Citizen science-based WEAP modeling of water use impact on environmental flow in urbanized Big Akaki catchment, Ethiopia

Big Akaki is the headwater catchment for Ethiopia's Awash River Basin. Despite its ecosystem service, environmental flows are ignored by water users in the catchment. Studies on the impacts of domestic and irrigation water abstractions on environmental flows are limited. This study evaluated these impacts using citizen science data-based integrated HEC-HMS and WEAP modeling. The assessment included a spatio-temporal analysis of domestic water demand and water supply data, irrigation water requirement, and environmental flow requirements. The WEAP model was calibrated using citizen science data, and unmet demands were evaluated. Finally, unmet environmental flows were evaluated for three scenarios of historical rainfall in normal, dry, and wet years. This study demonstrated citizen science data effectiveness in integrating HEC-HMS and WEAP models to evaluate the unmet demand and water use impacts on environmental flow. Our finding showed a large unmet water demand of 25.60 Mm³ in the dry season, although the catchment's annual surface water potential exceeds the demands. Environmental flow requirements, estimated at 31 % of the mean annual flow, were unmet by 24 %-55.2 % during dry seasons in the normal, dry, and wet years with critical deficits in the dry years . Meeting environmental flow requires reallocation of water through a catchment-wide water management that considers conflict-sensitive approaches. • Citizen scientists observed river stage and rainfall data over three years at multiple sites. • Citizen science data informed the customization and integration of hydrological models. • Supply and demand were imbalanced in the study site. • Water reallocation is required to meet environmental flow requirements that may lead to conflicts.