Southwest Saudi Arabia Research Articles

Site response assessment of an urban extension site using microtremor measurements, Ahud Rufeidah, Abha District, Southwest Saudi Arabia

Microtremor horizontal-to-vertical spectral ratio (HVSR) method has been conducted at 33 sites in Ahud Rufeidah urban expansion zone in order to assess the fundamental frequency and the corresponding amplitude of the sediments. Clear HVSR peaks have been identified in the majority of the surveyed area. The eastern and northern parts of the area are characterized by two well-separated peaks which indicate distinct shallow and deep impedance contrasts. The frequency map of sediments shows a distribution in the range of 0.86–3.13 Hz. The observed frequencies can be related to the total thickness of Quaternary alluvial sediments (sand, gravel, and shale) deposited over the gneiss bedrock. Lower resonance frequencies are attained at sites in the northern part, while the higher values are attained at sites in the southern part. The amplitudes of HVSR peaks are in the range 3–15. In general, the higher peak amplitudes are identified at lower frequencies. Since low fundamental frequencies are related to bedrock, this can be an indication of high-impedance contrast between alluvial sediments and gneiss bedrock. The results of this study represent one step for seismic hazard assessment and risk mitigation of this urban area where great damage can be attained in case of strong earthquakes. Hence, these results should be taken into consideration before establishing the new urban constructions in the area of study.

Practice and Attitude of Cigarette Smoking: A Community-Based Study

BackgroundIn Saudi Arabia many studies have addressed cigarette smoking from various perspectives. Most of these studies, however, were conducted among males and confined to Riyadh, the capital city. Such limitations have enhanced the need for community-based epidemiological studies that include both genders and various age groups and socio-demographic features, as well as different regions.ObjectiveThis cross-sectional study aims to assess the prevalence of cigarette smoking and to discuss the association between cigarette smoking habits and socio-demographic factors among community members of the Jazan area in southwest Saudi Arabia.MethodsA pre-coded questionnaire was designed and tested for data consistency. A well-trained health team was assigned to gather the data from the 30 primary healthcare centers distributed across eight provinces. The response rate was 92.8% (4,326 respondents ≥13 years old). The associations among the subjects' socio-demographic characteristics were examined by the chi-square test. A multiple logistic regression and odds ratios were calculated as well.ResultsA total of 1,017 (23.5%), 1,042 (24.1%), and 3,284 (75.9%) respondents were, respectively, current smokers (TCS), ever-smokers (TES), and non-smokers (TNS). Though current smokers seem to be more prevalent in urban populations (13.8%) than in rural populations (9.7%), the association of urbanization with a current smoking habit is insignificant.ConclusionHaving fun, relieving stress, and the influence of parents, particularly of mothers, were the main motives that encouraged participants' cigarette-smoking habits. This situation was worsened by the fact that accessing cigarettes was either very easy or easy for over 90% of the respondents.

Magnetic and seismic refraction survey for site investigation of an urban expansion site in Abha District, Southwest Saudi Arabia

Ground magnetic and seismic refraction survey is carried out on an urban extension site in the southwest of Ahud Rufeidah town, southwest Saudi Arabia. The purpose of the survey was to map the surface topography of the bedrock and thickness of the alluvium overburden. The ground magnetic survey based on an assumption that the alluvial sediments is less or non-magnetic relative to the underlying gneiss basement rock. In this context, a total of 3,750 survey stations were measured along 40 east–west survey profiles, striking roughly perpendicular to the extension of the expected structures. In addition, 13 seismic refraction spreads were conducted along four seismic survey profiles across the expected pathways of buried alluvial channels in order to provide additional details about the depth and boundaries of the buried channels. The ground magnetic survey results show the presence of a basin combining two sub-basins filled with alluvium sediments that occupy the middle area of the investigated site. This basin is a closed basin that has no outlet, and there are four small and narrow channels that convey water and sediments from the eastern and southern hills into sub-basins. These channels are represented by narrow and elongated low magnetic anomalies extending towards the basinal area. The thickness of the alluvial sediments is verified using seismic refraction survey that indicates a greater thickness, exceeds 20 m, of low velocity sedimentary overburden inside the interpreted sub-basins and surrounding buried alluvial channels. These soft alluvial sediments can be deceptive and dangerous for urban foundations.

