Current Condition in Lowland Irrigation Area Tahai: Challenges and Solutions

Abstract

The Tahai lowland irrigation area is one of the on-going lowland development national projects. This channel network consists of the primary channel and a number of secondary channels on its left and right banks at regular distances. This is known as comb (sisir) system. The primary channel starts at Kahayan River and ends at an upstream pond. Farmers currently do not use the water in the channels for irrigation. Channels are used to drain water from paddy fields. The upstream pond is no longer functioning because it is filled with sedimentation and has been covered by vegetation. In the past two years, dredging was carried out on a 7 km primary channel calculated from the upstream of the channel. Before dredging, the sediment had formed a mound in the center of the primary channel. Meanwhile, sedimentation in the secondary channel is left unchecked, resulting in reduced channel capacity. The poor drainage ability of the channel resulted in poor water circulation. Observations of water quality in the spring and neap tide periods have been carried out as a first step in proving this problem. Field observations were completed to obtain an overview of the existing condition of the channel network. An overview of the issues was also obtained from discussions with observers of the irrigation areas and local farmers. The development plan is discussed in this paper as a proposal for solving these problems. The plan is based on the results of the study and the discussions with farmers. It is expected that water from the land and channels can discharge into rivers at low tide and freshwater can flow into channels at high tide. The latter serves as the water supply for the paddy fields.