Regional-scale evaluation of tertiary irrigation system in Muda Irrigation Scheme from space

A tertiary irrigation system is essential for efficient water management in large-scale irrigation scheme and requires regular evaluation to understand their effectiveness. The current water balance method for tertiary irrigation system evaluation requires extensive data, making continuous monitoring over vast areas unfeasible. A better approach using geospatial data from the Google Earth Engine (GEE) is introduces to evaluate the efficiency of tertiary irrigation systems on a regional scale, aiding water management strategies. This study aims to (1) define the rice cultivation boundary for accurate data collection and (2) quantitatively evaluate irrigation system performance using specific indicators. Remote sensing evapotranspiration (RS-ET) and yield derived from Normalized Difference Vegetation Index (NDVI) were collected within rice cultivation boundary across 60 irrigation blocks, including 14 blocks equipped with tertiary irrigation system in Region II of the Muda Irrigation Scheme. Three irrigation system performance indicators (equity, adequacy, and water productivity) were used as a key metric in over four rice-growing seasons to evaluate tertiary irrigation system. Results reveal that tertiary irrigation system performance varies with the current three-phase water management strategy. Equity performance was highest during the off-season, particularly in phase 1 (2–8 %). Adequacy was moderate across all phases and seasons (median: 0.6–0.67), while water productivity showed consistent strength in phases 1 and 3, with fluctuations in phase 2, across seasons. This study underscores the cost-effectiveness and efficiency of using geospatial data from space for continuous regional-scale monitoring, highlighting areas for improvement in the current water management strategy.