Water salinity distribution and irrigation pump management in a river intruded by sea water in Tanete Riaja Subdistrict Barru Regency.

In Tenete Riaja Subdistrict, Barru Regency, farmers use water in Lisu watershed as a source of irrigation water by pumping the river water and then flowing it to rice fields. However, when rainfall is low (dry season), the river water has increased salinity levels caused by the estuary of the river directly adjacent to the sea so that at high tide while the discharge of flow in the watershed decreases, it will cause the influx of seawater to the river water accompanied by the mass transfer of salt or commonly referred to as seawater intrusion. Increased salinity levels of river water affect the quality of irrigation water that irrigates rice fields and affect the productivity of crops produced. The purpose of this study is to map the salinity of irrigation water from rivers intruded by seawater in rice fields and know the form of pump management, both in terms of income financing and productivity of irrigation water produced. The research method conducted is to take river water samples and rice field water samples and then measure the salinity level. In addition, in-depth interviews with the pump operators are also conducted to obtain data on pump operation during the growing season. Based on the research, the salinity level of each rice field has different values, which is influenced by several factors, including the difference in the distance of observation stations with river estuaries, rainfall and irrigation water supply patterns. Then in terms of pump management, the R/C value is 1.77 shows that the farm is profitable, and the water productivity in each rice field area shows effective water use. [ABSTRACT FROM AUTHOR]