Suitability of Groundwater Quality for Irrigation with Reference to Hand Dug Wells, Hantebet Catchment, Tigray, Northern Ethiopia

Abstract

The purpose of the project has been to assess the suitability of groundwater quality for irrigation purpose in the Hantebet catchment (24.4 km2), Tigray region, northern Ethiopia. The total numbers of hand dug wells in the area are 154. Out of these, 110 are functional and the remaining dried out. Stratified and random sampling techniques were utilized to select representative samples of groundwater. Accordingly, twenty groundwater samples were collected from twenty hand dug wells for chemical analysis. Twenty soil samples were also collected from the command area of the hand dug wells from where the groundwater samples were collected. Both groundwater and soil samples were analyzed for Ca2+, Mg2+, K+, Na+, CO32-, HCO3-, Cl-, SO42-, and NO3- besides pH and electrical conductivity (EC). Further, the Sodium Adsorption Ratio (SAR) for the both the groundwater and soil samples and Exchangeable Sodium Percentage (ESP) for the soil samples were also computed. Out of the analyzed 20 groundwater samples, 8 show EC values below 0.7 and the remaining between 0.71 and 1.12 dS/m, and pH values from 6.55 to 7.26. Chloride ion concentrations in groundwater range from 0.435 to1.393 (meq/l); bicarbonate from 5.124 to 9.660 (meq/l); and nitrate (NO3- N) values below 5 (mg/l) except in one sample that has 5.87 mg/l. In soil samples, EC values range from 1.36 to 4.65 dS/m (at 25°C) (mean 2.487), and pH values range from 6.77 to 7.79 with a mean value 7.20. SAR values are well below 3 in groundwater, except in one sample and in soil it ranges from 0.111-1.571. ESP values in the soil vary from 2.016 to 4.863. The results indicate that the groundwater in general is suitable for irrigation purpose. In the case of soils about 80% of the soil samples indicate no hazard but 20% are saline. The soils are free of sodicity hazards. However, (i) to achieve a full yield potential; (ii) to sustain it for long period of time; (iii) to avoid the possibility of increase in salinity, and (iv) to avoid the possibility of occurrence of sodicity and toxicity hazardous in future, proper irrigation scheme is required in the form of crop selection, fertilizer usage and suitable alternative management.