1.2. General stratigraphy

The surface of Kuwait is formed by sedimentary rocks and sediments ranging from Middle Eocene to Recent. The Dammam Formation represents the oldest exposed sedimentary rocks. The Recent deposits of fine-grained beach sands cover the southern coast of Kuwait and the Neutral Zone. The Cenozoic (Tertiary-Quaternary) sediments can be divided into two groups: Hydrogeology and Groundwater Geochemistry of the Clastic Aquifer and Its Assessment for Irrigation, Southwest… http://dx.doi.org/10.5772/intechopen.71577 109

Figure 1. The topographic and the dominant northeast drainage patterns of Kuwait.

the Kuwait Group and the Hasa Group. The Mesozoic (Late Cretaceous) sediments are characterized by carbonate rocks [3]. A generalized lithostratigraphic subdivisions of Tertiary-Quaternary sediments in Kuwait with the groundwater conditions [4] is summarized and discussed below.

#### 1.3. The Kuwait Group

by the Kingdom of Saudi Arabia. The climate is extremely hot and dry in summer and mild-tocold in winter. The rainfall is scarce and limited to the period from October to May. The highest ever temperature recorded in Kuwait was 54C on July 2016. The average annual precipitation recorded during the period 2001–2016 is 114.5 mm. It lies within an arid-semiarid zone lacking renewable surface water. The natural water resources are the brackish groundwater located in the Kuwait Group and the Dammam Formation aquifers, which have been utilized since 1953 on a small scale and for limited purpose, but with increasing population and growth of demands, the production of groundwater embarked on a wide scale project to provide consumers with it through a separate pipe network. This groundwater is used for blending with distilled water for fresh water production, irrigation and landscaping plus household purposes, livestock watering, and construction works. The present total output installed capacity of groundwater wells is around 145 MIGD, meanwhile the maximum consumption hit 114.6 MIGD. However, the demand for water in Kuwait is met from three sectors: desalination,

The Al-Atraf field is one of the brackish groundwater fields and is located southwest of Kuwait between 29 18 to 29 24 north latitudes and 47 31 to 47 38 east longitudes. The area under study is about 87.75 km<sup>2</sup> and includes 83 water wells, producing groundwater from the Kuwait Group aquifer, where the nominal production capacity is 30 MIGPD. The salinity of

The topography of Kuwait is generally flat, with a gentle rise from sea level at the coast to an elevation of about 270 m in the southwest corner of the country (Figure 1). Local relief is low except in the Jal-Az-Zor escarpment, the Ahmadi Ridge, the Wara Hill, and the Wadi Al-Batin [1]. The Jal-Az-Zor escarpment, about 60 km in length and 145 m in height above MSL, borders the northwestern shore of Kuwait Bay. It trends from Al-Atraf southwest to Bahra northeast. The Ahmadi Ridge parallels to the coastline south of Kuwait City and rises to a height of 137 m above MSL. The east and west slopes of the ridge are very gentle. Another elevation is the Wara Hill, located southeastern Kuwait and has a local relief of about 31 m. The Wadi Al-Batin is a major and shallow depression marking the western boundary of the country for a distance of 75 km with an average width of 6–8 km. The central part of Kuwait and the Neutral Zone are featureless with few wadis and little vegetation. Furthermore, small and shallow depressions exist throughout the northern, western, and central areas. The northern and the western parts of the country have a dense drainage pattern of small and shallow wadi systems, draining northeast

the aquifer ranges from 3504 to 6366 mg/l, with an average value of 4441 mg/l.

toward the Iraq border and toward the shallow depressions near Al-Rawdhatain [2].

The surface of Kuwait is formed by sedimentary rocks and sediments ranging from Middle Eocene to Recent. The Dammam Formation represents the oldest exposed sedimentary rocks. The Recent deposits of fine-grained beach sands cover the southern coast of Kuwait and the Neutral Zone. The Cenozoic (Tertiary-Quaternary) sediments can be divided into two groups:

brackish groundwater, and tertiary treated waste water.

