A beel thicky infested with water hyacinth

an effective way of using natural resources for the beamnmt of man. However, the
ecosystem processes in open wata bodies me usually vay complex due to the
interaction of an array of physical, chanical and biological processes. Since the
synergistic effect of these factors influence the dynamics of biotic communities living in
these water bodies and govern the rate of output of harvestable biological material, it is
oRen dlficult to link their fish production potential with any particular ecological
parameters. The beel ecosystem is extraordinarily complex with wide temporal and
spat~al variations of many key pmeters. Among the various factors that influence the
wetland ecosystem arc depth, nature of catchment area or river basin, precipitation and
duration of connection to river etc.
Ecosystem processes in a beel is determined by a number of factors which can be
brought under three broad heads
Morphometry and hydrodynamics
8 Physico-chemical properties, and
b~ological characteristics
Morphometry and hydrodynamics
The main morphometric features that influence the productivity of beel
ecosystem are shoreline. area, dcpth and slope. These, in turn, are closely linked with
the hydrodynamics of wetlands. Water renewal pattern is often modified by a number of
natural and man-made processes. The important morphometric and hydrodynamic
characteristics of different beels scattered over Brahmaputra and Barak valley, studied
by CIFRI over the last few years, are described below:
Therc are thm main sources of water input into the beel ecosystem vr:. owrsp~ll
from [he river channel, sut$ace/low and regeneration. Since the state of Assam receives
one of the highest rainfalls in the world, the former two arc responsible for water
renewal in the beels in this State. Rainfall directly fills the lake or rain on the riverine
catchment feeds the parent river. Surface w-off and incnsse in river height due to
inflow of rain water from the upper stretch, cause inundation of the floodplains. often
causing resumption of connection between beels and parent rivers. The water gain or
exchange of wata in Assam takes plnce during southwest monsoon when the