Seismic refraction and resistivity imaging for assessment of groundwater seepage under a Dam site, Southwest of Saudi Arabia

Seismic refraction and resistivity imaging methods were used to investigate a Dam site in Southwest Saudi Arabia to delineate the source and pathway of groundwater seepage in the site. The selected methods have the possibility to give an image of the subsurface and map lateral and vertical variations in the subsurface geology of the site. For this purpose, 48-channels seismograph with geophone spacing of 5 m, near-offset distance of 10 m and a total far-offset distance which varies between 230 and 280 m was used. Three seismic lines were conducted and the acquired data were inverted to velocity sections using tomographic inversion. Velocity sections show that the subsurface is classified into four distinct seismic layers; starting with the topmost unconsolidated alluvium that is underlain by a second layer of saturated and/or compacted alluvium sediments. The third layer is associated with fractured basement, while the fourth layer is correlated to the hard massive bedrock with a relatively high velocity. These results indicate that the site is affected by faulting that resulted in two depressions which extends in the form of buried structural channels filled with porous alluvium and fractured greenstone. These depressions are considered zones of permeability and represent a favourable pathway for groundwater flow. These results and the zones of seepage are confirmed and verified using resistivity imaging, where a low resistivity zone of thickness up to 22 m is observed.This low resistivity zone is interpreted as a layer of alluvial sediment saturated with groundwater, which may indicate possible seepage flow. Key words: Seismic refraction, resistivity imaging, site investigation, Saudi Arabia.

Precipitation Amount and Intensity Trends Across Southwest Saudi Arabia

AbstractThis study examines precipitation accumulation and intensity trends across a region in southwest Saudi Arabia characterized by distinct seasonal weather patterns and mountainous terrain. The region is an example of an arid/semiarid area faced with maintaining sustainable water resources with a growing population. Annual and seasonal trends in precipitation amount were examined from 29 rain gages divided among four geographically unique regions from 1945/1946 to 2009. Two of the regions displayed significantly declining annual trends over the time series using a Mann‐Kendall test modified for autocorrelation (α < 0.05). Seasonal analysis revealed insignificant declining trends in at least two of the regions during each season. The largest and most consistent declining trends occurred during wintertime where all regions experienced negative trends. Several intensity metrics were examined in the study area from four additional stations containing daily data from 1985 to 2011. Intensity metrics included total precipitation, wet day count, simple intensity index, maximum daily annual rainfall, and upper/lower precipitation distribution changes. In general, no coherent trends were found among the daily stations suggesting precipitation is intensifying across the study area. The work represents the first of its size in the study area, and one of few in the region due to the lack of available long‐term data needed to properly examine precipitation changes.

Clinical experience with insulin detemir, biphasic insulin aspart and insulin aspart in people with type 2 diabetes: Results from the Southwest Saudi Arabia cohort of the A 1 chieve study

Background:The A1chieve, a multicentric (28 countries), 24-week, non-interventional study evaluated the safety and effectiveness of insulin detemir, biphasic insulin aspart and insulin aspart in people with T2DM (n = 66,726) in routine clinical care across four continents.Materials and Methods:Data was collected at baseline, at 12 weeks and at 24 weeks. This short communication presents the results for patients enrolled from southwest Saudi Arabia.Results:A total of 2561 patients were enrolled in the study. Four different insulin analogue regimens were used in the study. Study patients had started on or were switched to biphasic insulin aspart (n = 987), insulin detemir (n = 1121), insulin aspart (n = 21), basal insulin plus insulin aspart (n = 280) and missing or other insulin combinations (n = 152). At baseline glycaemic control was poor for both insulin naïve (mean HbA1c: 9.9%) and insulin user (mean HbA1c: 9.5%) groups. After 24 weeks of treatment, both the study groups showed improvement in HbA1c (insulin naïve: −2.5%, insulin users: −2.2%). Major hypoglycaemic events did not occur in any of the study patients. SADRs were reported in 0.1% of insulin naïve and 0.1% of insulin user groups.Conclusion:Starting or switching to insulin analogues was associated with improvement in glycaemic control with a low rate of hypoglycaemia.

