Overcoming Information Limitations for the Prescription of an Environmental Flow Regime for a Central American River

Abstract:

Hydropower dam construction is expanding rapidly in Central America because of the
increasing demand for electricity. Although hydropower can provide a low-carbon source of energy, dams
can also degrade socially valued riverine and riparian ecosystems and the services they provide. Such
degradation can be partially mitigated by the release of environmental flows below dams. However,
environmental flows have been applied infrequently to dams in Central America, partly because of the lack
of information on the ecological, social, and economic aspects of rivers. This paper presents a case study
of how resource and information limitations were addressed in the development of environmental flow
recommendations for the Patuca River in Honduras below a proposed hydroelectric dam. To develop flow
recommendations, we applied a multistep process that included hydrological analysis and modeling, the
collection of traditional ecological knowledge (TEK) during field trips, expert consultation, and
environmental flow workshops for scientists, water managers, and community members. The final
environmental flow recommendation specifies flow ranges for different components of river hydrology,
including low flows for each month, high-flow pulses, and floods, in dry, normal, and wet years. The TEK
collected from local and indigenous riverine communities was particularly important for forming hypotheses
about flow-dependent ecological and social factors that may be vulnerable to disruption from dam-modified
river flows. We show that our recommended environmental flows would have a minimal impact on the
dam’s potential to generate electricity. In light of rapid hydropower development in Central America, we suggest that environmental flows are important at the local scale, but that an integrated landscape perspective
is ultimately needed to pursue hydropower development in a manner that is as ecologically sustainable as
possible.