Identification of Potential Tides in Terusan Tengah Tidal Irrigation Area Canal Network and Its Surrounding Channels

Abstract The study focuses on the Terusan Tengah Tidal Irrigation Area (T3IA) in Central Kalimantan, which features a fork-type channel system with an upstream retention-pond, lacking a control gate. Water is sourced from the Terusan River, connecting the Kahayan and Kapuas Rivers. Farmers have constructed a minor channel connecting the primary channel to the Kapuas River and Java Strait coast. This study aims to identify external and internal water management factors that influence the optimization of the T3IA to improve irrigation water quality. External factors in this study are the tides and water quality coming from the neighboring channel networks, and internal factors are channel networks within T3IA. Field observations assessed hydrodynamics and water quality, measuring water elevation, pH, and pyrite depth in channel networks. Analysis data focused on potential energy from tides and the interplay between water elevation and pH. The results show that at the downstream end of the primary channel, acidity increased when the flood tide started. The energy head during flood tide was 0.147m, and during ebb tide was 0.543m, indicating that during flood tide, the irrigation network was capable of flowing water into the network, but the energy was less than that ebb tide. This flow affects water quality; during spring tide, pH values ranged from 4.02 to 3.27, and during neap tide, pH values ranged from 3.66 to 3.25. For future research, it is recommended to simulate unsteady flow simulations for evaluating several water management scenarios to increase the pH value at secondary channels.