Study of Tidal and Water Quality in Acid Sulphate Soil of Unit Tamban Lowland Irrigation Area Central Kalimantan

Abstract

Unit Tamban is one of the reclaimed lowlands in the tidal irrigation area, which is included in the food estate program located in Block D, Central Kalimantan. The water system used in the area is a fork-type with a settling pond at the end of each primary canal. Most of the soils are acid sulfate type with a pyrite depth of more than 50cm. Sedimentation of the canal causes the water supply and drainage processes to slow down, which compromises the water quality. At high tide, there is a process of acid water dilution, while at low tide, acid water will be evacuated out of agricultural land through a network of canals. The study was conducted of examining the effect of tides on water quality as indicated by the characteristics of pH, Total Dissolved Solids (TDS), and Electrical Conductivity (EC). Measurements were done at four points along the primary canal during spring tide and neap tide in the wet season. Water level and water quality were measured simultaneously for 27 hours. The results showed that water level fluctuations had a significant influence on the water quality in the canal. When it comes to peak tide during spring tide, the pH of the water increases while the EC and TDS values decrease. Rainfall at high tide also affects the quality of the canal surface water, which raises the pH.