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Table 2 Relevant intervention/exposure types assessed along with definitions

From: What are the effects of flow-regime changes on fish productivity in temperate regions? A systematic map

Intervention/exposure type



A change in the amount of water moving past a fixed location per unit time (e.g., m3/s): (1) peak flow (reported as alterations in flood, peak, or high flow); (2) base flow (reported as alteration in base flow, low flow or drought conditions); (3) average discharge (reported as alteration in total flow or mean flow); and (4) short-term variation (reported as a change in magnitude that occurred over a period of hours or less than 1 day)


The number of flow occurrences during a specified time period, where the magnitude of flow is either above or below a given threshold. Frequency could be defined as the count or average of high or low flows per time period (e.g., the number of high pulses that are three times the median daily flow per year, or the number of low flows where flow is below the 25th percentile per season), or as the probability of occurrence of a flow (e.g., the probability of a 100-year flood)


Period of time associated with a specific flow condition. Duration could be defined relative to a particular flow event (e.g., a floodplain may be inundated for a specific number of days by a 10-year flood), or as a composite expressed over a specified time period (e.g., the number of days in a year when flow exceeds some value). Antecedent flow, defined as the measure of time since a specific flow level, was also included in the context of the number of dry days (form of duration of low flow)


Timing, seasonality, or predictability of flows of defined magnitude (referring to the regularity with which they occur)

Rate of change

Rate of change, refers to how quickly flow changes from one magnitude to another


Surrogate of flow alteration e.g., water depth, flow stage (water level above an arbitrary point), water velocity, water area


An unspecified component of flow i.e., the study does not specify a flow component. For example, (1) the study compares an unregulated stream (or section of a stream) to a regulated stream (i.e., regulated via a hydro dam) but does not include an actual component of flow as outlined above); or (2) reports unspecified multiple components affecting flow (i.e., do not report effects of components separately to isolate individual effects of components)