ASSESSMENT OF SHALLOW WELL QUALITY FOR IRRIGATION: A CASE STUDY FROM LAGOS, NIGERIA

The study assessed shallow well quality used for vegetable irrigation in Amuwo-Odofin and Ojo LGAs in Lagos state.15 samples were randomly collected from shallow wells. PH, electrical conductivity and total dissolved solids were measured in situ while calcium, magnesium, total hardness, sodium, potassium, chloride, bicarbonate, carbonates and sulfate was determined using standard methods. Result shows that the mean values of the examined parameters HCO3,Ca/TH, pH, Mg/CO3/Cl, EC,TDS/Na/K and SO4 exceeded their level of detection in about66.7%,60%,53.3%,46.7%,40%,33.3%, and 20% respectively. The mean value of pH7.45 indicates slightly alkaline condition while the measured EC fall under low enrichment of salts. TDS value indicates freshwater. The suitability of shallow well for irrigation purpose was assessed using KR, MR, %Na, RSC and SAR indices.KR ranged from 0.03-0.12meq/L and exceeded the computed KR in about 20%.KR was found to be suitable for irrigation purpose. MR ranged from 29.19 to 43.21meq/L andexceeded the computed MR in about 66.7% .The computed MR value are suitable for irrigation.% Na varied from 3.38 to 11.96meq/L. Approximately 33.3% of the mean %Na exceeded the computed %Na in the study area. RSC ranged between -0.66 and - 4.38meq/L and all the samples fall in excellent category for irrigation purpose. SARranged between 0.05 and 0.5meq/L and exceeded the computed SAR in about 20%. Approximately 66.7% of the samples fall in low salinity while 26.7% and 6.7% falls under medium and high salinity zones respectively. The paper recommends adequate protection and thorough treatment of water for irrigation purpose.