The modification of channel system in Tahai lowland irrigation area to improve drainability

The Tahai lowland irrigation area relies on rainwater as a source of irrigation water. The channel system network in Tahai is comb-type with a primary channel connected to the Kahayan River and the end of the primary channel is not connected with other flow sources. The end of the secondary channel is also no longer connected with the collector channel. This condition impacts dissolved solids deposition at the end of the channels. Hydraulic simulations need to be conducted to determine the spread of dissolved solids derived from the fields in the existing water channel system. The existing water channel system could be transformed into a one-way flow system with a right collector channel to expedite water drainage into the Kahayan River. This water channel system plan is also modeled and simulated using HEC-RAS. Hydraulic simulations showed an improvement in channel drainability. At the end of the simulation, the number of dissolved solids in the secondary channel in the one-way flow system was less than that in the existing water channel system.