Advances in Arabian stratigraphy: Comparative studies of glaciogenic Juwayl and lower Unayzah strata (Carboniferous – Permian) of Saudi Arabia

ABSTRACT The Juwayl Member of the Wajid Formation, which crops out in the Wajid region of southwest Saudi Arabia, and the Unayzah C and B members of the lower Unayzah Formation in the subsurface of eastern and central parts of the country are all demonstrably late Carboniferous to early Permian in age, based on palynological analysis. Comparative studies of these two stratal units confirm strong genetic similarities between them, suggesting stratigraphic equivalence between the lower part of the Juwayl Member and the Unayzah C member, and the upper part of the Juwayl Member and the Unayzah B member, respectively. The boundary between the lower and upper parts of the Juwayl was not specifically recognized in outcrop, being covered with thick deposits of modern desert sand. The lower Juwayl and the Unayzah C are both interpreted to have been deposited in large glacial valley systems. In the Unayzah C, subsurface isopach mapping suggests down-valley transport from the north, implying that at least some of the ice was situated in localized, upland (alpine) ice caps. Multiple phases of glacial advance and retreat occurred. Glacial outwash sands and gravels (representing retreat phases) were subsequently cannibalized and severely deformed by re-advancing ice and they are identified now only as relict deposits. Glaciotectonic deformation is manifest in the lower Juwayl at outcrop as high to low-angle thrust sheets, and throughout the subsurface numerous shear zones are recognized in the Unayzah C member, both in core as well as in downhole wireline log responses (spectral gamma-ray and image logs). The multiple phases of glacial advance and retreat produced push moraine nappe complexes within which wholesale explosive disruption and redistribution of the sediment is observed. This was a consequence of fluidization related to glacially-induced overpressuring. Potentially significant reservoir heterogeneity arises in the subsurface Unayzah C member in relation to the shear zones, by the creation of reservoir compartments of widely varying extent and with unknown but potentially very poor interconnectedness. The upper Juwayl Member is represented at the outcrop by pebbly sandstones and conglomerates that were laid down upon a braided fluvial, glacial outwash plain. These pass upwards into boulder-bearing siltstones (stratified diamictites) that were deposited in a glaciolacustrine setting. Similar depositional sequences are seen in the subsurface Unayzah B member in the western (basin-marginal) part of the study area. Locally, subsurface data from the Unayzah B in these western areas suggests sustained ice-contact conditions, interpreted as evidence for local sustained “alpine” ice caps throughout Unayzah B time. Farther east, the more basin-central deposits of the Unayzah B member comprise a wide variety of depositional facies, all of which are nonetheless attributed generally to a glaciolacustrine setting. These include: (1) minor ice-contact push moraine deposits indicative of minor glacial re-advance during overall glacial retreat; (2) thick sequences of ice-proximal sublacustrine gravity flow sandstones and massive diamictites; and (3) significantly more ice-distal sublacustrine sandstones and mudrocks, including stratified diamictites and dropstones. In both basin-marginal and basin-central settings, the Unayzah B facies associations everywhere display strong evidence for sustained melting during terminal retreat of the Gondwanan ice sheets. This resulted in sustained infill and deepening and eventual overspilling of the basin-central lakes leading to widespread flooding throughout the basin. This flooding was ultimately manifest also at the basin margins in the west of the study area. A high degree of reservoir heterogeneity occurs within the subsurface Unayzah B member as a result of the wide variety of depositional facies. Reservoir quality correspondingly ranges from excellent to non-reservoir.

