Evaluation of surface water for agricultural irrigation in Lobalain District, Rote Ndao Regency, East Nusa Tenggara Province, Indonesia

Abstract

The average rice productivity of the Rote Ndao Regency is still below the national rice productivity. The cropping pattern’s lack of management and limited water sources can only be planted once a year. This study aims to determine the availability and quality of surface water used for irrigation with the existing rice-corn-fallow cropping pattern. The research was carried out by measuring discharge in the field, surveying the types and cropping patterns, irrigation area research, surface water quality analysis, and hydrological analysis. The results showed that the need for irrigation water for agriculture in the study area with the current cropping pattern was 0.84 lt/second/ha. Therefore, the existing irrigation area of ±3,762.00 Ha requires a water discharge of ±3.159 m3/second. The availability of surface water in the Lobalain District is low, with a discharge of ±1.598 m3/second. Surface water quality shows the percentage of sodium (Na%) dominated by excellent to permissible class, and the sodium adsorption ratio (SAR) excellent. The existing resource of surface water could not support agricultural irrigation. Therefore, it is necessary to find an alternative water source such as groundwater.