Linking the Flow Regime of Papyrus Wetlands to Biologically-relevant
Hydrologic Attributes
Abstract
The dominant plant species in many African wetlands is Cyperus papyrus.
Its adaption to saturated and low oxygen conditions and its dense
structure and height provide breeding and feeding grounds for unique
flora and fauna. As a keystone species adapted to local hydrology, the
flow regime of papyrus offers the full range of hydrologic conditions
and events essential to ecosystem health. However, no study has
attempted to link papyrus wetlands’ flow regimes to their
biologically-relevant hydrologic attributes. The Indicators of
Hydrologic Alteration (IHA) enable the evaluation of changes to flow
regimes by examining hydrologic records and linking them to
biologically-relevant hydrologic characteristics through the
Environmental Flow Components (EFCs) approach. This study assesses
hydrologic alterations of a papyrus wetland’s flow regime due to rice
irrigation. We develop a conceptual ecological model linking papyrus to
hydrologic attributes to determine the consequences of changed EFCs
(extreme low flows, base flow, high flow pulses, and small and large
floods) on papyrus as a habitat. We find that agricultural water
management considerably alters the magnitude, duration, timing and rate
of change of EFCs for the irrigated area to catchment area ratio greater
than 1:153, affecting both sexual and asexual reproduction in papyri
plants. Overall, a better understanding of the threats of water
diversion for agriculture is made by linking papyrus’ flow regimes to
biologically-relevant hydrologic attributes. Knowledge of the roles of
the various EFCs could provide opportunities for conserving and
protecting papyrus wetlands, especially for systems at risk of altered
flows.