Prevalence of Eimeria species of the domestic goats Capra hircus Linnaeus, 1758 in Al-Baha area, Saudi Arabia

This work aimed to identify Eimeria species of goats and to investigate the factors that might potentially influence their prevalence and parasite load. This study was conducted in Al-Baha area, south-west Saudi Arabia from September 2011 to June 2012. Out of 336 faecal samples examined, 180 (53.57%) were positive for Eimeria oocysts. The prevalence of Eimeria ranged from 39.64% to 61.40% in different localities. Nine different Eimeria species were identified from faecal samples of goats. Eimeria species were: Eimeria arloingi (35.71%), E. alijevi (26.19%), E. hirci (25.29%), E. ninakohlyakimovae (16.36%), E. christenseni (14.59%), E. caprina (11.31%), E. jolchijevi (9.52%), E. caprovina (5.59%) and E. apsheronica (3.27%). E. arloingi (35.71%), E. alijevi (26.19%) and E. hirci (25.29%) were the most prevalent species and E. apsheronica (3.27%) was the least prevalent one. The main factors affecting prevalence and parasite load of Eimeria species were host age, locality and season. Significant negative correlations were found between host age and both prevalence and OPG number. Multiple-species infections were detected in 89.44% of positive goats which carried two to five species. In conclusion, the prevalence of coccidiosis is relatively low compared to other studies. Moreover, no signs of clinical coccidiosis were found in this study. We need further research to study the interaction between multiple-species infections in coccidiosis and parasite load in natural host-parasite systems.

Facies, Depositional Environments, Reservoir Potential and Palaeogeography of the Cambro-Ordovician Dibsiyah Formation, Wajid Outcrop Belt, Saudi Arabia

This paper investigates the facies, palaeoenvironments, controls and sequence development of the Cambro-Ordovician Dibsiyah formation of the Wajid (Sandstone) Group in southwest Saudi Arabia. The facies analyses revealed that the lower member of the Dibsiyah formation is predominantly composed of coarse- to very coarse-grained, trough cross-bedded sandstone deposited in a high-energy braided stream channel and bar sub-environments. The facies form in vertically and laterally stacked fining-upward sequences, indicating a braided channel and bar aggradations and migrations. However, the upper member is composed of mature fine- to coarse-grained sandstone deposited in the middle- to upper shoreface to foreshore parts of a shallow marine environment. The lower member represents a low stand system tract overlain by marine shale and siltstone units of the Bukayriyah Member, representing the regional Ordovician transgression. This sequence is overlain by the high stand system tract of the shallow marine sandstone of the upper member. Several factors may have contributed to the sequence development, including periods of deformation, uplift and erosion, regional variations in the rate of subsidence around the plate margins, sediment supply and relative sea level changes. The Wajid Outcrop Belt, however, may have been subjected to a different sedimentation and palaeogeographic development than that in the central and northern Arabia basins. The Dibsiyah formation is the same as that of Risha, Bukayriyah and Sajir Members of the Saq formation in central and northern Saudi Arabia. Understanding the depositional and post-depositional heterogeneity of the Dibsiyah formation at the outcrop scales may provide a better understanding and prediction of reservoir quality and architecture in its subsurface equivalent.

Distribution of Drug Resistance Genotypes in Plasmodium falciparum in an Area of Limited Parasite Diversity in Saudi Arabia

Two hundred and three Plasmodium falciparum isolates from Jazan area, southwest Saudi Arabia, were typed for Pfcrt, Pfmdr1, dhps, and dhfr mutations associated with resistance to chloroquine, mefloquine, halofantrine, artemisinin, sulfadoxine-pyrimethamine, and the neutral polymorphic gene Pfg377. A large proportion (33%) of isolates harbored double mutant dhfr genotype (51I,59C,108N). However, only one isolate contained mutation dhps-437G. For Pfcrt, almost all examined isolates (163; 99%) harbored the mutant genotype (72C,73V,74I,75E,76T), whereas only 49 (31%) contained the mutant Pfmdr1 genotype (86Y,184F,1034S,1042N), 109 (66%) harbored the single mutant genotype (86N,184F,1034S,1042N), and no mutations were seen in codons 1034, 1042, and 1246. Nonetheless, three new single-nucleotide polymorphisms were detected at codons 182, 192, and 102. No differences were seen in distribution of drug resistance genes among Saudis and expatriates. There was a limited multiplicity (5%), mean number of clones (1.05), and two dominant multilocus genotypes among infected individuals in Jazan. A pattern consistent with limited cross-mating and recombination among local parasite was apparent.

