The Demarcation of Groundwater Quality for Irrigation purposes in Sirte, Libya

Abstract

 Efforts were made to check the quality of groundwater for irrigation purposes in Al-Swawa, Sirte district, Libya. Four dug wells (W₁, W₂, W₃ and W₄) and four open ground tanks (GT₁, GT₂, GT₃ and GT₄) supplied from the Great Man-Made River were randomly selected to represent the experimental area. Then the samples were analyzed for physicochemical parameters (pH, EC, Na, k, Ca, Mg, HCO3, Cl, SAR, SSP, RSC, Magnesium Adsorption Ratio (MAR), Kelly’s ratio (KR), Permeability Index (PI), and Total hardness (TH)). Some international standards namely; Eaton (1950), Richards (1954), USSL (1954), Kelly (1963) and FAO (1985) were used for water quality detection. The results showed wide variations in water quality parameters for both sources of water. Whereas, the average values of pH were (7.7 and 8.4), EC (8 and 0.7 ds/m) and SAR (12 and 4.8) recorded at wells water and great river water, respectively. Wells water classified as a very high salinity, while Great River located under medium hazard. Wells water gave values of Cl^- more than 10 me/l (W₁ (48.5), W₂ (51.5), W3 ₍147), and W₄ (13)), while great man-made river gave values less than 10 me/l, (GT₁ (4.4), GT₂ (4.4), GT3 ₍4.4), and GT₄ (4.2)) which classified as moderately Cl^- hazard. All tested water samples showed values of SSP more than 60%, which exceed Eaton’s measure value, except W₃, which recorded (56). The average values of RSC, MAR, KR, PI and TH with wells water were -23 me/l, 40 %, 1.8, 75% and 1554 mg/l, respectively  compared to the great river water (0.7 me/l, 45 %, 2, 100% and 149 mg/l, respectively). It is concluded that, wells water just suitable to irrigate a very salts tolerant crops, while the great river water is suitable for irrigation with moderate leaching if intensive management is adopted and followed.