Toxicologia Ambiental e Analítica

Assessment of Yatta Canal Water Quality for Irrigation, Machakos County, Kenya

Abstract

Manohar S, Mang’oka JM, Ndunda E and Gathuru G

Water is one of the most important global requirements for every activity in life but if it is polluted/contaminated, then it creates direct problems of alkalinity/salinity/toxicity through irrigation to agricultural farms and affects on the quality and nutritional value of cultivated crops. Water quality of Yatta Canal was studied from January to December, 2015 within Machakos County of Kenya. Twenty sampling stations were selected at an interval of 1 km along this canal and water samples were collected once in a month during the wet and dry seasons to monitor its suitability for irrigation. Annual average values of temperature, pH, total dissolved solids, turbidity, dissolved oxygen, and electrical conductivity show significant (P<0.05) seasonal variation. Annual average chemical concentrations of the water during wet and dry seasons are; Nitrates 13.1 ± 0.47 mg/l vs 4.8 ± 0.13 mg/l; Phosphates 0.02 ± 0.001 mg/l vs 0.02 ± 0.001 mg/l; Potassium 3.8 ± 0.098 mg/l vs 2.8 ± 0.031 mg/l; Sulphates 10.7 ± 0.31 mg/l vs 7.2 ± 0.25 mg/l; Bicarbonates 46.9 ± 1.20 mg/l vs 79.9 ± 2.06 mg/l; Chlorides 14.3 ± 0.59 mg/l vs 2.0 ± 0.10 mg/l; Sodium 14.7 ± 0.436 mg/l vs 17.7 ± 0.200 mg/l; Calcium 5.9 ± 0.124 mg/l vs 8.1 ± 0.058 mg/l; Magnesium 2.2 ± 0.020 mg/l vs 2.9 ± 0.029 mg/l, Sodium Adsorption Ratio 1.30 ± 0.030 me/l vs 1.35 ± 0.020 me/l and Iron 0.49 ± 0.007 mg/l vs 0.64 ± 0.041 mg/l respectively. These chemical parameters also show significant (P<0.05) seasonal variation. Most of the physical and chemical levels are within the permissible limits as recommended by FAO and also by Kenya’s National Environment Management Authority with the exception of turbidity (100.2 NTU) and nitrate concentration (13.1 mg/l) only during the wet season. Based on the results, the canal water is safe for irrigation during dry season.