Stroomduurcurves

Stroomduurcurves, often referred to in English as flow duration curves (FDCs), are graphical representations that summarize the distribution of river discharge over a chosen time period. The curve shows how discharge magnitude relates to the fraction of time that discharge is equaled or exceeded, providing a compact view of the variability of streamflow at a particular location.

Construction of a stroomduurcurve relies on a long record of discharge data, typically daily or monthly values. The data are ordered from highest to lowest, and for each value the exceedance probability or the fraction of time that discharge is exceeded is computed. The resulting curve plots discharge on the vertical axis against exceedance probability (or time) on the horizontal axis. The curve is monotone nonincreasing, with high discharges associated with low exceedance probabilities and low discharges with high exceedance probabilities.

Interpretation and use: Stroomduurcurves characterize the flow regime and are applied in hydrological planning and design. In hydropower, they help estimate potential energy production and assess plant capacity under varying flow conditions. In water resources management, they support reservoir operation, abstraction planning, and setting ecological or environmental flow requirements. They also enable comparisons of historical flow regimes and evaluation of changes under climate variability or future scenarios.

Limitations and considerations: The method assumes stationarity and can be sensitive to the length and quality of the data. Seasonal or interannual variability may require separate curves or seasonal analyses. Extreme events can disproportionately influence the curve, and the approach compresses temporal structure to a single frequency representation, potentially overlooking timing and autocorrelation of flows.