تقيم صلاحية المياه الجوفية والسطحية المستخدمة للري في مدينة درنة وضواحيها باستخدام الطرق الكيميائية والمؤشرات الحسابية المتبعة

Abstract

This study was conducted to evaluate the quality of irrigation water in the city of Derna and its environs, using chemical analyzes and mathematical indicators. It included five agricultural areas:Al-Dhahr Al-Hamar, Al-Fattayeh, Sidi Aoun, Karsah and Al-Bilad. All of the water from these areas is used for irrigation of vegetables and fruits . The results of the chemical analysis showed that the pH of the wells water of the study areas falls between (6.5-8.5), and it is classified according to the standardS of the Food and Agriculture Organization (FAO) as lightly alkaline water. The electrical conductivity (EC) of the areas of Sidi Aoun Karsa, Al- Fattayah and Al-Dhahr Al-Hamar were less than (3.0 dS/m), which therefore falls within the range of permissible FAO standardS, and is classified as light to medium-salinity water, while the well water of the Al-Bilad region exceeded the set limits with a value of (3.53 dS/m). Hence, it is classified as highly hazardous water. Also, the total dissolved salts (TDS) for all regions were within the acceptable range for FAO standardS, while the water of the Al Bilad region was higher than the same standardS . The results obtained showed that the cations of calcium (Ca+2), magnesium (Mg+2), sodium (Na+), and potassium (K+) fall within the normal range according to the FAO guide. As for anions, all the regions’ wells water contained chloride ion (Cl-) concentrations within the permissible range, except for the Al-Bilad region’s well water, which exceeded the permissible limits of FAO standardS, while bicarbonate (HCO3 -) was high for all the regions wells water. compared to the FAO guide. Moreover, sulfate values (SO4=) for all wells water were in the acceptable range for FAO standardS . The results obtained indicated that the water of all wells in the studied areas contained small amounts of pollutants, nitrate (NO3 -), boron (B), as well as heavy metal contamination of the elements, lead (Pd+2) and cadmium (Cd+2), all of which fell within the acceptable range for the specifications, used for irrigation water . The results of the mathematical indicators for the well water of the study areas showed that the sodium adSorption rate (%SAR) for all areas is classified as lowsalinity water, with the exception of the El-Bilad area, which is classified as medium-salinity according to the FAO standardS, and when applying the standardS of the US Salinity Laboratory (USSL). The waters of the five regions fall under the classification of low-sodium water (S1). When linking the relationship between the electrical conductivity values and the sodium adSorption rate (SAR%) and applying the last criterion, it was found that the areas of Dahar El Hamar, Sidi Aoun, Karsa and Al Fattayah have water classified as (C3-S1), that is, in terms of salinity, it is considered medium salinity, and in terms of sodium, it is of little harm and is suitable for irrigation of all crops. On the other hand, the water from the wells of the El-Bilad region fell under the category (C4-S1), and therefore, in terms of salinity, it was very salty and not suitable for irrigation. As for sodium, it fell within the water with little harm . The Adjusted sodium absorption ratio (Adj.SAR) values showed that the water of the Dahar El Hamar region is considered water suitable for irrigation, while the water of the Sidi Aoun, Karssa and Fataeh regions is medium saline water, while the water in the Bilad region was unsuitable for use. The calculated acidity (pHc) results also gave values less than 8.4 for all wells in the regions, which may lead to the precipitation of calcium carbonate. As for the percentage of residual sodium carbonate (%RSC), it indicated that the water in the areas of Dahr El Hamar, Sidi Aoun and Al Bilad is not suitable for irrigation, while the wells of the Karsa and Fataeh area are suitable for irrigation. Moreover, the values of soluble sodium percentage (SSP%) indicated that the wells water of all regions are good water for irrigation. Total hardness (TH) values also showed that wells water in all regions is considered soft (not hard), compared to FAO standardS. As for the magnesium risk ratio (%Mg.R), the water of all wells in different regions is considered to be of low risk, and the El-Blad region is close to dangerous, according to FAO standardS. Finally, the water from the wells of the studied areas was classified according to the permeability index (%PI), The water from the wells in the Dhaher El Hamar region was good and suitable for irrigation, while the water from the rest of the regions was suitable for irrigation . In general, it is clear from the results that there is a discrepancy in the quality of irrigation water, whether at the level of one region or between regions, but it was found that when applying different quality determinants, the water of the El-Blad region is considered Low quality water and not suitable for irrigation in terms of salinity and sodium absorption rate. The reason may be due to the interference of water with sea as well as its pollution with black water, and the various causes of deterioration must be addressed in order to use it in irrigation water .