RISK-BASED ASSESSMENT AND REHABILITATION PRIORITIZATION OF AGING IRRIGATION HYDRAULIC STRUCTURES UNDER VARIABLE FLOW CONDITIONS: A CASE STUDY OF ANDIJAN REGION, UZBEKISTAN
Keywords:
Irrigation hydraulic structures; technical condition assessment; operational reliability; variable flow conditions; risk-based rehabilitation; hydraulic capacity; failure probability; multicriteria decision-making; rehabilitation priority index; Andijan Region.Abstract
Aging irrigation hydraulic structures constitute one of the principal constraints on the reliable, equitable, and energy-efficient delivery of water in arid and semi-arid agricultural regions. Prolonged operation, insufficient preventive maintenance, abrasion, sediment accumulation, concrete deterioration, leakage through joints, deformation of canal sections, corrosion of mechanical components, and repeated exposure to variable hydraulic loads gradually reduce the functional capacity and operational reliability of water intake structures, regulators, canal drops, culverts, aqueducts, measuring structures, spillways, and associated control facilities. The problem is particularly important in Uzbekistan, where irrigated agriculture consumes the dominant share of available water resources, while a considerable proportion of irrigation infrastructure requires modernization, improved measurement, and more systematic asset-management procedures. This study develops an integrated risk-based framework for assessing the technical condition, hydraulic performance, operational reliability, and rehabilitation priority of aging irrigation hydraulic structures under variable flow conditions. The proposed methodology combines field inspection, defect classification, hydraulic capacity analysis, functional performance indicators, failure-probability assessment, consequence analysis, and multicriteria decision-making. The technical condition of each structure is represented by a condition index derived from the severity, extent, and progression rate of observed defects, whereas hydraulic reliability is assessed by comparing the actual conveyance or regulation capacity with the required discharge under low-flow, normal-flow, and peak-demand scenarios. Failure risk is formulated as a function of the probability of structural or functional failure and the corresponding hydraulic, agricultural, economic, environmental, and operational consequences. To avoid subjective prioritization based solely on visual deterioration, the framework introduces a composite rehabilitation priority index that integrates structural condition, hydraulic deficiency, service importance, failure consequences, maintainability, and intervention urgency. The methodology is intended for application to selected irrigation hydraulic structures in Andijan Region, where flow variability, sediment transport, seasonal water scarcity, intensive agricultural demand, and the aging of infrastructure create a strong need for transparent and technically justified rehabilitation decisions. The proposed approach enables irrigation authorities to distinguish structures requiring immediate intervention from those suitable for routine maintenance, monitoring, partial repair, or long-term reconstruction. The study contributes to the development of data-driven asset management for irrigation systems and provides a reproducible decision-support instrument for allocating limited rehabilitation funds to structures that generate the greatest improvement in hydraulic reliability, water-delivery performance, and system resilience.
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