215
D. Kar, Wetlands and Lakes of the World,
DOI 10.1007/978-81-322-1023-8_14, © Springer India 2013
Hydrologic conditions are of paramount importance for the maintenance of a wetland’s structure and function. They have impact on many
abiotic factors, like soil anaerobiosis, nutrient
availability and salinity (in coastal wetlands).
These, in turn, play a key role in developing the
biota in a wetland. Finally, the biotic components
are active in altering the wetland hydrology and
other physico-chemical features and the cycle is
completed. The ‘hydro-period’ or hydrologic signature of a wetland is the result of the balance
between inflows and outflows of water (called the
water budget), the wetland basin geomorphology
and the sub-surface conditions. It is important to
note here that the hydro-period may have dramatic seasonal and year-to-year variations. Yet, it
may be considered as the major determinant of
wetland processes. The principal components of
a wetland’s water budget include precipitation,
evapotranspiration and over-bank flooding in
riparian wetlands, and surface flows, groundwater fluxes and tides in the coastal wetlands.
Hydrology significantly affects species composition and richness, primary productivity, organic
accumulation and nutrient cycling in wetlands.
Further, wetlands with anaerobic standing water
have a process of decomposition in vogue than it
is under dry conditions. Moreover, many wetlands may be organic exporters, but this cannot
be generalised. Nutrient cycling is enhanced by
hydrology-mediated inputs and nutrient availability is often changed by reduced conditions in
wetland substrates.
14.1 The Importance of
Hydrology in Wetlands
It is known that wetlands are transitional systems
between terrestrial and open-water aquatic ecosystems. They are also transitional with regard to
the amount of water they store and process, and
in other ecological processes which result from
the water regime. Wetlands form the aquatic
boundary of the habitats of many terrestrial plants
and animals. As such, small changes in hydrology may result in significant changes in biology.
Hydrology is said to stimulate diversity when
the action of water and transported sediments
create spatial heterogeneity, thus opening up
additional ecological niches. Further, the hydrology of a wetland creates the unique physicochemical conditions which make such an
ecosystem quite different from both well-drained
terrestrial and deep water aquatic systems.
Hydrologic pathways include precipitation, surface run-off, groundwater, flooding rivers, transport energy and nutrients to and from wetlands.
Also, depth of water, flow patterns, duration and
frequency of flooding, etc., are the result of all
the hydrologic inputs and outputs. They influence
the biochemistry of the soil and are also the major
factors in the ultimate selection of the biota of
wetlands. Thus, biota ranging from microbial
communities to vegetation to waterfowl are all
constrained or enhanced by hydrologic conditions. It is to be noted here that ‘hydrology’ is,
perhaps, the single most important determinant
14
Wetland Hydrology
D. Kar, Wetlands and Lakes of the World,
DOI 10.1007/978-81-322-1023-8_14, © Springer India 2013
Hydrologic conditions are of paramount importance for the maintenance of a wetland’s structure and function. They have impact on many
abiotic factors, like soil anaerobiosis, nutrient
availability and salinity (in coastal wetlands).
These, in turn, play a key role in developing the
biota in a wetland. Finally, the biotic components
are active in altering the wetland hydrology and
other physico-chemical features and the cycle is
completed. The ‘hydro-period’ or hydrologic signature of a wetland is the result of the balance
between inflows and outflows of water (called the
water budget), the wetland basin geomorphology
and the sub-surface conditions. It is important to
note here that the hydro-period may have dramatic seasonal and year-to-year variations. Yet, it
may be considered as the major determinant of
wetland processes. The principal components of
a wetland’s water budget include precipitation,
evapotranspiration and over-bank flooding in
riparian wetlands, and surface flows, groundwater fluxes and tides in the coastal wetlands.
Hydrology significantly affects species composition and richness, primary productivity, organic
accumulation and nutrient cycling in wetlands.
Further, wetlands with anaerobic standing water
have a process of decomposition in vogue than it
is under dry conditions. Moreover, many wetlands may be organic exporters, but this cannot
be generalised. Nutrient cycling is enhanced by
hydrology-mediated inputs and nutrient availability is often changed by reduced conditions in
wetland substrates.
14.1 The Importance of
Hydrology in Wetlands
It is known that wetlands are transitional systems
between terrestrial and open-water aquatic ecosystems. They are also transitional with regard to
the amount of water they store and process, and
in other ecological processes which result from
the water regime. Wetlands form the aquatic
boundary of the habitats of many terrestrial plants
and animals. As such, small changes in hydrology may result in significant changes in biology.
Hydrology is said to stimulate diversity when
the action of water and transported sediments
create spatial heterogeneity, thus opening up
additional ecological niches. Further, the hydrology of a wetland creates the unique physicochemical conditions which make such an
ecosystem quite different from both well-drained
terrestrial and deep water aquatic systems.
Hydrologic pathways include precipitation, surface run-off, groundwater, flooding rivers, transport energy and nutrients to and from wetlands.
Also, depth of water, flow patterns, duration and
frequency of flooding, etc., are the result of all
the hydrologic inputs and outputs. They influence
the biochemistry of the soil and are also the major
factors in the ultimate selection of the biota of
wetlands. Thus, biota ranging from microbial
communities to vegetation to waterfowl are all
constrained or enhanced by hydrologic conditions. It is to be noted here that ‘hydrology’ is,
perhaps, the single most important determinant
14
Wetland Hydrology