The Nature Conservancy's Indicators of Hydrological Alteration (IHA) software manual, version 7.1. Provides comprehensive guidance on using the free IHA software for calculating all 33 IHA parameters organised in 5 groups, 34 Environmental Flow Component (EFC) parameters, and Range of Variability Approach (RVA) analysis. Covers data input requirements (daily mean discharge, tab/comma-delimited), parametric and non-parametric statistical options, pre-impact vs post-impact analysis, graphical outputs (hydrographs, box plots, parameter time series, RVA target range plots), and interpretation of results. Essential reference for anyone conducting practical IHA analysis for environmental flow assessment, ecological Reserve determination, or flow regime characterisation.