Table 2 Summary of hydrologic parameters used in IHA and their characteristics.
Group | IHA | Hydrological indicators | Symbol | Ecological Significance |
|---|---|---|---|---|
Group 1 | Magnitude of monthly water conditions (12 Indicators) | Mean monthly water level (january–december) | \(\:{IHA}_{1}\sim{IHA}_{12}\) | Aquatic organism habitats. Plant soil moisture. Terrestrial animal drinking water and food sources. Factors influencing water body environments. |
Group 2 | Magnitude and duration of annual extreme water conditions (12 Indicators) | Annual averages (minimum and maximum water level over 1, 3, 7, 30 and 90 days), number of days with zero flow and river base flow index | \(\:{IHA}_{13}\sim{IHA}_{17}\), \(\:{IHA}_{18}\sim{IHA}_{22}\), \(\:{IHA}_{23}\), \(\:{IHA}_{24}\) | Balancing competition, weeds, and tolerant organisms. Creating a plant- friendly environment. Building aquatic ecosystems. Shaping river morphology and habitats. Plant water stress. Animal dehydration. Anaerobic stress, nutrient exchange. Under persistent stressors (e.g., hypoxia, chemical concentration). Distribution of plants in lakes, ponds and floodplain. Treatment of sediment waste in river channels Improvement of spawning ground aeration. |
Group 3 | Timing of annual extreme water conditions (2 Indicators) | The time (Julian day) at which the minimum and maximum values were recorded over the course of a year. | \(\:{IHA}_{25}\sim{IHA}_{26}\) | Biological life cycles. The specialized habitats for fish migration, spawning, reproduction and predator avoidance. The evolution of life history strategies and behavioral mechanisms. |
Group 4 | Frequency and duration of high/low pulses (4 indicators) | Low and high water level pulse frequency and low and high water level pulse duration. | \(\:{IHA}_{27}\sim{IHA}_{28}\), \(\:{IHA}_{29}\sim{IHA}_{30}\) | Soil moisture and anaerobic stress frequency/intensity. Aquatic habitat availability. River-floodplain material exchange. Soil mineral accessibility. Waterbird nesting/breeding environments. High-flow impacts on riverbed geomorphology. |
Group 5 | Rate/Frequency of water condition changes (3 Indicators) | The mean rate of rise and fall in water level, and the number of reversals in water level. | \(\:{IHA}_{31}\), \(\:{IHA}_{32}\), \(\:{IHA}_{33}\) | Plant drought stress. Dehydration stress on low-mobility riverside organisms |
