River Border Lines was made and determined so that there some efforts were made for the protection, use and control of existing resources in the river. One of the river segments that are prioritized for determining river border lines is a river section adjacent to or within a developing area, one of which is the Manikin River in Kupang Regency, which is currently under construction of the Tefmo Dam which is targeted to be completed by the end of 2022. Therefore, in the future, of course, area around the weir will experience great pressure on land use which can have an impact on the function of the river due to developing community activities. The purpose of this study is to determine the width of the river border on the Manikin River. The length of the river segment where the width of the border line will be determined is 10 km from the Manikin weir to the downstream of the river. The results of this study are to obtain the width of the Manikin river border and get an overview of the location around the Manikin River about land conditions and functions, facilities and utilities that are included in the border area.