Quality of natural rainfall and rain-water from the Royal rain making to agricultural activities in Central River Basin [Thailand]

The central river basin is the cradle for economic agro-agriculture which depends on natural rainfall and the rain-water from the Royal Rainmaking especially in repeated drought areas as Nakorn Sawan and Lopburi. Increasing chemical applications in agriculture and other human activities may contaminate the rainfall naturally and artificially. Therefore, it is very important to examine the quality of rain-water. Study of rain-water quality from the Royal Rainmaking and natural rainfall was performed during 8 Aug 2005 to 24 June 2006. The rain-water samples from natural rainfall and the Royal Rainmaking were collected from 3 stations in the Central River Basin namely: Meteorological station, Amphor Muang, Lopburi; Agricultural Meteorological Station, Amphor Takpha, Nakhonsawan and Hydrometeorological station at Pasakchollasit Dam. One hundred and fourteen samples of natural rain-water and 204 samples of the Royal rain-water were analyzed for 19 standard parameters CpH, acidity, alkalinity, sulfate, chloride, hardness, ammonia, nitrite, nitrate, calcium, chromium, copper, iron, lead, cadmium, zinc, manganese, magnesium and mercury) for drinking water (WHO standard). The following parameters were significantly different between natural and Royal rain-water: sulfate, chloride, calcium, iron and magnesium. These chemicals were mainly the composition in rainmaking materials. Besides, it appeared that cadmium was present in both types of rain-water in high quality which should be monitored further. All parameters except cadmium are in acceptable limit of WHO standard for drinking water. Therefore, both types of rain-water can be generally used. However, the presence of some chemicals in both types of rain-water shows the alternative cycles of chemicals used in agricultural activities and the content in rain-water. It appeared that the more chemicals used in agriculture, the more chemicals presented in the rain-water and may finally be accumulated in soil and vegetation.