Effectiveness of Gambusia Holbrooki Fish in Domestic Water Containers and Controlling Aedes Aegypti Larvae ( Linnaeus , 1762 ) in Southwest Saudi Arabia ( Jeddah )

The objective of this study was to estimate the survival of Gambusia holbrooki (Cyprinodontiformes: Poeciliidae) fishin domestic containers in Jeddah, as well as its effectiveness in the control of immature A.aegypti. The use of G. holbrooki compared to Bacillus thuringiensis israelensis (B.t.i.)was donein domestic containers. In a first home visit, G. holbrooki or B.t.i were applied to water containers. Two follow-up visits were conducted after 3-4 & 5-6 months to assess the presence of viable fish in the containers and infestation by larvae. G. holbrooki fish were still present in 97.6% of containers 45-60 days after application. The infestation rate was significantly higher (P < 0.001) in the B.t.i group (IR ratio=21.60, 95% CI: 6.46-72.28). In deposits where the fish remained, efficacy was 85% better than B.t.i. The permanence of fish was higher in concrete tanks (48.5%) located outside the house (47.5%) and at ground level (53.3%).

From a single whole exome read to notions of clinical screening: primary ciliary dyskinesia and RSPH9 p.Lys268del in the Arabian Peninsula.

Primary ciliary dyskinesia (PCD) is a genetic disorder, usually autosomal recessive, causing early respiratory disease and later subfertility. Whole exome sequencing may enable efficient analysis for locus heterogeneous disorders such as PCD. We whole-exome-sequenced one consanguineous Saudi Arabian with clinically diagnosed PCD and normal laterality, to attempt ab initio molecular diagnosis. We reviewed 13 known PCD genes and potentially autozygous regions (extended homozygosity) for homozygous exon deletions, non-dbSNP codon, splice-site base variants or small indels. Homozygous non-dbSNP changes were also reviewed exome-wide. One single molecular read representing RSPH9 p.Lys268del was observed, with no wild-type reads, and a notable deficiency of mapped reads at this location. Among all observations, RSPH9 was the strongest candidate for causality. Searching unmapped reads revealed seven more mutant reads. Direct assay for p.Lys268del (MboII digest) confirmed homozygosity in the affected individual, then confirmed homozygosity in three siblings with bronchiectasis. Our finding in southwest Saudi Arabia indicates that p.Lys268del, previously observed in two Bedouin families (Israel, UAE), is geographically widespread in the Arabian Peninsula. Analogous with cystic fibrosis CFTR p.Phe508del, screening for RSPH9 p.Lys268del (which lacks sentinel dextrocardia) in those at risk would help in early diagnosis, tailored clinical management, genetic counselling and primary prevention.

Groundwater quality of the shallow alluvial aquifer of Wadi Jazan (Southwest Saudi Arabia) and its suitability for domestic and irrigation purpose

