Divert/block/stop freshwater inputs
Overall effectiveness category No evidence found (no assessment)
Number of studies: 0
Background information and definitions
Marshes and swamps may be threatened by inputs of the wrong type of water. This action involves limiting freshwater inputs to marshes or swamps, including (a) freshwater inputs to brackish or saline sites, (b) surface water inputs to sites normally fed by groundwater and (c) groundwater inputs to sites normally fed by surface water. Construction of pipes, channels, waterways, pumps, impoundments or dams can help to achieve these goals. Intervention may be permanent (e.g. blocking input channels) or temporary (e.g. diverting freshwater inputs during storms).
Stormwater might be deliberately diverted into wetlands. Otherwise, paved and tarmac surfaces in urban areas can increase the amount of runoff into neighbouring wetlands. Excess fresh water in brackish/saline marshes or swamps can alter the vegetation, including replacement of salt-tolerant plant species with freshwater species (Zedler 1983). Further, differences in temperatures, chemical composition and oxygen content between surface water and ground water can affect the type of plant communities that grow in sites fed by one or the other (Winter et al. 1999).
Caution: Clearly, diversions could shift the problem to another habitat: a suitable recipient habitat, where impacts will be minimal, should be chosen. Diverting freshwater inputs may deprive coastal marshes and swamps of the sediment they need to keep up with sea level rise (Ibáñez et al. 2010).
Related actions: Plug/dam canals or trenches (freshwater marshes – brackish/salt marshes – freshwater swamps – brackish/saline swamps); Facilitate tidal exchange to restore degraded habitats (freshwater marshes – brackish/salt marshes – freshwater swamps – brackish/saline swamps); Actively manage water level, including by adding fresh water (freshwater marshes – brackish/salt marshes – freshwater swamps – brackish/saline swamps); Divert/block/stop saltwater inputs.
Ibáñez C., Sharpe P.J., Day J.W. & Prat N. (2010) Vertical accretion and relative sea level rise in the Ebro Delta Wetlands (Catalonia, Spain). Wetlands, 30, 979–988.
Winter T.C., Harvey J.W., Franke O.L. & Alley W.M. (1999) Ground Water and Surface Water: a Single Resource. US Geological Survey Circular 1139.
Zedler J.B. (1983) Freshwater inputs in normally hypersaline marshes. Estuaries, 6, 346–355.