1.1. Topography

108 Aquifers - Matrix and Fluids

1.2. General stratigraphy

The Kuwait Group consists of sand, gravel, sandstone, clay, silt, calcareous and gypseous cemented sandstones, and marl covering the entire surface of Kuwait and extending down to the top of the underlying Dammam Formation. The thickness of the Kuwait Group increases from 150 m in the southwest to about 400 m in the northeast. The Kuwait Group is relatively dry in the extreme southwest and is almost saturated with water along the coast of the Arabian Gulf. In the north of Kuwait, the Kuwait Group can be divided into three formations based on the presence of an intermediate evaporite development. These divisions are Dibdibba, Lower Fars, and Ghar Formations, arranged from top to bottom. The undivided Kuwait Group extends under all of Kuwait with an extension eastwards beneath the Arabian Gulf. The Dibdibba Formation was named after the type locality Al-Dibdibba Plain, which extends from Basra to the northern part of Kuwait. The Dibdibba Formation is overlain by unconsolidated Recent and sub-Recent sediments of varying lithologies. The Lower Fars Formation ranges in thickness from 61 m in the west to more than 100 m in the eastern area into the offshore and it is absent in the south. It consists of fine to coarse-grained conglomeratic sandstone, variegated shale, and thin, fossiliferous limestone. The outcrop thickness of the Ghar Formation is only 33 m but it increases in subsurface and ranges from 195 to 250 m of marine to terrestrial, coarse-grained, unconsolidated sandstone with a few thin, sandy limestone, clay and anhydrite layers. At the base of the formation, above the eroded top of the Dammam Formation, is a brown, marly, coarse-grained sandstone with white, crystalline limestone resting unconformably over the Dammam Formation, and in gradational contact with the Lower Fars Formation.

state, in SW-NE direction, to be discharged finally by seepage into Kuwait Bay and the Arabian Gulf [6]. The Kuwait Group aquifer gains part of its water by leakage from the Dammam Formation aquifer. The other sources of aquifer replenishment are the infiltration through the well-developed wadies and depression system, and lateral flow coming from Saudi Arabia. It is generally estimated that the hydraulic conductivity in the aquifer conjunctively decreases with depth by the increase of cementation degree. The hydraulic conductivity is relatively high

Hydrogeology and Groundwater Geochemistry of the Clastic Aquifer and Its Assessment for Irrigation, Southwest…

The main objectives of this piece of research are to identify the aquifer type and its characteristics, to reveal the geochemistry of the study area in order to recognize the prevailing and the major geochemical processes that control the quality of the groundwater. Moreover, to evaluate the suitability of groundwater for drinking and irrigation, physiochemical and irrigation

Seventy-one groundwater samples have been collected and analyzed to determine physical parameters like pH, EC, TDS, total hardness (TH), total alkalinity, and SiO2. In addition, the

and Cl expressed in mg/l were analyzed and converted to equivalent per million (e.p.m), and % e.p.m. [7]. Ion balance equation was applied to validate the accuracy of the chemical analyses where 5% is acceptable [8]. The reaction error of all groundwater samples was less than the

A speciation model has been used to determine the degree of saturation of groundwater with respect to some minerals using WATEQ4F program [10]. A mass-balance modeling WATEVAL computer program [11] is used to reveal the major geochemical reactions that control the geochemistry of the study area, along with the application of Gibb's ratio to assess the functional sources of dissolved chemical constituents, and to recognize the main processes governing the groundwater chemistry of the study area [12]. Hydrochemical facies interpretation is used to determine flow pattern and origin of chemical histories of groundwater by plotting the major cations and anions on the Piper diagram [13]. The assessment of groundwater for irrigation purposes based on different irrigation indices is carried out which includes sodium adsorption ratio (SAR), residual sodium carbonate (RSC), %Na. permeability index (PI), potential salinity (PS), salinity hazard, magnesium ratio (MgR), Kelly's ratio (KR), and

Wilcox diagram Wilcox [15] and Doneen permeability index [16, 17] have also been utilized for

, K+

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111

, HCO3

, SO4 2,

chemical parameters of the major cations and anions such as Ca2+, Mg2+, Na+

in the upper saturated zones of the aquifer.

3. Objectives of the study

parameters have been determined.

4. Methodology

accepted limit of 10% [9].

chloro-alkaline index [14].

classification of groundwater for irrigation.
