Assessing Irrigation Performance of Bang Len Operation and Maintenance Project using Depleted Fraction Index and Satellite-derived Data from Google Earth Engine

Abstract

Depleted Fraction (DF) is an indicator of irrigation performance that assesses water supply adequacy and reflects water use efficiency in irrigated schemes. This study aims to evaluate irrigation performance in the Bang Len Operation and Maintenance Project during 2022-2024using irrigation water supply data combined with gridded monthly actual evapotranspiration (ETa) from Tema Climate and satellite-derived monthly precipitation from CHIRPS through the Google Earth Engine platform. The assessment revealed an average DF value of approximately 0.65, which falls within acceptable criteria (0.5-0.7), indicating efficient water use for crop production and balanced soil and groundwater storage in the project area. However, significant seasonal variations in DF values were observed, with dry season values typically exceeding 0.6, occasionally rising above 1.0, suggesting farmers may rely on alternative water sources such as groundwater or natural water bodies in the area. Conversely, during the rainy season, DF values were generally below 0.6, indicating excess water that may contribute to groundwater recharge or system outflow. The evaluation has limitations due to extensive aquaculture areas where ETa represents natural water evaporation rather than water productivity. This research demonstrates the potential of satellite-derived data for assessing irrigation water management performance, particularly in areas with limited field data availability. The findings can be applied to optimize water delivery plans and enhance crop production efficiency in irrigated areas.