at the crossing of, or on single lineaments (regional or local), their location is on alluvial terrain. Due to the gentle slope from NE to SW, tensional lineaments, which are oriented in the same manner, tend to drive groundwater in the direction of the slope. These are the cases where attention must be given to water quality as stated above.
Fig. 12. Priority area E 2
Fig. 13. Priority area E 7
Fig. 14. Priority area D 8
Fig. 15. Priority area S 7
Fig. 16. Priority area S 4