The groundwater quality of wadi Jazan (southwest Saudi Arabia) experienced degradation due to rapid urbanization and industrialization. On the basis of the groundwater chemistry, an evaluation of groundwater for domestic and irrigation uses is established. Thirty one groundwater samples were collected in February 2011 from wadi Jazan, southwest Saudi Arabia to study the chemical parameters such as hydrogen ion concentration, total dissolved solids, electrical conductivity, total hardness, calcium, magnesium, sodium, potassium, bicarbonate, sulfate and chloride. To classify water quality for irrigation, parameters such as sodium adsorption ratio and sodium percentage were calculated. Concentrations of major cations and anions of groundwater samples are exceeding the allowable concentration compared to their levels in potable water. The total dissolved solids are 5220 mg/l or below which indicates the presence of saline water. The saline water condition is also verified by low to high electrical conductivity (552 to 8030 mS/cm) and lowers than 7.92 hydrogen ion concentration values. The low to medium sodium adsorption ratio (0.99 to 10.62) coupled with low to high electrical conductivity gives the water medium, high to very high salinity hazard and low to medium sodium hazard. Thus, most of the study groundwater samples are generally unsuitable for domestic and irrigation purpose. Key words: Wadi Jazan, groundwater, physico-chemical parameter, hydrochemistry.

Aquifer boundaries explored by geoelectrical measurements in the Red Sea coastal plain of Jazan area, Southwest Saudi Arabia

Geoelectrical measurements using the vertical electrical sounding (VES) method were conducted on the Eastern Red Sea coast in Jazan area, Southwest Saudi Arabia. The objectives of the study were (1) to map the Quaternary sediments in areas where little is known about the subsurface geology and to infer shallow geological structure, and (2) to identify formations that may present fresh aquifer waters, and subsequently to estimate the relationship between groundwater resources and geological structures. Data collected at 9 locations were interpreted first with curve-matching techniques, using theoretically calculated master curves. The initial earth models were double checked and reinterpreted using a one-dimensional inversion program in order to obtain final earth models. Resistivity measurements show four zones with different resistivity values, corresponding to four different bearing formations: (1) A resistive surface layer at the top; (2) A basalt flow layer in the northern parts; (3) Strata saturated with fresh to brackish groundwater; and (4) A water-bearing formation containing Red Sea saltwater. Key words: Salt-water/fresh-water, geoelectrical measurements, Red Sea coastal plain,Saudi Arabia.

Developing GIS-Based Unit Hydrographs for Flood Management in Makkah Metropolitan Area, Saudi Arabia

Unit hydrographs (UH) are either determined from gauged data or derived using empirically-based synthetic unit hydrograph procedures. In Saudi Arabia, the discharge records may not be available either for several locations or for long time scales, and therefore synthetic unit hydrographs are crucial in flood and water resources management. Available metrological, geological, and land use datasets have been utilized in order to apply the US National Resources Conservative Services (NRCS) methodology in a Geographic Information Systems (GIS) environment. Furthermore, NRCS unit hydrographs have been developed for six watersheds within Makkah metropolitan area, southwest Saudi Arabia. The accomplished results show that the UH time to peak discharge vary from 1.15 hours to 4.47 hours, and the UH peak discharge quantities range from 10.14 m3/s to 16.74 m3/s. It is concluded that the third basin in Makkah city may be considered as the most hazardous catchment. Hence, it is recommended that careful flood protection procedures should be taken in this area within Makkah city.

Asthma knowledge and behaviours among mothers of asthmatic children in Aseer, south-west Saudi Arabia

Mothers of children with bronchial asthma consecutively admitted to Aseer central hospital, Saudi Arabia (n = 171), were interviewed using a questionnaire based on the Chicago Community Asthma Survey to study their knowledge and behaviours concerning bronchial asthma. The least known information among mothers was the complications of bronchial asthma. Breathing exercises during asthma attacks were the least practised behaviour. In a multivariate analysis, significant risk factors for poor knowledge and behaviours among mothers were female sex of the child, illiterate mother and young age of mother (< 30 years). More education is needed to help the mothers of asthmatic children to acquire the necessary knowledge and practices to care for their children.

The Ancient Dād in Southwest Saudi Arabia

AbstractAl-dād is a unique sound in Arabic. It is believed that this sound is what makes Arabic a distinguished language. However, its description has confused the linguists for long time. Some modern linguists believe that al-dād described by the ancient linguists is not used in the present time. On the other hand, Arabic speakers may not know that the sound they use for the classical pronunciation of al-dād is not the one described by the ancient Arab linguists. This study records the existence of a sound that has the features of al-dād as described by the ancient Arab linguists. It is used among some speakers in Southwest Saudi Arabia.

