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Land suitability analysis can help to achieve sustainable crop production with a proper use of the natural resources. The current study was carried out on the soils of northwestern area of Libya to assess their morphological, physical and chemical properties and their suitability for growing irrigated crops. The studied area lies between latitudes 32° 30′ 00.9" and 32° 57′ 34.2'' N and between longitudes 11° 35′ 08.4" and 11° 45′ 09.2" E. Two suitability methods (Sys &Verhey and Storie methods) were used to assess the land suitability of this area. According to Sys and Verhye method, the soils of the studied area varied in the suitability for irrigation between highly suitable (S1) to marginally suitable (S3). However, according to modified Storie index method the soils productivity, ranged from excellent (grade 1) for agriculture to non-agricultural (grade 6). The modified Storie index method was more effective in assessing the land suitability of this area. The drip irrigation system was also more suitable than surface irrigation method for most of the soils of the studied area. The indeces of soil suitability rating and percentage for growing alfalfa, sorghum, barley, maize, millets, wheat and safflower were higher compared to those for growing soybean, sunflower and sesame. Onion and green pepper crops were moderately suitable to be grown in 42% of the soils of the studied area while the other vegetables were not suitable to be grown in most of the soils of the studied area. The evaluated fruit trees could be arranged according to the soil suitability rating and percentage in the order of date palm > olives > guava > citrus > banana. The results also revealed that the studied area has a good potential to produce the selected crops under irrigation provided that the water requirements for these crops are met. The main limiting factors for land suitability for growing crops are soil texture, soil depth, calcium carbonate, alkaline pH and soil salinity.

Groundwater quality of the arid and semi-arid regions needs great attention because it is the main water exporter for household and irrigation purposes. In this study, the traditional method and the water quality index were applied to evaluate the suitability of groundwater quality for drinking and irrigation purposes in southwestern part of Libya. To achieve this, twenty groundwater samples were collected from different places representing the area understudy and the necessary physic-chemical analyzes were carried out to examine the suitability of groundwater for drinking purposes. Eleven parameters (pH, electrical conductivity, total dissolved solids, total hardness, calcium, magnesium, sodium, potassium, chloride, bicarbonate and sulphate) have been applied for calculating the WQI for drinking testes. The obtained values for water quality parameters were compared with World Health Organization (WHO) guideline values (traditional method). Also, seven parameters were selected for irrigation testes for calculating the WQI such as: EC, SSP, SAR, MAR, PI, KR and PS were used in traditional method. The results revealed that the groundwaters of most samples were fit for drinking purposes according to WHO (traditional method). However, the calculated DWQI for drinking propose showed that 35% of water samples are considered of excellent category, 20% good category, 15% poor category and 20% very poor category. On the other hand, two samples (only 10%) are of unsuitable categories. For irrigation purposes, most of studied samples were suitable for irrigation purposes (traditional method). The computed IWQI showed that 15% of water samples were in excellent category and 85% were in good category. The graphical interpretation of water quality was made according to Gibbs plots, Piper diagram, Chadha's scheme, USSL diagrams, Wilcox diagram and Doneen diagram. KEYWORDS Drinking water quality index (DWQI), Irrigation water quality index (IWQI), water quality parameters The main objective of this study is to using the traditional method and the water quality index (WQI) to assess the suitability of groundwater quality in the study area to drinking and irrigation. 2. LOCATION OF STUDY AREA The area under investigation is located on the northwestern area of Libya (Wadi Al-Hayaa). It lies between latitudes 26° 30′ and 28° 30′ N and longitudes 12° 15′ and 14° 30′ E (Figure 1). The area is characterized by the rural environment and the main activity of the people is agriculture. Water in this area is generally obtained from drilling wells that are used for different purposes.

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Groundwater quality of the arid and semi-arid regions needs great attention because it is the main water exporter for household and irrigation purposes. In this study, the traditional method and the water quality index were applied to evaluate the suitability of groundwater quality for drinking and irrigation purposes in south-western part of Libya. To achieve this, twenty groundwater samples were collected from different places representing the area understudy and the necessary physic-chemical analyzes were carried out to examine the suitability of groundwater for drinking purposes. Eleven parameters (pH, electrical conductivity, total dissolved solids, total hardness, calcium, magnesium, sodium, potassium, chloride, bicarbonate and sulphate) have been applied for calculating the WQI for drinking testes. The obtained values for water quality parameters were compared with World Health Organization (WHO) guideline values (traditional method). Also, seven parameters were selected for irrigation testes for calculating the WQI such as: EC, SSP, SAR, MAR, PI, KR and PS were used in traditional method. The results revealed that the groundwaters of most samples were fit for drinking purposes according to WHO (traditional method). However, the calculated DWQI for drinking propose showed that 35% of water samples are considered of excellent category, 20% good category, 15% poor category and 20% very poor category. On the other hand, two samples (only 10%) are of unsuitable categories. For irrigation purposes, most of studied samples were suitable for irrigation purposes (traditional method). The computed IWQI showed that 15% of water samples were in excellent category and 85% were in good category. The graphical interpretation of water quality was made according to Gibbs plots, Piper diagram, Chadha's scheme, USSL diagrams, Wilcox diagram and Doneen diagram.