River Discharge measures the volume of water (in m³/s) passing through a river cross-section per unit of time. It is one of the fundamental hydrological indicators for assessing water availability, flood risk, and river drought conditions within and around a study area. This KPI presents the historical time series of river discharge based on the Open-Meteo Flood API, powered by the GloFAS global hydrological model (Global Flood Awareness System), developed by ECMWF and the European Commission.
River discharge is a primary ecological indicator: extreme variations — whether prolonged floods or low-flow periods — directly affect aquatic biodiversity, water quality, groundwater recharge, and the availability of riparian habitats. The historical trend enables identification of seasonal anomalies, extreme events, and structural shifts in the hydrological regime associated with climate change.
This is a monitoring-only KPI: no A–E quality level is assigned. Instead, a time-series chart displays the absolute daily discharge, color-coded by severity relative to historical percentile ranges.
Data comes from the Open-Meteo Flood API, which delivers reanalysis and forecast time series of river discharge at 5 km spatial resolution covering 1984 to the present. The underlying model is GloFAS-ERA5 for historical periods and GloFAS v4 for projections.
The nearest GloFAS pixel to the study polygon centroid is identified and daily discharge values (m³/s) are retrieved for the full available period. Reference percentiles are computed for the 1984–2007 reference period. Monthly and annual means are calculated for trend visualization. Values are color-coded by severity derived from historical percentile thresholds.
Risk interpretation table:
| Condition | Discharge | Risk |
|---|---|---|
| Flood | Well above historical mean | Flood risk |
| Normal | Within 1 standard deviation of mean | Normal conditions |
| Moderate low flow | 50–80% of historical mean | Water stress |
| Severe low flow | Below 50% of historical mean | River drought risk |
Unit of measure: cubic metres per second (m³/s)
Line Chart. A time-series area/line chart showing daily river discharge values over time, with per-point severity coloring and a 7-month forecast segment.
Purpose: To answer the question "Is this site experiencing normal flow, drought, or flood risk?" by displaying the historical and forecast discharge of the nearest river.
Description: The chart renders one data point per day along the horizontal axis (time), with discharge in m³/s on the vertical axis. Each point is colored according to its severity relative to historical percentile ranges (green = normal, yellow = moderate stress, orange/red = drought or flood risk). A statistics row above the chart displays the Minimum, Average, and Maximum values for the currently selected period. A period filter allows viewing the full year, 6 months, 3 months, or 1 month of data. Forecast data (up to 7 months ahead) is rendered as dashed lines at 50% opacity to visually distinguish it from historical values. If no data has been generated yet, an empty state with a "Generate data" button is shown (credit-gated: 1.00 credit per generation).
How it's calculated: Each point represents the raw daily river discharge value (m³/s) retrieved from the Open-Meteo Flood API for the GloFAS grid cell nearest to the site centroid. Point color is assigned dynamically based on how the value compares to historical percentile thresholds (computed for the 1984–2007 reference period). The statistics row (min/mean/max) is calculated over the selected filter period from the loaded dataset.
Legend: Colors are assigned dynamically — no fixed frontend thresholds. Typical color mapping:
| Color | Condition | Meaning |
|---|---|---|
| ■ Green | Normal range | Flow within historical mean; no significant risk |
| ■ Yellow | Moderate low flow | Flow approximately 50–80% of historical mean; water stress signal |
| ■ Orange / ■ Red | Extreme conditions | Flow below 50% of mean (drought risk) or well above mean (flood risk) |
| Dashed line | Forecast segment | Future values (GloFAS v4), up to 7 months ahead |
Interpretation example:
If the chart shows a sustained red segment during July–August with values around 2 m³/s while the historical mean for the site is approximately 15 m³/s, this indicates a severe drought period with river flow reduced to less than 15% of normal — a significant risk for aquatic ecosystems and water availability.
| Source | Provider | Coverage | Resolution | Period |
|---|---|---|---|---|
| Open-Meteo Flood API (GloFAS-ERA5 + GloFAS v4) | Open-Meteo / ECMWF / European Commission | Global | 5 km, daily | 1984 — present (+7-month forecast) |
Daily river discharge values are extracted from the Open-Meteo Flood API, which serves GloFAS-ERA5 reanalysis data for the historical period and GloFAS v4 for forecast projections. The processing pipeline identifies the nearest GloFAS grid cell to the study polygon centroid at 5 km resolution.
Reference percentiles (q10, q20, q30, q40, q50, q60, q70, q80, q90, q95, q99) are computed over the 1984–2007 baseline period. These percentile thresholds are used to assign severity coloring to each daily data point. Monthly and annual aggregations are derived for trend visualization.
The forecast segment covers up to 7 months ahead using GloFAS v4 probabilistic outputs. Forecast values are visually differentiated through dashed rendering at 50% opacity.