Dicoma chatanensissp. nov. (Compositae) from Yemen, and notes on the other species of Dicomeae on the Arabian Peninsula and Socotra

Three species of Dicoma and one of the newly re-established segregate genus Macledium (Dicomeae) are recognized on the Arabian Peninsula and Socotra. The (sub)shrubby Dicoma chatanensis N. Kilian sp. nov. with affinities especially to D. aethiopica from southwest Ethiopia, is described from open habitats of the sea-facing escarpments of Jabal Chatan in east Al-Mahra, Yemen. Based on additional material, D. schimperi subsp. cinerea is reconsidered to have a disjunct distribution in north Somalia and southeast Yemen, in the latter region replacing subsp. schimperi. Dicoma tomentosa is very rare in the area and known only from southwest Saudi Arabia, north Yemen and, as a rare weed, from Socotra. The common description and illustration (under Dicoma) of the flowers of the Socotran endemic Macledium canum with lobes rolled backwards spirally is confirmed to be erroneous and a lectotype is designated for the basionym. A key to the four species is provided.

Multivariate geostatistical methods of mean annual and seasonal rainfall in southwest Saudi Arabia

A multivariate geostatistics (cokriging) is used for regional analysis and prediction of rainfall throughout the southwest region of Saudi Arabia. Elevation is intruded as a covariant factor in order to bring topographic influences into the methodology. Sixty-three representative weather stations are selected for a 21-year period covering different microclimate conditions. Results show that on an annual basis, there is no significant change using elevation. On the seasonal basis, the cokriging method gave more information about rainfall occurrence values, its accuracy related to the degree of correlation between elevation and rainfall by season. The prediction of spring and winter rainfall was improved owing to the importance of orographic processes, while the summer season was not affected within its monsoon climatology. In addition, fall season shows inverse and weak correlation of elevation with rainfall. Cross-validation and cokriging variances are also used for more accuracy of rainfall regional estimation. Moreover, even though the correlation is not significant, the isohyet values of cokriged estimates provided more information on rainfall changes with elevation. Finally, adding more secondary variables in addition to elevation could improve the accuracy of cokriging estimates.

Combined geo‐electrical and hydro‐chemical methods to detect salt‐water intrusion

PurposeSalt‐water intrusion has always been a source of contamination in coastal aquifers that hinders sustainable groundwater development. Classical techniques to detect its occurrence are costly and time consuming. The application of combined geo‐electrical and hydro‐chemical methods is cheaper, executable in reasonable time, and successfully applied in mapping the interface between saline and fresh groundwater. The current study aims at detecting and delineating salt‐water intrusion in the downstream part of Wadi Gizan in southwest Saudi Arabia using geo‐electrical and hydro‐chemical methods.Design/methodology/approachThe case study area is the downstream part of Wadi Gizan in southwestern Saudi Arabia. Geo‐electrical data were obtained from field measurements using both Shlumberger and Wenner procedures. A number of 65 groundwater samples were collected and analysed for its total dissolved solids and major ionic composition.FindingsThe results show variations in the resistivity of the water‐bearing strata in the study area. Resistivity values decrease towards the Red Sea, and, in separate pockets. The total dissolved solids (TDS) and chloride distributions show the same pattern. Overlapping the areal distributions of the resistivity, TDS, and chloride concentration yield a map showing the limits of salt‐water intrusion and up‐coning pockets of saline water.Practical implicationsPlanners, decision makers and other interest groups can use these findings for a sustainable groundwater development in the study area, and, to safeguard the aquifer from further advancement of salt‐water intrusion.Originality/valueThe case study indicates the importance of applying combined geo‐electrical and hydro‐chemical methods for groundwater quality variations and especially in detecting and delineating the contact between saline and fresh groundwater in coastal aquifers.