Assessment of water quality variation for agriculture in Bang Pakong River of Thailand

Abstract

The quality of water from the river was carried out from November, 2021 to April, 2022. The water samples were collected from 13 sampling points and analyzed pH, electricity conductivity (EC), salinity, calcium (Ca2+), magnesium (Mg2+), sodium (Na+), chloride (Cl-), sulphate (SO42-) and sodium adsorption ratio (SAR). The seawater mixing ratio was calculated using chloride concentration from the river and sea. The maximum pH value (7.56) was observed in February and the minimum value (6.53) was occurred in December among the collection months. The EC and salinity were the highest in February. The highest concentration of cation in water sample was Na+and the lowest value of cation was Ca2+. The concentration of Mg2+was higher than that of Ca2+from February to April. The sequence of major anions in water were Cl -> SO42-. All parameters were higher in February compared to other collection months. Additionally, the highest seawater mixing ratio was observed in February (25.40%) followed by March (3.87%) and April (1.27%). The acceptable limits of irrigation water were EC (<0.7 mS cm-1), SAR (< 10) and Cl-(<10 meq L-1). The EC (13.90 mS cm-1), SAR (22.81) and Cl-(117.00 meq L-1) values were high in the river water was unsuitable for irrigation in February, which caused many problems to soil and plants. Therefore, it was concluded that the properties of water in Bang Pakong River were changed in every month depend on precipitation and freshwater flow in this region. Besides, presence of high salinity and sodicity of irrigation water other than rainwater could deteriorate the soil properties of valuable agricultural land as well as damaged the crop production. The results provided that the river water was suitable for irrigation in agricultural fields in specific month in order to increase agricultural production in this area.